Macroautophagy is a multistep, vacuolar, degradation pathway terminating in the lysosomal compartment, and it is of fundamental importance in tissue homeostasis. In this review, we consider macroautophagy in the light...Macroautophagy is a multistep, vacuolar, degradation pathway terminating in the lysosomal compartment, and it is of fundamental importance in tissue homeostasis. In this review, we consider macroautophagy in the light of recent advances in our understanding of the formation of autophagosomes, which are double-membrane-bound vacuoles that sequester cytoplasmic cargos and deliver them to lysosomes. In most cases, this final step is preceded by a maturation step during which autophagosomes interact with the endocytic pathway. The discovery of AuTophaGyrelated genes has greatly increased our knowledge about the mechanism responsible for antophagosome formation, and there has also been progress in the understanding of molecular aspects of autophagosome maturation. Finally, the regulation of autophagy is now better understood because of the discovery that the activity of Atg complexes is targeted by protein kinases, and owing to the importance of nuclear regulation via transcription factors in regulating the expression of autophagy genes.展开更多
Endocytosis occurs at the cell surface and involves internalization of the plasma membrane （PM） along with its constituent membrane proteins and lipids. Endocytosis is involved in sampling of the extracellular milie...Endocytosis occurs at the cell surface and involves internalization of the plasma membrane （PM） along with its constituent membrane proteins and lipids. Endocytosis is involved in sampling of the extracellular milieu and also serves to regulate various processes initiated at the cell surface. These include nutrient uptake, signaling from cell- surface receptors, and many other processes essential for cell and tissue functioning in metazoans. It is also central to the maintenance of PM lipid and protein homeostasis. There are multiple means of internalization that operate concurrently, at the cell surface. With advancement in high-resolution visualization techniques, it is now possible to track multiple endocytic cargo at the same time, revealing a remarkable diversity of endocytic processes in a single cell. A combination of live cell imaging and efficient genetic manipulations has also aided in understanding the functional hierarchy of molecular players in these mechanisms of internalization. Here we provide an account of various endocytic routes, their mechanisms of operation and occurrence across phyla.展开更多
Recent discovery of PYR/PYL/RCAR-type abscisic acid （ABA） receptors has become one of most significant advances in plant science in the past decade. In mammals, endosomal sorting acts as an important pathway to down...Recent discovery of PYR/PYL/RCAR-type abscisic acid （ABA） receptors has become one of most significant advances in plant science in the past decade. In mammals, endosomal sorting acts as an important pathway to downregulate different types of receptors, but its role in plant hormone signaling is poorly understood. Here, we report that an ubiquitin E2-1ike protein, VPS23A, which is a key component of ESCRT-I, negatively regulates ABA signaling. VPS23A has epistatic relationship with PYR/PYL/RCAR-type ABA receptors and disruption of VPS23A enhanced the activity of key kinase OST1 in the ABA signaling pathway under ABA treatment. Moreover, VPS23A interacts with PYR1/PYLs and K63-1inked diubiquitin, and PYL4 possesses K63-1inked ubiquitinated modification in vivo. Further analysis revealed that VPS23A affects the subcellular localization of PYR 1 and the stability of PYL4. Taken together, our results suggest that VPS23A affects PYR1/ PYL4 via vacuole-mediated degradation, providing an advanced understanding of both the turnover of ABA receptors and ESCRTs in plant hormone signaling.展开更多
After nearly three decades of being virtually drug free, use of heroin and other illicit drugs has re-emerged in China as a major public health problem. One result is that drug abuse, particularly heroin injection, ha...After nearly three decades of being virtually drug free, use of heroin and other illicit drugs has re-emerged in China as a major public health problem. One result is that drug abuse, particularly heroin injection, has come to play a predomi- nant role in fueling China’s AIDS epidemic. The first outbreak of HIV among China’s IDUs was reported in the border area of Yunnan province between China and Myanmar where drug trafficking is heavy. Since then drug-related HIV has spread to all 31 provinces, autonomous regions and municipalities. This paper provides an overview to HIV/AIDS transmission through injection drug use in China. It begins with a brief history of the illicit drug trade in China, followed by a discussion of the emergence of drug related AIDS, and a profile of drug users and their sexual partners who have contracted the virus or who are vulnerable to infection. It ends by summarizing three national strategies being used by China to address both drug use and AIDS as major health threats.展开更多
To accommodate two seemingly contradictory biological roles in plant physiology, providing both the rigid structural support of plant cells and the adjustable elasticity needed for cell expansion, the composition of t...To accommodate two seemingly contradictory biological roles in plant physiology, providing both the rigid structural support of plant cells and the adjustable elasticity needed for cell expansion, the composition of the plant cell wall has evolved to become an intricate network of cellulosic, hemicellulosic, and pectic polysaccharides and protein. Due to its complexity, many aspects of the cell wall influence plant cell expansion, and many new and insightful observations and technologies are forthcoming. The biosynthesis of cell wall polymers and the roles of the variety of proteins involved in polysaccharide synthesis continue to be characterized. The interactions within the cell wall polymer network and the modification of these interactions provide insight into how the plant cell wall provides its dual function. The complex cell wall architecture is controlled and organized in part by the dynamic intracellular cytoskeleton and by diverse trafficking pathways of the cell wall polymers and cell wall-related machinery. Meanwhile, the cell wall is continually influenced by hormonal and integrity sensing stimuli that are perceived by the cell. These many processes cooperate to construct, maintain, and manipulate the intricate plant cell wall--an essential structure for the sustaining of the plant stature, growth, and life.展开更多
The plant NHX gene family encodes Na＋/H＋ antiporters which are crucial for salt tolerance, potassium homeostasis and cellular pH regulation. Understanding the role of NHX antiporters in membrane trafficking is becom...The plant NHX gene family encodes Na＋/H＋ antiporters which are crucial for salt tolerance, potassium homeostasis and cellular pH regulation. Understanding the role of NHX antiporters in membrane trafficking is becoming an increasingly interesting subject of study. Membrane trafficking is a central cellular process during which proteins, lipids and polysaccharides are continuously exchanged among membrane compartments. Yeast ScNhxlp, a prevacuole/ vacuolar Na＋/H＋ antiporter, plays an important role in regulating pH to control trafficking out of the endosome. Evidence begins to accumulate that plant NHX antiporters might function in regulating membrane trafficking in plants.展开更多
Plants employ sophisticated mechanisms to interact with pathogenic as well as beneficial microbes. Of those, membrane trafficking is key in establishing a rapid and precise response. Upon interaction with pathogenic m...Plants employ sophisticated mechanisms to interact with pathogenic as well as beneficial microbes. Of those, membrane trafficking is key in establishing a rapid and precise response. Upon interaction with pathogenic microbes, surface-localized immune receptors undergo endocytosis for signal transduction and activity regulation while cell wall components, antimicrobial compounds, and defense proteins are delivered to pathogen invasion sites through polarized secretion. To sustain mutualistic associations, host cells also reprogram the membrane trafficking system to accommodate invasive structures of symbi- otic microbes. Here, we provide an analysis of recent advances in understanding the roles of secretory and endocytic membrane trafficking pathways in plant immune activation. We also discuss strategies deployed by adapted microbes to manipulate these pathways to subvert or inhibit plant defense.展开更多
Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlar...Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlarging the pore size of plasmodesmata （PD） and actively transporting the viral nucleic acid into the adjacent cell. As our knowledge of intercellular transport has increased, it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD. Just as viruses are too large to fit through an unmodified plasmodesma, they are also too large to be freely diffused through the cytoplasm of the cell. Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP, including viral proteins originally associated with replication or gene expression. In this review, we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD, in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.展开更多
AIM: To characterize the nuclear import of hepatitis B virus (HBV) polymerase (P) and its relevance for the viral life cycle.METHODS: Sequence analysis was performed to predict functional motives within P. Phosphoryla...AIM: To characterize the nuclear import of hepatitis B virus (HBV) polymerase (P) and its relevance for the viral life cycle.METHODS: Sequence analysis was performed to predict functional motives within P. Phosphorylation of P was analyzed by in vitro phosphorylation. Phosphorylation site and nuclear localization signal (NLS) were destroyed by site directed mutagenesis. Functionality of the identified NLS was analyzed by confocal fluorescence microscopy and characterizing the karyopherin binding. Relevance of the structural motives for viral life cycle was studied by infection of primary Tupaia hepatocytes with HBV.RESULTS: We identified by sequence alignment and functional experiments a conserved bipartite NLS containing a casein kinase II (CKII) phosphorylation site located within the terminal protein domain (TP) of the HBV polymerase. Inhibition of CKII impairs the functionality of this NLS and thereby prevents the nuclear import of the polymerase. Binding of the import factor karyopherin-α2 to the polymerase depends on its CKII-mediated phosphorylation of the bipartite NLS. In HBV-infected primary Tupaia hepatocytes CKII inhibition in the early phase (post entry phase) of the infection process prevents the establishment of the infection.CONCLUSION: Based on these data it is suggested that during HBV infection the final import of the genome complex into the nucleus is mediated by a novel bipartite NLS localized in the TP domain of HBV polymerase.展开更多
The sessile life style of plants creates the need to deal with an often adverse environment, in which water availability can change on a daily basis, challenging the cellular physiology and integrity. Changes in os- m...The sessile life style of plants creates the need to deal with an often adverse environment, in which water availability can change on a daily basis, challenging the cellular physiology and integrity. Changes in os- motic conditions disrupt the equilibrium of the plasma membrane： hypoosmotic conditions increase and hyperosmotic environment decrease the cell volume. Here, we show that short-term extracellular osmotic treatments are closely followed by a shift in the balance between endocytosis and exocytosis in root mer- istem cells. Acute hyperosmotic treatments （ionic and nonionic） enhance clathrin-mediated endocytosis simultaneously attenuating exocytosis, whereas hypoosmotic treatments have the opposite effects. In addition to clathrin recruitment to the plasma membrane, components of early endocytic trafficking are essential during hyperosmotic stress responses. Consequently, growth of seedlings defective in elements of clathrin or early endocytic machinery is more sensitive to hyperosmotic treatments. We also found that the endocytotic response to a change of osmotic status in the environment is dominant over the presum- ably evolutionary more recent regulatory effect of plant hormones, such as auxin. These results imply that osmotic perturbation influences the balance between endocytosis and exocytosis acting through clathrin- mediated endocytosis. We propose that tension on the plasma membrane determines the addition or removal of membranes at the cell surface, thus preserving cell integrity.展开更多
The viral protein 22 (VP22) in the tegument of Marek’s disease virus serotype 1 (MDV-1) plays an im-portant role in cell-to-cell spread and viral propagation. Antiserum against the carboxyl terminus of VP22 was prepa...The viral protein 22 (VP22) in the tegument of Marek’s disease virus serotype 1 (MDV-1) plays an im-portant role in cell-to-cell spread and viral propagation. Antiserum against the carboxyl terminus of VP22 was prepared by immunizing mice with recombinant VP22 expressed in E. coli, and used to in-vestigate its expression in chicken embryo fibroblast (CEF) cells infected with different MDV-1 strains. At an infection dose of PFU=50, intercellular trafficking of the VP22 into the nuclei of the surrounding receipt cells was detected as early as 3 hours post infection. By 6 hours after infection (before viral plague formation), the protein was detected in the whole nuclei of the recipient cells with no difference among MDV-1 strains CVI988/Rispens, GA and RB1B. Intra-nuclear accumulation of the VP22 protein was further increased when the viral plagues started to form. These results indicate that, albeit the ex-istence of the 201TKSERT206 deletion, the VP22 of the CVI988/Rispens vaccine strain has also intercel-lular-trafficking function, which might serve as a potential alternative delivering protein instead of virulent strains VP22.展开更多
Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane dom...Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane domain in the growing tips of these cells. Presence of a tip-focused calcium gradient, control of actin cytoskeleton dynamics, and formation and targeting of secretory vesicles are essential to tip growth. Similar to cells undergoing diffuse growth, cellulose, hemi-celluloses, and pectins are also deposited in the growing apices of tip-growing cells. However, differences in the manner in which these cell wall components are targeted and inserted in the expanding portion of tip-growing cells is reflected by the identification of elements of the plant cell wall synthesis machinery which have been shown to play unique roles in tip-growing cells. In this review, we summarize our current understanding of the tip growth process, with a particular focus on the subcellular targeting of newly synthesized cell wall components, and their roles in this form of plant cell expansion.展开更多
Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translatio...Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases.In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation,and discuss how palmitoylation affects AMPA receptors function at synapses in recent years.Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases.展开更多
Organization of proteins into complexes is crucial for many cellular functions. Recently, the SUT1 protein was shown to form homodimeric complexes, to be associated with lipid raft-like microdomains in yeast as well a...Organization of proteins into complexes is crucial for many cellular functions. Recently, the SUT1 protein was shown to form homodimeric complexes, to be associated with lipid raft-like microdomains in yeast as well as in plants and to undergo endocytosis in response to brefeldin A. We therefore aimed to identify SUTl-interacting proteins that might be involved in dimerization, endocytosis, or targeting of SUT1 to raft-like microdomains. Therefore, we identified potato membrane proteins, which are associated with the detergent-resistant membrane （DRM） fraction. Among the proteins identified, we clearly confirmed StSUT1 as part of DRM in potato source leaves. We used the yeast two-hybrid split ubiq- uitin system （SUS） to systematically screen for interaction between the sucrose transporter StSUT1 and other membrane- associated or soluble proteins in vivo. The SUS screen was followed by immunoprecipitation using affinity-purified StSUTl-specific peptide antibodies and mass spectrometric analysis of co-precipitated proteins. A large overlap was ob- served between the StSUTl-interacting proteins identified in the co-immunoprecipitation and the detergent-resistant membrane fraction. One of the SUTl-interacting proteins, a protein disulfide isomerase （PDI）, interacts also with other sucrose transporter proteins. A potential role of the PDI as escort protein is discussed.展开更多
ALG-2(a gene product of PDCD6) is a 22-kD protein containing five serially repetitive EF-hand structures and belongs to the penta-EF-hand(PEF) family,including the subunits of typical calpains.ALG-2 is the most conser...ALG-2(a gene product of PDCD6) is a 22-kD protein containing five serially repetitive EF-hand structures and belongs to the penta-EF-hand(PEF) family,including the subunits of typical calpains.ALG-2 is the most conserved protein among the PEF family members and its homologs are widely found in eukaryotes.X-ray crystal structures of various PEF proteins including ALG-2 have common features:presence of eightα-helices and dimer formation via paired EF5s that are positioned in anti-parallel orientation.ALG-2 forms a homodimer and a heterodimer with its closest paralog peflin.Like calmodulin,a well-known four-EF-hand protein,ALG-2 interacts with various proteins in a Ca2+-dependent fashion,but the binding motifs are completely different.With some exceptions,ALG-2-interacting proteins commonly contain Pro-rich regions,and ALG-2 recognizes at least two distinct Pro-containing motifs:PPYP(X) nYP(X,variable;n=4 in ALIX and PLSCR3) and PXPGF(represented by Sec31A) .A shorter alternatively spliced isoform,lacking two residues and designated ALG-2 GF122,does not bind ALIX but maintains binding capacity to Sec31A.X-ray crystal structural analyses have revealed that binding of calcium ions induces the configuration of the side chain of R125 so that it opens Pocket 1,which accepts PPYP,but Pocket 1 remains closed in the case of ALG-2 GF122.ALG-2 dimer has two ligand-binding sites,each in a monomer molecule,and appears to function as a Ca2+-dependent adaptor protein to either stabilize a preformed complex or to bridge two proteins on scaffolds in systems of the endosomal sorting complex required for transport(ESCRT) and ER-to-Golgi transport.展开更多
Semaphorins were originally identified as axon guidance factors involved in the development of the neuronal system. However, accumulating evidence indicates that several members of semaphorins, so-called ＇immune sema...Semaphorins were originally identified as axon guidance factors involved in the development of the neuronal system. However, accumulating evidence indicates that several members of semaphorins, so-called ＇immune semaphorins＇, are crucially involved in various phases of immune responses. These semaphorins regulate both immune cell interactions and immune cell trafficking during physiological and pathological immune responses. Here, we review the following two functional aspects of semaphorins and their receptors in immune responses： their functions in cell-cell interactions and their involvement in immune cell trafficking.展开更多
This paper presents a comprehensive analysis of global human trafficking trends over a twenty-year period, leveraging a robust dataset from the Counter Trafficking Data Collaborative (CTDC). The study unfolds in a sys...This paper presents a comprehensive analysis of global human trafficking trends over a twenty-year period, leveraging a robust dataset from the Counter Trafficking Data Collaborative (CTDC). The study unfolds in a systematic manner, beginning with a detailed data collection phase, where ethical and legal standards for data usage and privacy are strictly observed. Following collection, the data undergoes a rigorous preprocessing stage, involving cleaning, integration, transformation, and normalization to ensure accuracy and consistency for analysis. The analytical phase employs time-series analysis to delineate historical trends and utilizes predictive modeling to forecast future trajectories of human trafficking using the advanced analytical capabilities of Power BI. A comparative analysis across regions—Africa, the Americas, Asia, and Europe—is conducted to identify and visualize the distribution of human trafficking, dissecting the data by victim demographics, types of exploitation, and duration of victimization. The findings of this study not only offer a descriptive and predictive outlook on trafficking patterns but also provide insights into the regional nuances that influence these trends. The article underscores the prevalence and persistence of human trafficking, identifies factors contributing to its evolution, and discusses the implications for policy and law enforcement. By integrating a methodological approach with quantitative analysis, this research contributes to the strategic planning and resource allocation for combating human trafficking. It highlights the necessity for continued research and international cooperation to effectively address and mitigate this global issue. The implications of this research are significant, offering actionable insights for policymakers, law enforcement, and advocates in the ongoing battle against human trafficking.展开更多
The 76 amino acid protein ubiquitin （Ub） is highly conserved in all eukaryotic species. It plays important roles in many cellular processes by covalently attaching to the target proteins. The best known function of ...The 76 amino acid protein ubiquitin （Ub） is highly conserved in all eukaryotic species. It plays important roles in many cellular processes by covalently attaching to the target proteins. The best known function of Ub is marking substrate proteins for degra- dation by the 26S proteasome. In fact, other consequences of ubiquitination have been discovered in yeast and mammals, such as membrane trafficking, DNA repair, chromatin modification, and protein kinase activation. The common mechanism underlying these processes is that Ub serves as a signal to sort proteins to the vacuoles or lysosomes for degradation as opposed to 26S proteasome-dependent degradation. To date, several reports have indicated that a similar function of Ub also exists in plants. This review focuses on a summary and analysis of the recent research progress on Ub acting as a signal to mediate endocytosis and endosomal trafficking in plants.展开更多
文摘Macroautophagy is a multistep, vacuolar, degradation pathway terminating in the lysosomal compartment, and it is of fundamental importance in tissue homeostasis. In this review, we consider macroautophagy in the light of recent advances in our understanding of the formation of autophagosomes, which are double-membrane-bound vacuoles that sequester cytoplasmic cargos and deliver them to lysosomes. In most cases, this final step is preceded by a maturation step during which autophagosomes interact with the endocytic pathway. The discovery of AuTophaGyrelated genes has greatly increased our knowledge about the mechanism responsible for antophagosome formation, and there has also been progress in the understanding of molecular aspects of autophagosome maturation. Finally, the regulation of autophagy is now better understood because of the discovery that the activity of Atg complexes is targeted by protein kinases, and owing to the importance of nuclear regulation via transcription factors in regulating the expression of autophagy genes.
文摘Endocytosis occurs at the cell surface and involves internalization of the plasma membrane （PM） along with its constituent membrane proteins and lipids. Endocytosis is involved in sampling of the extracellular milieu and also serves to regulate various processes initiated at the cell surface. These include nutrient uptake, signaling from cell- surface receptors, and many other processes essential for cell and tissue functioning in metazoans. It is also central to the maintenance of PM lipid and protein homeostasis. There are multiple means of internalization that operate concurrently, at the cell surface. With advancement in high-resolution visualization techniques, it is now possible to track multiple endocytic cargo at the same time, revealing a remarkable diversity of endocytic processes in a single cell. A combination of live cell imaging and efficient genetic manipulations has also aided in understanding the functional hierarchy of molecular players in these mechanisms of internalization. Here we provide an account of various endocytic routes, their mechanisms of operation and occurrence across phyla.
文摘Recent discovery of PYR/PYL/RCAR-type abscisic acid （ABA） receptors has become one of most significant advances in plant science in the past decade. In mammals, endosomal sorting acts as an important pathway to downregulate different types of receptors, but its role in plant hormone signaling is poorly understood. Here, we report that an ubiquitin E2-1ike protein, VPS23A, which is a key component of ESCRT-I, negatively regulates ABA signaling. VPS23A has epistatic relationship with PYR/PYL/RCAR-type ABA receptors and disruption of VPS23A enhanced the activity of key kinase OST1 in the ABA signaling pathway under ABA treatment. Moreover, VPS23A interacts with PYR1/PYLs and K63-1inked diubiquitin, and PYL4 possesses K63-1inked ubiquitinated modification in vivo. Further analysis revealed that VPS23A affects the subcellular localization of PYR 1 and the stability of PYL4. Taken together, our results suggest that VPS23A affects PYR1/ PYL4 via vacuole-mediated degradation, providing an advanced understanding of both the turnover of ABA receptors and ESCRTs in plant hormone signaling.
文摘After nearly three decades of being virtually drug free, use of heroin and other illicit drugs has re-emerged in China as a major public health problem. One result is that drug abuse, particularly heroin injection, has come to play a predomi- nant role in fueling China’s AIDS epidemic. The first outbreak of HIV among China’s IDUs was reported in the border area of Yunnan province between China and Myanmar where drug trafficking is heavy. Since then drug-related HIV has spread to all 31 provinces, autonomous regions and municipalities. This paper provides an overview to HIV/AIDS transmission through injection drug use in China. It begins with a brief history of the illicit drug trade in China, followed by a discussion of the emergence of drug related AIDS, and a profile of drug users and their sexual partners who have contracted the virus or who are vulnerable to infection. It ends by summarizing three national strategies being used by China to address both drug use and AIDS as major health threats.
文摘To accommodate two seemingly contradictory biological roles in plant physiology, providing both the rigid structural support of plant cells and the adjustable elasticity needed for cell expansion, the composition of the plant cell wall has evolved to become an intricate network of cellulosic, hemicellulosic, and pectic polysaccharides and protein. Due to its complexity, many aspects of the cell wall influence plant cell expansion, and many new and insightful observations and technologies are forthcoming. The biosynthesis of cell wall polymers and the roles of the variety of proteins involved in polysaccharide synthesis continue to be characterized. The interactions within the cell wall polymer network and the modification of these interactions provide insight into how the plant cell wall provides its dual function. The complex cell wall architecture is controlled and organized in part by the dynamic intracellular cytoskeleton and by diverse trafficking pathways of the cell wall polymers and cell wall-related machinery. Meanwhile, the cell wall is continually influenced by hormonal and integrity sensing stimuli that are perceived by the cell. These many processes cooperate to construct, maintain, and manipulate the intricate plant cell wall--an essential structure for the sustaining of the plant stature, growth, and life.
基金supported by a grant from the National Natural Science Foundation of China (31070222 to Quan-Sheng Qiu)
文摘The plant NHX gene family encodes Na＋/H＋ antiporters which are crucial for salt tolerance, potassium homeostasis and cellular pH regulation. Understanding the role of NHX antiporters in membrane trafficking is becoming an increasingly interesting subject of study. Membrane trafficking is a central cellular process during which proteins, lipids and polysaccharides are continuously exchanged among membrane compartments. Yeast ScNhxlp, a prevacuole/ vacuolar Na＋/H＋ antiporter, plays an important role in regulating pH to control trafficking out of the endosome. Evidence begins to accumulate that plant NHX antiporters might function in regulating membrane trafficking in plants.
文摘Plants employ sophisticated mechanisms to interact with pathogenic as well as beneficial microbes. Of those, membrane trafficking is key in establishing a rapid and precise response. Upon interaction with pathogenic microbes, surface-localized immune receptors undergo endocytosis for signal transduction and activity regulation while cell wall components, antimicrobial compounds, and defense proteins are delivered to pathogen invasion sites through polarized secretion. To sustain mutualistic associations, host cells also reprogram the membrane trafficking system to accommodate invasive structures of symbi- otic microbes. Here, we provide an analysis of recent advances in understanding the roles of secretory and endocytic membrane trafficking pathways in plant immune activation. We also discuss strategies deployed by adapted microbes to manipulate these pathways to subvert or inhibit plant defense.
文摘Plant viruses are a class of plant pathogens that specialize in movement from cell to cell. As part of their arsenal for infection of plants, every virus encodes a movement protein （MP）, a protein dedicated to enlarging the pore size of plasmodesmata （PD） and actively transporting the viral nucleic acid into the adjacent cell. As our knowledge of intercellular transport has increased, it has become apparent that viruses must also use an active mechanism to target the virus from their site of replication within the cell to the PD. Just as viruses are too large to fit through an unmodified plasmodesma, they are also too large to be freely diffused through the cytoplasm of the cell. Evidence has accumulated now for the involvement of other categories of viral proteins in intracellular movement in addition to the MP, including viral proteins originally associated with replication or gene expression. In this review, we will discuss the strategies that viruses use for intracellular movement from the replication site to the PD, in particular focusing on the role of host membranes for intracellular transport and the coordinated interactions between virus proteins within cells that are necessary for successful virus spread.
文摘AIM: To characterize the nuclear import of hepatitis B virus (HBV) polymerase (P) and its relevance for the viral life cycle.METHODS: Sequence analysis was performed to predict functional motives within P. Phosphorylation of P was analyzed by in vitro phosphorylation. Phosphorylation site and nuclear localization signal (NLS) were destroyed by site directed mutagenesis. Functionality of the identified NLS was analyzed by confocal fluorescence microscopy and characterizing the karyopherin binding. Relevance of the structural motives for viral life cycle was studied by infection of primary Tupaia hepatocytes with HBV.RESULTS: We identified by sequence alignment and functional experiments a conserved bipartite NLS containing a casein kinase II (CKII) phosphorylation site located within the terminal protein domain (TP) of the HBV polymerase. Inhibition of CKII impairs the functionality of this NLS and thereby prevents the nuclear import of the polymerase. Binding of the import factor karyopherin-α2 to the polymerase depends on its CKII-mediated phosphorylation of the bipartite NLS. In HBV-infected primary Tupaia hepatocytes CKII inhibition in the early phase (post entry phase) of the infection process prevents the establishment of the infection.CONCLUSION: Based on these data it is suggested that during HBV infection the final import of the genome complex into the nucleus is mediated by a novel bipartite NLS localized in the TP domain of HBV polymerase.
文摘The sessile life style of plants creates the need to deal with an often adverse environment, in which water availability can change on a daily basis, challenging the cellular physiology and integrity. Changes in os- motic conditions disrupt the equilibrium of the plasma membrane： hypoosmotic conditions increase and hyperosmotic environment decrease the cell volume. Here, we show that short-term extracellular osmotic treatments are closely followed by a shift in the balance between endocytosis and exocytosis in root mer- istem cells. Acute hyperosmotic treatments （ionic and nonionic） enhance clathrin-mediated endocytosis simultaneously attenuating exocytosis, whereas hypoosmotic treatments have the opposite effects. In addition to clathrin recruitment to the plasma membrane, components of early endocytic trafficking are essential during hyperosmotic stress responses. Consequently, growth of seedlings defective in elements of clathrin or early endocytic machinery is more sensitive to hyperosmotic treatments. We also found that the endocytotic response to a change of osmotic status in the environment is dominant over the presum- ably evolutionary more recent regulatory effect of plant hormones, such as auxin. These results imply that osmotic perturbation influences the balance between endocytosis and exocytosis acting through clathrin- mediated endocytosis. We propose that tension on the plasma membrane determines the addition or removal of membranes at the cell surface, thus preserving cell integrity.
基金the National Natural Science Foundation of China (Grant No. 30371070)
文摘The viral protein 22 (VP22) in the tegument of Marek’s disease virus serotype 1 (MDV-1) plays an im-portant role in cell-to-cell spread and viral propagation. Antiserum against the carboxyl terminus of VP22 was prepared by immunizing mice with recombinant VP22 expressed in E. coli, and used to in-vestigate its expression in chicken embryo fibroblast (CEF) cells infected with different MDV-1 strains. At an infection dose of PFU=50, intercellular trafficking of the VP22 into the nuclei of the surrounding receipt cells was detected as early as 3 hours post infection. By 6 hours after infection (before viral plague formation), the protein was detected in the whole nuclei of the recipient cells with no difference among MDV-1 strains CVI988/Rispens, GA and RB1B. Intra-nuclear accumulation of the VP22 protein was further increased when the viral plagues started to form. These results indicate that, albeit the ex-istence of the 201TKSERT206 deletion, the VP22 of the CVI988/Rispens vaccine strain has also intercel-lular-trafficking function, which might serve as a potential alternative delivering protein instead of virulent strains VP22.
基金funded by the Division of Chemical Sciences, Geosciences, and Biosciences, Offce of Basic Energy Sciences of the U.S. Department of Energy through Grant DE‐FG02‐07ER15887funds from the National Science Foundation grant 0937323 provided salary support for F.G
文摘Root hairs and pollen tubes are formed through tip growth, a process requiring synthesis of new cell wall material and the precise targeting and integration of these components to a selected apical plasma membrane domain in the growing tips of these cells. Presence of a tip-focused calcium gradient, control of actin cytoskeleton dynamics, and formation and targeting of secretory vesicles are essential to tip growth. Similar to cells undergoing diffuse growth, cellulose, hemi-celluloses, and pectins are also deposited in the growing apices of tip-growing cells. However, differences in the manner in which these cell wall components are targeted and inserted in the expanding portion of tip-growing cells is reflected by the identification of elements of the plant cell wall synthesis machinery which have been shown to play unique roles in tip-growing cells. In this review, we summarize our current understanding of the tip growth process, with a particular focus on the subcellular targeting of newly synthesized cell wall components, and their roles in this form of plant cell expansion.
基金supported by grants from the National Basic Research Program of China (the 973 Program, No. 2013CB531303 to Dr. Jianguo Chen No. 2014CB744601 to Fang Wang)+3 种基金the National Natural Scientific Foundation of China (NSFC, No. 81222048 to Fang Wang No. 81302754 to Peng Fei Wu)supported by the International Science & Technology Cooperation Program of China (No. 2011DFA32670 to Jianguo Chen)PCSIRT (No. IRT13016)
文摘Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases.In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation,and discuss how palmitoylation affects AMPA receptors function at synapses in recent years.Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases.
文摘Organization of proteins into complexes is crucial for many cellular functions. Recently, the SUT1 protein was shown to form homodimeric complexes, to be associated with lipid raft-like microdomains in yeast as well as in plants and to undergo endocytosis in response to brefeldin A. We therefore aimed to identify SUTl-interacting proteins that might be involved in dimerization, endocytosis, or targeting of SUT1 to raft-like microdomains. Therefore, we identified potato membrane proteins, which are associated with the detergent-resistant membrane （DRM） fraction. Among the proteins identified, we clearly confirmed StSUT1 as part of DRM in potato source leaves. We used the yeast two-hybrid split ubiq- uitin system （SUS） to systematically screen for interaction between the sucrose transporter StSUT1 and other membrane- associated or soluble proteins in vivo. The SUS screen was followed by immunoprecipitation using affinity-purified StSUTl-specific peptide antibodies and mass spectrometric analysis of co-precipitated proteins. A large overlap was ob- served between the StSUTl-interacting proteins identified in the co-immunoprecipitation and the detergent-resistant membrane fraction. One of the SUTl-interacting proteins, a protein disulfide isomerase （PDI）, interacts also with other sucrose transporter proteins. A potential role of the PDI as escort protein is discussed.
文摘ALG-2(a gene product of PDCD6) is a 22-kD protein containing five serially repetitive EF-hand structures and belongs to the penta-EF-hand(PEF) family,including the subunits of typical calpains.ALG-2 is the most conserved protein among the PEF family members and its homologs are widely found in eukaryotes.X-ray crystal structures of various PEF proteins including ALG-2 have common features:presence of eightα-helices and dimer formation via paired EF5s that are positioned in anti-parallel orientation.ALG-2 forms a homodimer and a heterodimer with its closest paralog peflin.Like calmodulin,a well-known four-EF-hand protein,ALG-2 interacts with various proteins in a Ca2+-dependent fashion,but the binding motifs are completely different.With some exceptions,ALG-2-interacting proteins commonly contain Pro-rich regions,and ALG-2 recognizes at least two distinct Pro-containing motifs:PPYP(X) nYP(X,variable;n=4 in ALIX and PLSCR3) and PXPGF(represented by Sec31A) .A shorter alternatively spliced isoform,lacking two residues and designated ALG-2 GF122,does not bind ALIX but maintains binding capacity to Sec31A.X-ray crystal structural analyses have revealed that binding of calcium ions induces the configuration of the side chain of R125 so that it opens Pocket 1,which accepts PPYP,but Pocket 1 remains closed in the case of ALG-2 GF122.ALG-2 dimer has two ligand-binding sites,each in a monomer molecule,and appears to function as a Ca2+-dependent adaptor protein to either stabilize a preformed complex or to bridge two proteins on scaffolds in systems of the endosomal sorting complex required for transport(ESCRT) and ER-to-Golgi transport.
文摘Semaphorins were originally identified as axon guidance factors involved in the development of the neuronal system. However, accumulating evidence indicates that several members of semaphorins, so-called ＇immune semaphorins＇, are crucially involved in various phases of immune responses. These semaphorins regulate both immune cell interactions and immune cell trafficking during physiological and pathological immune responses. Here, we review the following two functional aspects of semaphorins and their receptors in immune responses： their functions in cell-cell interactions and their involvement in immune cell trafficking.
文摘This paper presents a comprehensive analysis of global human trafficking trends over a twenty-year period, leveraging a robust dataset from the Counter Trafficking Data Collaborative (CTDC). The study unfolds in a systematic manner, beginning with a detailed data collection phase, where ethical and legal standards for data usage and privacy are strictly observed. Following collection, the data undergoes a rigorous preprocessing stage, involving cleaning, integration, transformation, and normalization to ensure accuracy and consistency for analysis. The analytical phase employs time-series analysis to delineate historical trends and utilizes predictive modeling to forecast future trajectories of human trafficking using the advanced analytical capabilities of Power BI. A comparative analysis across regions—Africa, the Americas, Asia, and Europe—is conducted to identify and visualize the distribution of human trafficking, dissecting the data by victim demographics, types of exploitation, and duration of victimization. The findings of this study not only offer a descriptive and predictive outlook on trafficking patterns but also provide insights into the regional nuances that influence these trends. The article underscores the prevalence and persistence of human trafficking, identifies factors contributing to its evolution, and discusses the implications for policy and law enforcement. By integrating a methodological approach with quantitative analysis, this research contributes to the strategic planning and resource allocation for combating human trafficking. It highlights the necessity for continued research and international cooperation to effectively address and mitigate this global issue. The implications of this research are significant, offering actionable insights for policymakers, law enforcement, and advocates in the ongoing battle against human trafficking.
基金supported by a grant from the National BasicResearch Program of China (973 Program, 2011CB915402)the National Science Foundation of China (CNSF31030047/90717006)
文摘The 76 amino acid protein ubiquitin （Ub） is highly conserved in all eukaryotic species. It plays important roles in many cellular processes by covalently attaching to the target proteins. The best known function of Ub is marking substrate proteins for degra- dation by the 26S proteasome. In fact, other consequences of ubiquitination have been discovered in yeast and mammals, such as membrane trafficking, DNA repair, chromatin modification, and protein kinase activation. The common mechanism underlying these processes is that Ub serves as a signal to sort proteins to the vacuoles or lysosomes for degradation as opposed to 26S proteasome-dependent degradation. To date, several reports have indicated that a similar function of Ub also exists in plants. This review focuses on a summary and analysis of the recent research progress on Ub acting as a signal to mediate endocytosis and endosomal trafficking in plants.
