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
Objective Formation of the endophilin II-Ca 2＋ channel complex is Ca 2＋ -dependent in clathrin-mediated endocytosis. However, little is known about whether the other two endophilin isoforms have the same features. T...Objective Formation of the endophilin II-Ca 2＋ channel complex is Ca 2＋ -dependent in clathrin-mediated endocytosis. However, little is known about whether the other two endophilin isoforms have the same features. The present study aimed to investigate the characteristics of the interactions of all three isoforms with Ca 2＋ channels and dynamin I. Methods N-type Ca 2＋ channel C-terminal fragments （NCFs） synthesized with a 3 H-leucine-labeled kit, were incubated with endophilin-GST fusion proteins, followed by pull-down assay. Results were counted on a scintillation counter. In addition, the different endophilin isoforms were each co-transfected with dynamin I into 293T cells, followed by flow cytometry and co-immunoprecipitation assay. Immunostaining was performed and an image analysis program was used to evaluate the overlap coefficient of cells expressing endophilin and dynamin I. Results All three isoforms interacted with NCF. Endophilins I and II demonstrated clear Ca 2＋ -dependent interactions with NCF, whereas endophilin III did not. Co-immunoprecipitation showed that, compared to endophilin I/II, the interaction between endophilin III and dynamin I was significantly increased. Similar results were obtained from flow cytometry. Furthermore, endophilin III had a higher overlap coefficient with dynamin I in co-transfected 293T cells. Conclusion Endophilin isoforms have distinct characteristics in interactions with NCF and dynamin I. Endophilin III binding to NCF is Ca 2＋ -independent, implying that it plays a different role in clathrin-mediated endocytosis.展开更多
The current study examined a rat model of vascular dementia. The model rats exhibited obvious morphological and ultrastructural changes in neurons in the brain, and significantly reduced dynamin 1 expression in hippoc...The current study examined a rat model of vascular dementia. The model rats exhibited obvious morphological and ultrastructural changes in neurons in the brain, and significantly reduced dynamin 1 expression in hippocampal CA1 region along with decreased learning and memory performance. Following atorvastatin treatment, the morphology and ultrastructure of cells in the model rat brain were significantly improved, dynamin 1 expression in hippocampal CA1 region was significantly enhanced, and learning and memory ability was significantly improved. The results demonstrated that impaired learning and memory abilities in vascular dementia model rats were closely correlated with decreased dynamin 1 expression. These findings indicate that atorvastatin can protect model rats against cognitive impairment by increasing dynamin 1 expression.展开更多
Background During the blood stage of malaria infection, parasites internalize in the host red blood cells and degrade massive amounts of hemoglobin for their development. Although the morphology of the parasite＇s hem...Background During the blood stage of malaria infection, parasites internalize in the host red blood cells and degrade massive amounts of hemoglobin for their development. Although the morphology of the parasite＇s hemoglobin uptake pathway has been clearly observed, little has been known about its molecular mechanisms. Methods The recombinant proteins from Plasmodium falciparum, dynamin like protein 1 （PfDYN1） and 2 （PfDYN2） GTPase domain, were expressed in E .coil and showed GTPase activity. By using a dynamin inhibitor, dynasore, we demonstrated the involvement of PfDYN1 in the hemoglobin uptake pathway. Results The GTPase activity of the two recombinant proteins was inhibited by dynasore in vitro. Treatment of parasite cultures with 80 μmol/L dynasore at the ring and early trophozoite stage resulted in substantial inhibition of parasite growth and in an obvious decline of hemoglobin quantum. Furthermore, reduced intracellular hemozoin accumulation and decreased uptake of the FITC-dextran were also observed, together with distinctive changes in the ultrastructure of parasites after the dynasore treatment. Conclusions Our results show that PfDYN1 plays an important role in the hemoglobin uptake pathway of P. falciparum and suggest its possibility of being a novel target for malaria chemotherapy.展开更多
Autophagy is a central lysosomal degradation pathway required for maintaining cellular homeostasis and its dysfunction is associated with numerous human diseases. To identify players in autophagy, we tested ~ 1200 che...Autophagy is a central lysosomal degradation pathway required for maintaining cellular homeostasis and its dysfunction is associated with numerous human diseases. To identify players in autophagy, we tested ~ 1200 chemically induced mutations on the X chromosome in Drosophila fat body clones and discovered that shibire （shi） plays an essential role in starvation-induced autophagy, shi encodes a dynamin protein required for fission of clathrin-coated vesicles from the plasma membrane during endocytosis. We showed that Shi is dispensable for autophagy initiation and autophagosome--lysosome fusion, but required for lysosomal/autolysosomal acidification. We also showed that other endocytic core machinery components like clathrin and AP2 play similar but not identical roles in regulating autophagy and lysosomal function as dynamin. Previous studies suggested that dynamin directly regulates autophagosome formation and autophagic lysosome reformation （ALR） through its excision activity, Here, we provide evidence that dynamin also regulates autophagy indirectly by regulating lysosomal function.展开更多
Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus...Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus. Recently, dynamin-like proteins were also found in some plant cells. We demonstrate here the presence of dynamin with molecular weight of 100 kD in day-lily ( Hemerocallis fulva) pollen based on molecular estimation and Western blotting. The highly purified pollen Dynamin had GTPase activity, which could be stimulated 1.64 fold by calf brain microtubules in vitro. The results from electron microscopic examination showed that the pollen dynamin readily self-assembled into ring-like structures.展开更多
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.
基金supported by grants from the National Natural Science Foundation of China (30870785)the Natural Science Foundation of Guangdong Province, China (9351008901000003)
文摘Objective Formation of the endophilin II-Ca 2＋ channel complex is Ca 2＋ -dependent in clathrin-mediated endocytosis. However, little is known about whether the other two endophilin isoforms have the same features. The present study aimed to investigate the characteristics of the interactions of all three isoforms with Ca 2＋ channels and dynamin I. Methods N-type Ca 2＋ channel C-terminal fragments （NCFs） synthesized with a 3 H-leucine-labeled kit, were incubated with endophilin-GST fusion proteins, followed by pull-down assay. Results were counted on a scintillation counter. In addition, the different endophilin isoforms were each co-transfected with dynamin I into 293T cells, followed by flow cytometry and co-immunoprecipitation assay. Immunostaining was performed and an image analysis program was used to evaluate the overlap coefficient of cells expressing endophilin and dynamin I. Results All three isoforms interacted with NCF. Endophilins I and II demonstrated clear Ca 2＋ -dependent interactions with NCF, whereas endophilin III did not. Co-immunoprecipitation showed that, compared to endophilin I/II, the interaction between endophilin III and dynamin I was significantly increased. Similar results were obtained from flow cytometry. Furthermore, endophilin III had a higher overlap coefficient with dynamin I in co-transfected 293T cells. Conclusion Endophilin isoforms have distinct characteristics in interactions with NCF and dynamin I. Endophilin III binding to NCF is Ca 2＋ -independent, implying that it plays a different role in clathrin-mediated endocytosis.
基金the Science and Technology Development Program of Hunan Province,No.2008FJ3195
文摘The current study examined a rat model of vascular dementia. The model rats exhibited obvious morphological and ultrastructural changes in neurons in the brain, and significantly reduced dynamin 1 expression in hippocampal CA1 region along with decreased learning and memory performance. Following atorvastatin treatment, the morphology and ultrastructure of cells in the model rat brain were significantly improved, dynamin 1 expression in hippocampal CA1 region was significantly enhanced, and learning and memory ability was significantly improved. The results demonstrated that impaired learning and memory abilities in vascular dementia model rats were closely correlated with decreased dynamin 1 expression. These findings indicate that atorvastatin can protect model rats against cognitive impairment by increasing dynamin 1 expression.
基金This work was supported by the research grants from the National Basic Research Program of China （973 Program, No. 2007CB513100）, the High-Tech Research and Development Program of China （863 Program, No. 2006AA028471）, the China＇s Major Infectious Diseases of Major Special Program （No. 2008ZX10004-011）, and the grant of National Natural Science Foundation of China （No. 30170876）.
文摘Background During the blood stage of malaria infection, parasites internalize in the host red blood cells and degrade massive amounts of hemoglobin for their development. Although the morphology of the parasite＇s hemoglobin uptake pathway has been clearly observed, little has been known about its molecular mechanisms. Methods The recombinant proteins from Plasmodium falciparum, dynamin like protein 1 （PfDYN1） and 2 （PfDYN2） GTPase domain, were expressed in E .coil and showed GTPase activity. By using a dynamin inhibitor, dynasore, we demonstrated the involvement of PfDYN1 in the hemoglobin uptake pathway. Results The GTPase activity of the two recombinant proteins was inhibited by dynasore in vitro. Treatment of parasite cultures with 80 μmol/L dynasore at the ring and early trophozoite stage resulted in substantial inhibition of parasite growth and in an obvious decline of hemoglobin quantum. Furthermore, reduced intracellular hemozoin accumulation and decreased uptake of the FITC-dextran were also observed, together with distinctive changes in the ultrastructure of parasites after the dynasore treatment. Conclusions Our results show that PfDYN1 plays an important role in the hemoglobin uptake pathway of P. falciparum and suggest its possibility of being a novel target for malaria chemotherapy.
基金supported by the National Natural Science Foundation of China(No.31271432)the National Basic Research Program of China(Nos.2012CB966600 and 2014CB943100)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20130101110116)
文摘Autophagy is a central lysosomal degradation pathway required for maintaining cellular homeostasis and its dysfunction is associated with numerous human diseases. To identify players in autophagy, we tested ~ 1200 chemically induced mutations on the X chromosome in Drosophila fat body clones and discovered that shibire （shi） plays an essential role in starvation-induced autophagy, shi encodes a dynamin protein required for fission of clathrin-coated vesicles from the plasma membrane during endocytosis. We showed that Shi is dispensable for autophagy initiation and autophagosome--lysosome fusion, but required for lysosomal/autolysosomal acidification. We also showed that other endocytic core machinery components like clathrin and AP2 play similar but not identical roles in regulating autophagy and lysosomal function as dynamin. Previous studies suggested that dynamin directly regulates autophagosome formation and autophagic lysosome reformation （ALR） through its excision activity, Here, we provide evidence that dynamin also regulates autophagy indirectly by regulating lysosomal function.
文摘Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus. Recently, dynamin-like proteins were also found in some plant cells. We demonstrate here the presence of dynamin with molecular weight of 100 kD in day-lily ( Hemerocallis fulva) pollen based on molecular estimation and Western blotting. The highly purified pollen Dynamin had GTPase activity, which could be stimulated 1.64 fold by calf brain microtubules in vitro. The results from electron microscopic examination showed that the pollen dynamin readily self-assembled into ring-like structures.
