Mammalian sperm must undergo a series of biochemical and physiological modifications, collectively called capacitation, in the female reproductive tract prior to the acrosome reaction （AR）. The mechanisms of these m...Mammalian sperm must undergo a series of biochemical and physiological modifications, collectively called capacitation, in the female reproductive tract prior to the acrosome reaction （AR）. The mechanisms of these modifications are not well characterized though protein kinases were shown to be involved in the regulation of intracellular Ca2＋ during both capacitation and the AR. In the present review, we summarize some of the signaling events that are involved in capacitation. During the capacitation process, phosphatidyl-inositol-3-kinase （PI3K） is phosphorylated/activated via a protein kinase A （PKA）-dependent cascade, and downregulated by protein kinase C a （PKCa）. PKCa is active at the beginning of capacitation, resulting in PI3K inactivation. During capacitation, PKCa as well as PP172 is degraded by a PKA-dependent mechanism, allowing the activation of PI3K. The activation of PKA during capacitation depends mainly on cyclic adenosine monophosphate （cAMP） produced by the bicarbonate-dependent soluble adenylyl cyclase. This activation of PKA leads to an increase in actin polymerization, an essential process for the development of hyperactivated motility, which is necessary for successful fertilization. Actin polymerization is mediated by PIP2 in two ways： first, PIP2 acts as a cofactor for phospholipase D （PLD） activation, and second, as a molecule that binds and inhibits actin-severing proteins such as gelsolin. Tyrosine phosphorylation of gelsolin during capacitation by Src family kinase （SFK） is also important for its inactivation. Prior to the AR, gelsolin is released from PIP2 and undergoes dephosphorylation/activation, resulting in fast F-actin depolymerization, leading to the AR.展开更多
Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide(LPS)leading to pyroptosis that has critical role in defensing against bacterial infection,whereas its excess activation under pathoge...Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide(LPS)leading to pyroptosis that has critical role in defensing against bacterial infection,whereas its excess activation under pathogenic circumstances may cause various inflammatory diseases.However,there are few known drugs that can control caspase-11 activation.We report here that scutellarin,a flavonoid from Erigeron breviscapus,acted as an inhibitor for caspase-11 activation in macrophages.Scutellarin dosedependently inhibited intracellular LPS-induced release of caspase-11 p26(indicative of caspase-11 activation)and generation of N-terminal fragment of gasdermin D(GSDMD-NT),leading to reduced pyroptosis.It also suppressed the activation of non-canonical nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3(NLRP3)inflammasome as evidenced by reduced apoptosisassociated speck-like protein containing a CARD(ASC)speck formation and decreased interleukin-1 beta(IL-1 b)and caspase-1 p10 secretion,whereas the NLRP3-specific inhibitor MCC950 only inhibited IL-1 b and caspase-1 p10 release and ASC speck formation but not pyroptosis.Scutellarin also suppressed LPS-induced caspase-11 activation and pyroptosis in RAW 264.7 cells lacking ASC expression.Moreover,scutellarin treatment increased Ser/Thr phosphorylation of caspase-11 at protein kinase A(PKA)-specific sites,and its inhibitory action on caspase-11 activation was largely abrogated by PKAinhibitor H89 or by adenylyl cyclase inhibitor MDL12330 A.Collectively,our data indicate that scutellarin inhibited caspase-11 activation and pyroptosis in macrophages at least partly via regulating the PKA signaling pathway.展开更多
文摘Mammalian sperm must undergo a series of biochemical and physiological modifications, collectively called capacitation, in the female reproductive tract prior to the acrosome reaction （AR）. The mechanisms of these modifications are not well characterized though protein kinases were shown to be involved in the regulation of intracellular Ca2＋ during both capacitation and the AR. In the present review, we summarize some of the signaling events that are involved in capacitation. During the capacitation process, phosphatidyl-inositol-3-kinase （PI3K） is phosphorylated/activated via a protein kinase A （PKA）-dependent cascade, and downregulated by protein kinase C a （PKCa）. PKCa is active at the beginning of capacitation, resulting in PI3K inactivation. During capacitation, PKCa as well as PP172 is degraded by a PKA-dependent mechanism, allowing the activation of PI3K. The activation of PKA during capacitation depends mainly on cyclic adenosine monophosphate （cAMP） produced by the bicarbonate-dependent soluble adenylyl cyclase. This activation of PKA leads to an increase in actin polymerization, an essential process for the development of hyperactivated motility, which is necessary for successful fertilization. Actin polymerization is mediated by PIP2 in two ways： first, PIP2 acts as a cofactor for phospholipase D （PLD） activation, and second, as a molecule that binds and inhibits actin-severing proteins such as gelsolin. Tyrosine phosphorylation of gelsolin during capacitation by Src family kinase （SFK） is also important for its inactivation. Prior to the AR, gelsolin is released from PIP2 and undergoes dephosphorylation/activation, resulting in fast F-actin depolymerization, leading to the AR.
基金supported by the National Natural Science Foundation of China(Nos.81773965,81873064,and 81673664)
文摘Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide(LPS)leading to pyroptosis that has critical role in defensing against bacterial infection,whereas its excess activation under pathogenic circumstances may cause various inflammatory diseases.However,there are few known drugs that can control caspase-11 activation.We report here that scutellarin,a flavonoid from Erigeron breviscapus,acted as an inhibitor for caspase-11 activation in macrophages.Scutellarin dosedependently inhibited intracellular LPS-induced release of caspase-11 p26(indicative of caspase-11 activation)and generation of N-terminal fragment of gasdermin D(GSDMD-NT),leading to reduced pyroptosis.It also suppressed the activation of non-canonical nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3(NLRP3)inflammasome as evidenced by reduced apoptosisassociated speck-like protein containing a CARD(ASC)speck formation and decreased interleukin-1 beta(IL-1 b)and caspase-1 p10 secretion,whereas the NLRP3-specific inhibitor MCC950 only inhibited IL-1 b and caspase-1 p10 release and ASC speck formation but not pyroptosis.Scutellarin also suppressed LPS-induced caspase-11 activation and pyroptosis in RAW 264.7 cells lacking ASC expression.Moreover,scutellarin treatment increased Ser/Thr phosphorylation of caspase-11 at protein kinase A(PKA)-specific sites,and its inhibitory action on caspase-11 activation was largely abrogated by PKAinhibitor H89 or by adenylyl cyclase inhibitor MDL12330 A.Collectively,our data indicate that scutellarin inhibited caspase-11 activation and pyroptosis in macrophages at least partly via regulating the PKA signaling pathway.
