Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca2+-dependent manner. In diabetic animal models, different aspects of the calcium signaling path- way in beta-cells are altered, but there is no con...Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca2+-dependent manner. In diabetic animal models, different aspects of the calcium signaling path- way in beta-cells are altered, but there is no consensus regarding their relative contributions to the development of beta-cell dysfunction. In this study, we compared the increase in cytosolic Ca2* ([Ca2*]~) via Ca2+ influx, Ca2* mobilization from endoplasmic reticulum (ER) calcium stores, and the removal of Ca2+ via multiple mechanisms in beta-cells from both diabetic db/db mice and non- diabetic C57BL/6J mice. We refined our previous quan- titative model to describe the slow [Ca2+]i recovery after depolarization in beta-cells from db/db mice. According to the model, the activity levels of the two subtypes of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) pump, SERCA2 and SERCA3, were severely down-reg- ulated in diabetic cells to 65% and 0% of the levels in normal cells. This down-regulation may lead to a reduc- tion in the Ca2+ concentration in the ER, a compensatory up-regulation of the plasma membrane Na+/Ca2+ exchanger (NCX) and a reduction in depolarizationevoked Ca2+ influx. As a result, the patterns of glucosestimulated calcium oscillations were significantly different in db/db diabetic beta-cells compared with normal cells. Overall, quantifying the changes in the calcium signaling pathway in db/db diabetic beta-cells will aid in the development of a disease model that could provide insight into the adaptive transformations of beta-cell function during diabetes development.展开更多
Caenorhabditis elegans hid-1 gene was first identified in a screen for mutants with a high-temperature-induced dauer formation(Hid)phenotype.Despite the fact that the hid-1 gene encodes a novel protein(HID-1)which is ...Caenorhabditis elegans hid-1 gene was first identified in a screen for mutants with a high-temperature-induced dauer formation(Hid)phenotype.Despite the fact that the hid-1 gene encodes a novel protein(HID-1)which is highly conserved from Caenorhabditis elegans to mammals,the domain structure,subcellular localization,and exact function of HID-1 remain unknown.Previous studies and various bioinformatic softwares predicted that HID-1 contained many transmembrane domains but no known functional domain.In this study,we revealed that mammalian HID-1 localized to the medial-and transGolgi apparatus as well as the cytosol,and the localization was sensitive to brefeldin A treatment.Next,we demonstrated that HID-1 was a peripheral membrane protein and dynamically shuttled between the Golgi apparatus and the cytosol.Finally,we verified that a conserved N-terminal myristoylation site was required for HID-1 binding to the Golgi apparatus.We propose that HID-1 is probably involved in the intracellular trafficking within the Golgi region.展开更多
Dear Editor, Endocytosis is a crucial process employed by cells to internal- ize nutrients and turnover membrane components and is essential for many functions, including nutrient uptake, signal transduction, cytokine...Dear Editor, Endocytosis is a crucial process employed by cells to internal- ize nutrients and turnover membrane components and is essential for many functions, including nutrient uptake, signal transduction, cytokinesis, morphogenesis, cell adhesion and migration. Endocytosis is classified as clathrin-dependent endocytosis (CDE) or clathrin-independent endocytosis (CIE) according to its dependence on clathrin. Several different CIE pathways have been proposed, including caveolin-dependent endocytosis, flotillin-dependent endocytosis, the clathrin-inde- pendent carrier pathway, ARF6-dependent endocytosis, phagocytosis, macropinocytosis, the IL2RI3 pathway (Doherty and McMahon, 2009), the newly identified fast endophilin-me- diated endocytosis pathway (Boucrot et al., 2015) and the EGFR-NCE pathway (Caldieri et al., 2017).展开更多
Endocytosis is a fundamental cellular activity that plays crucial roles in a variety of biological processes,including nutrient uptake,signal transduction,immune response,morphogenesis,neurotransmission,cell migration...Endocytosis is a fundamental cellular activity that plays crucial roles in a variety of biological processes,including nutrient uptake,signal transduction,immune response,morphogenesis,neurotransmission,cell migration and tissue development[1–3].Endocytosis has been classified into two subtypes:the展开更多
Although bulk endocytosis has been found in a number of neuronal and endocrine cells,the molecular mechanism and physiological function of bulk endocytosis remain elusive.In pancreatic beta cells,we have observed bulk...Although bulk endocytosis has been found in a number of neuronal and endocrine cells,the molecular mechanism and physiological function of bulk endocytosis remain elusive.In pancreatic beta cells,we have observed bulk-like endocytosis evoked both by flash photolysis and trains of depolarization.Bulk-like endocytosis is a clathrin-independent process that is facilitated by enhanced extracellular Ca^(2+) entry and suppressed by the inhibition of dynamin function.Moreover,defects in bulklike endocytosis are accompanied by hyperinsulinemia in primary beta cells dissociated from diabetic KKAy mice,which suggests that bulk-like endocytosis plays an important role in maintaining the exo-endocytosis balance and beta cell secretory capability.展开更多
文摘Upon glucose elevation, pancreatic beta-cells secrete insulin in a Ca2+-dependent manner. In diabetic animal models, different aspects of the calcium signaling path- way in beta-cells are altered, but there is no consensus regarding their relative contributions to the development of beta-cell dysfunction. In this study, we compared the increase in cytosolic Ca2* ([Ca2*]~) via Ca2+ influx, Ca2* mobilization from endoplasmic reticulum (ER) calcium stores, and the removal of Ca2+ via multiple mechanisms in beta-cells from both diabetic db/db mice and non- diabetic C57BL/6J mice. We refined our previous quan- titative model to describe the slow [Ca2+]i recovery after depolarization in beta-cells from db/db mice. According to the model, the activity levels of the two subtypes of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA) pump, SERCA2 and SERCA3, were severely down-reg- ulated in diabetic cells to 65% and 0% of the levels in normal cells. This down-regulation may lead to a reduc- tion in the Ca2+ concentration in the ER, a compensatory up-regulation of the plasma membrane Na+/Ca2+ exchanger (NCX) and a reduction in depolarizationevoked Ca2+ influx. As a result, the patterns of glucosestimulated calcium oscillations were significantly different in db/db diabetic beta-cells compared with normal cells. Overall, quantifying the changes in the calcium signaling pathway in db/db diabetic beta-cells will aid in the development of a disease model that could provide insight into the adaptive transformations of beta-cell function during diabetes development.
基金the National Science Foundation of China(Grant Nos.30870564,and 30900268),The Beijing Natural Science Foundation(No.5092017)the Major State Basic Research Program of China(No.2010CB833701)the CAS Project(KSCX2-SW-224 and Novo Nordisk-CAS to P Xu).
文摘Caenorhabditis elegans hid-1 gene was first identified in a screen for mutants with a high-temperature-induced dauer formation(Hid)phenotype.Despite the fact that the hid-1 gene encodes a novel protein(HID-1)which is highly conserved from Caenorhabditis elegans to mammals,the domain structure,subcellular localization,and exact function of HID-1 remain unknown.Previous studies and various bioinformatic softwares predicted that HID-1 contained many transmembrane domains but no known functional domain.In this study,we revealed that mammalian HID-1 localized to the medial-and transGolgi apparatus as well as the cytosol,and the localization was sensitive to brefeldin A treatment.Next,we demonstrated that HID-1 was a peripheral membrane protein and dynamically shuttled between the Golgi apparatus and the cytosol.Finally,we verified that a conserved N-terminal myristoylation site was required for HID-1 binding to the Golgi apparatus.We propose that HID-1 is probably involved in the intracellular trafficking within the Golgi region.
文摘Dear Editor, Endocytosis is a crucial process employed by cells to internal- ize nutrients and turnover membrane components and is essential for many functions, including nutrient uptake, signal transduction, cytokinesis, morphogenesis, cell adhesion and migration. Endocytosis is classified as clathrin-dependent endocytosis (CDE) or clathrin-independent endocytosis (CIE) according to its dependence on clathrin. Several different CIE pathways have been proposed, including caveolin-dependent endocytosis, flotillin-dependent endocytosis, the clathrin-inde- pendent carrier pathway, ARF6-dependent endocytosis, phagocytosis, macropinocytosis, the IL2RI3 pathway (Doherty and McMahon, 2009), the newly identified fast endophilin-me- diated endocytosis pathway (Boucrot et al., 2015) and the EGFR-NCE pathway (Caldieri et al., 2017).
基金supported by the National Natural Science Foundation of China(31770900,31270884,30900268)the Beijing Natural Science Foundation(5122026,5092017)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2011087)
文摘Endocytosis is a fundamental cellular activity that plays crucial roles in a variety of biological processes,including nutrient uptake,signal transduction,immune response,morphogenesis,neurotransmission,cell migration and tissue development[1–3].Endocytosis has been classified into two subtypes:the
基金supported by a grant from the National Natural Science Foundation of China(Grant No.30871225)a grant from Beijing Municipal Science and Technology Commission(Grant No.7121008)+1 种基金a grant from the Ministry of Science and Technology(Grant No.SQ2011SF11B01041)the fund from The Key Construction Program of the National“985”Project from the Department of Education of China to Peking University.
文摘Although bulk endocytosis has been found in a number of neuronal and endocrine cells,the molecular mechanism and physiological function of bulk endocytosis remain elusive.In pancreatic beta cells,we have observed bulk-like endocytosis evoked both by flash photolysis and trains of depolarization.Bulk-like endocytosis is a clathrin-independent process that is facilitated by enhanced extracellular Ca^(2+) entry and suppressed by the inhibition of dynamin function.Moreover,defects in bulklike endocytosis are accompanied by hyperinsulinemia in primary beta cells dissociated from diabetic KKAy mice,which suggests that bulk-like endocytosis plays an important role in maintaining the exo-endocytosis balance and beta cell secretory capability.