Molecular Biological Studies of Calcium Signaling in Insulin Secretion ; their implication for the development of diabetes mellitus

细胞内钙是胰岛素分泌的主要信号。由于引起胰岛β细胞内[Ca~(2+)]i升高的主要途径是跨β细胞膜的内流和细胞内钙库的动员，因此这些途径中涉及的蛋白质在调节胰岛素的分泌中起着关键作用。我们克隆并鉴定了大鼠β细胞/神经内分泌型电压依赖性钙(VDCC)的Aopha1亚基。利用CHO细胞和非洲爪哇卵母细胞进行的功能表达表明，Aopha1和β亚基的共表达产生了典型的L型VDCC活性，提示β细胞/神经内分泌型VDCC在胰岛素分泌中发挥作用。我们已经确定了人类β细胞/神经内分泌型VDCα1亚单位的基因结构，该基因已定位于3号染色体，带p14.3。该基因全长120kb，有50个外显子。非胰岛素依赖型…患者该基因序列变异分析更多的糖尿病(NIDDM)目前正在进行中。我们还克隆了编码三磷酸肌醇(IP3)受体(IP3R-3)第三亚型的基因，该受体在胰岛和一个克隆性β细胞系中表达。由于一些胰岛素促分泌剂如CCK和乙酰胆碱通过PI水解物刺激胰岛素的分泌，IP3R-3被认为参与了胰岛素的调节。已知许多激素和神经递质通过其特定的受体来调节胰岛素的分泌。我们克隆了编码生长抑素受体(SSTR-3)和垂体腺苷酸环化酶激活多肽(PACAP)受体(PACAPR-3)的cDNA，它们在胰岛中表达。PACAPR-3的功能表达表明，它可以与磷脂酶C偶联，也可以与腺苷环化酶偶联，提示PACAPR-3参与胰岛素分泌的钙信号转导。综上所述，我们的研究阐明了胰岛素分泌中涉及钙信号的一些重要因素的分子基础，并为这些基因在NIDDM的发生发展中的作用以及对胰岛素分泌的分子机制的理解提供了有价值的见解。较少

Intracellular calcium[Ca^<2+>]i is the principal signal for insulin secretion. Since major pathways causing an increase in [Ca^<2+>]i in pancreatic beta-cells are the influx across beta-cell membrane and the mobilization from intracellular calcium stores, the proteins involved in these pathways play crucial roles in the regulation insulin secretion. We have cloned and characterized a aopha1-subunit of rat beta-cell/neuroendocrine type voltage-dependent calcium (VDCC).Functional expression using CHO CELLS AND Xenopus oocytes shows that coexpression of the aopha1 and beta subunit generates a typical L-type VDCC activity, suggesting that the beta-cell/neuroendocrine type VDCC plays a role in insulin secretion. We have determined the structure of the human gene for the alpha1 subunit of beta-cell/neuroendocrine type VDCC.The gene has been localized to chromosome 3, band p14.3. The gene spans more than 120kb and has 50 exons. Analysis of sequence variations of this gene in non-insulin depen … More dent diabetes mellitus (NIDDM) is currently underway. We have also cloned a cDNA encoding a third subtype of inositol 1,4,5 triphosphate (IP3) receptor (IP3R-3) expressed in pancreatic islets and a clonal beta-cell line. Since some insulin secretagogues such as CCK and acetylcholine stimulate insulin secretion via PI hydrolysis, the IP3R-3 is suggested to be involved in the regulation of insulin. Many hormones and neurotransmtters are known to modulate insulin secretion through their specific receptors.We have cloned cDNAs encoding a somatostatin receptor (SSTR-3) and a pituitary adenylyl cyclase-activating, polypeptide (PACAP) receptor (PACAPR-3) expressed in pancreatic islets. Functional expression of PACAPR-3 shows that it can be coupled to phospholipase C as well as to adenylyl cyclase, suggesting that PACAPR-3 is involved in calcium signaling in insulin secretion. In conclusion, our studies have clarified molecular basis for some of the important factors involved in calcium signaling in insulin secretion and have provided valuable insight into the contribution of these genes to the development of NIDDM as well as the understanding of the molecular mechanisms of insulin secretion. Less