MECHANISM OF EXOCYTOTIC MUCIN RELEASEIN SUBLINGUAL GLAND

在唾液腺腺泡细胞中，分泌功能受毒蕈碱和β -肾上腺素能受体两种主要信号通路的调控。毒蕈碱受体的刺激引起细胞内钙离子（Ca^<2+>）的增加。然而，Ca^<2+>依赖性分泌通路的机制尚未明确。我们通过Ca^<2+>信号通路研究了胞吐作用的机制。在这项研究中，我们首先证明了毒蕈碱受体刺激引起的细胞内Ca^<2+>的增加激活了一氧化氮合酶。随后，一氧化氮在唾液腺腺泡细胞中产生受刺激的可溶性鸟酰环化酶，诱导环状GMP的形成。我们随后发现，一种小的gtp结合蛋白Arfi存在于大鼠腮腺腺泡细胞中。此外，我们证明了在GTP γ存在的情况下，Arf1转运到分泌颗粒。大鼠舌下腺腺泡细胞是研究Ca^<2+>-依赖性胞吐的有效模型，因为Ca^<2+>-动员受体激活可诱导黏液胞吐。我们通过免疫印迹发现舌下腺泡细胞的膜部分有高浓度的syntaxin1A。在大鼠唾液腺如舌下腺和颌下腺中检测到syntaxin1A mRNA的表达。然而，我们没有检测到与syntaxinlA结合的蛋白，如VAMP-2和SNAP-25。进一步研究syntaxin1A与Ca^<2+>-一氧化氮-环GMP信号传导的关系以及syntaxin1A结合蛋白的鉴定是必要的。

In salivary gland acinar cells, the secretory function is rcgulated by two main signaling pathways via muscarinic and beta-adrenergic receptors.Stimulation of muscarinic receptors causes the increase in intracellular calcium ions (Ca^<2+>). However, the mechanism with Ca^<2+>-dependent secretory pathway has not well elucidated. We here studied with the mechanism of exocytosis via Ca^<2+> signaling pathway.During this study, we first demonstrated that the increase in intracellular Ca^<2+> induced by muscarinic receptor stimulation activated nitric oxide synthase. Subsequently, nitric oxide generated stimulated soluble guanylyl cyclase and induced cyclic GMP formation in salivary gland acinar cells. We next found that Arfi, a small GTP-binding protein, existed in rat parotid acinar cells. Furthermore, we demonstrated that the Arf1 translocated to secretory granules in the presence of GTP gammaS.Rat sublingual gland acinar cells are an useful model for the study with Ca^<2+>-dependent exocytosis, since Ca^<2+>-mobilizing receptor activation induces mucin exocytosis. We found that high concentration of syntaxin1A in the membrane fraction of sublingual acinar cells by immuno blotting.The expression of mRNA of syntaxin1A was detected in rat salivary glands such as sublingual and submandibular glands. However, we failed to detectthe binding proteins to syntaxinlA such as VAMP-2 and SNAP-25.Further studies with the relationship between syntaxin1A and Ca^<2+>-nitric oxide-cyclic GMP signaling and identification of syntaxin 1A binding proteins are necessary.