MECHANISM OF EXOCYTOTIC MUCIN RELEASEIN SUBLINGUAL GLAND

在涎腺腺泡细胞中，分泌功能由两条主要的信号通路通过M受体和β-肾上腺素能受体调节，M受体的刺激引起细胞内钙离子的增加。然而，钙依赖的分泌途径的机制还没有很好地阐明。在本研究中，我们首先证明了毒扁豆碱受体刺激引起的细胞内钙离子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刺激的可溶性鸟苷酸环化酶并诱导环状GMP的形成。接下来，我们发现ARFI是一种小的GTP结合蛋白，存在于大鼠腮腺腺泡细胞中。大鼠舌下腺腺泡细胞是研究钙依赖性胞吐作用的有用模型，因为钙动员受体激活可诱导粘蛋白胞吐。免疫印迹显示舌下腺泡细胞膜组分中有较高浓度的Synaxin1AmRNA表达，在大鼠唾液腺如舌下腺和颌下腺中也有表达。然而，我们没有检测到与Synaxin1A结合的蛋白，如VAMP-2和SNAP-25。有必要进一步研究Synaxin1A与Ca^&lt；2&gt；-一氧化氮-环状GMP信号的关系，并鉴定Synaxin 1A结合蛋白。

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.