Cyclic AMP potentiates Ca2+-dependent exocytosis in pancreatic duct epithelial cells.
Cyclic AMP potentiates Ca2+-dependent exocytosis in pancreatic duct epithelial cells.
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DOI：
10.1085/jgp.200910355
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发表时间：
2010-05
期刊：
影响因子：
--
通讯作者：
Koh DS
中科院分区：
文献类型：
--
作者：
Jung SR;Hille B;Nguyen TD;Koh DS
胞吐是由细胞内信号引起的，包括Ca2+和蛋白激酶。我们确定了这些信号如何相互作用以促进外分泌胰管上皮细胞（PDECs）的胞吐。使用碳纤维微安计检测到的胞吐是由离子霉素引起的Ca2+内流或P2Y2或蛋白酶激活受体2受体的激活引起的[Ca2+]i增加刺激的。在每种情况下，当环AMP （cAMP）通过激活腺苷酸环化酶或激活内源性血管活性肠肽受体而升高时，胞外分泌都被强烈增强。这种增强作用被H-89完全抑制，被蛋白激酶a的抑制剂rp -8- br - camp部分阻断。光学监测荧光标记的分泌颗粒显示，在Ca2+升高期间，向质膜缓慢迁移。这种Ca2+依赖的颗粒运动和在质膜附近发现的颗粒数量都没有通过提高cAMP而明显改变，这表明cAMP在后期增强了Ca2+依赖的胞吐作用。建立了cAMP升高和不升高时UTP、胰蛋白酶和Ca2+离子载体刺激胞吐的动力学模型。在模型中，没有cAMP升高，受体激活通过Ca2+升高和另一个信使的作用刺激胞吐。随着cAMP的升高，分泌颗粒的对接/启动步骤加快，增加了可释放颗粒池的大小，最终融合步骤的Ca2+敏感性增加，增加了胞吐率。据推测，这两种cAMP的作用都需要依赖cAMP的靶蛋白磷酸化。camp依赖性增强Ca2+诱导的胞吐对粘蛋白分泌和可能的膜蛋白插入胰管具有生理意义。此外，这种缓慢胞吐增强的机制也可能存在于其他细胞系统中。
Exocytosis is evoked by intracellular signals, including Ca2+ and protein kinases. We determined how such signals interact to promote exocytosis in exocrine pancreatic duct epithelial cells (PDECs). Exocytosis, detected using carbon-fiber microamperometry, was stimulated by [Ca2+]i increases induced either through Ca2+ influx using ionomycin or by activation of P2Y2 or protease-activated receptor 2 receptors. In each case, the exocytosis was strongly potentiated when cyclic AMP (cAMP) was elevated either by activating adenylyl cyclase with forskolin or by activating the endogenous vasoactive intestinal peptide receptor. This potentiation was completely inhibited by H-89 and partially blocked by Rp-8-Br-cAMPS, inhibitors of protein kinase A. Optical monitoring of fluorescently labeled secretory granules showed slow migration toward the plasma membrane during Ca2+ elevations. Neither this Ca2+-dependent granule movement nor the number of granules found near the plasma membrane were detectably changed by raising cAMP, suggesting that cAMP potentiates Ca2+-dependent exocytosis at a later stage. A kinetic model was made of the exocytosis stimulated by UTP, trypsin, and Ca2+ ionophores with and without cAMP increase. In the model, without a cAMP rise, receptor activation stimulates exocytosis both by Ca2+ elevation and by the action of another messenger(s). With cAMP elevation the docking/priming step for secretory granules was accelerated, augmenting the releasable granule pool size, and the Ca2+ sensitivity of the final fusion step was increased, augmenting the rate of exocytosis. Presumably both cAMP actions require cAMP-dependent phosphorylation of target proteins. cAMP-dependent potentiation of Ca2+-induced exocytosis has physiological implications for mucin secretion and, possibly, for membrane protein insertion in the pancreatic duct. In addition, mechanisms underlying this potentiation of slow exocytosis may also exist in other cell systems.
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DOI：
10.1111/j.1600-0854.2009.00884.x
发表时间：
2009-04
期刊：
Traffic (Copenhagen, Denmark)
影响因子：
--
作者：
Jung SR;Kim MH;Hille B;Koh DS
通讯作者：
Koh DS
影响因子：
16.2
作者：
Nagy, G;Reim, K;Sorensen, JB
通讯作者：
Sorensen, JB
影响因子：
3.5
作者：
Gaisano, HY;Sheu, L;Trimble, WS
通讯作者：
Trimble, WS
影响因子：
5.5
作者：
Chen, Y;Warner, JD;Giovannucci, DR
通讯作者：
Giovannucci, DR
影响因子：
5.6
作者：
Hisama, FM;Schellenberg, GD
通讯作者：
Schellenberg, GD