Nina Vardjan,Vladimir Parpuraand Robert Zorec

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Loose Excitation-Secretion Coupling in Astrocytes

Nina Vardjan1,2,Vladimir Parpura3and Robert Zorec1,2

1.Celica Biomedical,Ljubljana,Slovenia;

2.Laboratory of Neuroendocrinology-Molecular Cell Physiology,Institute of Pathophysiology,Faculty of Medicine,University of Ljubljana,Ljubljana,Slovenia;

3.Department of Neurobiology,Center for Glial Biology in Medicine,Civitan International Research Center, Atomic Force Microscopy&Nanotechnology Laboratories,Evelyn F.McKnight Brain Institute,University of Alabama at Birmingham,Birmingham,Alabama

Astrocytes play an important housekeeping role in the central nervous system.Additionally,as secretory cells,they actively participate in cell-to-cell communication,which can be mediated by membrane-bound vesicles.The gliosignaling molecules stored in these vesicles are discharged into the extracellular space after the vesicle membrane fuses with the plasma membrane.This process is termed exocytosis,regulated by SNARE proteins,and triggered by elevations in cytosolic calcium levels,which are necessary and sufficient for exocytosis in astrocytes.For astrocytic exocytosis,calcium is sourced from the intracellular endoplasmic reticulum store,although its entry from the extracellular space contributes to cytosolic calcium dynamics in astrocytes.Here,we discuss calcium management in astrocytic exocytosis and the properties of the membranebound vesicles that store gliosignaling molecules,including the vesicle fusion machinery and kinetics of vesicle content discharge. In astrocytes,the delay between the increase in cytosolic calcium activity and the discharge of secretions from the vesicular lumen is orders of magnitude longer than that in neurons.This relatively loose excitation-secretion coupling is likely tailored to the participation of astrocytes in modulating neural network processing.

calcium homeostasis,GPCR,vesicular release,exocytosis,astrocyte secretion,SNAREs

（王晶編譯）

星形膠質(zhì)細(xì)胞松散的興奮-分泌耦合

星形膠質(zhì)細(xì)胞在中樞神經(jīng)系統(tǒng)中扮演重要角色。此外，作為分泌性細(xì)胞，星形膠質(zhì)細(xì)胞還活躍地參與被膜囊泡介導(dǎo)的細(xì)胞間通訊。當(dāng)囊泡膜與細(xì)胞質(zhì)膜融合時，儲存在這些囊泡中的膠質(zhì)細(xì)胞信號分子流出細(xì)胞外。這個過程稱之為胞吐作用，受SNARE蛋白調(diào)節(jié)，為細(xì)胞內(nèi)鈣水平升高所引起。鈣來源于細(xì)胞內(nèi)的內(nèi)質(zhì)網(wǎng)儲存，它從細(xì)胞外的進入歸因于星形膠質(zhì)細(xì)胞的細(xì)胞鈣動力學(xué)。本文探討星形膠質(zhì)細(xì)胞胞吐作用中的鈣管理，以及儲存膠質(zhì)細(xì)胞信號分子的膜囊泡特性，包括囊泡融合和囊泡內(nèi)容物流出的機械動力學(xué)。在星形膠質(zhì)細(xì)胞中，細(xì)胞內(nèi)鈣水平增加和囊泡腔中分泌物流出的延遲略長于神經(jīng)元。這種相對松散的興奮-分泌耦合可能根據(jù)星形膠質(zhì)細(xì)胞在神經(jīng)網(wǎng)絡(luò)調(diào)控中的參與來調(diào)整。

鈣平衡；GPCR；囊泡釋放；胞吐作用；星形膠質(zhì)細(xì)胞分泌；SNAREs

R741;R741.02

ADOI10.16780/j.cnki.sjssgncj.2016.03.018

摘自

《Glia》2016;64:655-667