Pericellular Ca2+ recycling potentiates thrombin‐evoked Ca2+ signals in human platelets

Physiological Reports

Stewart O. Sage²  Nicholas Pugh¹  Richard W. Farndale¹ 

[1] Department of Biochemistry, University of Cambridge, Cambridge, U.K;Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, U.K

关键词: Ca2+;    FFP‐18;    nanojunction;    open canalicular system;    pericellular;    platelets;   

DOI  :  10.1002/phy2.85

来源: Wiley

【 摘 要 】

Abstract

We have previously demonstrated that Na⁺/Ca²⁺ exchangers (NCXs) potentiate Ca²⁺ signaling evoked by thapsigargin in human platelets, via their ability to modulate the secretion of autocoids from dense granules. This link was confirmed in platelets stimulated with the physiological agonist, thrombin, and experiments were performed to examine how Ca²⁺ removal by the NCX modulates platelet dense granule secretion. In cells loaded with the near-membrane indicator FFP-18, thrombin stimulation was observed to elicit an NCX-dependent accumulation of Ca²⁺ in a pericellular region around the platelets. To test whether this pericellular Ca²⁺ accumulation might be responsible for the influence of NCXs over platelet function, platelets were exposed to fast Ca²⁺ chelators or had their glycocalyx removed. Both manipulations of the pericellular Ca²⁺ rise reduced thrombin-evoked Ca²⁺ signals and dense granule secretion. Blocking Ca²⁺-permeable ion channels had a similar effect, suggesting that Ca²⁺ exported into the pericellular region is able to recycle back into the platelet cytosol. Single cell imaging with extracellular Fluo-4 indicated that thrombin-evoked rises in extracellular [Ca²⁺] occurred within the boundary described by the cell surface, suggesting their presence within the open canalicular system (OCS). FFP-18 fluorescence was similarly distributed. These data suggest that upon thrombin stimulation, NCX activity creates a rise in [Ca²⁺] within the pericellular region of the platelet from where it recycles back into the platelet cytosol, acting to both accelerate dense granule secretion and maintain the initial rise in cytosolic [Ca²⁺].

【 授权许可】

CC BY   
© 2013 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

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