Membrane fusion protein synexin (annexin VII) as a Ca2+/GTP sensor in exocytotic secretion

被引:89
作者
Hung, CH [1 ]
Srivastava, M [1 ]
Pollard, HB [1 ]
机构
[1] NIDDKD, CELL BIOL & GENET LAB, NIH, BETHESDA, MD 20892 USA
关键词
D O I
10.1073/pnas.93.20.10797
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
Exocytotic membrane fusion and secretion are promoted by the concerted action of GTP and Ca2+, although the precise site(s) of action in the process are not presently known, However, the calcium-dependent membrane fusion reaction driven by synexin (annexin VII) is an in vitro model for this process, which we have now found to be further activated by GTP, The mechanism of fusion activation depends on the unique ability of synexin to bind and hydrolyze GTP in a calcium-dependent manner, both in vitro and in vivo in streptolysin O-permeabilized chromaffin cells, The required [Ca2+] for GTP binding by synexin is in the range of 50-200 mu M, which is known to occur at exocytotic sites in chromaffin cells, neurons, and other cell types, Previous immunolocalization studies place synexin at exocytotic sites in chromaffin cells, and we conclude that synexin is an atypical G protein that may be responsible for both detecting and mediating the Ca2+/GTP signal for exocytotic membrane fusion.
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收藏
页码:10797 / 10802
页数:6
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