Ca²⁺ binding protein-1 inhibits Ca²⁺ currents and exocytosis in bovine chromaffin cells

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• 作者：Ming-Ling Chen ; Yong-Cyuan Chen ; I-Wei Peng ; Ruo-Lin Kang ; Meng-Pei Wu ; Po-Wen Cheng ; Po-Yuan Shih ; Li-Long Lu ; Chih-Cheng Yang and Chien-Yuan Pan
• 关键词：calcium binding proteins ; Ca2+ currents ; chromaffin cells ; exocytosis ; neuronal calcium sensor ; 1 ; N ; type Ca2+ channel
• 刊名：Journal of Biomedical Science
• 出版年：2008
• 出版时间：March, 2008
• 年：2008
• 卷：15
• 期：2
• 页码：169-181
• 全文大小：369.3 KB

文摘

Calcium binding protein-1 (CaBP1) is a calmodulin like protein shown to modulate Ca2+ channel activities. Here, we explored the functions of long and short spliced CaBP1 variants (L- and S-CaBP1) in modulating stimulus-secretion coupling in primary cultured bovine chromaffin cells. L- and S-CaBP1 were cloned from rat brain and fused with yellow fluorescent protein at the C-terminal. When expressed in chromaffin cells, wild-type L- and S-CaBP1s could be found in the cytosol, plasma membrane and a perinuclear region; in contrast, the myristoylation-deficient mutants were not found in the membrane. More than 20 and 70 % of Na+ and Ca2+ currents, respectively, were inhibited by wild-type isoforms but not myristoylation-deficient mutants. The [Ca2+] _i response evoked by high K+ buffer and the exocytosis elicited by membrane depolarizations were inhibited only by wild-type isoforms. Neuronal Ca2+ sensor-1 and CaBP5, both are calmodulin-like proteins, did not affect Na+, Ca2+ currents, and exocytosis. When expressed in cultured cortical neurons, the [Ca2+] _i responses elicited by high-K+ depolarization were inhibited by CaBP1 isoforms. In HEK293T cells cotransfected with N-type Ca2+ channel and L-CaBP1, the current was reduced and activation curve was shifted positively. These results demonstrate the importance of CaBP1s in modulating the stimulus-secretion coupling in excitable cells.