Ca2+ binding protein-1 inhibits Ca2+ currents and exocytosis in bovine chromaffin cells
Resource
Journal of Biomedical Science 15 (2): 169-181
Journal
Journal of Biomedical Science
Journal Volume
15
Journal Issue
2
Pages
169-181
Date Issued
2008
Date
2008
Author(s)
Chen, Ming-Ling
Chen, Yong-Cyuan
Peng, I-Wei
Kang, Ruo-Lin
Wu, Meng-Pei
Cheng, Po-Wen
Shih, Po-Yuan
Lu, Li-Long
Yang, Chih-Cheng
Abstract
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 N(+, 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.
Type
journal article
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