451. Ca2+ binding protein-1 inhibits Ca2+ currents and exocytosis in bovine chromaffin cells.
- Author
-
Chen ML, Chen YC, Peng IW, Kang RL, Wu MP, Cheng PW, Shih PY, Lu LL, Yang CC, and Pan CY
- Subjects
- Animals, Calcium metabolism, Calcium-Binding Proteins genetics, Cattle, Cell Line, Cell Membrane genetics, Cerebral Cortex physiology, Chromaffin Cells cytology, Embryo, Mammalian cytology, Embryo, Mammalian metabolism, Female, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Humans, Mutation, Myristates metabolism, Neurons cytology, Neurons metabolism, Potassium metabolism, Protein Isoforms genetics, Protein Isoforms metabolism, Protein Processing, Post-Translational physiology, Rats, Rats, Sprague-Dawley, Recombinant Fusion Proteins genetics, Recombinant Fusion Proteins metabolism, Sodium metabolism, Calcium-Binding Proteins metabolism, Cell Membrane metabolism, Chromaffin Cells metabolism, Exocytosis physiology, Membrane Potentials physiology
- 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.
- Published
- 2008
- Full Text
- View/download PDF