title: Ca2+ binding protein-1 inhibits Ca2+ currents and exocytosis in bovine chromaffin cells.
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.
authors.affiliation: Institute of Zoology, National Taiwan University, Rm730, Life Science Building, 1 Roosevelt Rd., Sec. 4, Taipei, 106, Taiwan, ROC.
authors.forename: Ming-Ling
authors.initials: ML
authors.lastname: Chen
authors.forename: Yong-Cyuan
authors.initials: YC
authors.lastname: Chen
authors.forename: I-Wei
authors.initials: IW
authors.lastname: Peng
authors.forename: Ruo-Lin
authors.initials: RL
authors.lastname: Kang
authors.forename: Meng-Pei
authors.initials: MP
authors.lastname: Wu
authors.forename: Po-Wen
authors.initials: PW
authors.lastname: Cheng
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Shih
authors.forename: Li-Long
authors.initials: LL
authors.lastname: Lu
authors.forename: Chih-Cheng
authors.initials: CC
authors.lastname: Yang
authors.forename: Chien-Yuan
authors.initials: CY
authors.lastname: Pan
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D002540:Cerebral Cortex / Q000502:physiology; D019439:Chromaffin Cells / Q000166:cytology / Q000378:metabolism*; D004622:Embryo, Mammalian / Q000166:cytology / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology*; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008564:Membrane Potentials / Q000502:physiology*; D009154:Mutation; D009226:Myristates / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D009226:Myristates; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D012964:Sodium; C085577:Ca2+-binding protein-1; D011188:Potassium; D002118:Calcium