title: Calneuron I inhibits Ca(2+) channel activity in bovine chromaffin cells.
abstract: Calneuron I (CalnI) is a calmodulin-like protein that contains two functional EF-hand motifs at the N-terminal and a hydrophobic segment at the C-terminal. CalnI was cloned from the adult rat cortex and fused with GFP at its N-terminal. When expressed in bovine chromaffin cells, wild-type CalnI was localized at the plasma membrane. However, a mutant that lacked the hydrophobic segment was localized in the cytosol and nucleus, while a Ca(2+)-binding-deficient mutant was found in the cytosol and at the plasma membrane. Evaluation using the whole-cell patch-clamp technique revealed that Ca(2+) currents were inhibited by both wild-type CalnI and the Ca(2+)-binding-deficient mutant. When the bovine N-type Ca(2+) channel was expressed in 293T cells, Ca(2+) currents were mostly inhibited by co-expression of CalnI, but not by the mutant without the hydrophobic tail. These results suggest that CalnI attenuates Ca(2+) channel activity and that its subcellular localization is important for this effect.
authors.affiliation: Institute of Zoology, National Taiwan University, Taipei, Taiwan, ROC.
authors.forename: Po-Yuan
authors.initials: PY
authors.lastname: Shih
authors.forename: Chih-Lung
authors.initials: CL
authors.lastname: Lin
authors.forename: Po-Wen
authors.initials: PW
authors.lastname: Cheng
authors.forename: Jia-Hong
authors.initials: JH
authors.lastname: Liao
authors.forename: Chien-Yuan
authors.initials: CY
authors.lastname: Pan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D019439:Chromaffin Cells / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D051381:Rats
chemical_list: D015220:Calcium Channels; D002135:Calcium-Binding Proteins; C516555:calneuron I, rat