Sorcin associates with the pore-forming subunit of voltage-dependent L-type Ca2+ channels.
J Biol Chem
; 273(30): 18930-5, 1998 Jul 24.
Article
in En
| MEDLINE
| ID: mdl-9668070
ABSTRACT
Intracellular Ca2+ release in muscle is governed by functional communication between the voltage-dependent L-type Ca2+ channel and the intracellular Ca2+ release channel by processes that are incompletely understood. We previously showed that sorcin binds to cardiac Ca2+ release channel/ryanodine receptors and decreases channel open probability in planar lipid bilayers. In addition, we showed that sorcin antibody immunoprecipitates ryanodine receptors from metabolically labeled cardiac myocytes along with a second protein having a molecular weight similar to that of the alpha1 subunit of cardiac L-type Ca2+ channels. We now demonstrate that sorcin biochemically associates with cardiac and skeletal muscle L-type Ca2+ channels specifically within the cytoplasmically oriented C-terminal region of the alpha1 subunits, providing evidence that the second protein recovered by sorcin antibody from cardiac myocytes was the 240-kDa L-type Ca2+ channel alpha1 subunit. Anti-sorcin antibody immunoprecipitated full-length alpha1 subunits from cardiac myocytes, C2C12 myotubes, and transfected non-muscle cells expressing alpha1 subunits. In contrast, the anti-sorcin antibody did not immunoprecipitate C-terminal truncated forms of alpha1 subunits that were detected in myotubes. Recombinant sorcin bound to cardiac and skeletal HIS6-tagged alpha1 C termini immobilized on Ni2+ resin. Additionally, anti-sorcin antibody immunoprecipitated C-terminal fragments of the cardiac alpha1 subunit exogenously expressed in mammalian cells. The results identified a putative sorcin binding domain within the C terminus of the alpha1 subunit. These observations, along with the demonstration that sorcin accumulated substantially during physiological maturation of the excitation-contraction coupling apparatus in developing postnatal rat heart and differentiating C2C12 muscle cells, suggest that sorcin may mediate interchannel communication during excitation-contraction coupling in heart and skeletal muscle.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Calcium-Binding Proteins
/
Calcium Channels
Type of study:
Risk_factors_studies
Limits:
Animals
/
Humans
Language:
En
Journal:
J Biol Chem
Year:
1998
Document type:
Article
Affiliation country:
United States