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Sorcin associates with the pore-forming subunit of voltage-dependent L-type Ca2+ channels.

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.

Pubmed ID: 9668070


  • Meyers MB
  • Puri TS
  • Chien AJ
  • Gao T
  • Hsu PH
  • Hosey MM
  • Fishman GI


The Journal of biological chemistry

Publication Data

July 24, 1998

Associated Grants

  • Agency: NIMH NIH HHS, Id: 1 F30-MH10770
  • Agency: NHLBI NIH HHS, Id: HL23306

Mesh Terms

  • Animals
  • Antibodies
  • COS Cells
  • Calcium Channels
  • Calcium Channels, L-Type
  • Calcium-Binding Proteins
  • Cell Line
  • Humans
  • Ion Channel Gating
  • Muscle, Skeletal
  • Myocardium
  • Rats
  • Sarcolemma
  • Spodoptera