Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Association of Calcium Channel α 1S and β 1a Subunits is Required for the Targeting of β 1a but not of α 1S into Skeletal Muscle Triads

Birgit Neuhuber, Uli Gerster, Frank Doring, Hartmut Glossmann, Tsutomu Tanabe and Bernhard E. Flucher
Proceedings of the National Academy of Sciences of the United States of America
Vol. 95, No. 9 (Apr. 28, 1998), pp. 5015-5020
Stable URL: http://www.jstor.org/stable/44658
Page Count: 6
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Association of Calcium Channel α 1S and β 1a Subunits is Required for the Targeting of β 1a but not of α 1S into Skeletal Muscle Triads
Preview not available

Abstract

The skeletal muscle L-type Ca2+ channel is a complex of five subunits that is specifically localized in the triad. Its primary function is the rapid activation of Ca2+ release from cytoplasmic stores in a process called excitation-contraction coupling. To study the role of α 1S-β 1a interactions in the incorporation of the functional channel complex into the triad, α 1S and β 1a [or a β 1a-green fluorescent protein (GFP) fusion protein] were expressed alone and in combination in myotubes of the dysgenic cell line GLT. β GFP expressed in dysgenic myotubes that lack the skeletal muscle α 1S subunit was diffusely distributed in the cytoplasm. On coexpression with the α 1S subunit β GEP distribution became clustered and colocalized with α 1S immunofluorescence. Based on the colocalization of β GFP and α 1S with the ryanodine receptor the clusters were identified as T-tubule/sarcoplasmic reticulum junctions. Expression of α 1S with and without β 1a restored Ca2+ currents and depolarization-induced Ca2+ release. The translocation of β GFP from the cytoplasm into the junctions failed when β GFP was coexpressed with α 1S mutants in which the β interaction domain had been altered (α 1S-Y366S) or deleted (α 1S-Δ 351-380). Although α 1S-Y366S did not associate with β GFP it was incorporated into the junctions, and it restored Ca2+ currents and depolarization-induced Ca2+ release. Thus, β 1a requires the association with the β interaction domain in the I-II cytoplasmic loop of α 1S for its own incorporation into triad junctions, but stable α 1S-β 1a association is not necessary for the targeting of α 1S into the triads or for its normal function in Ca2+ conductance and excitation-contraction coupling.

Page Thumbnails

  • Thumbnail: Page 
5015
    5015
  • Thumbnail: Page 
5016
    5016
  • Thumbnail: Page 
5017
    5017
  • Thumbnail: Page 
5018
    5018
  • Thumbnail: Page 
5019
    5019
  • Thumbnail: Page 
5020
    5020