Caveolin-3 Is Adjacent To A Group Of Extra-Dyadic Ryanodine Receptors

¹ University of British Columbia
² University of Massachusetts Medical Center
³ Univ. of British Columbia

^* To whom correspondence should be addressed. E-mail: edmoore{at}interchange.ubc.ca.

Submitted on April 7, 2005
Revised on May 13, 2005
Accepted on 15 June 2005

	Abstract

Caveolae are present in almost all cells and concentrate a wide variety of signaling molecules, receptors, transporters and ion pumps. We have investigated the distribution of the ryanodine receptor, the Na+/Ca2+ exchanger; the predominant Na+ channel isoform rH1, and Cav1.2, relative to the muscle-specific caveolin isoform, caveolin-3, in adult rat ventricular myocytes. Three-dimensional immunofluorescence images were deconvolved and analyzed. Caveolin-3 colocalizes with all of these molecules at the surface of the cell, but there is no significant colocalization between caveolin-3 and either the Na+/Ca2+ exchanger or the Na+ channel in the cell interior. The distribution of the surface colocalization indicates that the caveolae that colocalize with each molecule form distinct populations. In the interior of the cell, caveolin-3 shows a marked colocalization with a population of ryanodine receptors that are separate from those within the dyad. This organization indicates that there are multiple populations of caveolae separable by location and occupants. The signaling molecules contained within the t-tubular caveolae might have, because of their location, a preferred access to the neighbouring non-dyadic ryanodine receptors.

Key Words: Caveolae, Deconvolution, Excitation-contraction coupling, Morphology, Myocytes, T-tubule

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