Journal article
Frog Cardiac Calsequestrin: Identification, Characterization, and Subcellular Distribution in Two Structurally Distinct Regions of Peripheral Sarcoplasmic Reticulum in Frog Ventricular Myocardium
Circulation research, Vol.69(2), pp.344-359
08/1991
DOI: 10.1161/01.RES.69.2.344
PMID: 1860177
Abstract
Calsequestrin is a calcium-binding protein known to sequester calcium accumulated in the sarcoplasmic reticulum (SR) of muscle cells during relaxation. In the present study, we used affinity-purified antibodies to chicken cardiac calsequestrin to identify a 60,000-Da calsequestrin in frog myocardium. Like previously identified cardiac calsequestrins, it is enriched in cardiac microsomes, it is enriched by biochemical procedures previously used to purify cardiac and skeletal calsequestrins, and it exhibits a pH-dependent shift in its apparent Mr on a two-dimensional gel system. Finally, the NH2-terminal amino acid sequence of this 60,000-Da immunoreactive protein purified by fast protein liquid chromatography was identical to that of rabbit skeletal and canine cardiac calsequestrin. Thus, we conclude that this protein corresponds to the calsequestrin isoform in frog ventricular muscle. Frog calsequestrin was localized in discrete foci present at the periphery but absent from the central regions of frog ventricular myocytes as determined by immunofluorescence labeling. Immunoelectron microscopic labeling demonstrated that calsequestrin was confined to the lumen of two structurally distinct regions of the SR, where it was localized in the subsarcolemmal region of the myofibers. One of these appeared to correspond to the terminal SR previously reported to be closely apposed to the sarcolemma of frog myofibers. The other region, although close to the sarcolemma, was not physically joined to it and appeared to correspond to corbular SR. It generally is believed that frog cardiac SR does not provide activator Ca required for excitation-contraction coupling. However, the identification of a calsequestrin isoform very similar to mammalian cardiac calsequestrin that is confined to specialized regions of frog cardiac SR lends support to the idea that frog cardiac SR has the ability to store Ca and thus function in some capacity in frog cardiac muscle contraction. (Circulation Research 1991;69:344-359)
Details
- Title: Subtitle
- Frog Cardiac Calsequestrin: Identification, Characterization, and Subcellular Distribution in Two Structurally Distinct Regions of Peripheral Sarcoplasmic Reticulum in Frog Ventricular Myocardium
- Creators
- Anne McLeod - From the Department of Anatomy (A.G.M., A.C.-Y.S., A.O.J.), University of Toronto, Toronto, Canada; the Howard Hughes Medical Institute and the Department of Physiology and Biophysics (K.P.C.), the University of Iowa, Iowa City, Iowa; and the Cardiovascular Disease Research Group (M.M.), Departments of Pediatrics and Biochemistry, University of Alberta, Edmonton, Alberta, CanadaAmy ShenKevin CampbellMarek MichalalkAnnelise Jorgensen
- Resource Type
- Journal article
- Publication Details
- Circulation research, Vol.69(2), pp.344-359
- DOI
- 10.1161/01.RES.69.2.344
- PMID
- 1860177
- NLM abbreviation
- Circ Res
- ISSN
- 0009-7330
- eISSN
- 1524-4571
- Publisher
- American Heart Association, Inc
- Language
- English
- Date published
- 08/1991
- Academic Unit
- Neurology; Molecular Physiology and Biophysics; Iowa Neuroscience Institute
- Record Identifier
- 9984068275602771
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