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A caveolae-targeted L-type Ca²+ channel antagonist inhibits hypertrophic signaling without reducing cardiac contractility.

ABSTRACT: The source of Ca(2+) to activate pathological cardiac hypertrophy is not clearly defined. Ca(2+) influx through the L-type Ca(2+) channels (LTCCs) determines "contractile" Ca(2+), which is not thought to be the source of "hypertrophic" Ca(2+). However, some LTCCs are housed in caveolin-3 (Cav-3)-enriched signaling microdomains and are not directly involved in contraction. The function of these LTCCs is unknown.To test the idea that LTCCs in Cav-3-containing signaling domains are a source of Ca(2+) to activate the calcineurin-nuclear factor of activated T-cell signaling cascade that promotes pathological hypertrophy.We developed reagents that targeted Ca(2+) channel-blocking Rem proteins to Cav-3-containing membranes, which house a small fraction of cardiac LTCCs. Blocking LTCCs within this Cav-3 membrane domain eliminated a small fraction of the LTCC current and almost all of the Ca(2+) influx-induced NFAT nuclear translocation, but it did not reduce myocyte contractility.We provide proof of concept that Ca(2+) influx through LTCCs within caveolae signaling domains can activate "hypertrophic" signaling, and this Ca(2+) influx can be selectively blocked without reducing cardiac contractility.

SUBMITTER: Makarewich CA

PROVIDER: S-EPMC3324037 | biostudies-literature | 2012 Mar

REPOSITORIES: biostudies-literature

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A caveolae-targeted L-type Ca²+ channel antagonist inhibits hypertrophic signaling without reducing cardiac contractility.

Makarewich Catherine A CA Correll Robert N RN Gao Hui H Zhang Hongyu H Yang Baohua B Berretta Remus M RM Rizzo Victor V Molkentin Jeffery D JD Houser Steven R SR

Circulation research 20120202 5

<h4>Rationale</h4>The source of Ca(2+) to activate pathological cardiac hypertrophy is not clearly defined. Ca(2+) influx through the L-type Ca(2+) channels (LTCCs) determines "contractile" Ca(2+), which is not thought to be the source of "hypertrophic" Ca(2+). However, some LTCCs are housed in caveolin-3 (Cav-3)-enriched signaling microdomains and are not directly involved in contraction. The function of these LTCCs is unknown.<h4>Objective</h4>To test the idea that LTCCs in Cav-3-containing si ...[more]

PMID: 22302787

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Project description:Mutations that lead to muscular dystrophy often create deficiencies in cytoskeletal support of the muscle sarcolemma causing hyperactive mechanosensitive cation channel (MSC) activity and elevated intracellular Ca(2+). Caveolae are cholesterol-rich microdomains that form mechanically deformable invaginations of the sarcolemma. Mutations to caveolin-3, the main scaffolding protein of caveolae in muscle, cause Limbe-Girdle muscular dystrophy. Using genetic and acute chemical perturbations of developing myotubes we investigated whether caveolae are functionally linked to MSCs. MSC sensitivity was assayed using suction application to patches and probe-induced indentation during whole-cell recordings. Membrane mechanical stress in patches was monitored using patch capacitance/impedance. Cholesterol depletion disrupted caveolae and caused a large increase in MSC current. It also decreased the membrane mechanical relaxation time, likely reflecting cytoskeleton dissociation from the bilayer. Reduction of Cav3 expression with miRNA also increased MSC current and decreased patch relaxation time. In contrast Cav3 overexpression produced a small decrease in MSC currents. To acutely and specifically inhibit Cav3 interactions, we made a chimeric peptide containing the antennapedia membrane translocation domain and the Cav3 scaffolding domain (A-CSD3). A-CSD3 action was time dependent initially producing a mild Ca(2+) leak and increased MSC current, while longer exposures decreased MSC currents coinciding with increased patch stiffening. Images of GFP labeled Cav3 in patches showed that Cav3 doesn't enter the pipette, showing patch composition differed from the cell surface. However, disruption via cholesterol depletion caused Cav3 to become uniformly distributed over the sarcolemma and Cav3 appearance in the patch dome. The whole-cell indentation currents elicited under the different caveolae modifying conditions mirror the patch response supporting the role of caveolae in MSC function. These studies show that normal expression levels of Cav3 are mechanoprotective to the sarcolemma through multiple mechanisms, and Cav3 upregulation observed in some dystrophies may compensate for other mechanical deficiencies.

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Dataset Information

A caveolae-targeted L-type Ca²+ channel antagonist inhibits hypertrophic signaling without reducing cardiac contractility.

Publications

A caveolae-targeted L-type Ca²+ channel antagonist inhibits hypertrophic signaling without reducing cardiac contractility.

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