Expression of the muscular dystrophy-associated caveolin-3P104L mutant in adult mouse skeletal muscle specifically alters the Ca2+ channel function of the dihydropyridine receptor

Abstract

Caveolins are plasma-membrane-associated proteins potentially involved in a variety of signalling pathways. Different mutations in CAV3, the gene encoding for the muscle-specific isoform caveolin-3 (Cav-3), lead to muscle diseases, but the underlying molecular mechanisms remain largely unknown. Here, we explored the functional consequences of a Cav-3 mutation (P104L) inducing the 1C type limb-girdle muscular dystrophy (LGMD 1C) in human on intracellular Ca(2+) regulation of adult skeletal muscle fibres. A YFP-tagged human Cav-3(P104L) mutant was expressed in vivo in muscle fibres from mouse. Western blot analysis revealed that expression of this mutant led to an approximately 80% drop of the level of endogenous Cav-3. The L-type Ca(2+) current density was found largely reduced in fibres expressing the Cav-3(P104L) mutant, with no change in the voltage dependence of activation and inactivation. Interestingly, the maximal density of intramembrane charge movement was unaltered in the Cav-3(P104L)-expressing fibres, suggesting no change in the total amount of functional voltage-sensing dihydropyridine receptors (DHPRs). Also, there was no obvious alteration in the properties of voltage-activated Ca(2+) transients in the Cav-3(P104L)-expressing fibres. Although the actual role of the Ca(2+) channel function of the DHPR is not clearly established in adult skeletal muscle, its specific alteration by the Cav-3(P104L) mutant suggests that it may be involved in the physiopathology of LGMD 1C.

Elevated resting H+ current in the R1239H type 1 hypokalaemic periodic paralysis mutated Ca2+ channel

“…; Weiss et al . ). Mice were anaesthetized by isoflurane inhalation using a commercial delivery system (Univentor 400 Anaesthesia Unit, Uninventor, Zejtun, Malta).…”

The transmembrane domain of caveolin-1 exhibits a helix–break–helix structure

“…Caveolin is the most important protein found in caveolae, as caveolae structures are lost when the caveolin gene is silenced [5]. Furthermore, misregulation and mutations to caveolin have been implicated in a variety of diseases including cancer, muscular dystrophy, Alzheimer’s, and heart disease [6–10]. In addition to the caveolin protein, caveolae are enriched in cholesterol, and sphingolipids when compared to the bulk plasma membrane [11].…”

Lack of functional caveolae in Cav3 mutated human dystrophic myotubes results in deficient mechanoprotection and IL6/STAT3 mechanosignaling

“…Furthermore, Cav3 is involved in the regulation of different signaling pathways important for muscle function such as calcium homeostasis (Weiss et al, 2008), the insulin/GLUT4/Akt pathway (Fecchi et al, 2006) or TrkA and EGFR signaling (Brauers et al, 2010). Finally, we showed a role of Cav3 in membrane tension buffering and mechanoprotection in P28L FHCK human myotubes (Sinha et al, 2011).…”