Involvement of TRPC in the abnormal calcium influx observed in dystrophic (mdx) mouse skeletal muscle fibers.
Duchenne muscular dystrophy results from the lack of dystrophin, a cytoskeletal protein associated with the inner surface membrane, in skeletal muscle. The absence of dystrophin induces an abnormal increase of sarcolemmal calcium influx through cationic channels in adult skeletal muscle fibers from dystrophic (mdx) mice. We observed that the activity of these channels was increased after depletion of the stores of calcium with thapsigargin or caffeine. By analogy with the situation observed in nonexcitable cells, we therefore hypothesized that these store-operated channels could belong to the transient receptor potential channel (TRPC) family. We measured the expression of TRPC isoforms in normal and mdx adult skeletal muscles fibers, and among the seven known isoforms, five were detected (TRPC1, 2, 3, 4, and 6) by RT-PCR. Western blot analysis and immunocytochemistry of normal and mdx muscle fibers demonstrated the localization of TRPC1, 4, and 6 proteins at the plasma membrane. Therefore, an antisense strategy was used to repress these TRPC isoforms. In parallel with the repression of the TRPCs, we observed that the occurrence of calcium leak channels was decreased to one tenth of its control value (patch-clamp technique), showing the involvement of TRPC in the abnormal calcium influx observed in dystrophic fibers.
Vandebrouck
Clarisse
C
Département de Physiologie, Université Catholique de Louvain (UCL 5540), Avenue Hippocrate 55, 1200 Brussels, Belgium.
Martin
Dominique
D
Colson-Van Schoor
Monique
M
Debaix
Huguette
H
Gailly
Philippe
P
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured; D016189:Dystrophin / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport; D008564:Membrane Potentials; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018485:Muscle Fibers, Skeletal / Q000378:metabolism* / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000503:physiopathology; D009137:Muscular Dystrophy, Animal / Q000378:metabolism* / Q000503:physiopathology; D018408:Patch-Clamp Techniques; D012508:Sarcolemma / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D050052:TRPC Cation Channels; D019284:Thapsigargin / Q000494:pharmacology
D015220:Calcium Channels; D016189:Dystrophin; D004791:Enzyme Inhibitors; D007473:Ion Channels; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C096351:transient receptor potential cation channel, subfamily C, member 1; D002110:Caffeine; D019284:Thapsigargin; D012964:Sodium; D002118:Calcium