Voltage-dependent Na+ channel phenotype changes in myoblasts. Consequences for cardiac repair.
OBJECTIVE
Cellular cardiomyoplasty using skeletal myoblasts is a promising therapy for myocardial infarct repair. Once transplanted, myoblasts grow, differentiate and adapt their electrophysiological properties towards more cardiac-like phenotypes. Voltage-dependent Na(+) channels (Na(v)) are the main proteins involved in the propagation of the cardiac action potential, and their phenotype affects cardiac performance. Therefore, we examined the expression of Na(v) during proliferation and differentiation in skeletal myocytes.


RESULTS
We used the rat neonatal skeletal myocyte cell line L6E9. Proliferation of L6E9 cells induced Na(v)1.4 and Na(v)1.5, although neither protein has an apparent role in cell growth. During myogenesis, Na(v)1.5 was largely induced. Electrophysiological and pharmacological properties, as well as mRNA expression, indicate that cardiac-type Na(v)1.5 accounts for almost 90% of the Na(+) current in myotubes. Unlike in proliferation, this protein plays a pivotal role in myogenesis. The adoption of a cardiac-like phenotype is further supported by the increase in Na(v)1.5 colocalization in caveolae. Finally, we demonstrate that the treatment of myoblasts with neuregulin further increased Na(v)1.5 in skeletal myocytes.


CONCLUSIONS
Our results indicate that skeletal myotubes adopt a cardiac-like phenotype in cell culture conditions and that the expression of Na(v)1.5 acts as an underlying molecular mechanism.
Martínez-Mármol
Ramón
R
Molecular Physiology Laboratory, Universitat de Barcelona, Barcelona, Spain.
David
Miren
M
Sanches
Rosario
R
Roura-Ferrer
Meritxell
M
Villalonga
Núria
N
Sorianello
Eleonora
E
Webb
Susan M
SM
Zorzano
Antonio
A
Gumà
Anna
A
Valenzuela
Carmen
C
Felipe
Antonio
A
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001706:Biopsy; D018421:Cardiomyoplasty / Q000379:methods*; D021941:Caveolae / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D024510:Muscle Development / Q000502:physiology; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009203:Myocardial Infarction / Q000628:therapy; D062554:NAV1.5 Voltage-Gated Sodium Channel; D020890:Neuregulin-1 / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010641:Phenotype; D051381:Rats; D015222:Sodium Channels / Q000378:metabolism*
D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D020890:Neuregulin-1; C568320:SCN5A protein, human; C466180:Scn4a protein, rat; C568322:Scn5a protein, rat; D015222:Sodium Channels