Na,K-ATPase expression in C2C12 cells during myogenesis: minimal contribution of alpha 2 isoform to Na,K transport.
Cells of the murine skeletal muscle line, C2C12, undergo differentiation from mononuclear myoblasts to multinuclear myotubes that express a number of proteins associated with striated muscle. We examined the relationship between the abundance of the mRNAs encoding the fast-twitch Ca-ATPase and the alpha isoforms of Na,K-ATPase and the subsequent expression of their respective polypeptides. Both the mRNA and protein levels of the alpha 1 isoform remained constant throughout differentiation. In contrast, the content of mRNAs encoding the alpha 2 isoform and fast-twitch Ca-ATPase increased coordinately with the abundance of their corresponding polypeptides during myotube development. Despite the dramatic increase in alpha 2 expression, estimates of in vitro Na,K-ATPase activity and assessments of in vivo transport activity suggest that alpha 2 contributes little to ionic homeostasis in C2C12 myotubes.
Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225.
S C
SC
Higham
J
J
Melikian
N J
NJ
Karin
F
F
Ismail-Beigi
T A
TA
Pressley
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D017136:Ion Transport / Q000187:drug effects; D051379:Mice; D009132:Muscles / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010042:Ouabain / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D010042:Ouabain; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase