Human skeletal muscle cell differentiation is associated with changes in myogenic markers and enhanced insulin-mediated MAPK and PKB phosphorylation.
OBJECTIVE
We hypothesized that myogenic differentiation of HSMC would yield a more insulin responsive phenotype.


METHODS
We assessed expression of several proteins involved in insulin action or myogenesis during differentiation of primary human skeletal muscle cultures (HSMC).


RESULTS
Differentiation increased creatine kinase activity and expression of desmin and myocyte enhancer factor (MEF)2C. No change in expression was observed for big mitogen-activated protein kinase (BMK1/ERK5), MEF2A, insulin receptor (IR), hexokinase II, and IR substrates 1 and 2, while expression of glycogen synthase, extracellular signal-regulated kinase 1 and 2 (ERK1/2 MAP kinase) and the insulin responsive aminopeptidase increased after differentiation. In contrast to protein kinase B (PKB)a, expression of (PKB)b increased, with differentiation. Both basal and insulin-stimulated PI 3-kinase activity increased with differentiation. Insulin-mediated phosphorylation of PKB and ERK1/2 MAP kinase increased after differentiation.


CONCLUSIONS
Components of the insulin-signalling machinery are expressed in myoblast and myotube HSMC; however, insulin responsiveness to PKB and ERK MAP kinase phosphorylation increases with differentiation.
Al-Khalili
L
L
Department of Surgical Science, Karolinska Institutet, Stockholm, Sweden.
Krämer
D
D
Wretenberg
P
P
Krook
A
A
D015415:Biomarkers / Q000032:analysis; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D003402:Creatine Kinase / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000032:analysis; D003893:Desmin / Q000032:analysis; D005260:Female; D006593:Hexokinase / Q000032:analysis; D006801:Humans; D007328:Insulin / Q000378:metabolism; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D008297:Male; D008875:Middle Aged; D020928:Mitogen-Activated Protein Kinases / Q000032:analysis*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D018006:Myogenic Regulatory Factors / Q000032:analysis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000032:analysis*; D051057:Proto-Oncogene Proteins c-akt; D011972:Receptor, Insulin / Q000032:analysis; D014157:Transcription Factors / Q000032:analysis
D015415:Biomarkers; D003402:Creatine Kinase; D004268:DNA-Binding Proteins; D003893:Desmin; D006593:Hexokinase; D007328:Insulin; D026161:MADS Domain Proteins; D064326:MEF2 Transcription Factors; D020928:Mitogen-Activated Protein Kinases; D018006:Myogenic Regulatory Factors; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011972:Receptor, Insulin; D014157:Transcription Factors; C578035:MEF2A protein, human; C578040:MEF2C protein, human