Knockout of the predominant conventional PKC isoform, PKCalpha, in mouse skeletal muscle does not affect contraction-stimulated glucose uptake.
Conventional (c) protein kinase C (PKC) activity has been shown to increase with skeletal muscle contraction, and numerous studies using primarily pharmacological inhibitors have implicated cPKCs in contraction-stimulated glucose uptake. Here, to confirm that cPKC activity is required for contraction-stimulated glucose uptake in mouse muscles, contraction-stimulated glucose uptake ex vivo was first evaluated in the presence of three commonly used cPKC inhibitors (calphostin C, Gö-6976, and Gö-6983) in incubated mouse soleus and extensor digitorum longus (EDL) muscles. All potently inhibited contraction-stimulated glucose uptake by 50-100%, whereas both Gö compounds, but not calphostin C, inhibited insulin-stimulated glucose uptake modestly. AMP-activated protein kinase (AMPK) and eukaryotic elongation factor 2 phosphorylation was unaffected by the blockers. PKCalpha was estimated to account for approximately 97% of total cPKC protein expression in skeletal muscle. However, in muscles from PKCalpha knockout (KO) mice, neither contraction- nor phorbol ester-stimulated glucose uptake ex vivo differed compared with the wild type. Furthermore, the effects of calphostin C and Gö-6983 on contraction-induced glucose uptake were similar in muscles lacking PKCalpha and in the wild type. It can be concluded that PKCalpha, representing approximately 97% of cPKC in skeletal muscle, is not required for contraction-stimulated glucose uptake. Thus the effect of the PKC blockers on glucose uptake is either nonspecific working on other parts of contraction-induced signaling or the remaining cPKC isoforms are sufficient for stimulating glucose uptake during contractions.
Jensen
Thomas E
TE
Department of Exercise and Sport Sciences, Sectionof Human Physiology, University of Copenhagen, Copenhagen Muscle Research Centre, Copenhagen, Denmark.
Maarbjerg
Stine J
SJ
Rose
Adam J
AJ
Leitges
Michael
M
Richter
Erik A
EA
D000818:Animals; D001692:Biological Transport; D002227:Carbazoles / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D007211:Indoles; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D008301:Maleimides; D051379:Mice; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000235:genetics / Q000502:physiology*; D018482:Muscle, Skeletal / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
C465664:2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide; D002227:Carbazoles; D004791:Enzyme Inhibitors; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D009281:Naphthalenes; C081021:Go 6976; D051571:Protein Kinase C-alpha; C058819:calphostin C; D005947:Glucose