Role of PKC isoforms in glucose transport in 3T3-L1 adipocytes: insignificance of atypical PKC.
To elucidate the involvement of protein kinase C (PKC) isoforms in insulin-induced and phorbol ester-induced glucose transport, we expressed several PKC isoforms, conventional PKC-alpha, novel PKC-delta, and atypical PKC isoforms of PKC-lambda and PKC-zeta, and their mutants in 3T3-L1 adipocytes using an adenovirus-mediated gene transduction system. Endogenous expression and the activities of PKC-alpha and PKC-lambda/zeta, but not of PKC-delta, were detected in 3T3-L1 adipocytes. Overexpression of each wild-type PKC isoform induced a large amount of PKC activity in 3T3-L1 adipocytes. Phorbol 12-myristrate 13-acetate (PMA) activated PKC-alpha and exogenous PKC-delta but not atypical PKC-lambda/zeta. Insulin also activated the overexpressed PKC-delta but not PKC-alpha. Expression of the wild-type PKC-alpha or PKC-delta resulted in significant increases in glucose transport activity in the basal and PMA-stimulated states. Dominant-negative PKC-alpha expression, which inhibited the PMA activation of PKC-alpha, decreased in PMA-stimulated glucose transport. Glucose transport activity in the insulin-stimulated state was increased by the expression of PKC-delta but not of PKC-alpha. These findings demonstrate that both conventional and novel PKC isoforms are involved in PMA-stimulated glucose transport and that other novel PKC isoforms could participate in PMA-stimulated and insulin-stimulated glucose transport. Atypical PKC-lambda/zeta was not significantly activated by insulin, and expression of the wild-type, constitutively active, and dominant-negative mutants of atypical PKC did not affect either basal or insulin-stimulated glucose transport. Thus atypical PKC enzymes do not play a major role in insulin-stimulated glucose transport in 3T3-L1 adipocytes.
Third Department of Internal Medicine, Yamaguchi University School of Medicine, Ube, Yamaguchi 755-8505, Japan.
Masatoshi
M
Tsuru
Hideki
H
Katagiri
Tomoichiro
T
Asano
Tetsuya
T
Yamada
Shigeo
S
Ohno
Takehide
T
Ogihara
Yoshitomo
Y
Oka
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D007328:Insulin / Q000494:pharmacology; D007527:Isoenzymes / Q000494:pharmacology / Q000502:physiology*; D051379:Mice; D010703:Phorbol Esters / Q000494:pharmacology; D011493:Protein Kinase C / Q000494:pharmacology / Q000502:physiology*; D051745:Protein Kinase C-delta; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta
D005947:Glucose; D007328:Insulin; D007527:Isoenzymes; D010703:Phorbol Esters; D011493:Protein Kinase C; D051745:Protein Kinase C-delta; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta; C119222:phorbol-12-myristate; C497259:Prkcd protein, mouse