Role of PKC isoforms in glucose transport in 3T3-L1 adipocytes: Insignificance of atypical PKC

Masatoshi Tsuru, Hideki Katagiri, Tomoichiro Asano, Tetsuya Yamada, Shigeo Ohno, Takehide Ogihara, Yoshitomo Oka

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)

Abstract

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-α, novel PKC-δ, and atypical PKC isoforms of PKC-λ and PKC-ζ, and their mutants in 3T3-L1 adipocytes using an adenovirus-mediated gene transduction system. Endogenous expression and the activities of PKC-α and PKC-λ/ζ, but not of PKC-δ, 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-α and exogenous PKC-δ but not atypical PKC-λ/ζ. Insulin also activated the overexpressed PKC-δ but not PKC-α. Expression of the wild-type PKC-α or PKC-δ resulted in significant increases in glucose transport activity in the basal and PMA-stimulated states. Dominant-negative PKC-α expression, which inhibited the PMA activation of PKC-α, decreased in PMA PM-A-stimulated glucose transport. Glucose transport activity in the insulin-stimulated state was increased by the expression of PKC-δ but not of PKC-α. 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-λ/ζ 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.

Original languageEnglish
Pages (from-to)E338-E345
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume283
Issue number2 46-2
DOIs
Publication statusPublished - 2002
Externally publishedYes

Keywords

  • Glucose transport
  • Insulin
  • Phorbol 12-myristate 13-acetate
  • Protein kinase C

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Physiology
  • Physiology (medical)

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