Insulin activates protein kinases C-zeta and C-lambda by an autophosphorylation-dependent mechanism and stimulates their translocation to GLUT4 vesicles and other membrane fractions in rat adipocytes.

TitleInsulin activates protein kinases C-zeta and C-lambda by an autophosphorylation-dependent mechanism and stimulates their translocation to GLUT4 vesicles and other membrane fractions in rat adipocytes.
Publication TypeJournal Article
Year of Publication1999
AuthorsStandaert ML, Bandyopadhyay G, Perez L, Price D, Galloway L, Poklepovic A, Sajan MP, Cenni V, Sirri A, Moscat J, Toker A, Farese RV
JournalJ Biol Chem
Volume274
Issue36
Pagination25308-16
Date Published1999 Sep 03
ISSN0021-9258
KeywordsAdipocytes, Animals, Biological Transport, Cell Line, Cell Membrane, Cytoplasmic Granules, Glucose Transporter Type 4, Hypoglycemic Agents, Insulin, Isoenzymes, Mice, Monosaccharide Transport Proteins, Muscle Proteins, Phosphorylation, Protein Kinase C, Rats, Signal Transduction
Abstract

In rat adipocytes, insulin provoked rapid increases in (a) endogenous immunoprecipitable combined protein kinase C (PKC)-zeta/lambda activity in plasma membranes and microsomes and (b) immunoreactive PKC-zeta and PKC-lambda in GLUT4 vesicles. Activity and autophosphorylation of immunoprecipitable epitope-tagged PKC-zeta and PKC-lambda were also increased by insulin in situ and phosphatidylinositol 3,4,5-(PO(4))(3) (PIP(3)) in vitro. Because phosphoinositide-dependent kinase-1 (PDK-1) is required for phosphorylation of activation loops of PKC-zeta and protein kinase B, we compared their activation. Both RO 31-8220 and myristoylated PKC-zeta pseudosubstrate blocked insulin-induced activation and autophosphorylation of PKC-zeta/lambda but did not inhibit PDK-1-dependent (a) protein kinase B phosphorylation/activation or (b) threonine 410 phosphorylation in the activation loop of PKC-zeta. Also, insulin in situ and PIP(3) in vitro activated and stimulated autophosphorylation of a PKC-zeta mutant, in which threonine 410 is replaced by glutamate (but not by an inactivating alanine) and cannot be activated by PDK-1. Surprisingly, insulin activated a truncated PKC-zeta that lacks the regulatory (presumably PIP(3)-binding) domain; this may reflect PIP(3) effects on PDK-1 or transphosphorylation by endogenous full-length PKC-zeta. Our findings suggest that insulin activates both PKC-zeta and PKC-lambda in plasma membranes, microsomes, and GLUT4 vesicles by a mechanism requiring increases in PIP(3), PDK-1-dependent phosphorylation of activation loop sites in PKC-zeta and lambda, and subsequent autophosphorylation and/or transphosphorylation.

DOI10.1074/jbc.274.36.25308
Alternate JournalJ Biol Chem
PubMed ID10464256
Grant ListR01 DK065969 / DK / NIDDK NIH HHS / United States
2RO1DK38079-09A1 / DK / NIDDK NIH HHS / United States
R01CA75134 / CA / NCI NIH HHS / United States
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