CELL BIOLOGY AND METABOLISM
In NIH-3T3 Fibroblasts, Insulin Receptor Interaction with Specific Protein Kinase C Isoforms Controls Receptor Intracellular Routing*

https://doi.org/10.1074/jbc.273.21.13197Get rights and content
Under a Creative Commons license
open access

Insulin increased protein kinase C (PKC) activity by 2-fold in both membrane preparations and insulin receptor (IR) antibody precipitates from NIH-3T3 cells expressing human IRs (3T3hIR). PKC-α, -δ, and -ζ were barely detectable in IR antibody precipitates of unstimulated cells, while increasing by 7-, 3.5-, and 3-fold, respectively, after insulin addition. Preexposure of 3T3hIR cells to staurosporine reduced insulin-induced receptor coprecipitation with PKC-α, -δ, and -ζ by 3-, 4-, and 10-fold, respectively, accompanied by a 1.5-fold decrease in insulin degradation and a similar increase in insulin retroendocytosis. Selective depletion of cellular PKC-α and -δ, by 24 h of 12-O-tetradecanoylphorbol-13-acetate (TPA) exposure, reduced insulin degradation by 3-fold and similarly increased insulin retroendocytosis, with no change in PKC-ζ. In lysates of NIH-3T3 cells expressing the R1152Q/K1153A IRs (3T3Mut), insulin-induced coprecipitation of PKC-α, -δ, and -ζ with the IR was reduced by 10-, 7-, and 3-fold, respectively. Similar to the 3T3hIR cells chronically exposed to TPA, untreated 3T3Mut featured a 3-fold decrease in insulin degradation, with a 3-fold increase in intact insulin retroendocytosis. Thus, in NIH-3T3 cells, insulin elicits receptor interaction with multiple PKC isoforms. Interaction of PKC-α and/or -δ with the IR appears to control its intracellular routing.

Cited by (0)

*

This work was supported in part by the Biomed2 Program of the European Community, Grant BMH4-CT-0751 (to F. B.), Telethon Grant E.554 (to F. B.), a grant of the Associazione Italiana per la Ricerca sul Cancro (AIRC) (to P. F.), the Ministero dell' Università e della Ricerca Scientifica, and the Progetto Finalizzato Biotecnologie del CNR.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The authors dedicate this paper to the late Professor Gaetano Salvatore.

Recipient of a fellowship of the Federazione Italiana per la Ricerca sul Cancro (FIRC).