Serine phosphorylation of insulin receptor substrate-1 (IRS-1) has been proposed as a counter-regulatory mechanism in insulin and cytokine signalling. Here we report that IRS-1 is phosphorylated by a wortmannin insensitive phosphatidylinositol 3´-kinase (PI 3-kinase)-associated serine kinase (PAS kinase) distinct from PI 3-kinase serine kinase. We found that PI 3-kinase immune complexes contain 5-fold more wortmannin-insensitive serine kinase activity than SH2-containing protein tyrosine phosphatase-2 (SHP2) and IRS-1 immune complexes. Affinity chromatography of cell lysates with a glutathione S-transferase fusion protein for the p85 subunit of PI 3-kinase showed that PAS kinase associated with the p85 subunit of PI 3-kinase. This interaction required unoccupied SH2 domain(s) but did not require the PI 3-kinase p110 subunit binding domain. In terms of function, PAS kinase phosphorylated IRS-1 and, after insulin stimulation, PAS kinase phosphorylated IRS-1 in PI 3-kinase–IRS-1 complexes. Phosphopeptide mapping showed that insulin-dependent in vivo sites of IRS-1 serine phosphorylation were comparable to those of PAS kinase phosphorylated IRS-1. More importantly, PAS kinase-dependent phosphorylation of IRS-1 reduced by 4-fold the ability of IRS-1 to act as an insulin receptor substrate. Taken together, these findings indicate that: (a) PAS kinase is distinct from the intrinsic serine kinase activity of PI 3-kinase, (b) PAS kinase associates with the p85 subunit of PI 3-kinase through SH2 domain interactions, and (c) PAS kinase is an IRS-1 serine kinase that can reduce the ability of IRS-1 to serve as an insulin receptor substrate.
Skip Nav Destination
Article navigation
October 1998
-
Cover Image
Cover Image
- PDF Icon PDF LinkFront Matter
- PDF Icon PDF LinkTable of Contents
Research Article|
October 15 1998
Phosphatidylinositol 3′-kinase associates with an insulin receptor substrate-1 serine kinase distinct from its intrinsic serine kinase
Keith A. CENGEL;
Keith A. CENGEL
*Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.
Search for other works by this author on:
Rosanne E. KASON;
Rosanne E. KASON
*Department of Animal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.
Search for other works by this author on:
Gregory G. FREUND
Gregory G. FREUND
1
†Department of Pathology University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.
1To whom correspondence should be addressed (e-mail: freun@ux1.cso.uiuc.edu). Department of Pathology, College of Medicine, 506 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, IL 61801, U.S.A.
Search for other works by this author on:
Publisher: Portland Press Ltd
Received:
February 04 1998
Revision Received:
June 29 1998
Accepted:
August 06 1998
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London © 1998
1998
Biochem J (1998) 335 (2): 397–404.
Article history
Received:
February 04 1998
Revision Received:
June 29 1998
Accepted:
August 06 1998
Citation
Keith A. CENGEL, Rosanne E. KASON, Gregory G. FREUND; Phosphatidylinositol 3′-kinase associates with an insulin receptor substrate-1 serine kinase distinct from its intrinsic serine kinase. Biochem J 15 October 1998; 335 (2): 397–404. doi: https://doi.org/10.1042/bj3350397
Download citation file:
Sign in
Don't already have an account? Register
Sign in to your personal account
You could not be signed in. Please check your email address / username and password and try again.
Captcha Validation Error. Please try again.