Identification and characterization of the autophosphorylation sites of phosphoinositide 3-kinase isoforms beta and gamma

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Item Type:	Article
Title:	Identification and characterization of the autophosphorylation sites of phosphoinositide 3-kinase isoforms beta and gamma
Creators Name:	Czupalla, C., Culo, M., Mueller, E.C., Brock, C., Reusch, H.P., Spicher, K., Krause, E. and Nuernberg, B.
Abstract:	Class I phosphoinositide 3-kinases (PI3Ks) are bifunctional enzymes possessing lipid kinase activity and the capacity to phosphorylate their catalytic and/or regulatory subunits. In this study, in vitro autophosphorylation of the G protein-sensitive p85-coupled class I(A) PI3K beta and p101-coupled class I(B) PI3K gamma was examined. Autophosphorylation sites of both PI3K isoforms were mapped to C-terminal serine residues of the catalytic p110 subunit (i.e. serine 1070 of p110 beta and serine 1101 of p110 gamma). Like other class I(A) PI3K isoforms, autophosphorylation of p110 beta resulted in down-regulated PI3K beta lipid kinase activity. However, no inhibitory effect of p110 gamma autophosphorylation on PI3K gamma lipid kinase activity was observed. Moreover, PI3K beta and PI3K gamma differed in the regulation of their autophosphorylation. Whereas p110 beta autophosphorylation was stimulated neither by G beta gamma complexes nor by a phosphotyrosyl peptide derived from the platelet-derived growth factor receptor, autophosphorylation of p110 gamma was significantly enhanced by G beta gamma in a time- and concentration-dependent manner. In summary, we show that autophosphorylation of both PI3K beta and PI3K gamma occurs in a C-terminal region of the catalytic p110 subunit but differs in its regulation and possible functional consequences, suggesting distinct roles of autophosphorylation of PI3K beta and PI3K gamma.
Keywords:	Amino Acid Sequence, Amino Acid Sequence Homology, Base Sequence, Catalysis, Cell Line, DNA Primers, Isoenzymes, Mass Matrix-Assisted Laser Desorption-Ionization Spectrometry, Molecular Sequence Data, Phosphatidylinositol 3-Kinases, Phosphorylation, Recombinant Proteins, Serine
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	278
Number:	13
Page Range:	11536-11545
Date:	28 March 2003
Official Publication:	https://doi.org/10.1074/jbc.M210351200
PubMed:	View item in PubMed

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