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Andrey Bondev, Ignacio Rubio, Reinhard Wetzker

Differential Regulation of Lipid and Protein Kinase Activities of Phosphoinositide 3-Kinase ? in Vitro

G protein sensitive phosphoinositide 3-kinase ?(PI3K?) has been characterised as a pleiotropic signalling protein expressing lipid kinase and protein kinase activities. Whereas the regulation of the lipid kinase activity has been investigated in detail, the regulatory features of PI3K? protein kinase activity are unknown. Here we report that G?? subunits of heterotrimeric G proteins induce a biphasic response of PI3K? autophosphorylation in vitro, which contrasts the regulatory effects of the G proteins on PI3K? lipid kinase activity. In addition to autophosphorylation PI3K? is able to catalyse transphosphorylation of the adapter protein p101 and the protein kinase MEK-1. In the presence of the p101, G?? affects PI3K? protein kinase activities in a complex manner. In summary, the differential regulatory effects of heterotrimeric G proteins on PI3K? lipid and protein kinase activities in vitro reflect the functional diversity of the enzyme observed in vivo.

Biological Chemistry, Walter de Gruyter

Print ISSN: 1431-6730
Volume: 380, 11/1999
Pages: 1337 - 1340

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