Sa. Langhansrajasekaran et al., ACTIVATION OF TSK AND BTK TYROSINE KINASES BY G-PROTEIN BETA-GAMMA-SUBUNITS, Proceedings of the National Academy of Sciences of the United Statesof America, 92(19), 1995, pp. 8601-8605
Tsk/Itk and Btk are members of the pleckstrin-homology (PH) domain-con
taining tyrosine kinase family. The PH domain has been demonstrated to
be able to interact with beta gamma subunits of heterotrimeric guanin
e nucleotide-binding proteins (G proteins) (G(beta gamma)) and phospho
lipids. Using cotransfection assays, we show here that the kinase acti
vities of Tsk and Btk are stimulated by certain G(beta gamma) subunits
. Furthermore, using an in vitro reconstitution assay with purified bo
vine brain G(beta gamma) subunits and the immunoprecipitated Tsk, we f
ind that Tsk kinase activity is increased by G(beta gamma) subunits an
d another membrane factor(s). These results indicate that this family
of tyrosine kinases could be an effector of heterotrimeric G proteins.