RESUMO
Isoform-specific signaling by Class IA PI 3-kinases depends in part on the interactions between distinct catalytic subunits and upstream regulatory proteins. From among the class IA catalytic subunits (p110α, p110ß, and p110δ), p110ß has unique properties. Unlike the other family members, p110ß directly binds to Gßγ subunits, downstream from activated G-protein coupled receptors, and to activated Rab5. Furthermore, the Ras-binding domain (RBD) of p110ß binds to Rac and Cdc42 but not to Ras. Defining mutations that specifically disrupt these regulatory interactions is critical for defining their role in p110ß signaling. This chapter describes the approach that was used to identify the Rab5 binding site in p110ß, and discusses methods for the analysis of p110ß-Rab5 interactions.
