title: The RIalpha subunit of protein kinase A (PKA) binds to Grb2 and allows PKA interaction with the activated EGF-receptor.
abstract: Functional interactions between protein kinase A (PKA) and epidermal growth factor receptor (EGF-R) signalling pathways have been suggested. Unlike the type II isoform of PKA (PKAII), the type I (PKAI) and/or its regulatory subunit RIalpha are generally overexpressed in cancer cells and are induced following transforming growth factor alpha (TGF alpha)/EGF-R-dependent transformation. Downregulation of RIalpha/PKAI inhibits TGF alpha expression and EGF-R-dependent signalling. We have previously shown that addition of EGF to quiescent human normal epithelial MCF-10A cells determines PKAI expression and cell membrane translocation before cells enter S phase, while PKAI inhibition prevents S phase entry. Constitutive overexpression of PKAI confers the ability to grow in serum free medium, bypassing EGF requirement. Here we demonstrate a direct interaction of PKAI, but not of PKAII, with the activated EGF-R, that occurs within 5 min following EGF treatment of MCF-10A cells. Moreover, induction of mitogen-activated protein kinase (MAPK) activity following EGF-R activation is mimicked by PKAI overexpression and inhibited by downregulators of PKAI. Finally, the PKAI-EGF-R association occurs through the binding of RIalpha to the SH3 domain(s) of Grb2 adaptor protein, thus allowing the recruitment of the PKAI holoenzyme to the activated EGF-R. This is the first demonstration of a direct interaction of PKAI with the activated EGF-R macromolecular signalling complex.
authors.affiliation: Cattedra di Oncologia Medica, Dipartimento di Endocrinologia e Oncologia Molecolare e Clinica, Università di Napoli Federico II, Napoli, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Tortora
authors.forename: V
authors.initials: V
authors.lastname: Damiano
authors.forename: C
authors.initials: C
authors.lastname: Bianco
authors.forename: G
authors.initials: G
authors.lastname: Baldassarre
authors.forename: A R
authors.initials: AR
authors.lastname: Bianco
authors.forename: L
authors.initials: L
authors.lastname: Lanfrancone
authors.forename: P G
authors.initials: PG
authors.lastname: Pelicci
authors.forename: F
authors.initials: F
authors.lastname: Ciardiello
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000378:metabolism*; D051380:GRB2 Adaptor Protein; D006801:Humans; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; D011506:Proteins; D066246:ErbB Receptors; D054746:Cyclic AMP-Dependent Protein Kinase Type II; D017868:Cyclic AMP-Dependent Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases