title: The Cdc42 target ACK2 interacts with sorting nexin 9 (SH3PX1) to regulate epidermal growth factor receptor degradation.
abstract: Activated Cdc42-associated kinase-2 (ACK2) is a non-receptor tyrosine kinase that serves as a specific effector for Cdc42, a Rho family small G-protein. Recently, we have found that ACK2 directly interacts with clathrin heavy chain through a clathrin-binding motif that is conserved in all endocytic adaptor proteins and regulates clathrin assembly, suggesting that ACK2 plays a role in clathrin-coated vesicle endocytosis (Yang, W., Lo, C. G., Dispenza, T., and Cerione, R. A. (2001) J. Biol. Chem. 276, 17468-17473). Here we report the identification of another binding partner for ACK2 that has previously been implicated in endocytosis, namely the sorting nexin protein SH3PX1 (sorting nexin 9). The interaction occurs between a proline-rich domain of ACK2 and the Src homology 3 domain (SH3) of SH3PX1. Co-immunoprecipitation studies indicate that ACK2, clathrin, and SH3PX1 form a complex in cells. Epidermal growth factor (EGF) stimulated the tyrosine phosphorylation of SH3PX1, whereas co-transfection of ACK2 with SH3PX1 resulted in the constitutive phosphorylation of SH3PX1. However, co-transfection of the kinase-dead mutant ACK2(K158R) with SH3PX1 blocked EGF-induced tyrosine phosphorylation of SH3PX1, indicating that the EGF-stimulated phosphorylation of SH3PX1 is mediated by ACK2. EGF receptor levels were significantly decreased following EGF stimulation of cells co-expressing ACK2 and SH3PX1, thus highlighting a novel role for ACK2, working together with SH3PX1 to promote the degradation of the EGF receptor.
authors.affiliation: Department of Molecular Medicine and Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Lin
authors.forename: Charles G
authors.initials: CG
authors.lastname: Lo
authors.forename: Richard A
authors.initials: RA
authors.lastname: Cerione
authors.forename: Wannian
authors.initials: W
authors.lastname: Yang
mesh_terms: D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000378:metabolism*; D002966:Clathrin / Q000378:metabolism; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004705:Endocytosis; D066246:ErbB Receptors / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D058305:Sorting Nexins; D013997:Time Factors; D014162:Transfection; D014443:Tyrosine / Q000378:metabolism; D033921:Vesicular Transport Proteins; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: D002352:Carrier Proteins; D002966:Clathrin; D016895:Culture Media, Serum-Free; D011993:Recombinant Fusion Proteins; C400533:SNX9 protein, human; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; D066246:ErbB Receptors; D011505:Protein-Tyrosine Kinases; D020764:cdc42 GTP-Binding Protein