title: Protein tyrosine kinase 6 directly phosphorylates AKT and promotes AKT activation in response to epidermal growth factor.
abstract: Protein tyrosine kinase 6 (PTK6) is a nonmyristoylated Src-related intracellular tyrosine kinase. Although not expressed in the normal mammary gland, PTK6 is expressed in a majority of human breast tumors examined, and it has been linked to ErbB receptor signaling and AKT activation. Here we demonstrate that AKT is a direct substrate of PTK6 and that AKT tyrosine residues 315 and 326 are phosphorylated by PTK6. Association of PTK6 with AKT occurs through the SH3 domain of PTK6 and is enhanced through SH2 domain-mediated interactions following tyrosine phosphorylation of AKT. Using Src, Yes, and Fyn null mouse embryonic fibroblasts (SYF cells), we show that PTK6 phosphorylates AKT in a Src family kinase-independent manner. Introduction of PTK6 into SYF cells sensitized these cells to physiological levels of epidermal growth factor (EGF) and increased AKT activation. Stable introduction of active PTK6 into SYF cells also resulted in increased proliferation. Knockdown of PTK6 in the BPH-1 human prostate epithelial cell line led to decreased AKT activation in response to EGF. Our data indicate that in addition to promoting growth factor receptor-mediated activation of AKT, PTK6 can directly activate AKT to promote oncogenic signaling.
authors.affiliation: University of Illinois, Department of Biochemistry and Molecular Genetics, Chicago, IL 60607, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zheng
authors.forename: Maoyu
authors.initials: M
authors.lastname: Peng
authors.forename: Zebin
authors.initials: Z
authors.lastname: Wang
authors.forename: John M
authors.initials: JM
authors.lastname: Asara
authors.forename: Angela L
authors.initials: AL
authors.lastname: Tyner
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins; D009363:Neoplasm Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; C485645:TWF2 protein, mouse; D014443:Tyrosine; D004815:Epidermal Growth Factor; D011505:Protein-Tyrosine Kinases; C088375:PTK6 protein, human; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt