title: Srcasm modulates EGF and Src-kinase signaling in keratinocytes.
abstract: The Src-activating and signaling molecule (Srcasm) is a recently described activator and substrate of Src-family tyrosine kinases (SFKs). When phosphorylated at specific tyrosines, Srcasm associates with Grb2 and p85, the regulatory subunit of phosphoinositide 3-kinase; however, little is known about the role of Srcasm in cellular signaling. Data presented here demonstrate that epidermal growth factor (EGF) receptor ligands promote the tyrosine phosphorylation of endogenous and adenovirally transduced Srcasm in keratinocytes, and that increased levels of Srcasm activate endogenous SFKs, with a preference for Fyn and Src. In addition, Srcasm potentiates EGF-dependent signals transmitted by SFKs in keratinocytes. Tyrosine phosphorylation of Srcasm is dependent on growth factors and the activity of EGFR and SFKs. Increased Srcasm expression enhances p44/42 mitogen-activated protein kinase activity and Elk-1-dependent transcriptional events. Elevated Srcasm levels inhibit keratinocyte proliferation while promoting specific aspects of keratinocyte differentiation. Lastly, Srcasm levels are decreased in human cutaneous neoplasia. Collectively, these data demonstrate that Srcasm plays a role in linking EGF receptor- and SFK-dependent signaling to differentiation in keratinocytes.
authors.affiliation: Department of Dermatology, University of Pennsylvania Medical School, 415 Curie Blvd., Philadelphia, PA 19104, USA.
authors.forename: Weijie
authors.initials: W
authors.lastname: Li
authors.forename: Christine
authors.initials: C
authors.lastname: Marshall
authors.forename: Lijuan
authors.initials: L
authors.lastname: Mei
authors.forename: Leonard
authors.initials: L
authors.lastname: Dzubow
authors.forename: Chrysalene
authors.initials: C
authors.lastname: Schmults
authors.forename: Michael
authors.initials: M
authors.lastname: Dans
authors.forename: John
authors.initials: J
authors.lastname: Seykora
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D066246:ErbB Receptors / Q000378:metabolism; D000091344:Filaggrin Proteins; D005786:Gene Expression Regulation; D006801:Humans; D007381:Intermediate Filament Proteins / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism*; D008024:Ligands; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D008954:Models, Biological; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D050807:ets-Domain Protein Elk-1; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; C494112:ELK1 protein, human; D000091344:Filaggrin Proteins; D007381:Intermediate Filament Proteins; D008024:Ligands; D011518:Proto-Oncogene Proteins; C499446:TOM1L1 protein, human; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D004247:DNA; D066246:ErbB Receptors; D019061:src-Family Kinases; D019950:Mitogen-Activated Protein Kinase 1