EGFR signaling leads to downregulation of PTP-LAR via TACE-mediated proteolytic processing.
Proteolytic processing and ectodomain shedding have been described for a broad spectrum of transmembrane proteins under both normal and pathophysiological conditions and has been suggested as one mechanism to regulate a protein's function. It has also been documented for the receptor-like protein tyrosine phosphatase PTP-LAR, induced by treating cells with the tumor promoter TPA or the calcium ionophor A23187. Here we identified the epidermal growth factor receptor (EGFR) as both an association partner of PTP-LAR, that mediates phosphorylation of the latter, as well as an inducer of LAR-cleavage. Both overexpression of this kinase and stimulation of endogenous EGFR in various tumor cell lines were shown to induce proteolytic processing of the catalytic LAR-P-subunit. In contrast to TPA-induced shedding of PTP-LAR, EGFR-mediated cleavage did not require PKC-activity. For both stimuli, however, processing of the P-subunit turned out to be dependent on the activation of the MAP kinases ERK1 and ERK2, and was completely abrogated upon pre-treating cells with Batimastat, indicating the involvement of a metalloproteinase in this pathway. Being strongly impaired in fibroblasts derived from ADAM-17/TACE-knockout-mice or tumor cells that express a dominant negative mutant of ADAM-17/TACE, cleavage of PTP-LAR is suggested to be mediated by this metalloproteinase. Paralleled by rapid reduction of cell surface-localized LAR-E-subunit, EGFR-induced cleavage could be shown to lead to degradation of the catalytic LAR-P-subunit, thereby resulting in a significantly reduced overall cellular phosphatase activity of PTP-LAR. These results for the first time identify a protein tyrosine phosphatase as a potential substrate of TACE and describe proteolytic processing of PTP-LAR as a means of regulating phosphatase activity downstream and thus under the control of EGFR-mediated signaling pathways.
Department of Molecular Biology, Max-Planck-Institute for Biochemistry, Am Klopferspitz 18A, D-82152 Martinsried, Germany. jens@cmm.a-star.edu.sg
Jens E
JE
Ruhe
Sylvia
S
Streit
Stefan
S
Hart
Axel
A
Ullrich
D051722:ADAM Proteins / Q000378:metabolism*; D000072198:ADAM17 Protein; D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation; D066246:ErbB Receptors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D007527:Isoenzymes; D009419:Nerve Tissue Proteins; D021122:Protein Subunits; D011956:Receptors, Cell Surface; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C516772:PTPRF protein, human; D017027:Protein Tyrosine Phosphatases; C000709129:Ptprf protein, mouse; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606463:Adam17 protein, mouse