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Mol. Cell. Biol., 03 1996, 1189-1202, Vol 16, No. 3
AM Bennett, SF Hausdorff, AM O'Reilly, RM Freeman and BG Neel
Using transient overexpression and microinjection approaches, we examined
SHPTP2's function in growth factor signaling. Overexpression of
catalytically inactive SHPTP2 (PTP2CS) but not catalytically inactive
SHPTP1, inhibited mitogen-activated protein (MAP) kinase activation and
Elk-1 transactivation following epidermal growth factor (EGF) stimulation
of 293 cells. An SHPTP2 mutant with both C-terminal tyrosyl phosphorylation
sites converted to phenylalanine (PTP2YF) was also without effect;
moreover, PTP2YF rescued PTP2CS-induced inhibition of EGF-induced Elk-1
transactivation. PTP2CS did not inhibit transactivation by activated Ras,
suggesting that SHPTP2 acts upstream of or parallel to Ras. Neither PTP2CS
nor PTP2YF inhibited platelet- derived growth factor (PDGF)-induced Elk-1
transactivation. Thus, protein-tyrosine phosphatase activity, but not
tyrosyl phosphorylation of SHPTP2, is required for the immediate-early
responses to EGF but not to PDGF. To determine whether SHPTP2 is required
later in the cell cycle, we assessed S-phase entry in NIH 3T3 cells
microinjected with anti-SHPTP2 antibodies or with a glutathione
S-transferase (GST) fusion protein encoding both SH2 domains (GST-SH2).
Microinjection of anti- SHPTP2 antibodies prior to stimulation inhibited
EGF- but no PDGF- or serum-induced S-phase entry. Anti-SHPTP2 antibodies or
GST-SH2 fusion protein could inhibit EGF-induced S-phase entry for up to 8
h after EGF addition. Although MAP kinase activation was detected shortly
after EGF stimulation, no MAP kinase activation was detected around the
restriction point. Therefore, SHPTP2 is absolutely required for
immediate-early and late events induced by some, but not all, growth
factors, and the immediate-early and late signal transduction pathways
regulated by SHPTP2 are distinguishable.
Copyright © 1996, American Society for Microbiology
Multiple requirements for SHPTP2 in epidermal growth factor-mediated cell cycle progression
Molecular Medicine Unit, Beth Israel Hospital, Boston, Massachusetts, USA.
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