Syp (SH-PTP2) is a positive mediator of growth factor-stimulated mitogenic signal transduction.
Syp (SH-PTP2) was recently identified as a phosphotyrosine phosphatase containing two SH2 domains within its primary structure. In response to appropriate growth factor stimulation, Syp becomes phosphorylated on tyrosine residues and associates with insulin receptor substrate 1 (IRS-1) and/or the corresponding growth factor receptor via its SH2 domains, leading to increased Syp activity. To assess the importance of Syp in mitogenic signaling, we microinjected mammalian fibroblasts with several reagents designed to interfere with Syp SH2/phosphotyrosine interaction in vivo. Insulin-, insulin-like growth factor-1-, and epidermal growth factor-stimulated DNA synthesis, indicated by bromodeoxyuridine (BrdUrd) incorporation, was dramatically decreased following microinjection of a Syp antibody (Ab) (65-85%) or a Syp GST-SH2 fusion protein (approximately 90%) in comparison with cells microinjected with control IgG or glutathione S-transferase (GST), respectively. In addition, microinjection of an IRS-1-derived phosphonopeptide, which inhibits in vitro binding of Syp-SH2 to IRS-1 with an ED50 value of approximately 23 microM, also decreased BrdUrd incorporation in vivo by approximately 50-75%. Microinjection of the Syp Ab, Syp GST-SH2 fusion protein, or the phosphonopeptide had no effect on serum-stimulated BrdUrd incorporation. In conclusion, disruption of Syp function in living cells inhibited cell cycle progression in response to growth factor stimulation, indicating that Syp is a critical positive regulator of mitogenic signal transduction.
Xiao
S
S
Department of Medicine, University of California, San Diego, La Jolla 92093.
Rose
D W
DW
Sasaoka
T
T
Maegawa
H
H
Burke
T R
TR
Roller
P P
PP
Shoelson
S E
SE
Olefsky
J M
JM
D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D002478:Cells, Cultured; D005982:Glutathione Transferase / Q000378:metabolism; D006133:Growth Substances / Q000378:metabolism*; D007074:Immunoglobulin G; D047908:Intracellular Signaling Peptides and Proteins; D008845:Microinjections; D008969:Molecular Sequence Data; D010766:Phosphorylation; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
D006133:Growth Substances; D007074:Immunoglobulin G; D047908:Intracellular Signaling Peptides and Proteins; D011993:Recombinant Fusion Proteins; D014443:Tyrosine; D005982:Glutathione Transferase; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat