Nerve Growth Factor Stimulates Tyrosine Phosphorylation and Activation of Src Homology-containing Protein-tyrosine Phosphatase 1 in PC12 Cells

Abstract

Rat PC12 cells respond to extracellular peptide growth factors in at least two distinct ways. When treated with nerve growth factor (NGF) PC12 cells exit the cell cycle and differentiate to a neuronal phenotype, whereas when treated with epidermal growth factor, they proliferate. We examined the potential role of Src homology 2 (SH2)-containing protein tyrosine phosphatases (PTPs) in the differentiation process. PC12 cells express substantial amounts of both SH-PTP1 and 2. SH-PTP1, but not SH-PTP2, becomes tyrosine phosphorylated following NGF, but not epidermal growth factor treatment. The enzymatic activity of SH-PTP1 toward an exogenous substrate following NGF treatment is increased 2-fold. We found that SH-PTP1 binds to the NGF receptor TrkA in vitro and that anti-TrkA immunoprecipitates have PTP activity. These results show that SH-PTP1 is differentially phosphorylated and activated by NGF in PC12 cells and suggest that this activation may play a role in NGF-induced differentiation.Diverse extracellular growth factors use one of a few common strategies to transmit their messages to the cell interior. Among the best understood of these strategies is that utilized by ligands that bind to receptor protein tyrosine kinases (RPTKs). 1 The general scheme by which these signals are transduced includes receptor dimerization and autophosphorylation, followed by the recruitment of an array of Src homology 2 (SH2)-containing molecules (1). These recruited SH2-containing proteins include enzymes such as kinases, phosphatases, GTPase-activating proteins, and phospholipases, and adaptor proteins, which bind to activators of the Ras family of GTPases, thus linking the signaling complex to downstream effectors (2).One of the SH2-containing proteins recruited by several different RPTKs is protein tyrosine phosphatase (PTP) SH-PTP2 (3-6). In the case of the platelet-derived growth factor (PDGF)-␤ receptor SH-PTP2 binds to phosphorylated tyrosine 1009, and itself becomes tyrosine phosphorylated by the receptor (7,8). Tyrosine-phosphorylated SH-PTP2 then serves as a docking site for the SH2-containing adaptor protein Grb2 (8,9). In this way, one function of SH-PTP2 binding to the PDGF receptor appears to be as a platform for the assembly of additional adaptor proteins required to generate an active signaling complex. The role of the phosphatase activity itself is not well established at present.Although structurally similar to SH-PTP2, the second known SH2-containing PTP (SH-PTP1) (10 -12) appears to have a different role in signal transduction. Disruption of SH-PTP1 function gives rise to the motheaten and viable motheaten mouse strains, which have severe immunologic defects as well as multiple other hematopoietic abnormalities (13)(14)(15). These mice exhibit a large increase in the number of myeloid precursor cells as a result of colony-stimulating factor 1-independent proliferation of macrophages and increased sensitivity of colony-forming units to erythropoietin. In addition, there is also an increase in the numbers of er...

Drosophila terminal structure development is regulated by the compensatory activities of positive and negative phosphotyrosine signaling sites on the Torso RTK.

“…4). Consistent with the observation that SH-PTP2/Syp, the mammalian homolog of Csw, is not a substrate of the Trk receptor (Vambutas et al 1996), activation of Trk with NGF treatment did not alter the phosphorylation state of Csw (Fig. 4).…”

c-abl is involved in the association of p53 and trk A

“…There are data suggesting that PI-3K does not bind directly to trk A, but probably through shc since mutation of Y490 a ects the level of PI-3K activation when cells are stimulated by NGF (Ashcroft et al, 1999;Hallberg et al, 1998). trk A can also bind to several proteins which include shp-1, shp-2 (Vambutas et al, 1995;Goldsmith and Koizumi, 1997), Chk (Yamashita et al, 1999), Aps and SH2-B (Qian et al, 1998), but the signi®cance of these associations needs to be de®ned.…”

Profiling Subcellular Protein Phosphatase Responses to Coxsackievirus B3 Infection of Cardiomyocytes

“…We evaluated protein phosphatase specificity of the activity assays by using small-molecule inhibitors. With the panphosphatase inhibitor sodium pyrophosphate (NaPP) (77,78), all activity measurements were potently inhibited as expected (Fig. 5A-5F).…”