SHP-1 Binds and Negatively Modulates the c-Kit Receptor by Interaction with Tyrosine 569 in the c-Kit Juxtamembrane Domain

Abstract

The SH2 domain-containing SHP-1 tyrosine phosphatase has been shown to negatively regulate a broad spectrum of growth factor-and cytokine-driven mitogenic signaling pathways. Included among these is the cascade of intracellular events evoked by stem cell factor binding to c-Kit, a tyrosine kinase receptor which associates with and is dephosphorylated by SHP-1. Using a series of glutathione S-transferase ( The pivotal role of the SH2 domain-containing SHP-1 (PTP1C, HCP, or SHPTP1) tyrosine phosphatase in the regulation of hemopoietic cell growth and development is now well recognized (1). In contrast to the structurally similar, ubiquitously expressed SHP-2 (Syp or PTP1D) tyrosine phosphatase and its Drosophila csw homolog (10, 37), SHP-1 appears to exert primarily inhibitory effects on the signaling cascades in which it participates (34). SHP-1 has been shown, for example, to suppress the growth-promoting properties of the activated interleukin 3 (IL-3), erythropoietin, and colony-stimulating factor 1 receptors, an effect mediated either directly by receptor dephosphorylation or indirectly by dephosphorylation of receptor-associated protein tyrosine kinases (PTKs) (4,19,55,56). SHP-1 has also been implicated in downregulation of the signaling pathways evoked by engagement of the B-and Tlymphocyte antigen receptors (5, 32, 33), antigen receptor comodulators such as CD22, Fc␥RIIB, and CD5, and cytosolic signaling molecules such as Vav and Grb2/Sos1 which are involved in Ras activation (6,8,20). The capacity of SHP-1 to negatively modulate this broad spectrum of signaling effectors is consistent with the enormous overexpansion of multiple hemopoietic cell populations manifested by motheaten (me) and viable motheaten (me v ) mice, animals now known to be homozygous for loss-of-function mutations in the SHP-1 gene (21,46). The presence of two SH2 domains in SHP-1, as well as the possibility for altering its C-terminal SH2 domain by alternative splicing of a 39-amino-acid segment (46), provides a structural explanation for the diverse range of molecular interactions in which this phosphotyrosine phosphatase (PTP) appears to participate. Thus, while the precise structural basis for and physiologic effects of SHP-1 interactions with the molecules with which it has been shown to associate require further investigation, the current data concerning SHP-1 functions identify this PTP as a critical player in the modulation of hemopoietic cell growth and function.In addition to the regulation of cell proliferation, SHP-1 has also been implicated in the control of signaling cascades coupling growth factor receptors to hemopoietic cell differentiation. This role for SHP-1 has become particularly well appreciated in the context of data derived from studies of SHP-1 interactions with the transmembrane PTK receptor encoded by the c-Kit proto-oncogene. The latter receptor subserves pivotal functions in promoting the development, survival, and proliferation of hemopoietic stem cells, neural crest-derived cells, and germ cells, a role...

Phosphorylation of Shc by Src family kinases is necessary for stem cell factor receptor/c-kit mediated activation of the Ras/MAP kinase pathway and c-fos induction

“…However, in PAE cells expressing the Kit/ SCFR, we were unable to detect any such interactions. Furthermore, in contrast to our ®ndings and ®ndings by Timokhina et al (1998), Kozlowski et al (1998) demonstrated an increased mitogenic response in cells expressing the Y568F and Y570F Kit/SCFR mutants. These di erences in cellular response might be due to the di erent repertoire of signal transduction molecules expressed in the di erent cell types, e.g.…”

“…Five tyrosine residues are located in the juxtamembrane region, out of which two are phosphorylated in vivo following SCF-stimulation. Tyr568 and Tyr570 have been shown by several groups to be phosphorylation sites (Kozlowski et al, 1998;Linnekin et al, 1997;Price et al, 1997;Timokhina et al, 1998). Linnekin et al (1997) could show that these tyrosine residues mediate binding of the Src family member Lyn in Mo7e cells, and demonstrate by an antisense approach and by the use of the Src inhibitor PP1 the importance of Src family kinases for Kit/SCFR mediated mitogenesis.…”

“…Timokhina et al (1998) could demonstrate decreased SCF-stimulated DNA-synthesis in cells expressing the Y568F mutant. In contrast, Kozlowski et al (1998) showed an increased mitogenicity in cells expressing either the Y568F or the Y570F mutant Kit/SCFR (Kozlowski et al 1998).…”

“…This suggests that there might be additional signal transduction molecules binding to Tyr568 and Tyr570. Using Ba/F3 cells, Kozlowski et al (1998) demonstrated binding of the protein tyrosine phosphatases SHP-1 and SHP-2 to Tyr568 and Tyr570, respectively. However, in PAE cells expressing the Kit/ SCFR, we were unable to detect any such interactions.…”

Regulation of theLeishmania-induced innate inflammatory response by the protein tyrosine phosphatase SHP-1

“…In a subsequent study [11], we demonstrated that this pV-mediated protection against leishmaniasis was in part due to an increased production of nitric oxide and pro-inflammatory molecules (such as IL-6, IL-1b, MCP-1/CCL2 and MIP-2/CXCL1), accompanied by increased leukocyte recruitment. Furthermore, we showed that the PTP Src homology 2 domain phosphotyrosine phosphatase 1 (SHP-1), recognized as a negative regulator of numerous phosphotyrosine-dependent signaling pathways in hematopoietic cells [12][13][14][15][16][17], is specifically induced by Leishmania infection and involved in the deactivation of the IFN-c-induced JAK2-dependent signaling pathway [6].…”