The SH2 Inositol 5-Phosphatase Ship1 Is Recruited in an SH2-dependent Manner to the Erythropoietin Receptor

Jacqueline M Mason,Bryan K Beattie,Qiurong Liu,Daniel J Dumont,Dwayne L Barber

doi:10.1074/jbc.275.6.4398

Jacqueline M Mason, Bryan K Beattie + Show 3 more

Open Access

https://doi.org/10.1074/jbc.275.6.4398

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Abstract

Ship1 (SH2 inositol 5-phosphatase 1) has been shown to be a target of tyrosine phosphorylation downstream of cytokine and immunoregulatory receptors. In addition to its catalytic activity on phosphatidylinositol substrates, it can serve as an adaptor protein in binding Shc and Grb2. Erythropoietin (EPO), the primary regulator of erythropoiesis, has been shown to activate the tyrosine phosphorylation of Shc, resulting in recruitment of Grb2. However, the mechanism by which the erythropoietin receptor (EPO-R) recruits Shc remains unknown. EPO activates the tyrosine phosphorylation of Ship1, resulting in the interdependent recruitment of Shc and Grb2. Ship1 is recruited to the EPO-R in an SH2-dependent manner. Utilizing a panel of EPO-R deletion and tyrosine mutants, we have discovered remarkable redundancy in Ship1 recruitment. EPO-R Tyr(401) appears to be a major site of Ship1 binding; however, Tyr(429) and Tyr(431) can also serve to recruit Ship1. In addition, we have shown that EPO stimulates the formation of a ternary complex consisting of Ship1, Shc, and Grb2. Ship1 may modulate several discrete signal transduction pathways. EPO-dependent activation of ERK1/2 and protein kinase B (PKB)/Akt was examined utilizing a panel of EPO-R deletion mutants. Activation of ERK1/2 was observed in EPO-RDelta99, which retains only the most proximal tyrosine, Tyr(343). In contrast, EPO-dependent PKB activation was observed in EPO-RDelta43, but not in EPO-RDelta99. It appears that EPO-dependent PKB activation is downstream of a region that indirectly couples to phosphatidylinositol 3-kinase.

Highlights

Ship1 (SH2 inositol 5-phosphatase 1) has been shown to be a target of tyrosine phosphorylation downstream of cytokine and immunoregulatory receptors
The critical role of EPO [3], erythropoietin receptor (EPO-R) [3, 4] and JAK2 in erythropoiesis [5, 6] has recently been elegantly demonstrated, as gene targeting experiments reveal that loss of any one of these genes leads to a fatal anemia and the embryos fail to traverse primitive to definitive erythropoiesis
Using a panel of EPO-R deletion and tyrosine mutants, we have demonstrated that Ship1 is recruited to the EPO-R in an SH2-dependent manner

Summary

Introduction

Ship1 (SH2 inositol 5-phosphatase 1) has been shown to be a target of tyrosine phosphorylation downstream of cytokine and immunoregulatory receptors. Erythropoietin (EPO), the primary regulator of erythropoiesis, has been shown to activate the tyrosine phosphorylation of Shc, resulting in recruitment of Grb2. EPO activates the tyrosine phosphorylation of Ship1, resulting in the interdependent recruitment of Shc and Grb2.

Results

Conclusion