SHP-1 regulation of p62(DOK) tyrosine phosphorylation in macrophages

SHP-1 plays key roles in the modulation of hematopoietic cell signaling. To ascertain the impact of SHP-1 on colony-stimulating factor-1 (CSF-1)-media ted survival and proliferative signaling, we compared the CSF-1 responses o f primary bone marrow macrophages (BMM) from wild-type and SHP-1-deficient motheaten (me/me) mice. CSF-1-induced protein tyrosine phosphorylation leve ls were similar in wild-type and me/me BMM, except for the constitutive hyp erphosphoryIation of a 62-kDa phosphoprotein (pp62) in me/me macrophages. p p62 was identified as the RASGAP-associated p62(DOK) and was shown to be th e major CSF-1R-associated tyrosine-phosphorylated protein in CSF-1-treated BMM, p62DOK was found to be constitutively associated with SHP-1 in BMM and in 293T cells, co-expressing p62(dok) and either wild-type or catalyticall y inert SHP-1 (SHP-1 C453S). In both cell types, the interaction of SHP-1 w ith p62DOK occurred independently of p62(DOK) tyrosine phosphorylation, but only the tyrosine-phosphorylated p62DOK was bound by SHP-1 C4535 in a far Western analysis. These findings suggest a constitutive association of SHP- 1 and p62DOK that is either conformation-dependent or indirect as well as a direct, inducible association of the SHP-1 catalytic domain with tyrosine- phosphorylated p62(DOK). P62(DOK) hyperphosphorylation is not associated wi th altered CSF-1-induced RAS signaling or proliferation. However, whereas w ild-type macrophages undergo cell death following CSF-1 removal, me/me macr ophages exhibit prolonged survival in the absence of growth factor. Thus, p 62(DOK) is a major SHP-1 substrate whose tyrosine phosphorylation correlate s with growth factor-independent survival in macrophages.