Expression of Mona (monocytic adapter) in myeloid progenitor cells results in increased and prolonged MAP kinase activation upon macrophage colony-stimulating factor stimulation.

Mona is an SH3 and SH2 domain-containing adapter molecule that is induced during monocytic differentiation. Here we have first shown that M-CSFR is the major Mona partner in M-CSF signaling, the interaction being mediated through tyrosine 697 of the receptor. Next we asked whether Mona expression would alter the Ras/MAP kinase pathway since Mona is a likely competitor of Grb2 for binding to M-CSFR. We found that M-CSF induced late and massive phosphorylation of ERK molecules in Mona-expressing myeloid cells compared to non-expressing cells. These results suggest that Mona expression might modify M-CSF signaling during monocytic differentiation.