M-CSF induces the stable interaction of cFms with αVβ3 integrin in osteoclasts

Abstract

The macrophage colony stimulating factor receptor (cFms) and alpha(V)beta(3) integrin are both abundantly expressed and play critical roles in the differentiation, survival and migration of osteoclasts. We have previously demonstrated that cross-talk between cFms- and alpha(V)beta(3)-mediated signaling pathways regulated the cytoskeletal organization required for osteoclast migration. To investigate the nature of interaction between the two receptors, we sequentially used anion-exchange chromatography and immunoprecipitation to purify alpha(V)beta(3)-associated protein complexes. We have demonstrated that cFms stably associated with alpha(V)beta(3) in osteoclasts during adhesion, and that the association was induced by macrophage colony stimulating factor (M-CSF) stimulation. However, the kinetics of association of alpha(V)beta(3) and cFms did not correlate with the kinetics of tyrosine phosphorylation of cFms. Instead, maximally observed alpha(V)beta(3)/cFms association was after the peak of cFms tyrosine phosphorylation and correlated inversely with the total amount of cFms remaining. Furthermore, the complex containing cFms and alpha(V)beta(3) also contained a number of other signaling molecules including Pyk2, p130(Cas) and c-Cbl, known downstream regulators of the integrin-mediated signaling pathways in osteoclasts. In the presence of M-CSF, co-localization of alpha(V)beta(3) integrin and cFms was identified in the podosomal actin ring of the osteoclast during adhesion o…