| Authors | Vögtle, T., Sharma, S., Mori, J., Nagy, Z., Semeniak, D., Scandola, C., Geer, M., Smith, C., Lane, J., Pollack, S., Lassila, R., Jouppila, A., Barr, A.J., Ogg, D., Howard, T., McMiken, H., Warwicker, J., Geh, C., Rowlinson, R., Abbott, W., Eckly, A., Schulze, H., Wright, G., Mazharian, A., Fütterer, K., Rajesh, S., Douglas, M. and Senis, Y. |
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| Abstract | The immunoreceptor tyrosine-based inhibition motif (ITIM)-containing receptor G6b-B is critical for platelet production and activation. Loss of G6b-B results in severe macrothrombocytopenia, myelofibrosis and aberrant platelet function in mice and humans. Using a combination of immunohistochemistry, affinity chromatography and proteomics, we identified the extracellular matrix heparan sulfate (HS) proteoglycan perlecan as a G6b-B binding partner. Subsequent in vitro biochemical studies and a cell-based genetic screen demonstrated that the interaction is specifically mediated by the HS chains of perlecan. Biophysical analysis revealed that heparin forms a high-affinity complex with G6b-B and mediates dimerization. Using platelets from humans and genetically-modified mice, we demonstrate that binding of G6b-B to HS and multivalent heparin inhibits platelet and megakaryocyte function by inducing downstream signaling via the tyrosine phosphatases Shp1 and Shp2. Our findings provide novel insights into how G6b-B is regulated and contribute to our understanding of the interaction of megakaryocytes and platelets with glycans. |
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