Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B

Vögtle, T.; Sharma, S.; Mori, J.; Nagy, Z.; Semeniak, D.; Geer, M. J.; Smith, C. W.; Lane, J.; Pollack, S.; Lassila, R.; Jouppila, A.; Barr, A. J.; Ogg, D. J.; Howard, T. D.; McMiken, H. J.; Warwicker, J.; Geh, C.; Rowlinson, R.; Abbott, W. M.; Schulze, H.; Wright, G. J.; Mazharian, A.; Fütterer, K.; Rajesh, S.; Douglas, M. R.; Senis, Y. A.

doi:10.1101/584698

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bioRxiv · 10.1101/584698

Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B

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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 which results in severe macrothrombocytopenia 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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Vögtle, T., Sharma, S., Mori, J., Nagy, Z., Semeniak, D., Geer, M. J., Smith, C. W., Lane, J., Pollack, S., Lassila, R., Jouppila, A., Barr, A. J., Ogg, D. J., Howard, T. D., McMiken, H. J., Warwicker, J., Geh, C., Rowlinson, R., Abbott, W. M., Schulze, H., Wright, G. J., Mazharian, A., Fütterer, K., Rajesh, S., Douglas, M. R., Senis, Y. A.. 2019-03-25. Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B. https://doi.org/10.1101/584698

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