PT  - JOURNAL ARTICLE
AU  - Timo Vögtle
AU  - Sumana Sharma
AU  - Jun Mori
AU  - Zoltan Nagy
AU  - Daniela Semeniak
AU  - Mitchell J. Geer
AU  - Christopher W. Smith
AU  - Jordan Lane
AU  - Scott Pollack
AU  - Riitta Lassila
AU  - Annukka Jouppila
AU  - Alastair J. Barr
AU  - Derek J. Ogg
AU  - Tina D. Howard
AU  - Helen J. McMiken
AU  - Juli Warwicker
AU  - Catherine Geh
AU  - Rachel Rowlinson
AU  - W. Mark Abbott
AU  - Harald Schulze
AU  - Gavin J. Wright
AU  - Alexandra Mazharian
AU  - Klaus Fütterer
AU  - Sundaresan Rajesh
AU  - Michael R. Douglas
AU  - Yotis A. Senis
TI  - Heparan sulfates are critical regulators of the inhibitory megakaryocyte-platelet receptor G6b-B
AID  - 10.1101/584698
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 584698
4099  - http://biorxiv.org/content/early/2019/03/25/584698.short
4100  - http://biorxiv.org/content/early/2019/03/25/584698.full
AB  - 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.