1. Model depicting collagen types and collagen receptors during megakaryocyte maturation in bone marrow and proplatelet formation.
Model depicting collagen types and collagen receptors during megakaryocyte maturation in bone marrow and proplatelet formation. Both intraluminal megakaryocytes (MK) and megakaryocytes juxtaposed to the endothelial lining of bone marrow sinusoids are in contact with collagen type I (brown filaments) or type IV (yellow filaments, middle panel). Intraluminal megakaryocytes bind with high affinity to collagen type I through integrin α2β1 and transmit an inhibitory signal through GPVI to prevent premature proplatelet formation within the bone marrow cavity (left panel). At the vascular niche, megakaryocytes show increased contact to collagen type IV, suggesting that collagen type I is displaced from integrin α2β1. Thus, the intrinsic, inhibitory signal through GPVI is abrogated, and megakaryocytes polarize and allow directed proplatelet formation across the endothelial barrier into the blood stream.
Daniela Semeniak et al. J Cell Sci 2016;129:
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