Transient receptor potential vanilloid 2 and 4 are both required for effective platelet formation.

BACKGROUND

Platelets are generated by megakaryocytes (MKs) in the bone marrow. A key step in this process involves the extension of MK protrusions across the sinusoidal vessel barrier through tiny endothelial pores. While the MK cell body remains in the marrow stroma, proplatelets elongate in the bloodstream. Transendothelial migration and elongation impose strong deformation and stretching on the plasma membrane.

OBJECTIVES

Since MKs are known to sense and respond to mechanical cues, we investigated the contribution of stretch-activated mechanosensitive calcium channels to this process.

RESULTS

Absence of calcium prevented proplatelet formation from MK differentiated in a 3-dimensional medium but not in a 2-dimensional liquid medium. We found that the confined 3-dimensional environment promoted selective overexpression of both transient receptor potential vanilloid (TRPV) 4 and TRPV2 stretch-activated calcium channels. Using genetic and pharmacologic approaches, we showed that TRPV4 is essential for optimal proplatelet formation, independent of substrate adhesion. Mechanistically, the absence of TRPV4 maintained abnormally high active Ras homolog family member A levels, preventing optimal proplatelet formation. The TRPV2 receptor also contributes, as blocking both TRPV4 and TRPV2 produces an additive inhibitory effect. We confirmed these findings in human platelet formation. Inhibition of both TRPV4 and TRPV2 reduces platelet production from CD34+-derived MKs in culture.

CONCLUSIONS

These results highlight TRPV4 and TRPV2 as key mechanosensitive channels in platelet biogenesis, presenting potential targets to enhance platelet production.