Mouse podoplanin supports adhesion and aggregation of platelets under arterial shear: A novel mechanism of haemostasis

Abstract

The podoplanin-CLEC-2 axis is critical in mice for prevention of hemorrhage in the cerebral vasculature during mid-gestation. This raises the question as to how platelets are captured by podoplanin on neuroepithelial cells in a high shear environment. In this study, we demonstrate that mouse platelets form stable aggregates on mouse podoplanin at arterial shear through a CLEC-2 and Src kinase-dependent pathway. Adhesion and aggregation are also dependent on the platelet glycoprotein (GP) receptors, integrin αIIbβ3 and GPIb, and the feedback agonists ADP and thromboxane A (TxA). CLEC-2 does not bind to von Willebrand factor (VWF) suggesting that the interaction with podoplanin is sufficient to both tether and activate platelets. Consistent with this, the surface plasmon resonance measurements reveal that mouse CLEC-2 binds to mouse podoplanin with nanomolar affinity. The present findings demonstrate a novel pathway of hemostasis in which podoplanin supports platelet capture and activation at arteriolar rates of shear.

Podoplanin in Inflammation and Cancer

“…Podoplanin–CLEC-2 binding induces clustering of CLEC-2, activating a downstream signaling pathway involving Src family and Syk tyrosine kinases, the adaptor protein SLP-76, and activation of PLCγ2, as mentioned above [47,48,49,50]. It is worth mentioning that CLEC-2 binds podoplanin with high affinity, and the glycoprotein is able to support platelet capture and activation under arterial rates of shear [51].…”

Functional significance of the platelet immune receptors GPVI and CLEC-2

“…Podoplanin is markedly upregulated on neuroepithelial cells at this stage of development, providing a mechanism of platelet activation. Mouse podoplanin binds to mouse CLEC-2 with low nanomolar affinity, allowing it to capture and retain platelets on immobilized podoplanin at arteriolar shear forces (84).…”

Role of Podoplanin-Positive Cells in Cardiac Fibrosis and Angiogenesis After Ischemia

“…Treatment of animals with an anti-podoplanin neutralizing antibody resulted in the development of smaller thrombi; thus, Payne et al (2017) proposed a novel mechanism of deep vein thrombosis where CLEC-2 and the upregulation of podoplanin trigger the thrombus formation. Platelets form stable aggregates on mouse podoplanin at arterial shear through the CLEC-2 pathway, and podoplanin thus supports platelet capture and activation at arteriolar rates of shear (Lombard et al, 2018). Consistent with the expression of podoplanin in thrombi, this glycoprotein is highly relevant in the calcification of aortic valves (Napankangas et al, 2019) and atherosclerotic lesions (Hatakeyama et al, 2012).…”