The Motor Protein Myosin-X Transports VE-Cadherin along Filopodia To Allow the Formation of Early Endothelial Cell-Cell Contacts

Abstract

Vascular endothelium (VE), the monolayer of endothelial cells that lines the vascular tree, undergoes damage at the basis of some vascular diseases. Its integrity is maintained by VE-cadherin, an adhesive receptor localized at cell-cell junctions. Here, we show that VE-cadherin is also located at the tip and along filopodia in sparse or subconfluent endothelial cells. We observed that VE-cadherin navigates along intrafilopodial actin filaments. We found that the actin motor protein myosin-X is colocalized and moves synchronously with filopodial VE-cadherin. Immunoprecipitation and pulldown assays confirmed that myosin-X is directly associated with the VE-cadherin complex. Furthermore, expression of a dominant-negative mutant of myosin-X revealed that myosin-X is required for VE-cadherin export to cell edges and filopodia. These features indicate that myosin-X establishes a link between the actin cytoskeleton and VE-cadherin, thereby allowing VE-cadherin transportation along intrafilopodial actin cables. In conclusion, we propose that VE-cadherin trafficking along filopodia using myosin-X motor protein is a prerequisite for cell-cell junction formation. This mechanism may have functional consequences for endothelium repair in pathological settings.

Supplemental material for this article may be found at http://mcb.asm.org/.

We are indebted to the staff of the maternity ward from Hôpital Nord (Grenoble, France) for kindly collecting umbilical cords. The optical microscopy-cell imaging platform and the Institute Albert Bonniot are acknowledged for granting access to the confocal microscopy facilities and help with image acquisition and analysis. We thank R. E. Cheney for GFP-myoxin-X, R.-M. Mège, and R. Y. Tsien for DSRed cDNA constructs and L. Blanchoin for helpful discussions.

This work was supported by the Ligue Régionale de Savoie Contre le Cancer, the Agence Nationale de la Recherche (ANR, PCV), and the Association pour la Recherche sur le Cancer (grants 4447 and 3775). S.A. was a recipient of fellowships from the Commissariat à l'Energie Atomique (CEA) and the Agence Nationale de Recherche. A.C.-P., S.H., and M.D. are recipients of fellowships from the CEA, the Association de Recherche sur la Polyarthrite, and the Agence Nationale de Recherche (ANR-06-PCV), respectively.