Assembly of a mechanosensitive complex is required to initiate sprouting angiogenesis

Abstract

Endothelial cells (ECs) must respond rapidly to a variety of extracellular cues to initiate sprouting events. We undertook the current study to better understand how mechanical forces (shear stress) combine with biochemical cues to promote sprout outgrowth in a defined 3D model of EC invasion, because while the effects of shear stress have been widely studied in atherosclerosis, the molecular events directed by mechanical forces in angiogenic sprouting are incompletely understood. We initially focused on the known mechanosensitive protein Filamin A, which has been implicated in barrier regulation and vascular development. We found that Filamin A is required for EC sprouting in 3D and localizes to junctions with EC activation. Filamin A formed a complex with vascular endothelial (VE)‐cadherin and platelet endothelial cell adhesion molecule‐1 (PECAM‐1), two known members of mechanosensitive complex, following activation with shear stress and pro‐angiogenic factors. Silencing of Filamin A also disrupted the VE‐cadherin and PECAM‐1 complex, which correlates with decreased sprouting. Filamin A co‐localized with SHP2, a phosphatase previously implicated in barrier formation, following EC activation. SHP2 complexed with junctional molecules Filamin A, VE‐cadherin, and PECAM‐1, and complex formation between SHP2, VE‐cadherin, and PECAM‐1 was lost with Filamin A knockdown. In addition, in the absence of Filamin A expression, SHP2 failed to localize to endothelial junctions. Further, SHP2 silencing significantly reduced sprouting, and defects in sprouting were rescued by delivery of wild‐type SHP2. Altogether these data suggest that Filamin A recruits SHP2 to reinforce a transmembrane complex containing VE‐cadherin and PECAM‐1 that is needed to initiate EC sprouting. These data show for the first time that the formation of this mechanosensitive complex containing VE‐cadherin, PECAM‐1, Filamin A, and SHP2 is needed for successful sprout initiation.Support or Funding InformationWork supported by NIH RO1 HL095786, the Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, and AHA Grant‐in‐Aid, Southwest Affiliate.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.