Tanaka, K.; Chen, M.; Prendergast, A.; Zhuang, Z.; Nasiri, A.; Joshi, D.; Hintzen, J.; Chung, M.; Kumar, A.; Mani, A.; Koleske, A.; Crawford, J.; Nicoli, S.; Schwartz, M. A.

Endothelial cell responses to fluid shear stress from blood flow are crucial for vascular development, function and disease. A complex of PECAM-1, VE-cadherin, VEGF receptors (VEGFRs) and PlexinD1 located at cell-cell junctions mediates many of these events. But available evidence suggests that another mechanosensor upstream of PECAM-1 initiates signaling. Hypothesizing that GPCR and Galpha proteins may serve this role, we performed siRNA screening of Galpha subunits and found that Galphai2 and Galphaq/11 are required for activation of the junctional complex. We then developed a new activation assay, which showed that these G proteins are activated by flow. We next mapped the Galpha residues required for activation and developed an affinity purification method that used this information to identify latrophilin-2 (Lphn-2/ADGRL2) as the upstream GPCR. Latrophilin-2 is required for all PECAM-1 downstream events tested. In both mice and zebrafish, latrophilin-2 is required for flow-dependent angiogenesis and artery remodeling. Furthermore, endothelial specific knockout demonstrates that latrophilin plays a role in flow-dependent artery remodeling. Human genetic data reveal a correlation between the latrophilin-2-encoding Adgrl2 gene and cardiovascular disease. Together, these results define a pathway that connects latrophilin-dependent G protein activation to subsequent endothelial signaling, vascular physiology and disease.