Exocyst Complex Component 3-like 2 (EXOC3L2) Associates with the Exocyst Complex and Mediates Directional Migration of Endothelial Cells*

The exocyst is a protein complex that ensures spatial targeting of exocytotic vesicles to the plasma membrane. We present microarray data obtained from differentiating mouse embryonic stem cell cultures that identify an up-regulation of exocyst complex component 3-like 2 (exoc3l2) mRNA in sprouting blood vessels. Vascular expression of exoc3l2 is confirmed by qPCR analysis of different mouse tissues and immunofluorescence analyses of mouse brain sections. We detect an up-regulation of exoc3l2 mRNA synthesis in primary human endothelial cells in response to VEGFA, and this response is enhanced when the cells are grown on a three-dimensional collagen I matrix. Myc-tagged EXOC3L2 co-precipitates with the exocyst protein EXOC4, and immunofluorescence detection of EXOC3L2 shows partial subcellular colocalization with EXOC4 and EXOC7. Finally, we show that exoc3l2 silencing inhibits VEGF receptor 2 phosphorylation and VEGFA-directed migration of cultured endothelial cells.