Regulation of caveolae mediated endocytosis and endothelial cell permeability by intersectin-2L

This study addresses the possible role of the scaffold protein intersectin-2L, in regulating the function of caveolae as well as endothelial barrier function in endothelial cells (ECs). The analysis of intersectin-2L was driven by its unique GEF DH-PH domain that induces the selective activation of the RhoGTPase Cdc42, and hence promotes actin polymerization.;Expression of DH-PH domain of intersectin-2L in ECs induced activation of Cdc42. Expression of the DH-PH in ECs induced actin polymerization and decreased caveolae-mediated endocytosis. Biochemical analysis showed that ITSN interacted with the Cdc42-N-WASp-Arp2/3 actin polymerization pathway. While expression of the DH-PH region reduced caveolae internalization, there was a concomitant loss of interendothelial junction integrity as evident by the formation of gaps between contiguous ECs. We observed increased transendothelial albumin permeability in the face of decreased caveolae-mediated endocytosis. Intersectin-2L knockdown by siRNA showed dysregulation of the caveolar pathway and disruption of EC monolayer integrity.;Thus, this study uncovers a relationship between the caveolar pathway and junctional paracellular pathway that may be regulated by intersectin-dependent Cdc42 activation and actin polymerization. Such a cross-talk between the two essential endothelial permeability pathways may be an important in regulating lung fluid balance and dysregulation of the cross-talk may contribute to a leaky microvascular barrier.