MYADM controls endothelial barrier function through ERM-dependent regulation of ICAM-1 expression

This article was published online ahead of print in MBoC in Press (http://www .molbiolcell.org/cgi/doi/10.1091/mbc.E11-11-0914) on December 21, 2012Supplemental Material can be found at: http://www.molbiolcell.org/content/suppl/2012/12/17/mbc.E11-11-0914v1.DC1.htmlThe endothelium maintains a barrier between blood and tissue that becomes more permeable during inflammation. Membrane rafts are ordered assemblies of cholesterol, glycolipids, and proteins that modulate proinflammatory cell signaling and barrier function. In epithelial cells, the MAL family members MAL, MAL2, and myeloid-associated differentiation marker (MYADM) regulate the function and dynamics of ordered membrane domains. We analyzed the expression of these three proteins in human endothelial cells and found that only MYADM is expressed. MYADM was confined in ordered domains at the plasma membrane, where it partially colocalized with filamentous actin and cell–cell junctions. Small interfering RNA (siRNA)-mediated MYADM knockdown increased permeability, ICAM-1 expression, and leukocyte adhesion, all of which are features of an inflammatory response. Barrier function decrease in MYADM-silenced cells was dependent on ICAM-1 expression. Membrane domains and the underlying actin cytoskeleton can regulate each other and are connected by ezrin, radixin, and moesin (ERM) proteins. In endothelial cells, MYADM knockdown induced ERM activation. Triple-ERM knockdown partially inhibited ICAM-1 increase induced by MYADM siRNA. Importantly, ERM knockdown also reduced ICAM-1 expression in response to the proinflammatory cytokine tumor necrosis factor-α. MYADM therefore regulates the connection between the plasma membrane and the cortical cytoskeleton and so can control the endothelial inflammatory responseThis work was supported by grants SAF2011–22624 (to J.M.), BFU2012–32532 and CSD2009–00016 (to M.A.A.), and BFU2011-22859 (to I.C.) from the Ministerio de Ciencia e Innovación; and grant S2010/BMD-2305 from the Comunidad de Madrid (to I.C.). J.F.A. was the recipient of an EMBO short-term fellowship in A.J.R.’s laborator