on June 12, 2008
Published online before print June 12, 2008, doi: 10.1161/ATVBAHA.108.162511
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Submitted on February 19, 2007
Accepted on June 2, 2008
ECSM2, An Endothelial Specific Filamin A Binding Protein That Mediates Chemotaxis
Laura-Jane Armstrong ;
From the Angiogenesis Laboratory (L.-J.A., S.S., J.M.J.H., R.B.), Cancer Research UK, Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford; Cancer Research UK Angiogenesis Group (V.L.H., S.K., J.F.J.B., J.M.J.H., J.A.L., R.B.), The Institute for Biomedical Research, University of Birmingham Medical School, Edgbaston; and Cancer Research UK (R.P.), The London Research Institute, Lincoln's Inn Fields, London, UK.
* To whom correspondence should be addressed. E-mail: R.Bicknell{at}bham.ac.uk.
Objective—We aimed to characterize the expression and function of a novel transcript that bioinformatics analysis predicted to be endothelial specific, called endothelial-specific molecule-2 (ECSM2).
Methods and Results—A full-length cDNA was isolated and predicted ECSM2 to be a putative 205–amino acid transmembrane protein that bears no homology to any known protein. Quantitative polymerase chain reaction analysis in vitro and in situ hybridization analysis in vivo confirmed ECSM2 expression to be exclusively endothelial, and localization to the plasma membrane was shown. Knockdown of ECSM2 expression in human umbilical vein endothelial cells using siRNA resulted in both reduced chemotaxis and impaired tube formation on matrigel, a solubilized basement membrane, both processes involved in angiogenesis. A yeast 2 hybrid analysis using the ECSM2 intracellular domain identified filamin A, as an interacting protein. This interaction was confirmed by precipitation of filamin-A from endothelial cell lysates by a GST-tagged intracellular domain of ECSM2.
Conclusion—This study is the first to characterize a novel cell surface protein ECSM2 that regulates endothelial chemotaxis and tube formation, and interacts with filamin A. These studies implicate a role for ECSM2 in angiogenesis via modulation of the actin cytoskeleton.
Key words: endothelial genes • transmembrane proteins • filamin • cell signaling • chemotaxis • angiogenesis