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Blood, 1 January 2009, Vol. 113, No. 1, pp. 244-253. Prepublished online as a Blood First Edition Paper on September 29, 2008; DOI 10.1182/blood-2008-04-153874.
VASCULAR BIOLOGY The Amot/Patj/Syx signaling complex spatially controls RhoA GTPase activity in migrating endothelial cells1 Department of Oncology and Pathology, Cancer Centrum Karolinska, Karolinska Institutet, Karolinska Hospital, Stockholm, Sweden; 2 Inserm, U599, Centre de Recherche en Cancérologie de Marseille, Department of Molecular Pharmacology, Marseille, France; Institut Paoli-Calmettes, Marseille, France; Université de la Méditerranée, Marseille, France; 3 Angiogenesis Research Center and Section of Cardiology, Department of Medicine, Dartmouth Medical School, Lebanon, NH; 4 University Hospital Muenster, Department of Internal Medicine D, Division of Molecular Nephrology, Muenster, Germany; and 5 Division of Matrix Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden Controlled regulation of Rho GTPase activity is an essential component mediating growth factor–stimulated migration. We have previously shown that angiomotin (Amot), a membrane-associated scaffold protein, plays a critical role during vascular patterning and endothelial migration during embryogenesis. However, the signaling pathways by which Amot controls directional migration are not known. Here we have used peptide pull-down and yeast 2-hybrid (Y2H) screening to identify proteins that interact with the C-terminal PDZ-binding motifs of Amot and its related proteins AmotL1 and 2. We report that Amot and its related proteins bind to the RhoA GTPase exchange factor (RhoGEF) protein Syx. We show that Amot forms a ternary complex together with Patj (or its paralogue Mupp1) and Syx. Using FRET analysis, we provide evidence that Amot controls targeting of RhoA activity to lamellipodia in vitro. We also report that, similar to Amot, morpholino knockdown of Syx in zebrafish results in inhibition of migration of intersegmental arteries. Taken together, our results indicate that the directional migration of capillaries in the embryo is governed by the Amot:Patj/Mupp1:Syx signaling that controls local GTPase activity.
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