Myoferlin is critical for endocytosis in endothelial cells

1 The James Hogg iCAPTURE Centre for Cardiovascular and Pulmonary Research, Department of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, St. Paul's Hospital, Vancouver, British Columbia, Canada; and 2 Department of Pharmacology and Vascular Biology and Therapeutics Program and 3 Obstetrics and Gynecology, Yale University School of Medicine, New Haven, Connecticut Submitted 3 October 2008 ; accepted in final form 7 May 2009 Myoferlin is a member of the ferlin family of proteins that promotes endomembrane fusion with the plasma membrane in muscle cells and endothelial cells. In addition, myoferlin is necessary for the surface expression of vascular endothelial growth factor receptor 2 through the formation of a protein complex with dynamin-2 (Dyn-2). Since Dyn-2 is necessary for the fission of endocytic vesicles from the plasma membrane, we tested the hypothesis that myoferlin may regulates aspects of receptor-dependent endocytosis. Here we show that myoferlin gene silencing decreases both clathrin and caveolae/raft-dependent endocytosis, whereas ectopic myoferlin expression in COS-7 cells increases endocytosis by up to 125%. Interestingly, we have observed that inhibition of Dyn-2 activity or caveolin-1 (Cav-1) expression impairs endocytosis as well as membrane resealing after injury, indicating that Dyn-2 and Cav-1 also participate in both membrane fission and fusion processes. Mechanistically, myoferlin partially colocalizes with Dyn-2 and Cav-1 and forms a protein complex with Cav-1 solubilized from tissue extracts. Together, these data describe a new role for myoferlin in receptor-dependent endocytosis and an overlapping role for myoferlin-Dyn-2-Cav-1 protein complexes in membrane fusion and fission events. signaling; caveolin Address for reprint requests and other correspondence: W. C. Sessa, Dept. of Pharmacology, Yale University School of Medicine, New Haven, CT 06536 (e-mail: william.sessa{at}yale.edu ).