title: Cooperation of MICAL-L1, syndapin2, and phosphatidic acid in tubular recycling endosome biogenesis.
abstract: Endocytic transport necessitates the generation of membrane tubules and their subsequent fission to transport vesicles for sorting of cargo molecules. The endocytic recycling compartment, an array of tubular and vesicular membranes decorated by the Eps15 homology domain protein, EHD1, is responsible for receptor and lipid recycling to the plasma membrane. It has been proposed that EHD dimers bind and bend membranes, thus generating recycling endosome (RE) tubules. However, recent studies show that molecules interacting with CasL-Like1 (MICAL-L1), a second, recently identified RE tubule marker, recruits EHD1 to preexisting tubules. The mechanisms and events supporting the generation of tubular recycling endosomes were unclear. Here, we propose a mechanism for the biogenesis of RE tubules. We demonstrate that MICAL-L1 and the BAR-domain protein syndapin2 bind to phosphatidic acid, which we identify as a novel lipid component of RE. Our studies demonstrate that direct interactions between these two proteins stabilize their association with membranes, allowing for nucleation of tubules by syndapin2. Indeed, the presence of phosphatidic acid in liposomes enhances the ability of syndapin2 to tubulate membranes in vitro. Overall our results highlight a new role for phosphatidic acid in endocytic recycling and provide new insights into the mechanisms by which tubular REs are generated.
authors.affiliation: Department of Biochemistry and Molecular Biology and Eppley Cancer Center, University of Nebraska Medical Center, Omaha, NE 68198, USA.
authors.forename: Sai Srinivas Panapakkam
authors.initials: SS
authors.lastname: Giridharan
authors.forename: Bishuang
authors.initials: B
authors.lastname: Cai
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vitale
authors.forename: Naava
authors.initials: N
authors.lastname: Naslavsky
authors.forename: Steve
authors.initials: S
authors.lastname: Caplan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D011992:Endosomes / Q000378:metabolism*; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D060588:LIM Domain Proteins / Q000235:genetics / Q000378:metabolism*; D008840:Microfilament Proteins; D006899:Mixed Function Oxygenases; D010712:Phosphatidic Acids / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*; D000096985:Calponins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D003598:Cytoskeletal Proteins; D060588:LIM Domain Proteins; D008840:Microfilament Proteins; D006899:Mixed Function Oxygenases; D010712:Phosphatidic Acids; D033921:Vesicular Transport Proteins; C120700:EHD1 protein, human; C120714:PACSIN2 protein, human; C455272:MICAL1 protein, human; D000096985:Calponins