title: Slp2-a controls renal epithelial cell size through regulation of Rap-ezrin signaling independently of Rab27.
abstract: Synaptotagmin-like protein 2 (Slp2-a/Sytl2) is a Rab27 effector protein that regulates transport of Rab27-bearing vesicles and organelles through its N-terminal Rab27-binding domain and a phospholipid-binding C2A domain. Here we demonstrate a Rab27-independent function of Slp2-a in the control of renal cell size through a previously uncharacterized C2B domain. We found that by recruiting Rap1 GAPs to the plasma membrane of MDCK II cells through the C2B domain, Slp2-a inactivates Rap signaling and modulates the size of the cells. Functional ablation of Slp2-a resulted in an increase in the size of MDCK II cells. Drosophila Slp Bitesize was found to compensate for the function of Slp2-a in MDCK II cells, thereby indicating that the mechanism of the cell size control by Slp proteins has been evolutionarily conserved. Interestingly, blockade of the activity of ezrin, a downstream target of Rap, with the glucosylceramide synthase inhibitor, miglustat, effectively inhibited cell spreading of Slp2-a-knockdown cells. We also discovered aberrant expression of Slp2-a and increased activity of ezrin in pcy (Nphp3(pcy)) mice, a model of polycystic kidney disease that is characterized by renal cell spreading. Our findings indicate that Slp2-a controls renal cell size through regulation of Rap-ezrin signaling independently of Rab27.
authors.affiliation: Laboratory of Membrane Trafficking Mechanisms, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aobayama, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Yasuda
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D048429:Cell Size; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000075745:rab27 GTP-Binding Proteins; D000099149:Ezrin
chemical_list: D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D020691:rab GTP-Binding Proteins; D000075745:rab27 GTP-Binding Proteins; D000099149:Ezrin; C424134:Sytl2 protein, mouse; C512962:Rab27a protein, mouse
keywords: Cell size; Ezrin; Polycystic kidney disease; Rap1GAP; Slp2-a