title: TBC1D9B functions as a GTPase-activating protein for Rab11a in polarized MDCK cells.
abstract: Rab11a is a key modulator of vesicular trafficking processes, but there is limited information about the guanine nucleotide-exchange factors and GTPase-activating proteins (GAPs) that regulate its GTP-GDP cycle. We observed that in the presence of Mg(2+) (2.5 mM), TBC1D9B interacted via its Tre2-Bub2-Cdc16 (TBC) domain with Rab11a, Rab11b, and Rab4a in a nucleotide-dependent manner. However, only Rab11a was a substrate for TBC1D9B-stimulated GTP hydrolysis. At limiting Mg(2+) concentrations (<0.5 mM), Rab8a was an additional substrate for this GAP. In polarized Madin-Darby canine kidney cells, endogenous TBC1D9B colocalized with Rab11a-positive recycling endosomes but less so with EEA1-positive early endosomes, transferrin-positive recycling endosomes, or late endosomes. Overexpression of TBC1D9B, but not an inactive mutant, decreased the rate of basolateral-to-apical IgA transcytosis--a Rab11a-dependent pathway--and shRNA-mediated depletion of TBC1D9B increased the rate of this process. In contrast, TBC1D9B had no effect on two Rab11a-independent pathways--basolateral recycling of the transferrin receptor or degradation of the epidermal growth factor receptor. Finally, expression of TBC1D9B decreased the amount of active Rab11a in the cell and concomitantly disrupted the interaction between Rab11a and its effector, Sec15A. We conclude that TBC1D9B is a Rab11a GAP that regulates basolateral-to-apical transcytosis in polarized MDCK cells.
authors.affiliation: Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Luciana I
authors.initials: LI
authors.lastname: Gallo
authors.affiliation: Pathology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Yong
authors.initials: Y
authors.lastname: Liao
authors.affiliation: Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Wily G
authors.initials: WG
authors.lastname: Ruiz
authors.affiliation: Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Dennis R
authors.initials: DR
authors.lastname: Clayton
authors.affiliation: Pathology, University of Pittsburgh, Pittsburgh, PA 15261 Department of Pathology and Laboratory Medicine, Indiana University, Indianapolis, IN 46202.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Neurobiology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Yong-Jian
authors.initials: YJ
authors.lastname: Liu
authors.affiliation: Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Yu
authors.initials: Y
authors.lastname: Jiang
authors.affiliation: Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan.
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Departments of Medicine, University of Pittsburgh, Pittsburgh, PA 15261 Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261 gla6@pitt.edu xmyin@iupui.edu.
authors.forename: Gerard
authors.initials: G
authors.lastname: Apodaca
authors.affiliation: Pathology, University of Pittsburgh, Pittsburgh, PA 15261 Department of Pathology and Laboratory Medicine, Indiana University, Indianapolis, IN 46202.
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Yin
mesh_terms: D000818:Animals; D016764:Cell Polarity; D004285:Dogs; D004705:Endocytosis; D011992:Endosomes / Q000235:genetics* / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D020691:rab GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D000099193:rab11 GTP-Binding Proteins
chemical_list: D020690:GTPase-Activating Proteins; D020691:rab GTP-Binding Proteins; D000099193:rab11 GTP-Binding Proteins