title: Rab-regulated interaction of early endosomes with lipid droplets.
abstract: Recent studies indicate that lipid droplets isolated from a variety of different cells are rich in proteins known to regulate membrane traffic. Among these proteins are multiple Rab GTPases. Rabs are GTP switches that regulate intracellular membrane traffic through an ability to control membrane-membrane docking as well as vesicle motility. Here we present evidence that the multiple Rabs associated with droplets have a function in regulating membrane traffic. Droplet Rabs are removed by Rab GDP-dissociation inhibitor (RabGDI) in a GDP-dependent reaction, and are recruited to Rab-depleted droplets from cytosol in a GTP-dependent reaction. Rabs also control the recruitment of the early endosome (EE) marker EEA1 from cytosol. We use an in vitro reconstitution assay to show that transferrin receptor positive EEs bind to the droplet in a GTP/Rab-dependent reaction that appears not to lead to membrane fusion. This docking reaction is insensitive to ATP(gamma s) but is blocked by ATP. Finally, we show that when GTP bound active or GDP bound inactive Rab5 is targeted to the droplet, the active form recruits EEA1. We conclude that the Rabs associated with droplets may be capable of regulating the transient interaction of specific membrane systems, probably to transport lipids between membrane compartments.
authors: Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA.
authors: Pingsheng
authors: P
authors: Liu
authors: René
authors: R
authors: Bartz
authors: John K
authors: JK
authors: Zehmer
authors: Yun-shu
authors: YS
authors: Ying
authors: Meifang
authors: M
authors: Zhu
authors: Ginette
authors: G
authors: Serrero
authors: Richard G W
authors: RG
authors: Anderson
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D011992:Endosomes / Q000378:metabolism*; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008055:Lipids / Q000494:pharmacology*; D033921:Vesicular Transport Proteins / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000378:metabolism*
chemical_list: C086796:GDP dissociation inhibitor 1; D020730:Guanine Nucleotide Dissociation Inhibitors; D008055:Lipids; D033921:Vesicular Transport Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020691:rab GTP-Binding Proteins