title: Arl5b is a Golgi-localised small G protein involved in the regulation of retrograde transport.
abstract: Regulation of membrane transport is controlled by small G proteins, which include members of the Rab and Arf families. Whereas the role of the classic Arf family members are well characterized, many of the Arf-like proteins (Arls) remain poorly defined. Here we show that Arl5a and Arl5b are localised to the trans-Golgi in mammalian cells, and furthermore have identified a role for Arl5b in the regulation of retrograde membrane transport from endosomes to the trans-Golgi network (TGN). The constitutively active Arl5b (Q70L)-GFP mutant was localised efficiently to the Golgi in HeLa cells whereas the dominant-negative Arl5b (T30N)-GFP mutant was dispersed throughout the cytoplasm and resulted in perturbation of the Golgi apparatus. Stable HeLa cells expressing GFP-tagged Arl5b (Q70L) showed an increased rate of endosome-to-Golgi transport of the membrane cargo TGN38 compared with control HeLa cells. Depletion of Arl5b by RNAi resulted in an alteration in the intracellular distribution of mannose-6-phosphate receptor, and significantly reduced the endosome-to-TGN transport of the membrane cargo TGN38 and of Shiga toxin, but had no affect on the anterograde transport of the cargo E-cadherin. Collectively these results suggest that Arl5b is a TGN-localised small G protein that plays a key role in regulating transport along the endosome-TGN pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
authors.forename: Fiona J
authors.initials: FJ
authors.lastname: Houghton
authors.forename: Shayne A
authors.initials: SA
authors.lastname: Bellingham
authors.forename: Andrew F
authors.initials: AF
authors.lastname: Hill
authors.forename: Dorothée
authors.initials: D
authors.lastname: Bourges
authors.forename: Desmond K Y
authors.initials: DK
authors.lastname: Ang
authors.forename: Timothy
authors.initials: T
authors.lastname: Gemetzis
authors.forename: Isabelle
authors.initials: I
authors.lastname: Gasnereau
authors.forename: Paul A
authors.initials: PA
authors.lastname: Gleeson
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D019943:Amino Acid Substitution; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism*; D000077614:Golgi Matrix Proteins; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D050505:Mutant Proteins / Q000378:metabolism; D021381:Protein Transport; D034622:RNA Interference; D017527:Receptor, IGF Type 2 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D022621:Shiga Toxin / Q000378:metabolism
chemical_list: C108705:GORASP1 protein, human; D000077614:Golgi Matrix Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D050505:Mutant Proteins; D017527:Receptor, IGF Type 2; D011993:Recombinant Fusion Proteins; C072237:TGOLN2 protein, human; D049452:Green Fluorescent Proteins; D022621:Shiga Toxin; C477339:ARL5B protein, human; D020727:ADP-Ribosylation Factors; C475879:ARL5A protein, human