Rab18 and Rab43 have key roles in ER-Golgi trafficking

J Cell Sci. 2008 Aug 15;121(Pt 16):2768-81. doi: 10.1242/jcs.021808. Epub 2008 Jul 29.

Abstract

Rabs and Arfs/Arls are Ras-related small GTPases of particular relevance to membrane trafficking. It is thought that these proteins regulate specific pathways through interactions with coat, motor, tether and SNARE proteins. We screened a comprehensive list of Arf/Arl/Rab proteins, previously identified on purified Golgi membranes by a proteomics approach (37 in total), for Golgi or intra-Golgi localization, dominant-negative and overexpression phenotypes. Further analysis of two of these proteins, Rab18 and Rab43, strongly indicated roles in ER-Golgi trafficking. Rab43-T32N redistributed Golgi elements to ER exit sites without blocking trafficking of the secretory marker VSVG-GFP from ER to cell surface. Wild-type Rab43 redistributes the p150(Glued) subunit of dynactin, consistent with a specific role in regulating association of pre-Golgi intermediates with microtubules. Overexpression of wild-type GFP-Rab18 or incubation with any of three siRNAs directed against Rab18 severely disrupts the Golgi complex and reduces secretion of VSVG. Rab18 mutants specifically enhance retrograde Golgi-ER transport of the COPI-independent cargo beta-1,4-galactosyltransferase (Galtase)-YFP but not the COPI-dependent cargo p58-YFP from the Golgi to ER in a photobleach assay. Rab18-S22N also potentiated brefeldin-A-induced ER-Golgi fusion. This study is the first comprehensive application of large-scale proteomics to the cell biology of small GTPases of the secretory pathway.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Cells, Cultured
  • Chlorocebus aethiops
  • Endoplasmic Reticulum / metabolism*
  • Golgi Apparatus / metabolism*
  • Green Fluorescent Proteins / metabolism
  • HeLa Cells
  • Humans
  • Models, Biological
  • Mutant Proteins / physiology
  • Protein Transport / physiology
  • Rats
  • Recombinant Fusion Proteins / metabolism
  • Vero Cells
  • rab GTP-Binding Proteins / physiology*

Substances

  • Mutant Proteins
  • RAB18 protein, human
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • rab11 protein
  • rab GTP-Binding Proteins