title: The p58-positive pre-golgi intermediates consist of distinct subpopulations of particles that show differential binding of COPI and COPII coats and contain vacuolar H(+)-ATPase.
abstract: We have studied the structural and functional properties of the pre-Golgi intermediate compartment (IC) in normal rat kidney cells using analytical cell fractionation with p58 as the principal marker. The sedimentation profile (sediterm) of p58, obtained by analytical differential centrifugation, revealed in steady-state cells the presence of two main populations of IC elements whose average sedimentation coefficients, s(H)=1150+/-58S ('heavy') and s(L)=158+/-8S ('light'), differed from the s-values obtained for elements of the rough and smooth endoplasmic reticulum. High resolution analysis of these subpopulations in equilibrium density gradients further revealed that the large difference in their s-values was mainly due to particle size. The 'light' particle population contained the bulk of COPI and COPII coats, and redistribution of p58 to these particles was observed in transport-arrested cells, showing that the two types of elements are also compositionally distinct and have functional counterparts in intact cells. Using a specific antibody against the 16 kDa proteolipid subunit of the vacuolar H(+)-ATPase, an enrichment of the V(o )domain of the ATPase was observed in the p58-positive IC elements. Interestingly, these elements could contain both COPI and COPII coats and their density distribution was markedly affected by GTP(&ggr;)S. Together with morphological observations, these results demonstrate that, in addition to clusters of small tubules and vesicles, the IC also consists of large-sized structures and corroborate the proposal that the IC elements contain an active vacuolar H(+)-ATPase.
authors.affiliation: Departments of Biochemistry and Molecular Biology and Anatomy and Cell Biology, University of Bergen, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Ying
authors.forename: T
authors.initials: T
authors.lastname: Flatmark
authors.forename: J
authors.initials: J
authors.lastname: Saraste
mesh_terms: D000818:Animals; D022181:COP-Coated Vesicles / Q000378:metabolism*; D002458:Cell Fractionation; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D020755:Coat Protein Complex I / Q000378:metabolism*; D020756:Coatomer Protein / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins / Q000378:metabolism*; D015388:Organelles / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D021381:Protein Transport; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D051381:Rats; D019284:Thapsigargin / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases
chemical_list: D020755:Coat Protein Complex I; D020756:Coatomer Protein; C501458:Lman1 protein, rat; D037241:Mannose-Binding Lectins; D008565:Membrane Proteins; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D019284:Thapsigargin; D025262:Vacuolar Proton-Translocating ATPases; D006180:Proton-Translocating ATPases