Publications (47) View all
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Article: Take the 'A' train: on fast tracks to the cell surface.
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ABSTRACT: Cholesterol, certain lipids, membrane-bound and soluble proteins, as well as viruses that are synthesized in the endoplasmic reticulum (ER), reach the plasma membrane (PM) via non-classical pathway(s) that remain poorly understood. Typical for this transport is (i) its insensitivity to brefeldin A (BFA), which dissociates selected coat complexes from membranes, resulting in the disassembly of the Golgi apparatus; (ii) its rapid kinetics as compared to the classical secretory pathway; and (iii) its role in the trafficking of lipid raft components. Based on results showing that the intermediate compartment (IC) at the ER-Golgi boundary constitutes a stable tubular network that maintains its dynamics in the presence of BFA, we propose that two bidirectional Golgi-bypass pathways to the PM exist, a direct route from early IC elements, and another, reminiscent of the yeast secretory pathway, from late IC elements via the endosomal system. These pathways have implications for the organization of the secretory processes in different cell types.Cellular and Molecular Life Sciences CMLS 09/2008; 65(18):2859-74. · 6.57 Impact Factor -
Article: 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.
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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.Journal of Cell Science 10/2000; 113 ( Pt 20):3623-38. · 6.11 Impact Factor -
Article: Retrograde transport from the pre-Golgi intermediate compartment and the Golgi complex is affected by the vacuolar H+-ATPase inhibitor bafilomycin A1.
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ABSTRACT: The effect of the vacuolar H+-ATPase inhibitor bafilomycin A1 (Baf A1) on the localization of pre-Golgi intermediate compartment (IC) and Golgi marker proteins was used to study the role of acidification in the function of early secretory compartments. Baf A1 inhibited both brefeldin A- and nocodazole-induced retrograde transport of Golgi proteins to the endoplasmic reticulum (ER), whereas anterograde ER-to-Golgi transport remained largely unaffected. Furthermore, p58/ERGIC-53, which normally cycles between the ER, IC, and cis-Golgi, was arrested in pre-Golgi tubules and vacuoles, and the number of p58-positive approximately 80-nm Golgi (coatomer protein I) vesicles was reduced, suggesting that the drug inhibits the retrieval of the protein from post-ER compartments. In parallel, redistribution of beta-coatomer protein from the Golgi to peripheral pre-Golgi structures took place. The small GTPase rab1p was detected in short pre-Golgi tubules in control cells and was efficiently recruited to the tubules accumulating in the presence of Baf A1. In contrast, these tubules showed no enrichment of newly synthesized, anterogradely transported proteins, indicating that they participate in retrograde transport. These results suggest that the pre-Golgi structures contain an active H+-ATPase that regulates retrograde transport at the ER-Golgi boundary. Interestingly, although Baf A1 had distinct effects on peripheral pre-Golgi structures, only more central, p58-containing elements accumulated detectable amounts of 3-(2, 4-dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP), a marker for acidic compartments, raising the possibility that the lumenal pH of the pre-Golgi structures gradually changes in parallel with their translocation to the Golgi region.Molecular Biology of the Cell 01/1999; 9(12):3561-78. · 4.94 Impact Factor -
Article: Protein segregation in peripheral 15 degrees C intermediates in response to caffeine treatment.
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ABSTRACT: Previous studies have shown that caffeine treatment at 20 degrees C causes the intermediate compartment protein p58 to redistribute from the Golgi region without affecting the localization of the Golgi stack protein mannosidase II (J. Jäntti, E. Kuismanen, J. Cell Biol. 120, 1321-1335 (1993). Here we have dissected further the effect of caffeine on transport of Golgi and intermediate compartment proteins from the cell periphery to the perinuclear Golgi region. To accumulate proteins in the peripheral membranes, BHK-21 cells were treated with brefeldin A to redistribute marker proteins towards the ER. Following BFA wash-out and subsequent incubation at 15 degrees C, p58, the coat protein beta-COP, and Man II were all localized in the peripheral 15 degrees C-intermediates. When the cells were shifted from 15 degrees C to 20 degrees C all the proteins were recentralized to the Golgi region. However, if the temperature shift was carried out in the presence of 10 mM caffeine, p58 and beta-COP maintained their peripheral localization, whereas Man II was transported to the Golgi region. The results indicate that caffeine at 20 degrees C does not block the centralization of Man II from peripheral sites to the central Golgi region. Therefore, its effect on ER to Golgi transport appears to be manifested specifically at ER exit. Furthermore, our results indicate that segregation of intermediate compartment and Golgi stack proteins can occur at the level of the peripheral 15 degrees C-intermediates. Immunoelectron microscopic localization of p58 and Man II showed that these peripheral intermediates consisted of tubules and small stacks of cisternae. Within the tubular intermediates both p58 and Man II appeared to segregate to membrane subdomains. Finally, examination of serial and thick sections support the idea that the stacked structures can be generated from tubular intermediates.European Journal of Cell Biology 11/1997; 74(2):150-64. · 2.81 Impact Factor -
Article: Endoplasmic reticulum to Golgi trafficking in multinucleated skeletal muscle fibers.
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ABSTRACT: The organization of membrane trafficking between endoplasmic reticulum and Golgi within multinucleated muscle fibers was analyzed. We found that markers for the compartment involved in endoplasmic reticulum to Golgi trafficking exhibited perinuclear as well as interfibrillar localization. Furthermore, these markers showed prominent colocalization with microtubules. To analyze membrane trafficking, we followed the temperature-controlled transport of the G protein of the mutant vesicular stomatitis virus, tsO45, in isolated myofibers. Perinuclear and cross-striated staining were seen at 39 degrees C, while at 15 degrees C a diffuse staining component appeared along a subset of interfibrillar microtubules. At 20 degrees C, bright Golgi spots were seen to be associated with microtubules that appeared as circumnuclear rings and longitudinal bundles. Beneath the motor end plate, however, the organization of the Golgi elements and microtubules was found to be distinctive. Retrograde trafficking induced by brefeldin A resulted in the disappearance of the Golgi spots throughout the myofibers and the appearance of staining along microtubules. Thus, interfibrillar membranes seem to be active in protein export, and trafficking between endoplasmic reticulum and Golgi elements occurred throughout the myofibers. The results suggest that microtubules served as tracks for the two-way trafficking between the endoplasmic reticulum and the Golgi compartment.Experimental Cell Research 09/1997; 234(2):452-64. · 3.58 Impact Factor
