Scales, S. J., Pepperkok, R. & Kreis, T. E. Visualization of ER-to-Golgi transport in living cells reveals a sequential mode of action for COPII and COPI. Cell 90, 1137-1148

Department of Cell Biology, University of Geneva Sciences III, Switzerland.
Cell (Impact Factor: 32.24). 10/1997; 90(6):1137-48. DOI: 10.1016/S0092-8674(00)80379-7
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Exocytic transport from the endoplasmic reticulum (ER) to the Golgi complex has been visualized in living cells using a chimera of the temperature-sensitive glycoprotein of vesicular stomatitis virus and green fluorescent protein (ts-G-GFP[ct]). Upon shifting to permissive temperature, ts-G-GFP(ct) concentrates into COPII-positive structures close to the ER, which then build up to form an intermediate compartment or transport complex, containing ERGIC-53 and the KDEL receptor, where COPII is replaced by COPI. These structures appear heterogenous and move in a microtubule-dependent manner toward the Golgi complex. Our results suggest a sequential mode of COPII and COPI action and indicate that the transport complexes are ER-to-Golgi transport intermediates from which COPI may be involved in recycling material to the ER.

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Available from: Suzie J Scales, Apr 27, 2015
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    • "r results agree with the notion that EB1 complexes formed with other +TIPs mediate the attachment of microtubule tips to subcellular targets . Efficient ER - to - Golgi trafficking requires microtubules on which secretory cargos move towards the Golgi in association with the minus - end - directed motor dynein – dynactin ( Presley et al . , 1997 ; Scales et al . , 1997 ; Watson et al . , 2005 ) . Our results showed that MMG8 is required for microtubule - dependent ER - to - Golgi trafficking ( Fig . 2C , E ) . Interestingly , this function of MMG8 required its binding to EB1 or EB3 and thus the association of EB1 or EB3 with the Golgi ( Fig . 8 ) . We envision that the EB1 / EB3 - mediated attachment "
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    ABSTRACT: The Golgi apparatus of mammalian cells is known to be a major microtubule-organizing site that requires microtubules for its organization and protein trafficking. However, the mechanisms underlying the microtubule organization of the Golgi apparatus remain obscure. We used immunoprecipitation coupled with mass spectrometry to identify a widely expressed isoform of the poorly characterized muscle protein myomegalin. This novel isoform, myomegalin variant 8 (MMG8), localized predominantly to cis-Golgi networks by interacting with AKAP450, and this interaction with AKAP450 was required for the stability of both proteins. Disrupting MMG8 expression affected ER-to-Golgi trafficking and caused Golgi fragmentation. Furthermore, MMG8 associated with γ-tubulin complexes and with the microtubule plus-end tracking protein EB1, and MMG8 was required for the Golgi localization of these 2 molecules. On the Golgi, γ-tubulin complexes mediated microtubule nucleation, whereas EB1 functioned in ER-to-Golgi trafficking. These results indicate that MMG8 participates in Golgi microtubule organization and thereby plays a crucial role in the organization and function of the Golgi apparatus.
    Journal of Cell Science 09/2014; 127(22). DOI:10.1242/jcs.155408 · 5.43 Impact Factor
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    • "The cis-Golgi is a receiver of anterograde vesicles traveling from the ER, whereas the trans-Golgi is a departure site for vesicles traveling to endocytic compartments [1]. The ER resident proteins that escape to the Golgi and Golgi proteins cycle back to the ER via the retrograde pathway [2] [3] [4] [5] [6] [7] [8] [9]. Soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) [10] play a fundamental role in membrane fusion and have a polarized, gradient-like distribution in the Golgi. "
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    ABSTRACT: Two distinct sets of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) catalyze membrane fusion in the cis-Golgi and trans-Golgi. The mechanism that controls Golgi localization of SNAREs remains largely unknown. Here we tested three potential mechanisms, including vesicle recycling between the Golgi and the endoplasmic reticulum, partitioning in Golgi lipid microdomains, and selective intra-Golgi retention. Recycling rates showed a linear relationship with intra-Golgi mobility of SNAREs. The cis-Golgi SNAREs had higher mobility than intra-Golgi SNAREs, whereas vesicle SNAREs had higher mobility than target membrane SNAREs. The differences in SNARE mobility were not due to preferential partitioning into detergent-resistant membrane microdomains. We propose that intra-Golgi retention precludes entropy-driven redistribution of SNAREs to the endoplasmic reticulum and endocytic compartments.
    FEBS letters 06/2013; 587(15). DOI:10.1016/j.febslet.2013.06.004 · 3.17 Impact Factor
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    • "In the early secretory pathway, ERGIC is the first place where this process occurs. Here, the presence of COPI coats ensure the recycling of proteins to the ER while anterograde cargo is separated and concentrated (Scales et al., 1997; Klumperman et al., 1998; Martínez-Menárguez et al., 1999; Shima et al., 1999; Stephens et al., 2000). The function of the COPI coats in the Golgi-to-ER retrograde transport of soluble and membrane proteins has been convincingly demonstrated (Letourneur et al., 1994). "
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    ABSTRACT: In neuroendocrine cells, prohormones move from the endoplasmic reticulum to the Golgi complex (GC), where they are sorted and packed into secretory granules. The GC is considered the central station of the secretory pathway of proteins and lipids en route to their final destination. In most mammalian cells, it is formed by several stacks of cisternae connected by tubules, forming a continuous ribbon. This organelle shows an extraordinary structural and functional complexity, which is exacerbated by the fact that its architecture is cell type specific and also tuned by the functional status of the cell. It is, indeed, one the most beautiful cellular organelles and, for that reason, perhaps the most extensively photographed by electron microscopists. In recent decades, an exhaustive dissection of the molecular machinery involved in membrane traffic and other Golgi functions has been carried out. Concomitantly, detailed morphological studies have been performed, including 3D analysis by electron tomography, and the precise location of key proteins has been identified by immunoelectron microscopy. Despite all this effort, some basic aspects of Golgi functioning remain unsolved. For instance, the mode of intra-Golgi transport is not known, and two opposing theories (vesicular transport and cisternal maturation models) have polarized the field for many years. Neither of these theories explains all the experimental data so that new theories and combinations thereof have recently been proposed. Moreover, the specific role of the small vesicles and tubules which surround the stacks needs to be clarified. In this review, we summarize our current knowledge of the Golgi architecture in relation with its function and the mechanisms of intra-Golgi transport. Within the same framework, the characteristics of the GC of neuroendocrine cells are analyzed.
    Frontiers in Endocrinology 03/2013; 4:41. DOI:10.3389/fendo.2013.00041
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