Secretory Cargo Regulates the Turnover of COPII Subunits at Single ER Exit Sites

Forster, Rebecca; Weiß, Matthias; Zimmermann, Timo; Reynaud, Emmanuel G.; Verı́ssimo, Fátima; Stephens, David; Pepperkok, Rainer

doi:10.1016/j.cub.2005.11.076

Cited by 129 publications

(148 citation statements)

References 22 publications

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“…Sec23 overexpression might affect secretion due to its GTPase-activating protein activity (Yoshihisa et al, 1993;Antonny et al, 2001), whereas, although Sec13 labels cytosolic structures in BrightYellow 2 cells in the absence of Golgi cargo, these loci have not yet been equated unequivocally with ERES (Yang et al, 2005). We therefore chose to use Sec24, which is an established ERES marker in plants and other systems (Stephens et al, 2000;Forster et al, 2006;Matheson et al, 2006;Stefano et al, 2006). Moreover, we have demonstrated that Sec24 overexpression does not affect ER export (Fig.…”

Section: Eres Biogenesis Is Cargo Inducedmentioning

confidence: 98%

De Novo Formation of Plant Endoplasmic Reticulum Export Sites Is Membrane Cargo Induced and Signal Mediated

et al. 2007

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The plant endoplasmic reticulum (ER) contains functionally distinct subdomains at which cargo molecules are packed into transport carriers. To study these ER export sites (ERES), we used tobacco (Nicotiana tabacum) leaf epidermis as a model system and tested whether increased cargo dosage leads to their de novo formation. We have followed the subcellular distribution of the known ERES marker based on a yellow fluorescent protein (YFP) fusion of the Sec24 COPII coat component (YFP-Sec24), which, differently from the previously described ERES marker, tobacco Sar1-YFP, is visibly recruited at ERES in both the presence and absence of overexpressed membrane cargo. This allowed us to quantify variation in the ERES number and in the recruitment of Sec24 to ERES upon expression of cargo. We show that increased synthesis of membrane cargo leads to an increase in the number of ERES and induces the recruitment of Sec24 to these ER subdomains. Soluble proteins that are passively secreted were found to leave the ER with no apparent up-regulation of either the ERES number or the COPII marker, showing that bulk flow transport has spare capacity in vivo. However, de novo ERES formation, as well as increased recruitment of Sec24 to ERES, was found to be dependent on the presence of the diacidic ER export motif in the cytosolic domain of the membrane cargo. Our data suggest that the plant ER can adapt to a sudden increase in membrane cargo-stimulated secretory activity by signal-mediated recruitment of COPII machinery onto existing ERES, accompanied by de novo generation of new ERES.

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Section: Eres Biogenesis Is Cargo Inducedmentioning

confidence: 98%

De Novo Formation of Plant Endoplasmic Reticulum Export Sites Is Membrane Cargo Induced and Signal Mediated

et al. 2007

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“…a Golgi-resident glycosylation enzyme, may experience a negative mismatch in the ER after having passed the quality control machinery. It will hence form clusters that can modulate the local turnover rate of COPII proteins [20] to facilitate the formation of a COPII vesicle. Having pinched off, the vesicle eventually arrives at the Golgi apparatus and fuses with the cis-most cisterna.…”

Section: Model For Hydrophobic Mismatch-driven Protein Sorting Betweementioning

confidence: 99%

Hydrophobic mismatch-induced clustering as a primer for protein sorting in the secretory pathway

Schmidt

Weiß

2010

Biophysical Chemistry

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT AbstractSorting of transmembrane proteins is a central task of the secretory pathway. Due to the lack of an organizing mastermind, the decision whether a protein participates in anterograde/retrograde transport or rather stays in its compartment has to be made by a self-organization process on the molecular scale. Minimizing the hydrophobic mismatch between a protein and the surrounding lipid bilayer has been shown to be an important determinant of protein localization. It has remained elusive, however, how mislocalized proteins sense that remote organelles may provide a better lipid environment, i.e. how proteins differentially control their journey along the secretory pathway. Here we show by coarse-grained membrane simulations that proteins partition into the lipid phase with the smallest hydrophobic mismatch on heterogeneous membranes while they cluster and even segregate as homo-oligomers according to their hydrophobic mismatch on a homogeneous bilayer. We propose that protein sorting is facilitated by stabilizing coat proteins at clusters of mislocalized proteins that experience a hydrophobic mismatch.

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“…For COPII, FRAP experiments show that the coatomer exchange rate between the ER membrane and the cytosol is doubled in the absence of cargo. This has been attributed to the increase of k off with decreasing cargo density (15).…”

Section: Discussionmentioning

confidence: 98%

“…It occurs at a rate k off , assumed constant here for simplicity [see supporting information (SI) Appendix for a discussion of this assumption]. This rate can be estimated from FRAP experiments (10,12,14,15), k off ≈ 0.1 − 10 s −1 . Under the assumption of constant protein density in the coat, the dissociation of monomer from the coat is followed by a rapid rearrangement of the coat structure and by a slight shrinkage of the coat; monomer inactivation thus opposes coat expansion.…”

Section: Description Of the Modelmentioning

confidence: 99%

Kinetic regulation of coated vesicle secretion

Forêt

Sens²

2008

Proc. Natl. Acad. Sci. U.S.A.

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The secretion of vesicles for intracellular transport often relies on the aggregation of specialized membrane-bound proteins into a coat able to curve cell membranes. The nucleation and growth of a protein coat is a kinetic process that competes with the energyconsuming turnover of coat components between the membrane and the cytosol. We propose a generic kinetic description of coat assembly and the formation of coated vesicles and discuss its implication to the dynamics of COP vesicles that traffic within the Golgi and with the endoplasmic reticulum. We show that stationary coats of fixed area emerge from the competition between coat growth and the recycling of coat components, in a fashion resembling the treadmilling of cytoskeletal filaments. We further show that the turnover of coat components allows for a highly sensitive switching mechanism between a quiescent and a vesicle producing membrane, upon a slowing down of the exchange kinetics. We claim that the existence of this switching behavior, also triggered by factors, such as the presence of cargo and variation of the membrane mechanical tension, allows for efficient regulation of vesicle secretion. We propose a model, supported by different experimental observations, in which vesiculation of secretory membranes is impaired by the energy-consuming desorption of coat proteins, until the presence of cargo or other factors triggers a dynamical switch into a vesicle producing state.transport vesicle | protein coat | COP vesicles | self-assembly | nonequilibrium phase transition T he plasma membrane and the membrane of cell compartments such as the endoplasmic reticulum (ER) and the Golgi continually produce vesicles for cargo transport. Vesicle formation generally involves specific proteins that aggregate into semirigid coats of dimensions in the 100-nm range, well visible by electronic microscopy (1-3). The process of vesicle formation is now rather well established (4) and is sketched in Fig. 1. First, various cytosolic proteins assemble on the membrane into elementary coat-building units, called monomers. The membrane-bound monomers then polymerize into coat structures that locally bend the membrane and recruit cargo molecules. As the coat expands, the coated membrane invaginates until it forms a nearly spherical vesicle containing cargo (5, 6) that is eventually released from the membrane. The coat components soon disassemble and are ready to participate in the formation of a new vesicle.The coats are classified in three major classes, COPII, COPI, and clathrin. Although they involve distinct proteins, the three types of coat share many common features, from their size and shape to the mechanism by which polymerization, cargo recruitment, and membrane deformation is achieved (4). Our approach is primarily aimed at studying the formation of COPI and COPII vesicles. However, the generality and robustness of its outcome suggest relevance for the more sophisticated clathrin coats as well. The assembly of COPs and clathrin and the fission of COP vesicles can ...

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Secretory Cargo Regulates the Turnover of COPII Subunits at Single ER Exit Sites

Cited by 129 publications

References 22 publications

De Novo Formation of Plant Endoplasmic Reticulum Export Sites Is Membrane Cargo Induced and Signal Mediated

De Novo Formation of Plant Endoplasmic Reticulum Export Sites Is Membrane Cargo Induced and Signal Mediated

Hydrophobic mismatch-induced clustering as a primer for protein sorting in the secretory pathway

Kinetic regulation of coated vesicle secretion

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