Coordination of Golgin Tethering and SNARE Assembly

Diao, Aipo; Frost, Laura S.; Morohashi, Yuichi; Lowe, Martin

doi:10.1074/jbc.m708401200

Cited by 68 publications

(36 citation statements)

References 45 publications

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“…Of note, depletion of GM130 did not disrupt Golgi integrity or membrane trafficking, which is in agreement with others 28, 29 . Different findings by others 30–32 can be attributed to the use of different cell lines, different siRNA concentrations and transfection reagents. We interpret our data to mean that the Golgi might supply the leading edge of migrating cells with active Cdc42.…”

Section: Discussionmentioning

confidence: 88%

Spatial control of Cdc42 signalling by a GM130–RasGRF complex regulates polarity and tumorigenesis

et al. 2014

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The small GTPase Cdc42 is a key regulator of polarity, but little is known in mammals about its spatial regulation and the relevance of spatial Cdc42 pools for polarity. Here, we report the identification of a GM130-RasGRF complex as a regulator of Cdc42 at the Golgi. Silencing GM130 results in RasGRF-dependent inhibition of the Golgi pool of Cdc42, but does not affect Cdc42 at the cell surface. Furthermore, active Cdc42 at the Golgi is important to sustain asymmetric front-rear Cdc42-GTP distribution in directionally-migrating cells. Concurrently to Cdc42 inhibition, silencing GM130 also results in RasGRF-dependent Ras-ERK pathway activation. Moreover, depletion of GM130 is sufficient to induce E-cadherin down-regulation, indicative of a loss in cell polarity and epithelial identity. Accordingly, GM130 expression is frequently lost in colorectal and breast cancer patients. These findings establish a previously unrecognized role for the GM130-RasGRF-Cdc42 connection in regulating polarity and tumourigenesis.

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Section: Discussionmentioning

confidence: 88%

Spatial control of Cdc42 signalling by a GM130–RasGRF complex regulates polarity and tumorigenesis

et al. 2014

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“…The phosphorylation of giantin under mitotic conditions has been shown both in vitro and in vivo (45). In search of giantin-specific kinase, we focused on Polo-like kinase 3 (Plk3) because it is widely present in the Golgi and associated with giantin (46).…”

Section: Resultsmentioning

confidence: 99%

Restoration of Compact Golgi Morphology in Advanced Prostate Cancer Enhances Susceptibility to Galectin-1–Induced Apoptosis by Modifying Mucin O-Glycan Synthesis

Petrosyan

Holzapfel

Muirhead

et al. 2014

Molecular Cancer Research

114

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Prostate cancer progression is associated with up-regulation of sialyl-T antigen produced by β-galactoside α-2,3-sialyltransferase-1 (ST3Gal1) but not with core 2-associated polylactosamine despite expression of core 2 N-acetylglucosaminyltransferase-L (C2GnT-L/GCNT1). This property allows androgen-refractory prostate cancer cells to evade galectin-1 (LGALS1)-induced apoptosis, but the mechanism is not known. We have recently reported that Golgi targeting of glycosyltransferases is mediated by golgins: giantin (GOLGB1) for C2GnT-M (GCNT3) and GM130 (GOLGA2)-GRASP65 (GORASP1) or GM130-giantin for core 1 synthase. Here, we show that for Golgi targeting, C2GnT-L also uses giantin exclusively while ST3Gal1 employs either giantin or GM130-GRASP65. In addition, the compact Golgi morphology is detected in both androgen-sensitive prostate cancer and normal prostate cells, but fragmented Golgi and mislocalization of C2GnT-L are found in androgen-refractory cells as well as primary prostate tumors (Gleason grade 2–4). Furthermore, failure of giantin monomers to be phosphorylated and dimerized prevents Golgi from forming compact morphology and C2GnT-L from targeting the Golgi. On the other hand, ST3Gal1 reaches the Golgi by an alternate site, GM130-GRASP65. Interestingly, inhibition or knockdown of non-muscle myosin IIA (MYH9) motor protein frees up Rab6a GTPase to promote phosphorylation of giantin by polo-like kinase 3 (PLK3), which is followed by dimerization of giantin assisted by protein disulfide isomerase A3 (PDIA3), and restoration of compact Golgi morphology and targeting of C2GnT-L. Finally, the Golgi relocation of C2GnT-L in androgen-refractory cells results in their increased susceptibility to galectin-1-induced apoptosis by replacing sialyl-T antigen with polylactosamine.

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“…These two contact points, membrane binding by the myristic acid and GM130 binding, orient the GRASP65 homotypic binding interface in such a way that it can interact in trans but not in cis. GRASP65 self-association in trans is then followed by fusion, presumably mediated by a SNARE complex involving syntaxin-5, which interacts with GM130 (18). The resulting membrane rearrangement might then cause GRASP65 disassembly because it would impart a torque on the complex due to the orientation conferred by the dual anchors; that is, membrane rearrangement would force an unfavorable cis configuration leading to partner dissociation.…”

Section: Discussionmentioning

confidence: 99%

Dual Anchoring of the GRASP Membrane Tether Promotes trans Pairing

Bachert

Linstedt

2010

Journal of Biological Chemistry

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GRASP proteins share an N-terminal GRASP domain and mediate homotypic tethering of Golgi cisternae to form extended Golgi ribbons. The golgin GM130 is thought to bind the C-terminal side of the GRASP domain to recruit GRASP65 onto the Golgi whereas stable membrane association appears to also depend on anchoring of the N terminus by myristoylation. Here, we examine the nature of the GM130/GRASP65 interaction and test whether the dual membrane contacts of the GRASP domain have a role in tethering beyond membrane recruitment. GM130 was found to contain a C-terminal PDZ ligand that binds the putative groove of the second PDZ-like domain in GRASP65. To test tethering activity independent of targeting, we took advantage of a tethering assay carried out on the mitochondrial membrane in which the GRASP membrane attachment points were individually or simultaneously substituted with mitochondrially targeted transmembrane sequences. N-terminally anchored constructs tethered only if the C terminus was also anchored; and likewise, C-terminally anchored constructs tethered only if the N terminus was anchored. One explanation for the role of this dual anchoring is that it orients the GRASP domain to prevent cis interactions within the same membrane thereby favoring trans interactions between adjacent membranes. Indeed, singly anchored GRASP constructs, although nonfunctional in tethering, interacted with one another and also bound and inhibited dually anchored constructs. This work thus elucidates the GM130/GRASP65 interaction and supports a novel orientation-based model of membrane tether regulation in which dual membrane contact orients the tethering interaction interface to favor trans over cis interactions.The tethering of membranes prior to SNARE 2 -mediated fusion is accomplished by factors present in each membrane that interact to form a bridge thereby increasing the fidelity and efficiency of membrane fusion (1). The interaction can be heterotypic, such as vesicle fusion with a target organelle, or homotypic, as is the case when identical membranes fuse. In heterotypic tethering, each membrane contributes a distinct partner to form a heteromeric-tethering complex. After fusion, the complex is presumably disassembled, and one partner, if still membrane-associated, is sorted from the other in the plane of the membrane and packaged into vesicles for recycling. Disassembly and sorting are needed because interactions in cis between the tether partners would prevent further rounds of tethering just as cis SNARE interactions block membrane fusion (2). In homotypic tethering, each membrane may contribute distinct partners that bind to one another or identical partners that self-associate but because the membranes are identical each has a full complement of the tethering components, and this state is also maintained after fusion. Thus, for homotypic tethering, mechanisms other than sorting and recycling are needed to prevent cis complex formation.In higher eukaryotes, the juxtanuclear Golgi membrane network, or Golgi ribbon, is...

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Coordination of Golgin Tethering and SNARE Assembly

Cited by 68 publications

References 45 publications

Spatial control of Cdc42 signalling by a GM130–RasGRF complex regulates polarity and tumorigenesis

Spatial control of Cdc42 signalling by a GM130–RasGRF complex regulates polarity and tumorigenesis

Restoration of Compact Golgi Morphology in Advanced Prostate Cancer Enhances Susceptibility to Galectin-1–Induced Apoptosis by Modifying Mucin O-Glycan Synthesis

Dual Anchoring of the GRASP Membrane Tether Promotes trans Pairing

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