Mutations in a Highly Conserved Region of the Arf1p Activator<i>GEA2</i>Block Anterograde Golgi Transport but Not COPI Recruitment to Membranes

Park, Sei-Kyoung; Hartnell, Lisa M.; Jackson, Catherine

doi:10.1091/mbc.e05-04-0289

Cited by 24 publications

(28 citation statements)

References 50 publications

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“…In addition, mutations near the Sec7 domain in the N-terminal region of Gea2p result in defects in membrane trafficking, but not Gea2p targeting or activation of Arf1p (Park et al, 2005). Although the N-terminal region of Syt1p has not been previously found to contain any conserved domains or motifs, it was reported to contain eight phosphorylated residues (Gruhler et al, 2005;Chi et al, 2007;Li et al, 2007;Smolka et al, 2007;Albuquerque et al, 2008).…”

Section: Multiple Domains Are Required For the Function Of Syt1pmentioning

confidence: 99%

Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p

Chen

Tsai

Hsu

et al. 2010

Journal of Cell Science

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In yeast, Arl3p recruits Arl1p GTPase to regulate Golgi function and structure. However, the molecular mechanism involved in regulating activation of Arl1p at the Golgi is unknown. Here, we show that Syt1p promoted activation of Arl1p and recruitment of a golgin protein, Imh1p, to the Golgi. Deletion of SYT1 resulted in the majority of Arl1p being distributed diffusely throughout the cytosol. Overexpression of Syt1p increased Arl1p-GTP production in vivo and the Syt1-Sec7 domain promoted nucleotide exchange on Arl1p in vitro. Syt1p function required the N-terminal region, Sec7 and PH domains. Arl1p, but not Arl3p, interacted with Syt1p. Localization of Syt1p to the Golgi did not require Arl3p. Unlike arl1Δ or arl3Δ mutants, syt1Δ did not show defects in Gas1p transport, cell wall integrity or vacuolar structure. These findings reveal that activation of Arl1p is regulated in part by Syt1p, and imply that Arl1p activation, by using more than one GEF, exerts distinct biological activities at the Golgi compartment.

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Section: Multiple Domains Are Required For the Function Of Syt1pmentioning

confidence: 99%

Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p

Chen

Tsai

Hsu

et al. 2010

Journal of Cell Science

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“…37 The DCB and HUS domains of yeast Sec7 form a compact helical structure in which the conserved HUS motif is unstructured and they have no structural resemblance to known membrane-binding domains. 38 We demonstrate here that the DCB-HUS tandem is a membrane-binding element and that it contributes to the efficiency of Arf activation.…”

Section: Regulation Of Large Arfgefs By Direct and Small Gtpase-mediamentioning

confidence: 99%

Allosteric regulation of Arf GTPases and their GEFs at the membrane interface

2016

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Arf GTPases assemble protein complexes on membranes to carry out major functions in cellular traffic. An essential step is their activation by guanine nucleotide exchange factors (GEFs), whose Sec7 domain stimulates GDP/GTP exchange. ArfGEFs form 2 major families: ArfGEFs with DCB, HUS and HDS domains (GBF1 and BIG1/BIG2 in humans), which act at the Golgi; and ArfGEFs with a Cterminal PH domain (cytohesin, EFA6 and BRAG), which function at the plasma membrane and endosomes. In addition, pathogenic bacteria encode an ArfGEF with a unique membrane-binding domain. Here we review the allosteric regulation of Arf GTPases and their GEFs at the membrane interface. Membranes contribute several regulatory layers: at the GTPase level, where activation by GTP is coupled to membrane recruitment by a built-in structural device; at the Sec7 domain, which manipulates this device to ensure that Arf-GTP is attached to membranes; and at the level of noncatalytic ArfGEF domains, which form direct or GTPase-mediated interactions with membranes that enable a spectacular diversity of regulatory regimes. Notably, we show here that membranes increase the efficiency of a large ArfGEF (human BIG1) by 32-fold by interacting directly with its Nterminal DCB and HUS domains. The diversity of allosteric regulatory regimes suggests that ArfGEFs can function in cascades and circuits to modulate the shape, amplitude and duration of Arf signals in cells. Because Arf-like GTPases feature autoinhibitory elements similar to those of Arf GTPases, we propose that their activation also requires allosteric interactions of these elements with membranes or other proteins.

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“…However, the DCB domain has been shown to mediate dimerization of large ARF-GEFs in yeast twohybrid and in vitro experiments (Grebe et al, 2000), and the transgenic DCB-HUS fragment could therefore be passively tethered to the membrane by its interaction with endogenous fulllength GBF1. Also, a mutation of a conserved motif in the HUS domain reduces membrane association of yeast Gea2p, suggesting its functional requirement (Park et al, 2005). In addition, HDS domains of Gea1p and Gea2p interact with the integral membrane protein Gmh1p, which might act as their membrane receptor.…”

Section: Introductionmentioning

confidence: 99%

Membrane Association of theArabidopsisARF Exchange Factor GNOM Involves Interaction of Conserved Domains

et al. 2008

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The GNOM protein plays a fundamental role in Arabidopsis thaliana development by regulating endosome-to-plasma membrane trafficking required for polar localization of the auxin efflux carrier PIN1. GNOM is a family member of large ARF guanine nucleotide exchange factors (ARF-GEFs), which regulate vesicle formation by activating ARF GTPases on specific membranes in animals, plants, and fungi. However, apart from the catalytic exchange activity of the SEC7 domain, the functional significance of other conserved domains is virtually unknown. Here, we show that a distinct N-terminal domain of GNOM mediates dimerization and in addition interacts heterotypically with two other conserved domains in vivo. In contrast with N-terminal dimerization, the heterotypic interaction is essential for GNOM function, as mutations abolishing this interaction inactivate the GNOM protein and compromise its membrane association. Our results suggest a general model of large ARF-GEF function in which regulated changes in protein conformation control membrane association of the exchange factor and, thus, activation of ARFs.

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Mutations in a Highly Conserved Region of the Arf1p ActivatorGEA2Block Anterograde Golgi Transport but Not COPI Recruitment to Membranes

Cited by 24 publications

References 50 publications

Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p

Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p

Allosteric regulation of Arf GTPases and their GEFs at the membrane interface

Membrane Association of theArabidopsisARF Exchange Factor GNOM Involves Interaction of Conserved Domains

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