Plasma Membrane Association of p63 Rho Guanine Nucleotide Exchange Factor (p63RhoGEF) Is Mediated by Palmitoylation and Is Required for Basal Activity in Cells

Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) impairs translation initiation by inhibiting the guanine nucleotide exchange factor for eIF-2, known as eIF-2B. In Saccharomyces cerevisiae, phosphorylation of eIF-2 alpha by the protein kinase GCN2 specifically stimulates translation of GCN4 mRNA in addition to reducing general protein synthesis. We isolated mutations in several unlinked genes that suppress the growth-inhibitory effect of eIF-2 alpha phosphorylation catalyzed by mutationally activated forms of GCN2. These suppressor mutations, affecting eIF-2 alpha and the essential subunits of eIF-2B encoded by GCD7 and GCD2, do not reduce the level of eIF-2 alpha phosphorylation in cells expressing the activated GCN2c kinase. Four GCD7 suppressors were shown to reduce the derepression of GCN4 translation in cells containing wild-type GCN2 under starvation conditions or in GCN2c strains. A fifth GCD7 allele, constructed in vitro by combining two of the GCD7 suppressors mutations, completely impaired the derepression of GCN4 translation, a phenotype characteristic of deletions in GCN1, GCN2, or GCN3. This double GCD7 mutation also completely suppressed the lethal effect of expressing the mammalian eIF-2 alpha kinase dsRNA-PK in yeast cells, showing that the translational machinery had been rendered completely insensitive to phosphorylated eIF-2. None of the GCD7 mutations had any detrimental effect on cell growth under nonstarvation conditions, suggesting that recycling of eIF-2 occurs efficiently in the suppressor strains. We propose that GCD7 and GCD2 play important roles in the regulatory interaction between eIF-2 and eIF-2B and that the suppressor mutations we isolated in these genes decrease the susceptibility of eIF-2B to the inhibitory effects of phosphorylated eIF-2 without impairing the essential catalytic function of eIF-2B in translation initiation.

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cAMP regulates DEP domain-mediated binding of the guanine nucleotide exchange factor Epac1 to phosphatidic acid at the plasma membrane

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1117599109 ◽

2012 ◽

Vol 109 (10) ◽

pp. 3814-3819 ◽

Cited By ~ 55

Author(s):

S. V. Consonni ◽

M. Gloerich ◽

E. Spanjaard ◽

J. L. Bos

Keyword(s):

Plasma Membrane ◽

Phosphatidic Acid ◽

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

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GBF1, a Guanine Nucleotide Exchange Factor for ADP-Ribosylation Factors, is Localized to the cis -Golgi and Involved in Membrane Association of the COPI Coat

Traffic ◽

10.1034/j.1600-0854.2002.30705.x ◽

2002 ◽

Vol 3 (7) ◽

pp. 483-495 ◽

Cited By ~ 95

Author(s):

Kazumasa Kawamoto ◽

Yusaku Yoshida ◽

Hideaki Tamaki ◽

Seiji Torii ◽

Chisa Shinotsuka ◽

...

Keyword(s):

Guanine Nucleotide Exchange Factor ◽

Membrane Association ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Adp Ribosylation ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

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Norbin Stimulates the Catalytic Activity and Plasma Membrane Localization of the Guanine-Nucleotide Exchange Factor P-Rex1

Journal of Biological Chemistry ◽

10.1074/jbc.m115.686592 ◽

2016 ◽

Vol 291 (12) ◽

pp. 6359-6375 ◽

Cited By ~ 14

Author(s):

Dingxin Pan ◽

Mark A. Barber ◽

Kirsti Hornigold ◽

Martin J. Baker ◽

Judit M. Toth ◽

...

Keyword(s):

Plasma Membrane ◽

Catalytic Activity ◽

Guanine Nucleotide Exchange Factor ◽

Membrane Localization ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Plasma Membrane Localization ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

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Mutations in the GCD7 subunit of yeast guanine nucleotide exchange factor eIF-2B overcome the inhibitory effects of phosphorylated eIF-2 on translation initiation

Molecular and Cellular Biology ◽

10.1128/mcb.14.5.3208-3222.1994 ◽

1994 ◽

Vol 14 (5) ◽

pp. 3208-3222

Author(s):

C R Vazquez de Aldana ◽

A G Hinnebusch

Keyword(s):

Translation Initiation ◽

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Inhibitory Effects ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Suppressor Mutations ◽

Nucleotide Exchange Factor ◽

In Cells

Phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2 alpha) impairs translation initiation by inhibiting the guanine nucleotide exchange factor for eIF-2, known as eIF-2B. In Saccharomyces cerevisiae, phosphorylation of eIF-2 alpha by the protein kinase GCN2 specifically stimulates translation of GCN4 mRNA in addition to reducing general protein synthesis. We isolated mutations in several unlinked genes that suppress the growth-inhibitory effect of eIF-2 alpha phosphorylation catalyzed by mutationally activated forms of GCN2. These suppressor mutations, affecting eIF-2 alpha and the essential subunits of eIF-2B encoded by GCD7 and GCD2, do not reduce the level of eIF-2 alpha phosphorylation in cells expressing the activated GCN2c kinase. Four GCD7 suppressors were shown to reduce the derepression of GCN4 translation in cells containing wild-type GCN2 under starvation conditions or in GCN2c strains. A fifth GCD7 allele, constructed in vitro by combining two of the GCD7 suppressors mutations, completely impaired the derepression of GCN4 translation, a phenotype characteristic of deletions in GCN1, GCN2, or GCN3. This double GCD7 mutation also completely suppressed the lethal effect of expressing the mammalian eIF-2 alpha kinase dsRNA-PK in yeast cells, showing that the translational machinery had been rendered completely insensitive to phosphorylated eIF-2. None of the GCD7 mutations had any detrimental effect on cell growth under nonstarvation conditions, suggesting that recycling of eIF-2 occurs efficiently in the suppressor strains. We propose that GCD7 and GCD2 play important roles in the regulatory interaction between eIF-2 and eIF-2B and that the suppressor mutations we isolated in these genes decrease the susceptibility of eIF-2B to the inhibitory effects of phosphorylated eIF-2 without impairing the essential catalytic function of eIF-2B in translation initiation.

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Activation of Rab8 guanine nucleotide exchange factor Rabin8 by ERK1/2 in response to EGF signaling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1412089112 ◽

2014 ◽

Vol 112 (1) ◽

pp. 148-153 ◽

Cited By ~ 31

Author(s):

Juanfei Wang ◽

Jinqi Ren ◽

Bin Wu ◽

Shanshan Feng ◽

Guoping Cai ◽

...

Keyword(s):

Plasma Membrane ◽

Membrane Trafficking ◽

Guanine Nucleotide Exchange Factor ◽

Small Gtpases ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor ◽

Egf Signaling

Exocytosis is tightly regulated in many cellular processes, from neurite expansion to tumor proliferation. Rab8, a member of the Rab family of small GTPases, plays an important role in membrane trafficking from the trans-Golgi network and recycling endosomes to the plasma membrane. Rabin8 is a guanine nucleotide exchange factor (GEF) and major activator of Rab8. Investigating how Rabin8 is activated in cells is thus pivotal to the understanding of the regulation of exocytosis. Here we show that phosphorylation serves as an important mechanism for Rabin8 activation. We identified Rabin8 as a direct phospho-substrate of ERK1/2 in response to EGF signaling. At the molecular level, ERK phosphorylation relieves the autoinhibition of Rabin8, thus promoting its GEF activity. We further demonstrate that blocking ERK1/2-mediated phosphorylation of Rabin8 inhibits transferrin recycling to the plasma membrane. Together, our results suggest that ERK1/2 activate Rabin8 to regulate vesicular trafficking to the plasma membrane in response to extracellular signaling.

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Ypt32 recruits the Sec4p guanine nucleotide exchange factor, Sec2p, to secretory vesicles; evidence for a Rab cascade in yeast

The Journal of Cell Biology ◽

10.1083/jcb.200201003 ◽

2002 ◽

Vol 157 (6) ◽

pp. 1005-1016 ◽

Cited By ~ 199

Author(s):

Darinel Ortiz ◽

Martina Medkova ◽

Christiane Walch-Solimena ◽

Peter Novick

Keyword(s):

Plasma Membrane ◽

Guanine Nucleotide Exchange Factor ◽

Secretory Vesicles ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor ◽

Polarized Transport ◽

Exchange Activity

SEC2 is an essential gene required for polarized growth of the yeast Saccharomyces cerevisiae. It encodes a protein of 759 amino acids that functions as a guanine nucleotide exchange factor for the small GTPase Sec4p, a regulator of Golgi to plasma membrane transport. Activation of Sec4p by Sec2p is needed for polarized transport of vesicles to exocytic sites. Temperature-sensitive (ts) mutations in sec2 and sec4 result in a tight block in secretion and the accumulation of secretory vesicles randomly distributed in the cell. The proper localization of Sec2p to secretory vesicles is essential for its function and is largely independent of Sec4p. Although the ts mutation sec2-78 does not affect nucleotide exchange activity, the protein is mislocalized. Here we present evidence that Ypt31/32p, members of Rab family of GTPases, regulate Sec2p function. First, YPT31/YPT32 suppress the sec2-78 mutation. Second, overexpression of Ypt31/32p restores localization of Sec2-78p. Third, Ypt32p and Sec2p interact biochemically, but Sec2p has no exchange activity on Ypt32p. We propose that Ypt32p and Sec4p act as part of a signaling cascade in which Ypt32p recruits Sec2p to secretory vesicles; once on the vesicle, Sec2p activates Sec4p, enabling the polarized transport of vesicles to the plasma membrane.

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Oligomerization of the Sec7 domain Arf guanine nucleotide exchange factor GBF1 is dispensable for Golgi localization and function but regulates degradation

AJP Cell Physiology ◽

10.1152/ajpcell.00185.2015 ◽

2016 ◽

Vol 310 (6) ◽

pp. C456-C469 ◽

Cited By ~ 12

Author(s):

Jay M. Bhatt ◽

Ekaterina G. Viktorova ◽

Theodore Busby ◽

Paulina Wyrozumska ◽

Laura E. Newman ◽

...

Keyword(s):

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Wild Type ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor ◽

Sec7 Domain ◽

And Function ◽

In Cells

Members of the large Sec7 domain-containing Arf guanine nucleotide exchange factor (GEF) family have been shown to dimerize through their NH2-terminal dimerization and cyclophilin binding (DCB) and homology upstream of Sec7 (HUS) domains. However, the importance of dimerization in GEF localization and function has not been assessed. We generated a GBF1 mutant (91/130) in which two residues required for oligomerization (K91 and E130 within the DCB domain) were replaced with A and assessed the effects of these mutations on GBF1 localization and cellular functions. We show that 91/130 is compromised in oligomerization but that it targets to the Golgi in a manner indistinguishable from wild-type GBF1 and that it rapidly exchanges between the cytosolic and membrane-bound pools. The 91/130 mutant appears active as it integrates within the functional network at the Golgi, supports Arf activation and COPI recruitment, and sustains Golgi homeostasis and cargo secretion when provided as a sole copy of functional GBF1 in cells. In addition, like wild-type GBF1, the 91/130 mutant supports poliovirus RNA replication, a process requiring GBF1 but believed to be independent of GBF1 catalytic activity. However, oligomerization appears to stabilize GBF1 in cells, and the 91/130 mutant is degraded faster than the wild-type GBF1. Our data support a model in which oligomerization is not a key regulator of GBF1 activity but impacts its function by regulating the cellular levels of GBF1.

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