Multiple Phosphorylation Sites and Quaternary Organization of Guanine-Nucleotide Exchange Complex of Elongation Factor-1 (EF-1βγδ/ValRS) Control the Various Functions of EF-1α

1998 ◽  
Vol 18 (3) ◽  
pp. 119-127 ◽  
Author(s):  
Odile Minella ◽  
Odile Mulner-Lorillon ◽  
Guillaume Bec ◽  
Patrick Cormier ◽  
Robert Bellé
Keyword(s):  
Structural Model ◽  
Elongation Factor ◽  
Trna Synthetase ◽  
Macromolecular Complex ◽  
Phosphorylation Sites ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor

The eukaryotic guanine-nucleotide exchange factor commonly called elongation factor-1βγδ (EF-1βγδ), comprises four different subunits including valyl-tRNA synthetase (EF-1βγδ/ValRS). The factor is multiply-phosphorylated by three different protein kinases, protein kinase C, casein kinase II and cyclin dependent kinase 1 (CDK1). EF-1βγδ/ValRS is organized as a macromolecular complex for which we propose a new structural model. Evidence that EF-1βγδ/ValRS is a sophisticated supramolecular complex containing many phosphorylation sites, makes it a potential regulator of any of the functions of its partner EF-1α, not only involved in protein synthesis elongation, but also in many other cellular functions.

scholarly journals ARL3 and ARL13B GTPases participate in distinct steps of INPP5E targeting to the ciliary membrane

Biology Open ◽  
2021 ◽  
Vol 10 (9) ◽  
Author(s):  
Sayaka Fujisawa ◽  
Hantian Qiu ◽  
Shohei Nozaki ◽  
Shuhei Chiba ◽  
Yohei Katoh ◽  
...  
Keyword(s):  
Guanine Nucleotide Exchange Factor ◽  
Membrane Localization ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Ciliary Membrane ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Direct Binding ◽  
Ciliary Localization

ABSTRACT INPP5E, a phosphoinositide 5-phosphatase, localizes on the ciliary membrane via its C-terminal prenyl moiety, and maintains the distinct ciliary phosphoinositide composition. The ARL3 GTPase contributes to the ciliary membrane localization of INPP5E by stimulating the release of PDE6D bound to prenylated INPP5E. Another GTPase, ARL13B, which is localized on the ciliary membrane, contributes to the ciliary membrane retention of INPP5E by directly binding to its ciliary targeting sequence. However, as ARL13B was shown to act as a guanine nucleotide exchange factor (GEF) for ARL3, it is also possible that ARL13B indirectly mediates the ciliary INPP5E localization via activating ARL3. We here show that INPP5E is delocalized from cilia in both ARL3-knockout (KO) and ARL13B-KO cells. However, some of the abnormal phenotypes were different between these KO cells, while others were found to be common, indicating the parallel roles of ARL3 and ARL13B, at least concerning some cellular functions. For several variants of ARL13B, their ability to interact with INPP5E, rather than their ability as an ARL3-GEF, was associated with whether they could rescue the ciliary localization of INPP5E in ARL13B-KO cells. These observations together indicate that ARL13B determines the ciliary localization of INPP5E, mainly by its direct binding to INPP5E.

scholarly journals Rab11 is required for lysosome exocytosis through the interaction with Rab3a, Sec15 and GRAB

2021 ◽  
Author(s):  
Cristina Escrevente ◽  
Liliana Bento-Lopes ◽  
José S. Ramalho ◽  
Duarte C. Barral
Keyword(s):  
Plasma Membrane ◽  
Cell Periphery ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Membrane Repair ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Plasma Membrane Repair ◽  
Molecular Machinery

Lysosomes are dynamic organelles, capable of undergoing exocytosis. This process is crucial for several cellular functions, namely plasma membrane repair. Nevertheless, the molecular machinery involved in this process is poorly understood. Here, we identify Rab11a and Rab11b as regulators of calcium-induced lysosome exocytosis. Interestingly, Rab11-positive vesicles transiently interact with lysosomes at the cell periphery, indicating that this interaction is required for the last steps of lysosome exocytosis. Additionally, we found that the silencing of the exocyst subunit Sec15, a Rab11 effector, impairs lysosome exocytosis, suggesting that Sec15 acts together with Rab11 in the regulation of lysosome exocytosis. Furthermore, we show that Rab11 binds the guanine nucleotide exchange factor for Rab3a (GRAB) and also Rab3a, which we described previously as a regulator of the positioning and exocytosis of lysosomes. Thus, our study identifies new players required for lysosome exocytosis and suggest the existence of a Rab11-Rab3a cascade involved in this process.

scholarly journals A novel Rab11-Rab3a cascade required for lysosome exocytosis

2021 ◽  
Author(s):  
Cristina Escrevente ◽  
Liliana Bento-Lopes ◽  
José S Ramalho ◽  
Duarte C Barral
Keyword(s):  
Plasma Membrane ◽  
Cell Periphery ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Membrane Repair ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Plasma Membrane Repair ◽  
Molecular Machinery

AbstractLysosomes are dynamic organelles, capable of undergoing exocytosis. This process is crucial for several cellular functions, namely plasma membrane repair. Nevertheless, the molecular machinery involved in this process is poorly understood.Here, we identify Rab11a and Rab11b as regulators of calcium-induced lysosome exocytosis. Interestingly, Rab11-positive vesicles transiently interact with lysosomes at the cell periphery, indicating that this interaction is required for the last steps of lysosome exocytosis. Additionally, we found that the silencing of the exocyst subunit Sec15, a Rab11 effector, impairs lysosome exocytosis independently of the exocyst complex, suggesting that Sec15 acts together with Rab11 in the regulation of lysosome exocytosis. Furthermore, we show that Rab11 binds the guanine nucleotide exchange factor for Rab3a (GRAB) and also Rab3a, which we described previously as a regulator of the positioning and exocytosis of lysosomes.Thus, our studies suggest that Rab11-positive vesicles transport GRAB to activate Rab3a on lysosomes, establishing a Rab11-Rab3 cascade that is essential for lysosome exocytosis.

scholarly journals Kinetics of the Interactions between Yeast Elongation Factors 1A and 1Bα, Guanine Nucleotides, and Aminoacyl-tRNA

2007 ◽  
Vol 282 (49) ◽  
pp. 35629-35637 ◽  
Author(s):  
Kirill B. Gromadski ◽  
Tobias Schümmer ◽  
Anne Strømgaard ◽  
Charlotte R. Knudsen ◽  
Terri Goss Kinzy ◽  
...  
Keyword(s):  
Elongation Factor ◽  
Guanine Nucleotides ◽  
Stopped Flow ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Binding Properties ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Kinetics Of ◽  
Trna Binding

The interactions of elongation factor 1A (eEF1A) from Saccharomyces cerevisiae with elongation factor 1Bα (eEF1Bα), guanine nucleotides, and aminoacyl-tRNA were studied kinetically by fluorescence stopped-flow. eEF1A has similar affinities for GDP and GTP, 0.4 and 1.1 μm, respectively. Dissociation of nucleotides from eEF1A in the absence of the guanine nucleotide exchange factor is slow (about 0.1 s–1) and is accelerated by eEF1Bα by 320-fold and 250-fold for GDP and GTP, respectively. The rate constant of eEF1Bα binding to eEF1A (107–108m–1 s–1) is independent of guanine nucleotides. At the concentrations of nucleotides and factors prevailing in the cell, the overall exchange rate is expected to be in the range of 6 s–1, which is compatible with the rate of protein synthesis in the cell. eEF1A·GTP binds Phe-tRNAPhe with a Kd of 3 nm, whereas eEF1A·GDP shows no significant binding, indicating that eEF1A has similar tRNA binding properties as its prokaryotic homolog, EF-Tu.

scholarly journals Highly conserved motifs within the large Sec7 ARF guanine nucleotide exchange factor GBF1 target it to the Golgi and are critical for GBF1 activity

2018 ◽  
Vol 314 (6) ◽  
pp. C675-C689 ◽  
Author(s):  
Cristian A. Pocognoni ◽  
Ekaterina G. Viktorova ◽  
John Wright ◽  
Justyna M. Meissner ◽  
Garrett Sager ◽  
...  
Keyword(s):  
Brefeldin A ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Cellular Viability ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Α Helix

Cellular life requires the activation of the ADP-ribosylation factors (ARFs) by Golgi brefeldin A-resistant factor 1 (GBF1), a guanine nucleotide exchange factor (GEF) with a highly conserved catalytic Sec7 domain (Sec7d). In addition to the Sec7d, GBF1 contains other conserved domains whose functions remain unclear. Here, we focus on HDS2 (homology downstream of Sec7d 2) domain because the L1246R substitution within the HDS2 α-helix 5 of the zebrafish GBF1 ortholog causes vascular hemorrhaging and embryonic lethality (13). To dissect the structure/function relationships within HDS2, we generated six variants, in which the most conserved residues within α-helices 1, 2, 4, and 6 were mutated to alanines. Each HDS2 mutant was assessed in a cell-based “replacement” assay for its ability to support cellular functions normally supported by GBF1, such as maintaining Golgi homeostasis, facilitating COPI recruitment, supporting secretion, and sustaining cellular viability. We show that cells treated with the pharmacological GBF1 inhibitor brefeldin A (BFA) and expressing a BFA-resistant GBF1 variant with alanine substitutions of RDR1168 or LF1266 are compromised in Golgi homeostasis, impaired in ARF activation, unable to sustain secretion, and defective in maintaining cellular viability. To gain insight into the molecular mechanism of this dysfunction, we assessed the ability of each GBF1 mutant to target to Golgi membranes and found that mutations in RDR1168 and LF1266 significantly decrease targeting efficiency. Thus, these residues within α-helix 2 and α-helix 6 of the HDS2 domain in GBF1 are novel regulatory determinants that support GBF1 cellular function by impacting the Golgi-specific membrane association of GBF1.

Entamoeba histolytica: inhibition of cellular functions by overexpression of EhGEF1, a novel Rho/Rac guanine nucleotide exchange factor

2005 ◽  
Vol 109 (3) ◽  
pp. 150-162 ◽  
Author(s):  
Arturo Aguilar-Rojas ◽  
Ma. de Jesús Almaraz-Barrera ◽  
Mickaël Krzeminski ◽  
Martha Robles-Flores ◽  
Rosaura Hernández-Rivas ◽  
...  
Keyword(s):  
Entamoeba Histolytica ◽  
Guanine Nucleotide Exchange Factor ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Cellular Functions ◽  
Exchange Factor ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor
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