scholarly journals Molecular Interactions of Yeast Neo1p, an Essential Member of the Drs2 Family of Aminophospholipid Translocases, and Its Role in Membrane Trafficking within the Endomembrane System

2004 ◽  
Vol 24 (17) ◽  
pp. 7402-7418 ◽  
Author(s):  
Sidonie Wicky ◽  
Heinz Schwarz ◽  
Birgit Singer-Krüger
Keyword(s):  
Membrane Trafficking ◽  
Inhibitory Effect ◽  
Temperature Sensitive ◽  
Nucleotide Exchange ◽  
Endomembrane System ◽  
Nucleotide Exchange Factor ◽  
Golgi System ◽  
The Stability ◽  
Vacuolar Protein ◽  
Vacuole Biogenesis

ABSTRACT Neo1p is an essential yeast member of the highly conserved Drs2 family of P-type ATPases with proposed aminophospholipid translocase activity. Here we present evidence that Neo1p localizes to endosomes and Golgi elements. In agreement with that finding, the temperature-sensitive neo1-37 and neo1-69 mutants exhibit defects in receptor-mediated endocytosis, vacuole biogenesis, and vacuolar protein sorting. Furthermore, neo1 mutants accumulate aberrantly shaped membranous structures most likely derived from vacuoles and the endosomal/Golgi system. At permissive temperatures, HA-Neo1-69p, like wild-type Neo1p, is stable and associates with endosomes. In contrast, HA-Neo1-37p is rapidly degraded and is predominantly retained within the endoplasmic reticulum (ER). Thus, the two neo1 alleles affect the stability and localization of the mutant polypeptides in different ways. A C-terminally truncated and a C-terminally epitope-tagged version of Neo1p are nonfunctional and also mislocalize to the ER. In agreement with a role within the endomembrane system, Neo1p exhibits genetic and physical interactions with Ysl2p, a potential guanine nucleotide exchange factor for Arl1p. Interestingly, deletion of ARL1 rescues the temperature sensitivity of neo1-37 and neo1-69. We demonstrate that Arl1p in its myristoylated and GTP-bound form is responsible for the inhibitory effect. Thus, Neo1p, Ysl2p, and Arl1p represent three proteins that collaborate in membrane trafficking within the endosomal/Golgi system.

scholarly journals Yeast Ysl2p, Homologous to Sec7 Domain Guanine Nucleotide Exchange Factors, Functions in Endocytosis and Maintenance of Vacuole Integrity and Interacts with the Arf-Like Small GTPase Arl1p

2002 ◽  
Vol 22 (13) ◽  
pp. 4914-4928 ◽  
Author(s):  
Alexandra Jochum ◽  
David Jackson ◽  
Heinz Schwarz ◽  
Rüdiger Pipkorn ◽  
Birgit Singer-Krüger
Keyword(s):  
Fluorescent Protein ◽  
Genetic Interaction ◽  
Small Gtpase ◽  
Temperature Sensitive ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Green Fluorescent ◽  
Vacuolar Protein

ABSTRACT We previously described the isolation of ysl2-1 due to its genetic interaction with Δypt51/vps21, a mutant with a deletion of the coding sequence for the yeast Rab5 homolog, which regulates endocytic traffic between early and late endosomes. Here we report that Ysl2p is a novel 186.8-kDa peripheral membrane protein homologous to members of the Sec7 family. We provide multiple genetic and biochemical evidence for an interaction between Ysl12p and the Arf-like protein Arl1p, consistent with a potential function as an Arf guanine nucleotide exchange factor (GEF). The temperature-sensitive alleles ysl2-307 and ysl2-316 are specifically defective in ligand-induced degradation of Ste2p and α-factor and exhibit vacuole fragmentation directly upon a shift to 37°C. In living cells, green fluorescent protein (GFP)-Ysl2p colocalizes with endocytic elements that accumulate FM4-64. The GFP-Ysl2p staining is sensitive to a mutation in VPS27 resulting in the formation of an aberrant class E compartment, but it is not affected by a sec7 mutation. Consistent with the idea that Ysl2p and Arl1p have closely related functions, Δarl1 cells are defective in endocytic transport and in vacuolar protein sorting.

Putative GTPase Gtr1p genetically interacts with the RanGTPase cycle in Saccharomyces cerevisiae

1996 ◽  
Vol 109 (9) ◽  
pp. 2311-2318 ◽  
Author(s):  
N. Nakashima ◽  
N. Hayashi ◽  
E. Noguchi ◽  
T. Nishimoto
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Negative Regulator ◽  
Temperature Sensitive ◽  
Nucleotide Exchange ◽  
Sensitive Mutant ◽  
Temperature Sensitive Mutant ◽  
Importin Alpha ◽  
Nucleotide Exchange Factor ◽  
Cold Sensitive ◽  
Gtpase Cycle

In order to identify a protein interacting with RCC1, a guanine nucleotide-exchange factor for the nuclear GTPase Ran, we isolated a series of cold-sensitive suppressors of mtr1-2, a temperature-sensitive mutant of the Saccharomyces cerevisiae RCC1 homologue. One of the isolated suppressor mutants was mutated in the putative GTPase Gtr1p, being designated as gtr1-11. It also suppressed other alleles of mtr1-2, srm1-1 and prp20-1 in contrast to overexpression of the S. cerevisiae Ran/TC4 homologue Gsp1p, previously reported to suppress prp20-1, but not mtr1-2 or srm1-1. Furthermore, gtr1-11 suppressed the rna1-1, temperature-sensitive mutant of the Gsp1p GTPase-activating protein, but not the srp1-31, temperature-sensitive mutant of the S. cerevisiae importin alpha homologue. mtr1-2, srm1-1 and prp20-1 were also suppressed by overexpression of the mutated Gtr1p, Gtr1-11p. In summary, Gtr1p that was localized in the cytoplasm by immunofluoresence staining was suggested to function as a negative regulator for the Ran/TC4 GTPase cycle.

EHD2 mediates trafficking from the plasma membrane by modulating Rac1 activity

2011 ◽  
Vol 439 (3) ◽  
pp. 433-445 ◽  
Author(s):  
Sigi Benjamin ◽  
Hilla Weidberg ◽  
Debora Rapaport ◽  
Olga Pekar ◽  
Marina Nudelman ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rho Gtpases ◽  
Actin Polymerization ◽  
Inhibitory Effect ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
System A ◽  
Nucleotide Exchange Factor ◽  
Rac1 Activity ◽  
The Impact

EHDs [EH (Eps15 homology)-domain-containing proteins] participate in different stages of endocytosis. EHD2 is a plasma-membrane-associated EHD which regulates trafficking from the plasma membrane and recycling. EHD2 has a role in nucleotide-dependent membrane remodelling and its ATP-binding domain is involved in dimerization, which creates a membrane-binding region. Nucleotide binding is important for association of EHD2 with the plasma membrane, since a nucleotide-free mutant (EHD2 T72A) failed to associate. To elucidate the possible function of EHD2 during endocytic trafficking, we attempted to unravel proteins that interact with EHD2, using the yeast two-hybrid system. A novel interaction was found between EHD2 and Nek3 [NIMA (never in mitosis in Aspergillus nidulans)-related kinase 3], a serine/threonine kinase. EHD2 was also found in association with Vav1, a Nek3-regulated GEF (guanine-nucleotide-exchange factor) for Rho GTPases. Since Vav1 regulates Rac1 activity and promotes actin polymerization, the impact of overexpression of EHD2 on Rac1 activity was tested. The results indicated that wt (wild-type) EHD2, but not its P-loop mutants, reduced Rac1 activity. The inhibitory effect of EHD2 overexpression was partially rescued by co-expression of Rac1 as measured using a cholera toxin trafficking assay. The results of the present study strongly indicate that EHD2 regulates trafficking from the plasma membrane by controlling Rac1 activity.

scholarly journals Arf6 Can Trigger Wave Regulatory Complex-Dependent Actin Assembly Independent of Arno

2020 ◽  
Vol 21 (7) ◽  
pp. 2457 ◽  
Author(s):  
Vikash Singh ◽  
Anthony C. Davidson ◽  
Peter J. Hume ◽  
Vassilis Koronakis
Keyword(s):  
Lipid Bilayers ◽  
Membrane Trafficking ◽  
Actin Polymerization ◽  
Small Gtpase ◽  
Actin Dynamics ◽  
Actin Assembly ◽  
Nucleotide Exchange ◽  
Cortical Actin ◽  
Nucleotide Exchange Factor ◽  
Regulatory Complex

The small GTPase ADP-ribosylation factor 6 (Arf6) anchors at the plasma membrane to orchestrate key functions, such as membrane trafficking and regulating cortical actin cytoskeleton rearrangement. A number of studies have identified key players that interact with Arf6 to regulate actin dynamics in diverse cell processes, yet it is still unknown whether Arf6 can directly signal to the wave regulatory complex to mediate actin assembly. By reconstituting actin dynamics on supported lipid bilayers, we found that Arf6 in co-ordination with Rac1(Ras-related C3 botulinum toxin substrate 1) can directly trigger actin polymerization by recruiting wave regulatory complex components. Interestingly, we demonstrated that Arf6 triggers actin assembly at the membrane directly without recruiting the Arf guanine nucleotide exchange factor (GEF) ARNO (ARF nucleotide-binding site opener), which is able to activate Arf1 to enable WRC-dependent actin assembly. Furthermore, using labelled E. coli, we demonstrated that actin assembly by Arf6 also contributes towards efficient phagocytosis in THP-1 macrophages. Taken together, this study reveals a mechanism for Arf6-driven actin polymerization.

ARF-independent inhibition of the carbachol-induced contractions by brefeldin A in intestinal smooth muscle

1997 ◽  
Vol 273 (3) ◽  
pp. C816-C821 ◽  
Author(s):  
G. Loirand ◽  
C. Cario-Toumaniantz ◽  
P. Chardin ◽  
P. Pacaud
Keyword(s):  
Smooth Muscle ◽  
Brefeldin A ◽  
Inhibitory Effect ◽  
Intestinal Smooth Muscle ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Intact Cells ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Voltage Dependent

The aim of this study was to determine whether an ADP ribosylation factor (ARF)-regulated pathway is involved in the carbachol-induced contraction in rat intestinal smooth muscle. Brefeldin A, a known inhibitor of the guanine nucleotide exchange activity on ARF, reversibly inhibited the carbachol-induced contraction in intact ileal muscle strips, whereas the carbachol- and guanosine 5'-O-(3-thiotriphosphate)-induced increases in the Ca2+ sensitivity of myofilaments in beta-escin-permeabilized strips were not affected. The high-K(+)-induced contraction in intact strips was also inhibited by brefeldin A. In isolated ileal myocytes, brefeldin A inhibited the Ca2+ channel current, indicating that the inhibitory effect of brefeldin A in intact cells is related to an inhibition of voltage-dependent Ca2+ channels. Furthermore, the loading of permeabilized strips with the combination of the recombinant fully myristoylated ARF1, the guanine nucleotide exchange factor ARNO, and guanosine 5'-triphosphate did not change the tone at constant pCa (6.45) and did not modify the carbachol- and guanosine 5'-O-(3-thiotriphosphate)-induced Ca2+ sensitization. Taken together, these findings suggest that an ARF-dependent pathway is not involved in the carbachol-induced contraction.

Deletion of PIN4 Suppresses the Protein Transport Defects Caused by sec12-4 Mutation in Saccharomyces cerevisiae

2020 ◽  
Vol 30 (1-6) ◽  
pp. 25-35
Author(s):  
Akiko Murakami-Sekimata ◽  
Masayuki Sekimata ◽  
Natsumi Sato ◽  
Yuto Hayasaka ◽  
Akihiko Nakano
Keyword(s):  
Protein Transport ◽  
Cell Cycle Checkpoint ◽  
Secretory Proteins ◽  
Temperature Sensitive ◽  
Nucleotide Exchange ◽  
Casein Kinase I ◽  
Vesicle Budding ◽  
Nucleotide Exchange Factor ◽  
Cycle Checkpoint ◽  
Copii Vesicles

Newly synthesized secretory proteins are released into the lumen of the endoplasmic reticulum (ER). The secretory proteins are surrounded by coat protein complex II (COPII) vesicles, and transported from the ER and reach their destinations through the Golgi apparatus. Sec12p is a guanine nucleotide exchange factor for Sar1p, which initiates COPII vesicle budding from the ER. The activation of Sar1p by Sec12p and the subsequent COPII coat assembly have been well characterized, but the events that take place upstream of Sec12p remain unclear. In this study, we isolated the novel extragenic suppressor of <i>sec12-4</i>, <i>PIN4/MDT1</i>, a cell cycle checkpoint target. A yeast two-hybrid screening was used to identify Pin4/Mdt1p as a binding partner of the casein kinase I isoform Hrr25p, which we have previously identified as a modulator of Sec12p function. Deletion of <i>PIN4</i> suppressed both defects of temperature-sensitive growth and the partial protein transport observed in <i>sec12-4</i> mutants. The results of this study suggest that Pin4p provides novel aspects of Sec12p modulations.

scholarly journals The substrate specificity of the human TRAPPII complex’s Rab-guanine nucleotide exchange factor activity

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Meredith L. Jenkins ◽  
Noah J. Harris ◽  
Udit Dalwadi ◽  
Kaelin D. Fleming ◽  
Daniel S. Ziemianowicz ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Rab Gtpases ◽  
Guanine Nucleotide ◽  
Nucleotide Exchange ◽  
Guanine Nucleotide Exchange ◽  
Binding Interface ◽  
Nucleotide Exchange Factor ◽  
Biochemical Characterisation ◽  
Hydrogen Deuterium ◽  
Insight Into

AbstractThe TRAnsport Protein Particle (TRAPP) complexes act as Guanine nucleotide exchange factors (GEFs) for Rab GTPases, which are master regulators of membrane trafficking in eukaryotic cells. In metazoans, there are two large multi-protein TRAPP complexes: TRAPPII and TRAPPIII, with the TRAPPII complex able to activate both Rab1 and Rab11. Here we present detailed biochemical characterisation of Rab-GEF specificity of the human TRAPPII complex, and molecular insight into Rab binding. GEF assays of the TRAPPII complex against a panel of 20 different Rab GTPases revealed GEF activity on Rab43 and Rab19. Electron microscopy and chemical cross-linking revealed the architecture of mammalian TRAPPII. Hydrogen deuterium exchange MS showed that Rab1, Rab11 and Rab43 share a conserved binding interface. Clinical mutations in Rab11, and phosphomimics of Rab43, showed decreased TRAPPII GEF mediated exchange. Finally, we designed a Rab11 mutation that maintained TRAPPII-mediated GEF activity while decreasing activity of the Rab11-GEF SH3BP5, providing a tool to dissect Rab11 signalling. Overall, our results provide insight into the GTPase specificity of TRAPPII, and how clinical mutations disrupt this regulation.

scholarly journals The Ran GTPase System in Fission Yeast Affects Microtubules and Cytokinesis in Cells That Are Competent for Nucleocytoplasmic Protein Transport

2002 ◽  
Vol 22 (24) ◽  
pp. 8491-8505 ◽  
Author(s):  
Sandra S. Salus ◽  
Janos Demeter ◽  
Shelley Sazer
Keyword(s):  
Fission Yeast ◽  
Protein Transport ◽  
Temperature Sensitive ◽  
Nucleotide Exchange ◽  
Cellular Processes ◽  
Nucleotide Exchange Factor ◽  
Ring Structures ◽  
Dependent Processes ◽  
In Cells

ABSTRACT Misregulation of the evolutionarily conserved GTPase Ran in fission yeast results in defects in several cellular processes in cells that are competent for nucleocytoplasmic protein transport. These results suggest that transport is neither the only nor the primary Ran-dependent process in living cells. The ability of Ran to independently regulate multiple cellular processes in vivo is demonstrated by showing that (i) eight different transport-competent RanGEF (guanine nucleotide exchange factor) mutants have defects in mitotic spindle formation; (ii) the RanGEF temperature-sensitive mutant pim1-d1 has abnormal actin ring structures at the septum. Overexpression of Imp2p, which specifically destabilizes these structures, restores viability. (iii) Ran-dependent processes differ in their requirements for active Ran in vivo. Microtubule function, cytokinesis, and nuclear envelope structure are the Ran-dependent processes most sensitive to the amount of Ran protein in the cell, whereas nucleocytoplasmic protein transport is the most robust. Therefore, the ability of Ran from Schizosaccharomyces pombe to independently regulate multiple cellular processes may reflect differences in its interactions with the binding proteins that mediate these functions and explain the complex phenotypic consequences of its misregulation in vivo.

scholarly journals Characterization of yeast Vps33p, a protein required for vacuolar protein sorting and vacuole biogenesis.

1990 ◽  
Vol 10 (9) ◽  
pp. 4638-4649 ◽  
Author(s):  
L M Banta ◽  
T A Vida ◽  
P K Herman ◽  
S D Emr
Keyword(s):  
Sequence Similarity ◽  
Protein Sorting ◽  
Atp Binding ◽  
Temperature Sensitive ◽  
Cell Fractionation ◽  
Permissive Temperature ◽  
Sensitive Mutant ◽  
Temperature Sensitive Mutant ◽  
Vacuolar Protein ◽  
Vacuole Biogenesis

vps33 mutants missort and secrete multiple vacuolar hydrolases and exhibit extreme defects in vacuolar morphology. Toward a molecular understanding of the role of the VPS33 gene in vacuole biogenesis, we have cloned this gene from a yeast genomic library by complementation of a temperature-sensitive vps33 mutation. Gene disruption demonstrated that VPS33 was not essential but was required for growth at high temperatures. At the permissive temperature, vps33 null mutants exhibited defects in vacuolar protein localization and vacuole morphology similar to those seen in most of the original mutant alleles. Sequence analysis revealed a putative open reading frame sufficient to encode a protein of 691 amino acids. Hydropathy analysis indicated that the deduced product of the VPS33 gene is generally hydrophilic, contains no obvious signal sequence or transmembrane domains, and is therefore unlikely to enter the secretory pathway. Polyclonal antisera raised against TrpE-Vps33 fusion proteins recognized a protein in yeast cells of the expected molecular weight, approximately 75,000. In cell fractionation studies, Vps33p behaved as a cytosolic protein. The predicted VPS33 gene product possessed sequence similarity with a number of ATPases and ATP-binding proteins specifically in their ATP-binding domains. One vps33 temperature-sensitive mutant contained a missense mutation near this region of sequence similarity; the mutation resulted in a Leu-646----Pro substitution in Vps33p. This temperature-sensitive mutant strain contained normal vacuoles at the permissive temperature but lacked vacuoles specifically in the bud at the nonpermissive temperature. Our data suggest that Vps33p acts in the cytoplasm to facilitate Golgi-to-vacuole protein delivery. We propose that as a consequence of the vps33 protein-sorting defects, abnormalities in vacuolar morphology and vacuole assembly result.

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