The Arf-like GTPase Arl1 and its role in membrane traffic

2005 ◽  
Vol 33 (4) ◽  
pp. 601-605 ◽  
Author(s):  
S. Munro
Keyword(s):  
Membrane Trafficking ◽  
Coiled Coil ◽  
Membrane Traffic ◽  
Structural Features ◽  
Eukaryotic Cells ◽  
Cytoskeletal Reorganization ◽  
Vesicle Tethering ◽  
Adp Ribosylation Factor ◽  
Eukaryotic Genomes

Small GTP-binding proteins of the Rab and Arf (ADP-ribosylation factor) families play a central role in the membrane trafficking pathways of eukaryotic cells. The prototypical members of the Arf family are Arf1–Arf6 and Sar1, which have well-characterized roles in membrane traffic or cytoskeletal reorganization. However, eukaryotic genomes encode additional proteins, which share the characteristic structural features of the Arf family, but the role of these ‘Arf-like’ (Arl) proteins is less well understood. This review discusses Arl1, a GTPase that is widely conserved in evolution, and which is localized to the Golgi in all species so far examined. The best-characterized effectors of Arl1 are coiled-coil proteins which share a C-terminal GRIP domain, but other apparent effectors include the GARP (Golgi-associated retrograde protein)/VFT (Vps fifty-three) vesicle-tethering complex and Arfaptin 2. As least some of these proteins are believed to have a role in membrane traffic. Genetic analysis in a number of species has shown that Arl1 is not essential for exocytosis, but rather suggest that it is required for traffic from endosomes to the Golgi.

scholarly journals ADP-Ribosylation Factor 6 and a Functional PIX/p95-APP1 Complex Are Required for Rac1B-mediated Neurite Outgrowth

2003 ◽  
Vol 14 (4) ◽  
pp. 1295-1307 ◽  
Author(s):  
Chiara Albertinazzi ◽  
Lorena Za ◽  
Simona Paris ◽  
Ivan de Curtis
Keyword(s):  
Membrane Trafficking ◽  
Functional Connection ◽  
Actin Organization ◽  
Neurite Extension ◽  
Adp Ribosylation ◽  
Carboxy Terminal ◽  
Endocytic Vesicles ◽  
Adp Ribosylation Factor ◽  
Developing Nervous System

The mechanisms coordinating adhesion, actin organization, and membrane traffic during growth cone migration are poorly understood. Neuritogenesis and branching from retinal neurons are regulated by the Rac1B/Rac3 GTPase. We have identified a functional connection between ADP-ribosylation factor (Arf) 6 and p95-APP1 during the regulation of Rac1B-mediated neuritogenesis. P95-APP1 is an ADP-ribosylation factor GTPase-activating protein (ArfGAP) of the GIT family expressed in the developing nervous system. We show that Arf6 has a predominant role in neurite extension compared with Arf1 and Arf5. Cotransfection experiments indicate a specific and cooperative potentiation of neurite extension by Arf6 and the carboxy-terminal portion of p95-APP1. Localization studies in neurons expressing different p95-derived constructs show a codistribution of p95-APP1 with Arf6, but not Arf1. Moreover, p95-APP1–derived proteins with a mutated or deleted ArfGAP domain prevent Rac1B-induced neuritogenesis, leading to PIX-mediated accumulation at large Rab11-positive endocytic vesicles. Our data support a role of p95-APP1 as a specific regulator of Arf6 in the control of membrane trafficking during neuritogenesis.

scholarly journals Sphingomyelin metabolism controls the shape and function of the Golgi cisternae

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Felix Campelo ◽  
Josse van Galen ◽  
Gabriele Turacchio ◽  
Seetharaman Parashuraman ◽  
Michael M Kozlov ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Structural Organization ◽  
Structural Features ◽  
Membrane Curvature ◽  
Eukaryotic Cells ◽  
Golgi Cisterna ◽  
Golgi Membranes ◽  
And Function ◽  
Flat Cisternae

The flat Golgi cisterna is a highly conserved feature of eukaryotic cells, but how is this morphology achieved and is it related to its function in cargo sorting and export? A physical model of cisterna morphology led us to propose that sphingomyelin (SM) metabolism at the trans-Golgi membranes in mammalian cells essentially controls the structural features of a Golgi cisterna by regulating its association to curvature-generating proteins. An experimental test of this hypothesis revealed that affecting SM homeostasis converted flat cisternae into highly curled membranes with a concomitant dissociation of membrane curvature-generating proteins. These data lend support to our hypothesis that SM metabolism controls the structural organization of a Golgi cisterna. Together with our previously presented role of SM in controlling the location of proteins involved in glycosylation and vesicle formation, our data reveal the significance of SM metabolism in the structural organization and function of Golgi cisternae.

scholarly journals Resolution of two ADP-ribosylation factor 1 GTPase-activating proteins from rat liver

1997 ◽  
Vol 324 (2) ◽  
pp. 413-419 ◽  
Author(s):  
Paul A. RANDAZZO
Keyword(s):  
Dissociation Constant ◽  
Rat Liver ◽  
Potential Role ◽  
Membrane Traffic ◽  
Adp Ribosylation ◽  
Substrate Preferences ◽  
Gtpase Activating Proteins ◽  
Gtp Binding ◽  
Adp Ribosylation Factor

ADP-ribosylation factor 1 (ARF1) is a 21 kDa GTP-binding protein that regulates multiple steps in membrane traffic. Here, two ARF1 GTPase-activating proteins (GAPs) from rat liver were resolved. The GAPs were antigenically distinct. One reacted with a polyclonal antibody raised against the GAP catalytic peptide previously purified by Makler et al. [Makler, Cukierman, Rotman, Admon and Cassel (1995) J. Biol. Chem. 270, 5232–5237], and here is referred to as GAP1. The other GAP (GAP2) did not react with the antibody. These GAPs differed in phospholipid dependencies. GAP1 was activated 3–7-fold by the acid phospholipids phosphatidylinositol 4,5-bisphosphate (PIP2), phosphatidic acid (PA) and phosphatidylserine (PS). In contrast, GAP2 was stimulated 20–40-fold by PIP2. PA and PS had no effect by themselves but PA increased GAP2 activity in the presence of PIP2. The GAPs were otherwise similar in activity. In the presence of phosphoinositides, the Km of GAP1 for ARF1–GTP was estimated to be 8.1±1.6 μM and the dissociation constant for ARF1–guanosine 5′,3-O-(thio)triphosphate (GTP[S]) was 7.4±2.2 μM. GAP2 was similar with a Km for ARF1–GTP of 5.4±1.2 μM and a dissociation constant for ARF1–GTP[S] of 4.8±0.3 μM. Similarly, no differences were found in substrate preferences. Both GAP1 and GAP2 used ARF1 and ARF5 as substrates but not ARF6 or ARF-like protein-2. The potential role of multiple ARF GAPs in the independent regulation of ARF at specific steps in membrane traffic is discussed.

scholarly journals Timing the origin of eukaryotic cellular complexity with ancient duplications

2019 ◽  
Author(s):  
Julian Vosseberg ◽  
Jolien J. E. van Hooff ◽  
Marina Marcet-Houben ◽  
Anne van Vlimmeren ◽  
Leny M. van Wijk ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Eukaryotic Genome ◽  
Eukaryotic Cells ◽  
Gene Duplications ◽  
Evolutionary Transitions ◽  
Timing Events

AbstractEukaryogenesis is one of the most enigmatic evolutionary transitions, during which simple prokaryotic cells gave rise to complex eukaryotic cells. While evolutionary intermediates are lacking, gene duplications allow us to elucidate the order of events by which eukaryotes originated. Here we use a phylogenomics approach to reconstruct successive steps during eukaryogenesis. We found that gene duplications roughly doubled the proto-eukaryotic genome, with families inherited from the Asgard archaea-related host being duplicated most. By relatively timing events using phylogenetic distances we inferred that duplications in cytoskeletal and membrane trafficking families were among the earliest events, whereas most other families expanded primarily after mitochondrial endosymbiosis. Altogether, we demonstrate that the host that engulfed the proto-mitochondrion had some eukaryote-like complexity, which further increased drastically upon mitochondrial acquisition. This scenario bridges the signs of complexity observed in Asgard archaeal genomes to the proposed role of mitochondria in triggering eukaryogenesis.

scholarly journals GCC185 plays independent roles in Golgi structure maintenance and AP-1–mediated vesicle tethering

2011 ◽  
Vol 194 (5) ◽  
pp. 779-787 ◽  
Author(s):  
Frank C. Brown ◽  
Carmel H. Schindelhaim ◽  
Suzanne R. Pfeffer
Keyword(s):  
Coiled Coil ◽  
Retrograde Transport ◽  
Vesicle Tethering ◽  
Transport Vesicles ◽  
Late Endosomes ◽  
Transport Vesicle ◽  
Golgi Structure ◽  
Clathrin Adaptor ◽  
Golgi Network

GCC185 is a long coiled-coil protein localized to the trans-Golgi network (TGN) that functions in maintaining Golgi structure and tethering mannose 6-phosphate receptor (MPR)–containing transport vesicles en route to the Golgi. We report the identification of two distinct domains of GCC185 needed either for Golgi structure maintenance or transport vesicle tethering, demonstrating the independence of these two functions. The domain needed for vesicle tethering binds to the clathrin adaptor AP-1, and cells depleted of GCC185 accumulate MPRs in transport vesicles that are AP-1 decorated. This study supports a previously proposed role of AP-1 in retrograde transport of MPRs from late endosomes to the Golgi and indicates that docking may involve the interaction of vesicle-associated AP-1 protein with the TGN-associated tethering protein GCC185.

scholarly journals Role of the Kinesin Neck Region in Processive Microtubule-based Motility

1998 ◽  
Vol 140 (6) ◽  
pp. 1407-1416 ◽  
Author(s):  
Laura Romberg ◽  
Daniel W. Pierce ◽  
Ronald D. Vale
Keyword(s):  
Single Molecule ◽  
Fluorescent Protein ◽  
Catalytic Domain ◽  
Coiled Coil ◽  
Neck Region ◽  
Structural Features ◽  
Peptide Sequence ◽  
Mechanochemical Cycle ◽  
Green Fluorescent

Kinesin is a dimeric motor protein that can move along a microtubule for several microns without releasing (termed processive movement). The two motor domains of the dimer are thought to move in a coordinated, hand-over-hand manner. A region adjacent to kinesin's motor catalytic domain (the neck) contains a coiled coil that is sufficient for motor dimerization and has been proposed to play an essential role in processive movement. Recent models have suggested that the neck enables head-to-head communication by creating a stiff connection between the two motor domains, but also may unwind during the mechanochemical cycle to allow movement to new tubulin binding sites. To test these ideas, we mutated the neck coiled coil in a 560-amino acid (aa) dimeric kinesin construct fused to green fluorescent protein (GFP), and then assayed processivity using a fluorescence microscope that can visualize single kinesin–GFP molecules moving along a microtubule. Our results show that replacing the kinesin neck coiled coil with a 28-aa residue peptide sequence that forms a highly stable coiled coil does not greatly reduce the processivity of the motor. This result argues against models in which extensive unwinding of the coiled coil is essential for movement. Furthermore, we show that deleting the neck coiled coil decreases processivity 10-fold, but surprisingly does not abolish it. We also demonstrate that processivity is increased by threefold when the neck helix is elongated by seven residues. These results indicate that structural features of the neck coiled coil, although not essential for processivity, can tune the efficiency of single molecule motility.

Role of tethering factors in secretory membrane traffic

2006 ◽  
Vol 290 (1) ◽  
pp. C11-C26 ◽  
Author(s):  
Elizabeth Sztul ◽  
Vladimir Lupashin
Keyword(s):  
Coiled Coil ◽  
Membrane Traffic ◽  
Cellular Responses ◽  
Regulatory Proteins ◽  
Attachment Protein ◽  
Experimental Systems ◽  
Sensitive Factor ◽  
Protein Receptors ◽  
Protein Components

Coiled-coil and multisubunit tethers have emerged as key regulators of membrane traffic and organellar architecture. The restricted subcellular localization of tethers and their ability to interact with Rabs and soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) suggests that tethers participate in determining the specificity of membrane fusion. An accepted model of tether function considers them molecular “bridges” that link opposing membranes before SNARE pairing. This model has been extended by findings in various experimental systems, suggesting that tethers may have other functions. Recent reports implicate tethers in the assembly of SNARE complexes, cargo selection and transit, cytoskeletal events, and localized attachment of regulatory proteins. A concept of tethers as scaffolding machines that recruit protein components involved in varied cellular responses is emerging. In this model, tethers function as integration switches that simultaneously transmit information to coordinate distinct processes required for membrane traffic.

scholarly journals Role of vesicle tethering factors in the ER-Golgi membrane traffic

FEBS Letters ◽  
2009 ◽  
Vol 583 (23) ◽  
pp. 3770-3783 ◽  
Author(s):  
Elizabeth Sztul ◽  
Vladimir Lupashin
Keyword(s):  
Membrane Traffic ◽  
Golgi Membrane ◽  
Vesicle Tethering

The Role of Archpriest Eugene Popov in Enhancing of the Anglican-Orthodox Dialog

2020 ◽  
pp. 71-84
Author(s):  
Ярослав Очканов
Keyword(s):  
State Level ◽  
Structural Features ◽  
Russian Orthodox ◽  
Church Community ◽  
Anglican Church ◽  
Current State ◽  
The Church

Статья посвящена исследованию малоизученной стороны деятельности видного русского священнослужителя протоиерея Евгения Попова, бывшего с 1842 по 1875 гг. настоятелем русской посольской церкви в Лондоне. Его служение на Английской земле совпало с углублением диалога между Русской Православной и Англиканской церквами, явившегося следствием религиозных преобразований в Англии в 1830 - 1840-е гг. Отец Евгений в рассматриваемый период фактически стал связующим звеном между русским церковноначалием и англиканами - инициаторами единения двух Церквей. Он проделал огромную работу по популяризации православия в Англии и много сделал для ознакомления русской церковной общественности с вероучением и структурными особенностями англиканства. Материалом для исследования послужили, прежде всего, письма протоиерея Евгения Попова обер-прокурорам Святейшего Синода Н. А. Протасову и А. П. Толстому. Эти документы являются своеобразными отчётами о современном состоянии Англиканской Церкви, о религиозных течениях в ней и усилиях, предпринимаемых определёнными церковными кругами в Англии по сближению с православием. Результаты его деятельности имели важное значение в последующие десятилетия, когда англикано-православный диалог вышел на церковно-государственный уровень. The article is devoted to the insufficiently studied aspects of Russian prominent cleric Archpriest Eugene Popov, rector of Russian Embassy Church in London from 1842 to 1875. His Ministry on the English soil coincided with the deepening of the dialogue between the Russian Orthodox and Anglican Churches, which was the result of religious transformations in England in the 1830s and 1840s. Father Eugene in the period under consideration actually became a connecting link between the Russian Church authorities and the anglicans-initiators of the union of the two Churches. He had done a great job by popularizing Orthodoxy in England and by familiarizing the Russian Church community with the doctrine and structural features of Anglicanism. The study, first of all, is based the letters of Archpriest Yevgeny Popov to the chief prosecutors of the Holy Synod N. A. Protasov and A. P. Tolstoy, which were original reports on the current state of the Anglican Church, it’s religious trends, and the efforts made by certain Church circles in England to get closer to Orthodoxy. The fruits of his activities were important in the following decades, when the Anglican-Orthodox dialogue reached the Church-state level.

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