scholarly journals Role of Rab GTPases in Membrane Traffic and Cell Physiology

2011 ◽  
Vol 91 (1) ◽  
pp. 119-149 ◽  
Author(s):  
Alex H. Hutagalung ◽  
Peter J. Novick
Keyword(s):  
Membrane Traffic ◽  
Effector Proteins ◽  
Cell Physiology ◽  
Rab Gtpases ◽  
Disease States ◽  
Transport Vesicle ◽  
Target Membrane ◽  
The Many ◽  
Vesicle Movement ◽  
Regulatory Functions

Intracellular membrane traffic defines a complex network of pathways that connects many of the membrane-bound organelles of eukaryotic cells. Although each pathway is governed by its own set of factors, they all contain Rab GTPases that serve as master regulators. In this review, we discuss how Rabs can regulate virtually all steps of membrane traffic from the formation of the transport vesicle at the donor membrane to its fusion at the target membrane. Some of the many regulatory functions performed by Rabs include interacting with diverse effector proteins that select cargo, promoting vesicle movement, and verifying the correct site of fusion. We describe cascade mechanisms that may define directionality in traffic and ensure that different Rabs do not overlap in the pathways that they regulate. Throughout this review we highlight how Rab dysfunction leads to a variety of disease states ranging from infectious diseases to cancer.

scholarly journals In vivo identification of GTPase interactors by mitochondrial relocalization and proximity biotinylation

2019 ◽  
Author(s):  
Alison Gillingham ◽  
Jessie Bertram ◽  
Farida Begum ◽  
Sean Munro
Keyword(s):  
Cell Growth ◽  
Membrane Traffic ◽  
Effector Proteins ◽  
Rab Gtpases ◽  
Wide Range ◽  
Ras Superfamily ◽  
Ras Family ◽  
Regulate Cell Growth

AbstractThe GTPases of the Ras superfamily regulate cell growth, membrane traffic and the cytoskeleton, and a wide range of diseases are caused by mutations in particular members. They function as switchable landmarks with the active GTP-bound form recruiting to the membrane a specific set of effector proteins. The GTPases are precisely controlled by regulators that promote acquisition of GTP (GEFs) or its hydrolysis to GDP (GAPs). We report here MitoID, a method for identifying effectors and regulators by performing in vivo proximity biotinylation with mitochondrially-localized forms of the GTPases. Applying this to 11 human Rab GTPases identified many known effectors and GAPs, as well as putative novel effectors, with examples of the latter validated for Rab2, Rab5 and Rab9. MitoID can also efficiently identify effectors and GAPs of Rho and Ras family GTPases such as Cdc42, RhoA, Rheb, and N-Ras, and can identify GEFs by use of GDP-bound forms.

scholarly journals In vivo identification of GTPase interactors by mitochondrial relocalization and proximity biotinylation

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Alison K Gillingham ◽  
Jessie Bertram ◽  
Farida Begum ◽  
Sean Munro
Keyword(s):  
Cell Growth ◽  
Membrane Traffic ◽  
Effector Proteins ◽  
Rab Gtpases ◽  
Wide Range ◽  
Ras Superfamily ◽  
Ras Family ◽  
Regulate Cell Growth

The GTPases of the Ras superfamily regulate cell growth, membrane traffic and the cytoskeleton, and a wide range of diseases are caused by mutations in particular members. They function as switchable landmarks with the active GTP-bound form recruiting to the membrane a specific set of effector proteins. The GTPases are precisely controlled by regulators that promote acquisition of GTP (GEFs) or its hydrolysis to GDP (GAPs). We report here MitoID, a method for identifying effectors and regulators by performing in vivo proximity biotinylation with mitochondrially-localized forms of the GTPases. Applying this to 11 human Rab GTPases identified many known effectors and GAPs, as well as putative novel effectors, with examples of the latter validated for Rab2, Rab5, Rab9 and Rab11. MitoID can also efficiently identify effectors and GAPs of Rho and Ras family GTPases such as Cdc42, RhoA, Rheb, and N-Ras, and can identify GEFs by use of GDP-bound forms.

scholarly journals Lysosomes, Autophagy, and Hormesis in Cell Physiology, Pathology, and Age-Related Disease

Dose-Response ◽  
2020 ◽  
Vol 18 (3) ◽  
pp. 155932582093422 ◽  
Author(s):  
Michael N. Moore
Keyword(s):  
Intracellular Signaling ◽  
Adenosine Monophosphate ◽  
Target Of Rapamycin ◽  
Cell Physiology ◽  
Mechanistic Target Of Rapamycin ◽  
Age Related ◽  
Mechanistic Basis ◽  
The Many ◽  
Mtor Complex 1

Autophagy has been strongly linked with hormesis, however, it is only relatively recently that the mechanistic basis underlying this association has begun to emerge. Lysosomal autophagy is a group of processes that degrade proteins, protein aggregates, membranes, organelles, segregated regions of cytoplasm, and even parts of the nucleus in eukaryotic cells. These degradative processes are evolutionarily very ancient and provide a survival capability for cells that are stressed or injured. Autophagy and autophagic dysfunction have been linked with many aspects of cell physiology and pathology in disease processes; and there is now intense interest in identifying various therapeutic strategies involving its regulation. The main regulatory pathway for augmented autophagy is the mechanistic target of rapamycin (mTOR) cell signaling, although other pathways can be involved, such as 5′-adenosine monophosphate-activated protein kinase. Mechanistic target of rapamycin is a key player in the many highly interconnected intracellular signaling pathways and is responsible for the control of cell growth among other processes. Inhibition of mTOR (specifically dephosphorylation of mTOR complex 1) triggers augmented autophagy and the search is on the find inhibitors that can induce hormetic responses that may be suitable for treating many diseases, including many cancers, type 2 diabetes, and age-related neurodegenerative conditions.

scholarly journals Perturbation of host autophagy by the Irish potato famine pathogen

2014 ◽  
Vol 70 (a1) ◽  
pp. C826-C826
Author(s):  
Abbas Maqbool ◽  
Richard Richard ◽  
Tolga Bozkurt ◽  
Yasin Dagdas ◽  
Khaoula Belhai ◽  
...  
Keyword(s):  
Host Cell ◽  
Plant Cells ◽  
Irish Potato ◽  
Effector Proteins ◽  
Host Cells ◽  
Cell Physiology ◽  
Biochemical Basis ◽  
The Impact ◽  
Potato Famine ◽  
Irish Potato Famine

Autophagy is a catabolic process involving degradation of dysfunctional cytoplasmic components to ensure cellular survival under starvation conditions. The process involves formation of double-membrane vesicles called autophagosomes and delivery of the inner constituents to lytic compartments. It can also target invading pathogens, such as intracellular bacteria, for destruction and is thus implicated in innate immune pathways [1]. In response, certain mammalian pathogens deliver effector proteins into host cells that inhibit autophagy and contribute to enabling parasitic infection [2]. Pyhtophthora infestans, the Irish potato famine pathogen, is a causative agent of late blight disease in potato and tomato crops. It delivers a plethora of modular effector proteins into plant cells to promote infection. Once inside the cell, RXLR-type effector proteins engage with host cell proteins, to manipulate host cell physiology for the benefit of the pathogen. As plants lack an adaptive immune system, this provides a robust mechanism for pathogens to circumvent host defense. PexRD54 is an intracellular RXLR-type effector protein produced by P. infestans. PexRD54 interacts with potato homologues of autophagy protein ATG8 in plant cells. We have been investigating the structural and biochemical basis of the PexRD54/ATG8 interaction in vitro. We have purified PexRD54 and ATG8 independently and in complex from E. coli. Using protein/protein interaction studies we have shown that PexRD54 binds ATG8 with sub-micromolar affinity. We have also determined the structure of PexRD54 in the presence of ATG8. This crystal structure provides key insights into how the previously reported WY-fold of oomycete RXLR-type effectors [3] can be organized in multiple repeats. The structural data also provides insights into the interaction between PexRD54 and ATG8, suggesting further experiments to understand the impact of this interaction on host cell physiology and how this benefits the pathogen.

scholarly journals Structures ofDrosophila melanogasterRab2 and Rab3 bound to GMPPNP

2015 ◽  
Vol 71 (1) ◽  
pp. 34-40 ◽  
Author(s):  
Jennifer A. Lardong ◽  
Jan H. Driller ◽  
Harald Depner ◽  
Christoph Weise ◽  
Astrid Petzoldt ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Intracellular Trafficking ◽  
Large Family ◽  
Cysteine Residue ◽  
Effector Proteins ◽  
Rab Proteins ◽  
Rab Gtpases ◽  
Ras Proteins ◽  
Transport Vesicles ◽  
Switch Regions

Rab GTPases belong to the large family of Ras proteins. They act as key regulators of membrane organization and intracellular trafficking. Functionally, they act as switches. In the active GTP-bound form they can bind to effector proteins to facilitate the delivery of transport vesicles. Upon stimulation, the GTP is hydrolyzed and the Rab proteins undergo conformational changes in their switch regions. This study focuses on Rab2 and Rab3 fromDrosophila melanogaster. Whereas Rab2 is involved in vesicle transport between the Golgi and the endoplasmatic reticulum, Rab3 is a key player in exocytosis, and in the synapse it is involved in the assembly of the presynaptic active zone. Here, high-resolution crystal structures of Rab2 and Rab3 in complex with GMPPNP and Mg2+are presented. In the structure of Rab3 a modified cysteine residue is observed with an enigmatic electron density attached to its thiol function.

scholarly journals Spatiotemporal organization and protein dynamics involved in regulated exocytosis of MMP-9 in breast cancer cells

2019 ◽  
Vol 151 (12) ◽  
pp. 1386-1403 ◽  
Author(s):  
Dominique C. Stephens ◽  
Nicole Osunsanmi ◽  
Kem A. Sochacki ◽  
Tyrel W. Powell ◽  
Justin W. Taraska ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Secretory Vesicle ◽  
Effector Proteins ◽  
Cellular Transport ◽  
Secretory Vesicles ◽  
Rab Gtpases ◽  
Regulated Exocytosis ◽  
Endocytic Proteins

Altered regulation of exocytosis is an important mechanism controlling many diseases, including cancer. Defects in exocytosis have been implicated in many cancer cell types and are generally attributed to mutations in cellular transport, trafficking, and assembly of machinery necessary for exocytosis of secretory vesicle cargo. In these cancers, up-regulation of trafficking and secretion of matrix metalloproteinase-9 (MMP-9), a proteolytic enzyme, is responsible for degrading the extracellular matrix, a necessary step in tumor progression. Using TIRF microscopy, we identified proteins associated with secretory vesicles containing MMP-9 and imaged the local dynamics of these proteins at fusion sites during regulated exocytosis of MMP-9 from MCF-7 breast cancer cells. We found that many regulators of exocytosis, including several Rab GTPases, Rab effector proteins, and SNARE/SNARE modulator proteins, are stably assembled on docked secretory vesicles before exocytosis. At the moment of fusion, many of these components are quickly lost from the vesicle, while several endocytic proteins and lipids are simultaneously recruited to exocytic sites at precisely that moment. Our findings provide insight into the dynamic behavior of key core exocytic proteins, accessory proteins, lipids, and some endocytic proteins at single sites of secretory vesicle fusion in breast cancer cells.

scholarly journals Different Domains of the Essential GTPase Cdc42p Required for Growth and Development of Saccharomyces cerevisiae

2001 ◽  
Vol 21 (1) ◽  
pp. 235-248 ◽  
Author(s):  
Hans-Ulrich Mösch ◽  
Tim Köhler ◽  
Gerhard H. Braus
Keyword(s):  
Cell Division ◽  
Protein Kinase ◽  
Nitrogen Starvation ◽  
Effector Proteins ◽  
Single Amino Acid ◽  
Invasive Growth ◽  
Cell Morphogenesis ◽  
Mutant Proteins ◽  
Diploid Cells ◽  
Regulatory Functions

ABSTRACT In budding yeast, the Rho-type GTPase Cdc42p is essential for cell division and regulates pseudohyphal development and invasive growth. Here, we isolated novel Cdc42p mutant proteins with single-amino-acid substitutions that are sufficient to uncouple functions of Cdc42p essential for cell division from regulatory functions required for pseudohyphal development and invasive growth. In haploid cells, Cdc42p is able to regulate invasive growth dependent on and independent of FLO11 gene expression. In diploid cells, Cdc42p regulates pseudohyphal development by controlling pseudohyphal cell (PH cell) morphogenesis and invasive growth. Several of the Cdc42p mutants isolated here block PH cell morphogenesis in response to nitrogen starvation without affecting morphology or polarity of yeast form cells in nutrient-rich conditions, indicating that these proteins are impaired for certain signaling functions. Interaction studies between development-specific Cdc42p mutants and known effector proteins indicate that in addition to the p21-activated (PAK)-like protein kinase Ste20p, the Cdc42p/Rac-interactive-binding domain containing Gic1p and Gic2p proteins and the PAK-like protein kinase Skm1p might be further effectors of Cdc42p that regulate pseudohyphal and invasive growth.

Apicomplexans pulling the strings: manipulation of the host cell cytoskeleton dynamics

Parasitology ◽  
2016 ◽  
Vol 143 (8) ◽  
pp. 957-970 ◽  
Author(s):  
RITA CARDOSO ◽  
HELENA SOARES ◽  
ANDREW HEMPHILL ◽  
ALEXANDRE LEITÃO
Keyword(s):  
Host Cell ◽  
Life Cycle Stage ◽  
Effector Proteins ◽  
Cell Physiology ◽  
Apicomplexan Parasites ◽  
Cell Cytoskeleton ◽  
Cytoskeletal Filament ◽  
Associated Proteins ◽  
Organelle Trafficking ◽  
Cytoskeleton Dynamics

SUMMARYInvasive stages of apicomplexan parasites require a host cell to survive, proliferate and advance to the next life cycle stage. Once invasion is achieved, apicomplexans interact closely with the host cell cytoskeleton, but in many cases the different species have evolved distinct mechanisms and pathways to modulate the structural organization of cytoskeletal filaments. The host cell cytoskeleton is a complex network, largely, but not exclusively, composed of microtubules, actin microfilaments and intermediate filaments, all of which are modulated by associated proteins, and it is involved in diverse functions including maintenance of cell morphology and mechanical support, migration, signal transduction, nutrient uptake, membrane and organelle trafficking and cell division. The ability of apicomplexans to modulate the cytoskeleton to their own advantage is clearly beneficial. We here review different aspects of the interactions of apicomplexans with the three main cytoskeletal filament types, provide information on the currently known parasite effector proteins and respective host cell targets involved, and how these interactions modulate the host cell physiology. Some of these findings could provide novel targets that could be exploited for the development of preventive and/or therapeutic strategies.

What Can Transgenic and Gene-targeted Mouse Models Teach Us about Salivary Gland Physiology?

2000 ◽  
Vol 14 (1) ◽  
pp. 5-11 ◽  
Author(s):  
J.E. Melvin ◽  
H.-V. Nguyen ◽  
R.L. Evans ◽  
G.E. Shull
Keyword(s):  
Salivary Gland ◽  
Mouse Models ◽  
Recombinant Dna ◽  
Genetically Modified ◽  
Cell Physiology ◽  
Specific Expression ◽  
Disease States ◽  
Salivary Gland Secretion ◽  
Genetically Modified Mice ◽  
Gland Function

Thousands of genetically modified mice have been developed since the first reports of stable expression of recombinant DNA in this species nearly 20 years ago. This mammalian model system has revolutionized the study of whole-animal, organ, and cell physiology. Transgenic and gene-targeted mice have been widely used to characterize salivary-gland-specific expression and to identify genes associated with tumorigenesis. Moreover, several of these mouse lines have proved to be useful models of salivary gland disease related to impaired immunology, i.e., Sjogren's syndrome, and disease states associated with pathogens. Despite the availability of genetically modified mice, few investigators have taken advantage of this resource to better their understanding of salivary gland function as it relates to the production of saliva. In this article, we describe the methods used to generate transgenic and gene-targeted mice and provide an overview of the advantages of and potential difficulties with these models. Finally, using these mouse models, we discuss the advances made in our understanding of the salivary gland secretion process.

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