المؤلفون: Malis, Yehonathan¹, Armoza-Eilat, Shir², Nevo-Yassaf, Inbar¹, Dukhovny, Anna², Sklan, Ella H.² sklan@tauex.tau.ac.il, Hirschberg, Koret¹

المصدر: Science Advances. 5/31/2024, Vol. 10 Issue 22, p1-12. 12p.

مصطلحات موضوعية: *ACYLTRANSFERASES, *GUANOSINE triphosphatase, *HOMEOSTASIS, *FIBROBLASTS, *HEPATOCELLULAR carcinoma

مستخلص: Lipid droplets (LDs) comprise a triglyceride core surrounded by a lipid monolayer enriched with proteins, many of which function in LD homeostasis. How proteins are targeted to the growing LD is still unclear. Rab1b, a GTPase regulating secretory transport, was recently associated with targeting proteins to LDs in a Drosophila RNAi screen. LD formation was prevented in human hepatoma cells overexpressing dominant-negative Rab1b. We thus hypothesized that Rab1b recruits lipid-synthesizing enzymes, facilitating LD growth. Here, FRET between diacylglycerol acyltransferase 2 (DGAT2) and Rab1b and activity mutants of the latter demonstrated that Rab1b promotes DGAT2 ER to the LD surface redistribution. Last, alterations in LD metabolism and DGAT2 redistribution, consistent with Rab1b activity, were caused by mutations in the Rab1b-GTPase activating protein TBC1D20 in Warburg Micro syndrome (WARBM) model mice fibroblasts. These data contribute to our understanding of the mechanism of Rab1b in LD homeostasis and WARBM, a devastating autosomal-recessive disorder caused by mutations in TBC1D20. [ABSTRACT FROM AUTHOR]

المؤلفون: Chakraborty, Sukanya¹, Kanade, Manil¹, Gayathri, Pananghat¹ gayathri@iiserpune.ac.in

المصدر: Journal of Biological Chemistry. Apr2024, Vol. 300 Issue 4, p1-16. 16p.

مصطلحات موضوعية: *GUANINE nucleotide exchange factors, *GUANOSINE triphosphatase, *ALLOSTERIC regulation, *MYXOCOCCUS xanthus, *G proteins

مستخلص: Cell polarity oscillations in Myxococcus xanthus motility are driven by a prokaryotic small Ras-like GTPase, mutual gliding protein A (MglA), which switches from one cell pole to the other in response to extracellular signals. MglA dynamics is regulated by MglB, which functions both as a GTPase activating protein (GAP) and a guanine nucleotide exchange factor (GEF) for MglA. With an aim to dissect the asymmetric role of the two MglB protomers in the dual GAP and GEF activities, we generated a functional MglAB complex by coexpressing MglB with a linked construct of MglA and MglB. This strategy enabled us to generate mutations of individual MglB protomers (MglB1 or MglB2 linked to MglA) and delineate their role in GEF and GAP activities. We establish that the C-terminal helix of MglB1, but not MglB2, stimulates nucleotide exchange through a site away from the nucleotide-binding pocket, con- firming an allosteric mechanism. Interaction between the Nterminal β-strand of MglB1 and β0 of MglA is essential for the optimal GEF activity of MglB. Specific residues of MglB2, which interact with Switch-I of MglA, partially contribute to its GAP activity. Thus, the role of the MglB2 protomer in the GAP activity of MglB is limited to restricting the conformation of MglA active site loops. The direct demonstration of the allosteric mechanism of GEF action provides us new insights into the regulation of small Ras-like GTPases, a feature potentially present in many uncharacterized GEFs. [ABSTRACT FROM AUTHOR]

المؤلفون: Gurung, Sumiran Kumar^1,2 (AUTHOR), Sangeeta³ (AUTHOR), Dubey, Priyanka¹ (AUTHOR), Akhtar, Fatima¹ (AUTHOR), Saha, Abhik^1,4 (AUTHOR), Bhattacherjee, Arnab³ (AUTHOR) arnab@jnu.ac.in, Dhar, Suman Kumar¹ (AUTHOR)

المصدر: Journal of Biochemistry. Apr2024, Vol. 175 Issue 4, p405-417. 13p.

مصطلحات موضوعية: *HELICOBACTER pylori, *GUANOSINE triphosphatase, *PATHOGENIC bacteria, *MOLECULAR dynamics, *BACTERIAL cells

مستخلص: Actively treadmilling FtsZ acts as the pivotal scaffold for bacterial cell divisome components, providing them with a circumferential ride along the site of future division. FtsZ from slow-growing Helicobacter pylori (HpFtsZ), a class I carcinogen that thrives abundantly in the acidic environment, is poorly understood. We studied HpFtsZ as a function of pH, cations and time and compared it with well-studied Escherichia coli FtsZ (EcFtsZ). HpFtsZ shows pH-dependent GTPase activity, which is inhibited under acidic conditions. Mg+2 ions play an indispensable role in its GTPase activity; however, higher Mg+2 levels negatively affect its activity. As compared to EcFtsZ, HpFtsZ exhibits lower and slower nucleotide hydrolysing activity. Molecular dynamics simulation studies of FtsZ reveal that GTP binding induces a rewiring of the hydrogen bond network, which results in reduction of the binding cleft volume leading to the spontaneous release of GTP. The GTPase activity is linked to the extent of reduction in the binding cleft volume, which is also supported by the binding free energy analysis. Evidently, HpFtsZ is a pH-sensitive GTPase with low efficiency that may reflect on the overall slow growth rate of H. pylori. [ABSTRACT FROM AUTHOR]

المؤلفون: Soto, Flavia¹ (AUTHOR) flsoto@utalca.cl, San Martín-Davison, Alex¹ (AUTHOR), Salinas-Cornejo, Josselyn¹ (AUTHOR), Madrid-Espinoza, José¹ (AUTHOR), Ruiz-Lara, Simón¹ (AUTHOR) sruiz@utalca.cl

المصدر: Genes. Apr2024, Vol. 15 Issue 4, p453. 20p.

مصطلحات موضوعية: *TOMATOES, *GUANOSINE triphosphatase, *GENE expression, *GENES, *SALT, *ABIOTIC stress

مستخلص: Salinity in plants generates an osmotic and ionic imbalance inside cells that compromises the viability of the plant. Rab GTPases, the largest family within the small GTPase superfamily, play pivotal roles as regulators of vesicular trafficking in plants, including the economically important and globally cultivated tomato (Solanum lycopersicum). Despite their significance, the specific involvement of these small GTPases in tomato vesicular trafficking and their role under saline stress remains poorly understood. In this work, we identified and classified 54 genes encoding Rab GTPases in cultivated tomato, elucidating their genomic distribution and structural characteristics. We conducted an analysis of duplication events within the S. lycopersicum genome, as well as an examination of gene structure and conserved motifs. In addition, we investigated the transcriptional profiles for these Rab GTPases in various tissues of cultivated and wild tomato species using microarray-based analysis. The results showed predominantly low expression in most of the genes in both leaves and vegetative meristem, contrasting with notably high expression levels observed in seedling roots. Also, a greater increase in gene expression in shoots from salt-tolerant wild tomato species was observed under normal conditions when comparing Solanum habrochaites, Solanum pennellii, and Solanum pimpinellifolium with S. lycopersicum. Furthermore, an expression analysis of Rab GTPases from Solanum chilense in leaves and roots under salt stress treatment were also carried out for their characterization. These findings revealed that specific Rab GTPases from the endocytic pathway and the trans-Golgi network (TGN) showed higher induction in plants exposed to saline stress conditions. Likewise, disparities in gene expression were observed both among members of the same Rab GTPase subfamily and between different subfamilies. Overall, this work emphasizes the high degree of conservation of Rab GTPases, their high functional diversification in higher plants, and the essential role in mediating salt stress tolerance and suggests their potential for further exploration of vesicular trafficking mechanisms in response to abiotic stress conditions. [ABSTRACT FROM AUTHOR]

المؤلفون: Lee, Soo‐Yeon¹ (AUTHOR), Lee, Ki‐Young¹ (AUTHOR) kiyoung198395@gmail.com

المصدر: Angewandte Chemie. Mar2024, Vol. 136 Issue 13, p1-11. 11p.

مصطلحات موضوعية: *RAS proteins, *GUANOSINE triphosphatase, *RAS oncogenes, *MEMBRANE lipids, *CELL communication

مستخلص: Self‐assemblies (i.e. nanoclusters) of the RAS GTPase on the membrane act as scaffolds that activate downstream RAF kinases and drive MAPK signaling for cell proliferation and tumorigenesis. However, the mechanistic details of nanoclustering remain largely unknown. Here, size‐tunable nanodisc platforms and paramagnetic relaxation enhancement (PRE) analyses revealed the structural basis of the cooperative assembly processes of fully processed KRAS, mutated in a quarter of human cancers. The cooperativity is modulated by the mutation and nucleotide states of KRAS and the lipid composition of the membrane. Notably, the oncogenic mutants assemble in nonsequential pathways with two mutually cooperative 'α/α' and 'α/β' interfaces, while α/α dimerization of wild‐type KRAS promotes the secondary α/β interaction sequentially. Mutation‐based interface engineering was used to selectively trap the oligomeric intermediates of KRAS and probe their favorable interface interactions. Transiently exposed interfaces were available for the assembly. Real‐time NMR demonstrated that higher‐order oligomers retain higher numbers of active GTP‐bound protomers in KRAS GTPase cycling. These data provide a deeper understanding of the nanocluster‐enhanced signaling in response to the environment. Furthermore, our methodology is applicable to assemblies of many other membrane GTPases and lipid nanoparticle‐based formulations of stable protein oligomers with enhanced cooperativity. [ABSTRACT FROM AUTHOR]

المؤلفون: Layish, Bailey¹ (AUTHOR), Goli, Ram¹ (AUTHOR), Flick, Haley¹ (AUTHOR), Huang, Szu-Wei² (AUTHOR), Zhang, Robert Z.¹ (AUTHOR), Kvaratskhelia, Mamuka² (AUTHOR), Kane, Melissa¹ (AUTHOR) kaneme@pitt.edu

المصدر: PLoS Pathogens. 3/21/2024, Vol. 20 Issue 3, p1-27. 27p.

مصطلحات موضوعية: *NUCLEAR pore complex, *GUANOSINE triphosphatase, *NUCLEOCYTOPLASMIC interactions, *VIRAL nonstructural proteins, *CYCLOPHILINS, *VIRUS diseases, *VIRAL proteins

مستخلص: Human myxovirus resistance 2 (MX2/MXB) is an interferon-induced GTPase that inhibits human immunodeficiency virus-1 (HIV-1) infection by preventing nuclear import of the viral preintegration complex. The HIV-1 capsid (CA) is the major viral determinant for sensitivity to MX2, and complex interactions between MX2, CA, nucleoporins (Nups), cyclophilin A (CypA), and other cellular proteins influence the outcome of viral infection. To explore the interactions between MX2, the viral CA, and CypA, we utilized a CRISPR-Cas9/AAV approach to generate CypA knock-out cell lines as well as cells that express CypA from its endogenous locus, but with specific point mutations that would abrogate CA binding but should not affect enzymatic activity or cellular function. We found that infection of CypA knock-out and point mutant cell lines with wild-type HIV-1 and CA mutants recapitulated the phenotypes observed upon cyclosporine A (CsA) addition, indicating that effects of CsA treatment are the direct result of blocking CA-CypA interactions and are therefore independent from potential interactions between CypA and MX2 or other cellular proteins. Notably, abrogation of GTP hydrolysis by MX2 conferred enhanced antiviral activity when CA-CypA interactions were abolished, and this effect was not mediated by the CA-binding residues in the GTPase domain, or by phosphorylation of MX2 at position T151. We additionally found that elimination of GTPase activity also altered the Nup requirements for MX2 activity. Our data demonstrate that the antiviral activity of MX2 is affected by CypA-CA interactions in a virus-specific and GTPase activity-dependent manner. These findings further highlight the importance of the GTPase domain of MX2 in regulation of substrate specificity and interaction with nucleocytoplasmic trafficking pathways. Author summary: HIV-1 entry into the nucleus is an essential step in viral replication that involves complex interactions between the viral capsid and multiple cellular proteins, including the proline isomerase cyclophilin A. Nuclear entry of HIV-1 and other primate lentiviruses is inhibited by the antiviral protein MX2. Here, we show that direct interactions between capsid and cyclophilin A affect the antiviral activity and specificity of MX2, and that these interactions are altered when the enzymatic activity of MX2 is eliminated. We demonstrate that abolishing enzymatic activity of MX2 also alters the requirements for nuclear pore complex components for viral restriction. Our study provides new insights into how the enzymatic function of MX2 affects inhibition of lentiviral nuclear import. [ABSTRACT FROM AUTHOR]

المؤلفون: Bischof, Linnet¹ (AUTHOR) linnet.bischof@uni-osnabrueck.de, Schweitzer, Franziska¹ (AUTHOR), Heinisch, Jürgen J.¹ (AUTHOR) jheinisc@uos.de

المصدر: Cells (2073-4409). Mar2024, Vol. 13 Issue 6, p472. 17p.

مصطلحات موضوعية: *NADPH oxidase, *GUANOSINE triphosphatase, *CYTOSKELETON, *MOLECULAR switches, *YEAST

مستخلص: Small GTPases are molecular switches that participate in many essential cellular processes. Amongst them, human Rac1 was first described for its role in regulating actin cytoskeleton dynamics and cell migration, with a close relation to carcinogenesis. More recently, the role of Rac1 in regulating the production of reactive oxygen species (ROS), both as a subunit of NADPH oxidase complexes and through its association with mitochondrial functions, has drawn attention. Malfunctions in this context affect cellular plasticity and apoptosis, related to neurodegenerative diseases and diabetes. Some of these features of Rac1 are conserved in its yeast homologue Rho5. Here, we review the structural and functional similarities and differences between these two evolutionary distant proteins and propose yeast as a useful model and a device for high-throughput screens for specific drugs. [ABSTRACT FROM AUTHOR]

المؤلفون: Du, Xiaojuan¹ (AUTHOR), Gao, Yingmiao^2,3 (AUTHOR), Zhang, Hao¹ (AUTHOR), Xu, Xiaoyu¹ (AUTHOR), Li, Ying¹ (AUTHOR), Zhao, Lifeng¹ (AUTHOR) zhaolifeng@scau.edu.cn, Luo, Ming^2,3 (AUTHOR) luoming@scbg.ac.cn, Wang, Hao¹ (AUTHOR) wanghaohw@gmail.com

المصدر: New Phytologist. Mar2024, Vol. 241 Issue 6, p2523-2539. 17p.

مصطلحات موضوعية: *GUANOSINE triphosphatase, *EPIGENETICS, *CELL polarity, *ARABIDOPSIS, *PAVEMENTS

مستخلص: Summary: The transcriptional regulation of Rho‐related GTPase from plants (ROPs), which determine cell polarity formation and maintenance during plant development, still remains enigmatic.In this study, we elucidated the epigenetic mechanism of histone deacetylase HDA6 in transcriptional repression of ROP6 and its impact on cell polarity and morphogenesis in Arabidopsis leaf epidermal pavement cells (PCs).We found that the hda6 mutant axe1‐4 exhibited impaired jigsaw‐shaped PCs and convoluted leaves. This correlated with disruptions in the spatial organizations of cortical microtubules and filamentous actin, which is integral to PC indentation and lobe formation. Further transcriptional analyses and chromatin immunoprecipitation assay revealed that HDA6 specifically represses ROP6 expression through histone H3K9K14 deacetylation. Importantly, overexpression of dominant negative‐rop6 in axe1‐4 restored interdigitated cell morphology.Our study unveils HDA6 as a key regulator in Arabidopsis PC morphogenesis through epigenetic suppression of ROP6. It reveals the pivotal role of HDA6 in the transcriptional regulation of ROP6 and provides compelling evidence for the functional interplay between histone deacetylation and ROP6‐mediated cytoskeletal arrangement in the development of interdigitated PCs. [ABSTRACT FROM AUTHOR]

المؤلفون: Tran, Linh T.¹ (AUTHOR), Akıl, Caner^1,2 (AUTHOR), Senju, Yosuke¹ (AUTHOR), Robinson, Robert C.^1,3 (AUTHOR) robert.b@vistec.ac.th

المصدر: Communications Biology. 3/12/2024, Vol. 7 Issue 1, p1-13. 13p.

مصطلحات موضوعية: *GUANOSINE triphosphatase, *ARCHAEBACTERIA, *PROTEIN domains, *PROTEINS

مستخلص: Membrane-enclosed organelles are defining features of eukaryotes in distinguishing these organisms from prokaryotes. Specification of distinct membranes is critical to assemble and maintain discrete compartments. Small GTPases and their regulators are the signaling molecules that drive membrane-modifying machineries to the desired location. These signaling molecules include Rab and Rag GTPases, roadblock and longin domain proteins, and TRAPPC3-like proteins. Here, we take a structural approach to assess the relatedness of these eukaryotic-like proteins in Asgard archaea, the closest known prokaryotic relatives to eukaryotes. We find that the Asgard archaea GTPase core domains closely resemble eukaryotic Rabs and Rags. Asgard archaea roadblock, longin and TRAPPC3 domain-containing proteins form dimers similar to those found in the eukaryotic TRAPP and Ragulator complexes. We conclude that the emergence of these protein architectures predated eukaryogenesis, however further adaptations occurred in proto-eukaryotes to allow these proteins to regulate distinct internal membranes. A structural study of Asgard archaea signaling proteins identifies eukaryotic-like features that predate eukaryogenesis. However, characteristics specifying distinct eukaryotic membranes are absent, indicating these evolved during eukaryogenesis. [ABSTRACT FROM AUTHOR]

المؤلفون: Mills, Joshua¹, Gebhard, L. Johanna¹, Schubotz, Florence², Shevchenko, Anna³, Speth, Daan R.^4,5, Yan Liao⁶, Duggin, Iain G.⁶, Marchfelder, Anita⁷, Erdmann, Susanne¹ serdmann@mpi-bremen.de

المصدر: Proceedings of the National Academy of Sciences of the United States of America. 3/5/2024, Vol. 121 Issue 10, p1-12. 46p.

مصطلحات موضوعية: *EXTRACELLULAR vesicles, *GUANOSINE triphosphatase, *ELECTRIC vehicle industry, *HALOBACTERIUM, *OPERONS, *TELECOMMUNICATION systems

مستخلص: Since their discovery, extracellular vesicles (EVs) have changed our view on how organisms interact with their extracellular world. EVs are able to traffic a diverse array of molecules across different species and even domains, facilitating numerous functions. In this study, we investigate EV production in Euryarchaeota, using the model organism Haloferax volcanii. We uncover that EVs enclose RNA, with specific transcripts preferentially enriched, including those with regulatory potential, and conclude that EVs can act as an RNA communication system between haloarchaea. We demonstrate the key role of an EV-associated small GTPase for EV formation in H. volcanii that is also present across other diverse evolutionary branches of Archaea. We propose the name, ArvA, for the identified family of archaeal vesiculating GTPases. Additionally, we show that two genes in the same operon with arvA (arvB and arvC) are also involved in EV formation. Both, arvB and arvC, are closely associated with arvA in the majority of other archaea encoding ArvA. Our work demonstrates that small GTPases involved in membrane deformation and vesiculation, ubiquitous in Eukaryotes, are also present in Archaea and are widely distributed across diverse archaeal phyla. [ABSTRACT FROM AUTHOR]