Small GTPasesPub Date : 2024-12-01Epub Date: 2025-05-04DOI: 10.1080/21541248.2025.2498174
Masaki Ishii, Shinya Ohata
{"title":"Small GTPase Rac promotes hyphal formation and microconidiogenesis in <i>Trichophyton rubrum</i>.","authors":"Masaki Ishii, Shinya Ohata","doi":"10.1080/21541248.2025.2498174","DOIUrl":"https://doi.org/10.1080/21541248.2025.2498174","url":null,"abstract":"<p><p>Morphogenesis plays a pivotal role in the infection process of <i>Trichophyton rubrum</i>, a primary aetiological agent of dermatophytosis that inhabits superficial human tissues. <i>T. rubrum</i> proliferates by extending filamentous structures, or hyphae, which are composed of highly polarized cells. In response to environmental stimuli, <i>T. rubrum</i> also produces asexual spores called microconidia, consisting of individual cells. Although these dynamic morphological changes are critical for <i>T. rubrum</i> proliferation and environmental adaptation, the molecular mechanisms underlying these processes remain poorly understood. In previous research, we demonstrated that repressing Cdc24, a guanine nucleotide exchange factor (GEF) for the small GTPases Rac and Cdc42, disrupts fungal cell polarity and impairs hyphal formation in <i>T. rubrum</i>. In this study, we show that Rac deficiency in the Δ<i>rac</i> strain minimally affects hyphal formation, as indicated by the cell polarity index (the ratio of a cell's long to short diameter in hyphae). However, simultaneous Rac deficiency and Cdc42 repression in the Δ<i>rac</i>/P<sub><i>ctr4</i></sub> <i>cdc42</i> strain significantly disrupted cell polarity, suggesting that Rac and Cdc42 perform overlapping functions in hyphal morphogenesis. Interestingly, Rac deficiency inhibited microconidia formation, whereas <i>cdc42</i> repression had no detectable impact. Furthermore, adding cysteine, a radical scavenger abundant in keratins, to the growth medium reduced microconidia production in the wild-type strain but not in the Δ<i>rac</i> strain. These findings suggest that cysteine in host tissues inhibits Rac-mediated microconidia formation. Overall, this study identifies Rac as a key regulator of <i>T. rubrum</i> morphogenesis, with specific roles in both hyphal development and microconidia formation.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"15 1","pages":"1-8"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12054376/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144015257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2024-12-01Epub Date: 2025-05-20DOI: 10.1080/21541248.2025.2505441
Micah C Fernando, Gregory B Craven, Kevan M Shokat
{"title":"The structure of KRAS<sup>G12C</sup> bound to divarasib highlights features of potent switch-II pocket engagement.","authors":"Micah C Fernando, Gregory B Craven, Kevan M Shokat","doi":"10.1080/21541248.2025.2505441","DOIUrl":"10.1080/21541248.2025.2505441","url":null,"abstract":"<p><p>KRAS is the most frequently mutated oncogene in human cancer. In multiple types of cancer, a missense mutation at codon 12 substitutes a glycine for a cysteine, causing hyperactivation of the GTPase and enhanced MAPK signalling. Recent drug discovery efforts culminating from work during the past decade have resulted in two FDA-approved inhibitors, sotorasib and adagrasib, which target the KRAS<sup>G12C</sup> mutant allele. Ongoing medicinal chemistry efforts across academia and industry have continued developing more potent and efficacious KRAS<sup>G12C</sup> inhibitors. One agent in late-stage clinical trials, divarasib, has demonstrated robust overall response rates, in some cases greater than currently approved agents. Divarasib also exhibits enhanced covalent target engagement <i>in vitro</i> and significant specificity for KRAS<sup>G12C</sup>, yet the structural details of its binding have not been published. Here we report a high-resolution crystal structure of cysteine-light KRAS-4B<sup>G12C</sup> in complex with divarasib. Though it binds in the same allosteric pocket as sotorasib and adagrasib, the switch-II loop in each crystal structure takes on a distinct conformation differing as much as 5.6 Å between the Cα atom of residue 65 with sotorasib. Additionally, we highlight structural features of the drug complex that may guide future medicinal chemistry efforts targeting various <i>KRAS</i> alleles.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"15 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12101598/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144102744","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2024-12-01Epub Date: 2025-05-21DOI: 10.1080/21541248.2025.2505977
Cristina Uribe-Alvarez, Jonathan Chernoff
{"title":"The role of RAC1 in resistance to targeted therapies in cancer.","authors":"Cristina Uribe-Alvarez, Jonathan Chernoff","doi":"10.1080/21541248.2025.2505977","DOIUrl":"10.1080/21541248.2025.2505977","url":null,"abstract":"<p><p>RAC1 is a small 21 kDa RHO GTPase that plays a pivotal role in regulating actin cytoskeletal dynamics and cell growth. Alterations in the activity of RAC1 are implicated in a range of diseases, including cancer. Increased RAC1 activity, due to overexpression and/or activating mutations, drives transcriptional upregulation, reactive oxygen species production, mesenchymal-to-epithelial transition, membrane ruffling, and uncontrolled cell proliferation, which are hallmarks of an oncogenic phenotype. While RAC1-activating mutations alone do not appear sufficient to transform cells, their combination with other common mutations, such as BRAF, NRAS, or NF1, have been linked to drug resistance and significantly worsen patient prognosis and hinder treatment responses. The precise mechanisms underlying drug resistance, and the regulation of <i>RAC1</i> splicing remain poorly understood. RAC1 is a challenging therapeutic target due to its ubiquitous presence and essential cellular functions. To date, there are no established standard treatments for cancers that harbour an additional RAC1 mutation or for RAC1-mediated drug resistance. Current experimental strategies aim to target RAC1 localization, its activators (<i>e.g</i>. guanine nucleotide exchange factors) and downstream effectors. Regulating RAC1 expression by targeting epigenetic regulators, and direct targeting of RAC1 itself, may also be possible in the near future.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"15 1","pages":"1-14"},"PeriodicalIF":0.0,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12101591/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144111909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2023-12-01DOI: 10.1080/21541248.2023.2254437
Akash Chinchole, Shreyta Gupta, Shweta Tyagi
{"title":"To stay in shape and keep moving: MLL emerges as a new transcriptional regulator of Rho GTPases.","authors":"Akash Chinchole, Shreyta Gupta, Shweta Tyagi","doi":"10.1080/21541248.2023.2254437","DOIUrl":"10.1080/21541248.2023.2254437","url":null,"abstract":"<p><p>RhoA, Rac1 and CDC42 are small G proteins that play a crucial role in regulating various cellular processes, such as the formation of actin cytoskeleton, cell shape and cell migration. Our recent results suggest that MLL is responsible for maintaining the balance of these small Rho GTPases. MLL depletion affects the stability of Rho GTPases, leading to a decrease in their protein levels and loss of activity. These changes manifest in the form of abnormal cell shape and disrupted actin cytoskeleton, resulting in reduced cell spreading and migration. Interestingly, their chaperone protein RhoGDI1 but not the Rho GTPases, is under the direct transcriptional regulation of MLL. Here, we comment on the possible implications of these observations on the signalling by Rho GTPases protein network.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"14 1","pages":"55-62"},"PeriodicalIF":0.0,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/fc/63/KSGT_14_2254437.PMC10484036.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10184340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-06-06DOI: 10.1080/21541248.2022.2083895
Siqi Li, C. Counter
{"title":"An ultra-sensitive method to detect mutations in human RAS templates","authors":"Siqi Li, C. Counter","doi":"10.1080/21541248.2022.2083895","DOIUrl":"https://doi.org/10.1080/21541248.2022.2083895","url":null,"abstract":"ABSTRACT The RAS family of small GTPases is mutated in roughly a fifth of human cancers. Hotspot point mutations at codons G12, G13, and Q61 account for 95% of all these mutations, which are well established to render the encoded proteins oncogenic. In humans, this family comprises three genes: HRAS, NRAS, and KRAS. Accumulating evidence argues that oncogenic RAS point mutations may be initiating, as they are often truncal in human tumours and capable of inducing tumorigenesis in mice. As such, there is great interest in detecting oncogenic mutation in the RAS genes to understand the origins of cancer, as well as for early detection purposes. To this end, we previously adapted the microbial ultra-sensitive M aximum D epth S equencing (MDS) assay for the murine Kras gene, which was capable of detecting oncogenic mutations in the tissues of mice days after carcinogen exposure, essentially capturing the very first step in tumour initiation. Given this, we report here the adaption and details of this assay to detect mutations in a human KRAS sequence at an analytic sensitivity of one mutation in a million independently barcoded templates. This humanized version of MDS can thus be exploited to detect oncogenic mutations in KRAS at an incredible sensitivity and modified for the same purpose for the other RAS genes.","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"287 - 295"},"PeriodicalIF":0.0,"publicationDate":"2022-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42208867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-01-01DOI: 10.1080/21541248.2022.2141019
Dylan D Doxsey, Kristen Veinotte, Kuang Shen
{"title":"A New Crosslinking Assay to Study Guanine Nucleotide Binding in the Gtr Heterodimer of <i>S. cerevisiae</i>.","authors":"Dylan D Doxsey, Kristen Veinotte, Kuang Shen","doi":"10.1080/21541248.2022.2141019","DOIUrl":"https://doi.org/10.1080/21541248.2022.2141019","url":null,"abstract":"<p><p>The mechanistic target of rapamycin (mTOR) complex is responsible for coordinating nutrient availability with eukaryotic cell growth. Amino acid signals are transmitted towards mTOR via the Rag/Gtr heterodimers. Due to the obligatory heterodimeric architecture of the Rag/Gtr GTPases, investigating their biochemical properties has been challenging. Here, we describe an updated assay that allows us to probe the guanine nucleotide-binding affinity and kinetics to the Gtr heterodimers in <i>Saccharomyces cerevisiae</i>. We first identified the structural element that Gtr2p lacks to enable crosslinking. By using a sequence conservation-based mutation, we restored the crosslinking between Gtr2p and the bound nucleotides. Using this construct, we determined the nucleotide-binding affinities of the Gtr heterodimer, and found that it operates under a different form of intersubunit communication than human Rag GTPases. Our study defines the evolutionary divergence of the Gtr/Rag-mTOR axis of nutrient sensing.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"327-334"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/e4/6b/KSGT_13_2141019.PMC9639563.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9199885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-01-01DOI: 10.1080/21541248.2021.1892443
Lan Jiang, Tizhong Zhang, Kefeng Lu, Shiqian Qi
{"title":"The progress in <i>C9orf72</i> research: ALS/FTD pathogenesis, functions and structure.","authors":"Lan Jiang, Tizhong Zhang, Kefeng Lu, Shiqian Qi","doi":"10.1080/21541248.2021.1892443","DOIUrl":"https://doi.org/10.1080/21541248.2021.1892443","url":null,"abstract":"<p><p>The hexanucleotide repeat (GGGGCC) expansion in <i>C9orf72</i> is accounted for a large proportion of the genetic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The hypotheses of how the massive G4C2 repeats in <i>C9orf72</i> destroy the neurons and lead to ALS/FTD are raised and improving. As a multirole player, C9orf72 exerts critical roles in many cellular processes, including autophagy, membrane trafficking, immune response, and so on. Notably, the partners of C9orf72, through which C9orf72 participates in the cell activities, have been identified. Notably, the structures of the C9orf72-SMCR8-WDR41 complex shed light on its activity as GTPase activating proteins (GAP). In this manuscript, we reviewed the latest research progress in the C9orf72-mediated ALS/FTD, the physiological functions of C9orf72, and the putative function models of C9orf72/C9orf72-containing complex.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"56-76"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21541248.2021.1892443","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9230612","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-01-01DOI: 10.1080/21541248.2021.1903794
Alfredo L Porfírio-Sousa, Alexander K Tice, Matthew W Brown, Daniel J G Lahr
{"title":"Phylogenetic reconstruction and evolution of the Rab GTPase gene family in Amoebozoa.","authors":"Alfredo L Porfírio-Sousa, Alexander K Tice, Matthew W Brown, Daniel J G Lahr","doi":"10.1080/21541248.2021.1903794","DOIUrl":"https://doi.org/10.1080/21541248.2021.1903794","url":null,"abstract":"<p><p>Rab GTPase is a paralog-rich gene family that controls the maintenance of the eukaryotic cell compartmentalization system. Diverse eukaryotes have varying numbers of Rab paralogs. Currently, little is known about the evolutionary pattern of Rab GTPase in most major eukaryotic 'supergroups'. Here, we present a comprehensive phylogenetic reconstruction of the Rab GTPase gene family in the eukaryotic 'supergroup' Amoebozoa, a diverse lineage represented by unicellular and multicellular organisms. We demonstrate that Amoebozoa conserved 20 of the 23 ancestral Rab GTPases predicted to be present in the last eukaryotic common ancestor and massively expanded several 'novel' in-paralogs. Due to these 'novel' in-paralogs, the Rab family composition dramatically varies between the members of Amoebozoa; as a consequence, 'supergroup'-based studies may significantly change our current understanding of the evolution and diversity of this gene family. The high diversity of the Rab GTPase gene family in Amoebozoa makes this 'supergroup' a key lineage to study and advance our knowledge of the evolution of Rab in Eukaryotes.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"100-113"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21541248.2021.1903794","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9072723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-01-01DOI: 10.1080/21541248.2021.1888557
Viviane Tran, Marie-Anne Goyette, Mónica Martínez-García, Ana Jiménez de Domingo, Daniel Martín Fernández-Mayoralas, Ana Laura Fernández-Perrone, Pilar Tirado, Beatriz Calleja-Pérez, Sara Álvarez, Jean-François Côté, Alberto Fernández-Jaén
{"title":"Biallelic <i>ELMO3</i> mutations and loss of function for DOCK-mediated RAC1 activation result in intellectual disability.","authors":"Viviane Tran, Marie-Anne Goyette, Mónica Martínez-García, Ana Jiménez de Domingo, Daniel Martín Fernández-Mayoralas, Ana Laura Fernández-Perrone, Pilar Tirado, Beatriz Calleja-Pérez, Sara Álvarez, Jean-François Côté, Alberto Fernández-Jaén","doi":"10.1080/21541248.2021.1888557","DOIUrl":"https://doi.org/10.1080/21541248.2021.1888557","url":null,"abstract":"<p><p>The engulfment and cell motility 3 (ELMO3) protein belongs to the ELMO-family of proteins. ELMO proteins form a tight complex with the DOCK1-5 guanine nucleotide exchange factors that regulate RAC1 spatiotemporal activation and signalling. DOCK proteins and RAC1 are known to have fundamental roles in central nervous system development. Here, we searched for homozygous or compound heterozygous mutations in the <i>ELMO3</i> gene in 390 whole exomes sequenced <i>in trio</i> in individuals with neurodevelopmental disorders compatible with a genetic origin. We found a compound heterozygous mutation in <i>ELMO3</i> (c.1153A>T, p.Ser385Cys and c.1009 G > A, p.Val337Ile) in a 5 year old male child with autism spectrum disorder (ASD) and developmental delay. These mutations did not interfere with the formation of an ELMO3/DOCK1 complex, but markedly impaired the ability of the complex to promote RAC1-GTP-loading. Consequently, cells expressing DOCK1 and either of the ELMO3 mutants displayed impaired migration and invasion. Collectively, our results suggest that biallelic loss-of-function mutations in <i>ELMO3</i> may cause a developmental delay and provide new insight into the role of ELMO3 in neurodevelopmental as well as the pathological consequences of <i>ELMO3</i> mutations.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"48-55"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21541248.2021.1888557","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9089210","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Small GTPasesPub Date : 2022-01-01DOI: 10.1080/21541248.2021.1951590
Neda Z Ghanem, Michelle L Matter, Joe W Ramos
{"title":"Regulation of Leukaemia Associated Rho GEF (LARG/ARHGEF12).","authors":"Neda Z Ghanem, Michelle L Matter, Joe W Ramos","doi":"10.1080/21541248.2021.1951590","DOIUrl":"https://doi.org/10.1080/21541248.2021.1951590","url":null,"abstract":"<p><p>The Ras homologous (Rho) protein family of GTPases (RhoA, RhoB and RhoC) are the members of the Ras superfamily and regulate cellular processes such as cell migration, proliferation, polarization, adhesion, gene transcription and cytoskeletal structure. Rho GTPases function as molecular switches that cycle between GTP-bound (active state) and GDP-bound (inactive state) forms. Leukaemia-associated RhoGEF (LARG) is a guanine nucleotide exchange factor (GEF) that activates RhoA subfamily GTPases by promoting the exchange of GDP for GTP. LARG is selective for RhoA subfamily GTPases and is an essential regulator of cell migration and invasion. Here, we describe the mechanisms by which LARG is regulated to facilitate the understanding of how LARG mediates functions like cell motility and to provide insight for better therapeutic targeting of these functions.</p>","PeriodicalId":22139,"journal":{"name":"Small GTPases","volume":"13 1","pages":"196-204"},"PeriodicalIF":0.0,"publicationDate":"2022-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/21541248.2021.1951590","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10524920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}