Drug Vulnerabilities and Disease Prognosis Linked to the Stem Cell-Like Gene Expression Program Triggered by the RHO GTPase Activator VAV2 in Hyperplastic Keratinocytes and Head and Neck Cancer

We have recently shown that VAV2, a guanosine nucleotide exchange factor that catalyzes the stimulation step of RHO GTPases, is involved in a stem cell-like (SCL) regenerative proliferation program that is important for the development and subsequent maintenance of the tumorigenesis of both cutaneous (cSCC) and head and neck squamous cell carcinomas (hnSCC). In line with this, we have observed that the levels of the VAV2 mRNA and VAV2-regulated gene signatures are associated with poor prognosis in the case of human papillomavirus-negative hnSCC patients. These results suggest that the SCL program elicited by VAV2 in those cells can harbor therapeutically actionable downstream targets. We have addressed this issue using a combination of both in silico and wet-lab approaches. Here, we show that the VAV2-regulated SCL program does harbor a number of cell cycle- and signaling-related kinases that are essential for the viability of undifferentiated keratinocytes and hnSCC patient-derived cells endowed with high levels of VAV2 activity. Our results also show that the VAV2-regulated SCL gene signature is associated with poor hnSCC patient prognosis. Collectively, these data underscore the critical role of this VAV2-regulated SCL program for the viability of both preneoplastic and fully transformed keratinocytes.

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VAV2 signaling promotes regenerative proliferation in both cutaneous and head and neck squamous cell carcinoma

Nature Communications ◽

10.1038/s41467-020-18524-3 ◽

2020 ◽

Vol 11 (1) ◽

Author(s):

L. Francisco Lorenzo-Martín ◽

Natalia Fernández-Parejo ◽

Mauricio Menacho-Márquez ◽

Sonia Rodríguez-Fdez ◽

Javier Robles-Valero ◽

...

Keyword(s):

Squamous Cell Carcinoma ◽

Cell Carcinoma ◽

Head And Neck ◽

Squamous Cell ◽

Rho Gtpase ◽

Neck Squamous Cell Carcinoma ◽

Proliferation Capacity ◽

Poor Differentiation ◽

Patient Prognosis ◽

Hnscc Patient

Abstract Regenerative proliferation capacity and poor differentiation are histological features usually linked to poor prognosis in head and neck squamous cell carcinoma (hnSCC). However, the pathways that regulate them remain ill-characterized. Here, we show that those traits can be triggered by the RHO GTPase activator VAV2 in keratinocytes present in the skin and oral mucosa. VAV2 is also required to maintain those traits in hnSCC patient-derived cells. This function, which is both catalysis- and RHO GTPase-dependent, is mediated by c-Myc- and YAP/TAZ-dependent transcriptomal programs associated with regenerative proliferation and cell undifferentiation, respectively. High levels of VAV2 transcripts and VAV2-regulated gene signatures are both associated with poor hnSCC patient prognosis. These results unveil a druggable pathway linked to the malignancy of specific SCC subtypes.

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MicroRNA Regulation of the Small Rho GTPase Regulators—Complexities and Opportunities in Targeting Cancer Metastasis

Cancers ◽

10.3390/cancers12051092 ◽

2020 ◽

Vol 12 (5) ◽

pp. 1092 ◽

Cited By ~ 2

Author(s):

Brock A. Humphries ◽

Zhishan Wang ◽

Chengfeng Yang

Keyword(s):

Transcriptional Activation ◽

Rho Gtpases ◽

Cancer Metastasis ◽

Rho Gtpase ◽

Critical Role ◽

Large Family ◽

Actin Dynamics ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange

The small Rho GTPases regulate important cellular processes that affect cancer metastasis, such as cell survival and proliferation, actin dynamics, adhesion, migration, invasion and transcriptional activation. The Rho GTPases function as molecular switches cycling between an active GTP-bound and inactive guanosine diphosphate (GDP)-bound conformation. It is known that Rho GTPase activities are mainly regulated by guanine nucleotide exchange factors (RhoGEFs), GTPase-activating proteins (RhoGAPs), GDP dissociation inhibitors (RhoGDIs) and guanine nucleotide exchange modifiers (GEMs). These Rho GTPase regulators are often dysregulated in cancer; however, the underlying mechanisms are not well understood. MicroRNAs (miRNAs), a large family of small non-coding RNAs that negatively regulate protein-coding gene expression, have been shown to play important roles in cancer metastasis. Recent studies showed that miRNAs are capable of directly targeting RhoGAPs, RhoGEFs, and RhoGDIs, and regulate the activities of Rho GTPases. This not only provides new evidence for the critical role of miRNA dysregulation in cancer metastasis, it also reveals novel mechanisms for Rho GTPase regulation. This review summarizes recent exciting findings showing that miRNAs play important roles in regulating Rho GTPase regulators (RhoGEFs, RhoGAPs, RhoGDIs), thus affecting Rho GTPase activities and cancer metastasis. The potential opportunities and challenges for targeting miRNAs and Rho GTPase regulators in treating cancer metastasis are also discussed. A comprehensive list of the currently validated miRNA-targeting of small Rho GTPase regulators is presented as a reference resource.

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Autoinhibition Mechanism of Proto-Dbl

Molecular and Cellular Biology ◽

10.1128/mcb.21.5.1463-1474.2001 ◽

2001 ◽

Vol 21 (5) ◽

pp. 1463-1474 ◽

Cited By ~ 51

Author(s):

Feng Bi ◽

Balazs Debreceni ◽

Kejin Zhu ◽

Barbara Salani ◽

Alessandra Eva ◽

...

Keyword(s):

Rho Gtpases ◽

Rho Gtpase ◽

Cell Transformation ◽

Intramolecular Interaction ◽

Nucleotide Exchange ◽

Ph Domain ◽

Intracellular Targeting ◽

Nucleotide Exchange Factor ◽

Transforming Activity ◽

Dh Domain

ABSTRACT The dbl oncogene encodes a prototype member of the Rho GTPase guanine nucleotide exchange factor (GEF) family. Oncogenic activation of proto-Dbl occurs through truncation of the N-terminal 497 residues. The C-terminal half of proto-Dbl includes residues 498 to 680 and 710 to 815, which fold into the Dbl homology (DH) domain and the pleckstrin homology (PH) domain, respectively, both of which are essential for cell transformation via the Rho GEF activity or cytoskeletal targeting function. Here we have investigated the mechanism of the apparent negative regulation of proto-Dbl imposed by the N-terminal sequences. Deletion of the N-terminal 285 or C-terminal 100 residues of proto-Dbl did not significantly affect either its transforming activity or GEF activity, while removal of the N-terminal 348 amino acids resulted in a significant increase in both transformation and GEF potential. Proto-Dbl displayed a mostly perinuclear distribution pattern, similar to a polypeptide derived from its N-terminal sequences, whereas onco-Dbl colocalized with actin stress fibers, like the PH domain. Coexpression of the N-terminal 482 residues with onco-Dbl resulted in disruption of its cytoskeletal localization and led to inhibition of onco-Dbl transforming activity. The apparent interference with the DH and PH functions by the N-terminal sequences can be rationalized by the observation that the N-terminal 482 residues or a fragment containing residues 286 to 482 binds specifically to the PH domain, limiting the access of Rho GTPases to the catalytic DH domain and masking the intracellular targeting function of the PH domain. Taken together, our findings unveiled an autoinhibitory mode of regulation of proto-Dbl that is mediated by the intramolecular interaction between its N-terminal sequences and PH domain, directly impacting both the GEF function and intracellular distribution.

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Development of a Prognostic Pyroptosis-Related Gene Signature for Head and Neck Squamous Cell Carcinoma Patient

10.21203/rs.3.rs-907937/v1 ◽

2021 ◽

Author(s):

Weiwen Zhu ◽

Jiayi Zhang ◽

Mengyao Wang ◽

Rundong Zhai ◽

Yanbin Xu ◽

...

Keyword(s):

Squamous Cell Carcinoma ◽

Cell Death ◽

Cell Carcinoma ◽

Head And Neck ◽

Patient Outcomes ◽

Squamous Cell ◽

Gene Signature ◽

Related Gene ◽

Patient Prognosis ◽

Hnscc Patient

Abstract Objective: Head and neck squamous cell carcinoma (HNSCC) is a major threat to public health. Pyroptosis is a form of inflammatory programmed cell death that is still incompletely understood. The role of pyroptotic cell death in HNSCC remains to be fully defined. As such, the present study was developed to explore the potential prognostic utility of a pyroptosis-related gene (PRG) signature in HNSCC.Methods: PRG expression patterns and the associated mutational landscape in HNSCC were analyzed, after which a 6-gene prognostic model was constructed through least absolute shrinkage and selection operator (LASSO) and Cox regression analyses using the TCGA dataset, followed by validation with two GEO datasets (GSE41643 and GSE65858). Potential predictors of patient outcomes associated with this 6-gene model were identified through topological degree analyses of a protein-protein interaction network. Lastly, the prognostic value of NLRP3 as a predictor of HNSCC patient prognosis was established through immunohistochemical (IHC) analyses of samples from 176 HNSCC patients.Results: Differentially expressed PRGs were able to readily differentiate between HNSCC tumors and normal tissues. Risk scores derived from the 6-gene PRG model were independent predictors of HNSCC patient prognosis, and genes that were differentially expressed between low- and high-risk groups were associated with tumor immunity. IHC analyses further supported the value of NLRP3 as a predictor of HNSCC patient outcomes. Conclusions: Overall, these results highlight a novel prognostic gene signature that offers value in the context of HNSCC patient evaluation, although additional research will be essential to elucidate the mechanisms linking these PRGs to HNSCC outcomes.

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Selectivity of Guanine Nucleotide Exchange Factor-mediated Cdc42 activation in primary human endothelial cells

10.1101/541219 ◽

2019 ◽

Author(s):

Nathalie R. Reinhard ◽

Sanne van der Niet ◽

Anna Chertkova ◽

Marten Postma ◽

Peter L. Hordijk ◽

...

Keyword(s):

Endothelial Cells ◽

Single Cell ◽

Rho Gtpases ◽

Rho Gtpase ◽

Actin Dynamics ◽

Pleckstrin Homology Domain ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Dh Domain

AbstractThe Rho GTPase family is involved in actin dynamics and regulates the barrier function of the endothelium. One of the main barrier-promoting Rho GTPases is Cdc42, also known as cell division control protein 42 homolog. Currently, regulation of Cdc42-based signaling networks in endothelial cells (ECs) lack molecular details. To examine these, we focused on a subset of 15 Rho guanine nucleotide exchange factors (GEFs), which are expressed in the endothelium. By performing single cell FRET measurements with Rho GTPase biosensors in primary human ECs, we monitored GEF efficiency towards Cdc42 and Rac1. A new, single cell-based analysis was developed and used to enable the quantitative comparison of cellular activities of the full-length GEFs. Our data reveal a specific GEF dependent activation profile, with most efficient Cdc42 activation induced by PLEKHG2, FGD1, PLEKHG1 and pRex1 and the highest selectivity for FGD1. Additionally, we generated truncated GEF constructs that comprise only the catalytic dbl homology (DH) domain or together with the adjacent pleckstrin homology domain (DHPH). The DH domain by itself did not activate Cdc42, whereas the DHPH domain of ITSN1, ITSN2 and PLEKHG1 showed activity towards Cdc42. Together, our study characterized endothelial GEFs that may activate Cdc42, which will be of great value for the field of vascular biology.Abstract FigureGraphical Abstract

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ErbB2 directly activates the exchange factor Dock7 to promote Schwann cell migration

The Journal of Cell Biology ◽

10.1083/jcb.200709033 ◽

2008 ◽

Vol 181 (2) ◽

pp. 351-365 ◽

Cited By ~ 87

Author(s):

Junji Yamauchi ◽

Yuki Miyamoto ◽

Jonah R. Chan ◽

Akito Tanoue

Keyword(s):

Cell Migration ◽

Schwann Cell ◽

Rho Gtpase ◽

Morphological Changes ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor ◽

Schwann Cell Migration ◽

Subsequent Activation

The cellular events that precede myelination in the peripheral nervous system require rapid and dynamic morphological changes in the Schwann cell. These events are thought to be mainly controlled by axonal signals. But how signals on the axons are coordinately organized and transduced to promote proliferation, migration, radial sorting, and myelination is unknown. We describe that the axonal signal neuregulin-1 (NRG1) controls Schwann cell migration via activation of the atypical Dock180-related guanine nucleotide exchange factor (GEF) Dock7 and subsequent activation of the Rho guanine triphosphatases (GTPases) Rac1 and Cdc42 and the downstream c-Jun N-terminal kinase. We show that the NRG1 receptor ErbB2 directly binds and activates Dock7 by phosphorylating Tyr-1118. Dock7 knockdown, or expression of Dock7 harboring the Tyr-1118–to–Phe mutation in Schwann cells, attenuates the effects of NRG1. Thus, Dock7 functions as an intracellular substrate for ErbB2 to promote Schwann cell migration. This provides an unanticipated mechanism through which ligand-dependent tyrosine phosphorylation can trigger the activation of Rho GTPase-GEFs of the Dock180 family.

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Hormones Secretion and Rho GTPases in Neuroendocrine Tumors

Cancers ◽

10.3390/cancers12071859 ◽

2020 ◽

Vol 12 (7) ◽

pp. 1859

Author(s):

Laura Streit ◽

Laurent Brunaud ◽

Nicolas Vitale ◽

Stéphane Ory ◽

Stéphane Gasman

Keyword(s):

Neuroendocrine Tumors ◽

Rho Gtpases ◽

Rho Gtpase ◽

Secretory Activity ◽

Guanine Nucleotide Exchange Factors ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Gtpase Activating Proteins

Neuroendocrine tumors (NETs) belong to a heterogeneous group of neoplasms arising from hormone secreting cells. These tumors are often associated with a dysfunction of their secretory activity. Neuroendocrine secretion occurs through calcium-regulated exocytosis, a process that is tightly controlled by Rho GTPases family members. In this review, we compiled the numerous mutations and modification of expression levels of Rho GTPases or their regulators (Rho guanine nucleotide-exchange factors and Rho GTPase-activating proteins) that have been identified in NETs. We discussed how they might regulate neuroendocrine secretion.

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Apical polarity proteins recruit the RhoGEF Cysts to promote junctional myosin assembly

The Journal of Cell Biology ◽

10.1083/jcb.201807106 ◽

2019 ◽

Vol 218 (10) ◽

pp. 3397-3414 ◽

Cited By ~ 6

Author(s):

Jordan T. Silver ◽

Frederik Wirtz-Peitz ◽

Sérgio Simões ◽

Milena Pellikka ◽

Dong Yan ◽

...

Keyword(s):

Rho Gtpases ◽

Rho Gtpase ◽

Adherens Junctions ◽

Nucleotide Exchange ◽

Temporal Regulation ◽

Apical Polarity ◽

Polarity Proteins ◽

Spatio Temporal ◽

Crumbs Complex

The spatio-temporal regulation of small Rho GTPases is crucial for the dynamic stability of epithelial tissues. However, how RhoGTPase activity is controlled during development remains largely unknown. To explore the regulation of Rho GTPases in vivo, we analyzed the Rho GTPase guanine nucleotide exchange factor (RhoGEF) Cysts, the Drosophila orthologue of mammalian p114RhoGEF, GEF-H1, p190RhoGEF, and AKAP-13. Loss of Cysts causes a phenotype that closely resembles the mutant phenotype of the apical polarity regulator Crumbs. This phenotype can be suppressed by the loss of basolateral polarity proteins, suggesting that Cysts is an integral component of the apical polarity protein network. We demonstrate that Cysts is recruited to the apico-lateral membrane through interactions with the Crumbs complex and Bazooka/Par3. Cysts activates Rho1 at adherens junctions and stabilizes junctional myosin. Junctional myosin depletion is similar in Cysts- and Crumbs-compromised embryos. Together, our findings indicate that Cysts is a downstream effector of the Crumbs complex and links apical polarity proteins to Rho1 and myosin activation at adherens junctions, supporting junctional integrity and epithelial polarity.

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Rho GTPase Regulators and Effectors in Autism Spectrum Disorders: Animal Models and Insights for Therapeutics

Cells ◽

10.3390/cells9040835 ◽

2020 ◽

Vol 9 (4) ◽

pp. 835 ◽

Cited By ~ 1

Author(s):

Daji Guo ◽

Xiaoman Yang ◽

Lei Shi

Keyword(s):

Animal Models ◽

Rho Gtpases ◽

Rho Gtpase ◽

Autism Spectrum ◽

Neuronal Morphology ◽

Nucleotide Exchange ◽

Cellular Processes ◽

Research Initiative ◽

Genes Encoding ◽

And Function

The Rho family GTPases are small G proteins that act as molecular switches shuttling between active and inactive forms. Rho GTPases are regulated by two classes of regulatory proteins, guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs). Rho GTPases transduce the upstream signals to downstream effectors, thus regulating diverse cellular processes, such as growth, migration, adhesion, and differentiation. In particular, Rho GTPases play essential roles in regulating neuronal morphology and function. Recent evidence suggests that dysfunction of Rho GTPase signaling contributes substantially to the pathogenesis of autism spectrum disorder (ASD). It has been found that 20 genes encoding Rho GTPase regulators and effectors are listed as ASD risk genes by Simons foundation autism research initiative (SFARI). This review summarizes the clinical evidence, protein structure, and protein expression pattern of these 20 genes. Moreover, ASD-related behavioral phenotypes in animal models of these genes are reviewed, and the therapeutic approaches that show successful treatment effects in these animal models are discussed.

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Insulin Stimulates Phosphatidylinositol 3-Phosphate Production via the Activation of Rab5

Molecular Biology of the Cell ◽

10.1091/mbc.e08-01-0105 ◽

2008 ◽

Vol 19 (7) ◽

pp. 2718-2728 ◽

Cited By ~ 39

Author(s):

Irfan J. Lodhi ◽

Dave Bridges ◽

Shian-Huey Chiang ◽

Yanling Zhang ◽

Alan Cheng ◽

...

Keyword(s):

Plasma Membrane ◽

Glucose Uptake ◽

Critical Role ◽

Small Gtpase ◽

Dominant Negative ◽

Glut4 Translocation ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Nucleotide Exchange Factor ◽

Phosphatidylinositol 3

Phosphatidylinositol 3-phosphate (PI(3)P) plays an important role in insulin-stimulated glucose uptake. Insulin promotes the production of PI(3)P at the plasma membrane by a process dependent on TC10 activation. Here, we report that insulin-stimulated PI(3)P production requires the activation of Rab5, a small GTPase that plays a critical role in phosphoinositide synthesis and turnover. This activation occurs at the plasma membrane and is downstream of TC10. TC10 stimulates Rab5 activity via the recruitment of GAPEX-5, a VPS9 domain–containing guanyl nucleotide exchange factor that forms a complex with TC10. Although overexpression of plasma membrane-localized GAPEX-5 or constitutively active Rab5 promotes PI(3)P formation, knockdown of GAPEX-5 or overexpression of a dominant negative Rab5 mutant blocks the effects of insulin or TC10 on this process. Concomitant with its effect on PI(3)P levels, the knockdown of GAPEX-5 blocks insulin-stimulated Glut4 translocation and glucose uptake. Together, these studies suggest that the TC10/GAPEX-5/Rab5 axis mediates insulin-stimulated production of PI(3)P, which regulates trafficking of Glut4 vesicles.

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