ROPs: Molecular Switches of Multiple Signal Pathways in Plant Cells / 中国生物化学与分子生物学报

RHO-related GTPases of plants (ROPs) are a class of signal transduction G proteins (alsoknown as GTP binding proteins) widely existing in plants. ROP proteins act as " molecular switches" toregulate the signal transduction process during cellular activities such as plant cell polarity regulation, plant morphological development, hormone level regulation, stress responses and many other life activitiesby shifting between inactive GDP-binding and active GTP-binding forms in the cells. In this review, thedomain structure, classification, the mechanism of activity regulation and biological functions of ROPproteins were summarize. Furthermore, ROP proteins from Arabidopsis, maize, rice and barley werephylogenetically analyzed. The results show that ROP proteins were classified into two types based on thedomain structure of the proteins. However, these ROP proteins were divided into 4 clades based on thesimilarity of protein sequences. Furthermore, the mechanism of ROP proteins as a molecular switchregulating various signaling pathways in cells, and the specific functions and mechanisms of ROPs in thepolarized growth of pollen tubes, root hairs and plant pavement cells and other stress responses werecharacterized. In addition, the research progress of the function of ROPs in plant hormones such as ABA, IAA and BR mediated signal transduction were described as well. At last, the unanswered questions suchas why different ROP proteins play distinct roles in the same signaling pathway and how ROPs coordinatedifferent signal pathways to jointly regulate a plant’ s development or physiological process werediscussed, which may shed light on future research.

Psychiatric features and variable neurodevelopment outcome in four females with IQSEC2 spectrum disorder

IQSEC2 is an X-linked gene highly expressed at the excitatory synapses where it plays a crucial role in a-amino-3-hydroxy-5- methyl-4-isoxazolepropionic acid receptor trafficking and synaptic plasticity. To date, several males and females with severe to profound intellectual disability have been reported harbouring frameshift and nonsense variants in this gene, whereas a milder phenotype has been recognized in females carrying missense pathogenic variants. Here, we report two novel IQSEC2 variants in four females with psychiatric features and otherwise variable cognitive impairment. A female (case 1) with severe verbal language learning disorder and a psychotic episode (precipitated by exposure to anti-contraceptive pill) harboured a de novo pathogenic frameshift variant (c.1170dupG,p.Gln391Alafs*5), whereas the female proband of family 2, displaying severe psychomotor regression and complex psychiatric features carried a missense variant of uncertain significance (c.770G[A,p.Ser257Asn) that was maternally inherited. Skewed X-inactivation was noted in the carrier mother. The maternal aunt, affected by schizophrenia, was found to bear the same IQSEC2 variant. We discuss the variable clinical presentation of IQSEC2 spectrum disorders and the challenging genotype–phenotype correlation, including the possible role of environmental factors as triggers for decompensation. Our report highlights how psychiatric features may be the main clinical presentation in subtle IQSEC2 phenotype, suggesting that the prevalence of IQSEC2 mutations in patients with psychiatric disorders may be underestimated.

Quinacrine causes apoptosis in human cancer cell lines through caspase-mediated pathway and regulation of small-GTPase

Quinacrine (QC), an FDA-approved anti-malarial drug, has shown to have anticancer activities. Due to its‘shotgun’ nature, QC has become an inevitable candidate for combination chemotherapy. There is lack of studyof the molecular interplay between colorectal cancer (CRC) microenvironment and its metastasis. In this study,we focused on the differential anti-cancerous effect of QC on two different human cancer cell lines, HCT 116and INT 407. Results suggest that cytotoxicity increased in both the cell lines with an increase in QCconcentration. The expression patterns of small-GTPases and caspases were altered significantly in QC-treatedcells compared to non-treated cells. HSP70 and p53 showed comparable differences in the expression pattern.The wound-healing assay showed an increase in the denuded zone, with an increase in the concentration ofQC. The formation of apoptotic nuclei increased with a rise in the concentration of QC in both the cell lines.The decrease and increase in caspase 9 and caspase 3 expression respectively were studied, confirmingapoptosis by the extrinsic pathway

Sensors for the mTORC1 pathway regulated by amino acids / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth and metabolism in response to various environmental inputs, especially amino acids. In fact, the activity of mTORC1 is highly sensitive to changes in amino acid levels. Over past decades, a variety of proteins have been identified as participating in the mTORC1 pathway regulated by amino acids. Classically, the Rag guanosine triphosphatases (GTPases), which reside on the lysosome, transmit amino acid availability to the mTORC1 pathway and recruit mTORC1 to the lysosome upon amino acid sufficiency. Recently, several sensors of leucine, arginine, and S-adenosylmethionine for the amino acid-stimulated mTORC1 pathway have been coming to light. Characterization of these sensors is requisite for understanding how cells adjust amino acid sensing pathways to their different needs. In this review, we summarize recent advances in amino acid sensing mechanisms that regulate mTORC1 activity and highlight these identified sensors that accurately transmit specific amino acid signals to the mTORC1 pathway.

Sensors for the mTORC1 pathway regulated by amino acids / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

The mechanistic target of rapamycin complex 1 (mTORC1) controls cell growth and metabolism in response to various environmental inputs, especially amino acids. In fact, the activity of mTORC1 is highly sensitive to changes in amino acid levels. Over past decades, a variety of proteins have been identified as participating in the mTORC1 pathway regulated by amino acids. Classically, the Rag guanosine triphosphatases (GTPases), which reside on the lysosome, transmit amino acid availability to the mTORC1 pathway and recruit mTORC1 to the lysosome upon amino acid sufficiency. Recently, several sensors of leucine, arginine, and S-adenosylmethionine for the amino acid-stimulated mTORC1 pathway have been coming to light. Characterization of these sensors is requisite for understanding how cells adjust amino acid sensing pathways to their different needs. In this review, we summarize recent advances in amino acid sensing mechanisms that regulate mTORC1 activity and highlight these identified sensors that accurately transmit specific amino acid signals to the mTORC1 pathway.

The role of ubiquitination and deubiquitination in the regulation of cell junctions

Maintenance of cell junctions plays a crucial role in the regulation of cellular functions including cell proliferation, permeability, and cell death. Disruption of cell junctions is implicated in a variety of human disorders, such as inflammatory diseases and cancers. Understanding molecular regulation of cell junctions is important for development of therapeutic strategies for intervention of human diseases. Ubiquitination is an important type of post-translational modification that primarily regulates endogenous protein stability, receptor internalization, enzyme activity, and protein-protein interactions. Ubiquitination is tightly regulated by ubiquitin E3 ligases and can be reversed by deubiquitinating enzymes. Recent studies have been focusing on investigating the effect of protein stability in the regulation of cell-cell junctions. Ubiquitination and degradation of cadherins, claudins, and their interacting proteins are implicated in epithelial and endothelial barrier disruption. Recent studies have revealed that ubiquitination is involved in regulation of Rho GTPases' biological activities. Taken together these studies, ubiquitination plays a critical role in modulating cell junctions and motility. In this review, we will discuss the effects of ubiquitination and deubiquitination on protein stability and expression of key proteins in the cell-cell junctions, including junction proteins, their interacting proteins, and small Rho GTPases. We provide an overview of protein stability in modulation of epithelial and endothelial barrier integrity and introduce potential future search directions to better understand the effects of ubiquitination on human disorders caused by dysfunction of cell junctions.

RHO GTPasas como blancos moleculares en cáncer: Estrategias y oportunidades terapéuticas / Rho GTPases as molecular targets in cancer. Strategies and therapeutic opportunities

Las Rho GTPasas son una familia de proteínas que actúan como interruptores moleculares en diversas vías de señalización coordinando la regulación de distintos procesos celulares. La desregulación de dichas proteínas se vincula con transformación maligna y progresión tumoral en distintos tipos de cáncer. Por estos motivos, en los últimos años las Rho GTPasas fueron postuladas como blancos moleculares interesantes. En este trabajo describimos las distintas estrategias estudiadas utilizando a las Rho GTPasas como blanco y su grado de avance, mostrando una estrategia novedosa para el tratamiento del cáncer.

Rho GTPases are molecular switches that control the different cellular processes. Deregulation of these proteins is associated to transformation and malignant progression in several cancer types. Given the evidence available of the role of Rho GTPases in cancer it is suggested that these proteins can serve as potential therapeutic targets. This review focuses on the strategies used to develop Rho GTPases modulators and their potential use in therapeutic settings.

Research progress on the relationship between Rho GTPases and breast cancer / 天津医药

Breast cancer is one of the major causes of death in women,and its incidence has been increasing year after year.The Rho GTPases,their regulatory proteins and Rho GTPases play an important role in promoting the occurrence and distant metastasis of breast cancer.Here we summarized the current knowledge of the regulation network of Rho GTPases,their regulatory proteins and Rho GTPases on the occurrence and development of breast cancer,and targeted therapy for RHO GTP enzyme pathway in breast cancer.

Identification of guanine nucleotide exchange factor ARHGEF 10 and its relationship with tumor malig-nant phenotype / 实用肿瘤学杂志

Objective The guanine exchange factors( GEFs) of Dbl family is a major regulatory unit for the malignant transformation of Rho family proteins. It plays a role by converting Rho protein from inactive GDP form to GTP form of Rho protein. In this paper,we discuss the structure and function of a GEF molecule-ARH-GEF 10,and discuss its role in the process of tumor development. Methods The expression of ARHGEF 10 in 42 normal tissues was measured by Real-Time PCR. GST-pulldown technique was used to detect the GEF ac-tivity of ARHGEF 10 in vivo. The transcription factor activity of downstream small molecules was detected by dual-luciferase report gene assay. The high expressive effect of ARHGEF 10 on normal cytoskeleton morphology was performed by dual immunofluorescence staining labeling method. High expressive effects of ARHGEF 10 on cell proliferation,invasion and tumorigenic ability in vitro were examined using CCK8,Transwell and soft agar clony formation assays. Results ARHGEF 10 has a typical GEFs structure,which binds to RhoA in vitro and promotes the proliferation and invasion of NIH3T3 cells,and has significant ability to clone in vitro. Conclusion ARH-GEF 10 is a typical family molecule of guanosine exchange factor that activates RhoA of Rho family,which has obvious oncogene characteristics.

O papel de RhoA e Rac1 GTPases nas respostas celulares após danos no DNA induzidos por radiação ionizante gama / The role of RhoA and Rac1 GTPases in cellular responses after DNA damage induced by ionizing gamma radiation

O mecanismo pelo qual uma célula responde a algum dano no seu material genético é extremamente importante. Isto ocorre pela rápida ativação da maquinaria de reparo de danos no DNA, a qual é composta por uma rede intrincada de sinalização proteica, culminando no reparo do DNA; porém se o dano for irreparável ocorre ativação de mecanismos de morte celular. RhoA,e Rac1 pertencem a família das pequenas proteínas sinalizadoras Rho GTPases, as quais atuam como interruptores moleculares ciclando entre estado ativo (ligada a GTP) e inativo (ligada a GDP). Os componentes desta família estão relacionados ao controle dos mais diversos processos celulares como, por exemplo, remodelamento do citoesqueleto, migração, adesão, endocitose, progressão do ciclo celular e oncogênese. No entanto, apesar das proteínas Rho GTPases estarem envolvidas em um amplo espectro de atividades biológicas, há poucas informações sobre seu papel na manutenção da integridade genômica quando células são submetidas a algum agente genotóxico. Para investigar o envolvimento das GTPases RhoA e Rac1 nas respostas de células submetidas a radiação gama, foram gerados, a partir de células de carcinoma de cervix humano - HeLa, sublinhagens clonais mutantes de RhoA e Rac1 expressando exogenamente RhoA constitutivamente ativa (HeLa-RhoA V14), RhoA dominante negativa (HeLa-RhoA N19), Rac1 constitutivamente ativa (HeLa-Rac1 V12) e Rac1 dominante negativa (HeLa-Rac N17). Após estas linhagens celulares serem expostas a diferentes doses de radiação gama, observamos que ambas GTPases, RhoA e Rac1, são ativadas em resposta aos efeitos da radiação. Além disso, a modulação da atividade destas enzimas, através das mutações, levou a uma alteração das respostas celulares frente aos danos no DNA, como uma redução da capacidade de reparar quebras simples e duplas nas fitas do DNA. Por outro lado, a deficiência de RhoA ou Rac1 GTPase levou a uma redução da ativação de Chk1 e Chk2 ou da fosforilação da histona H2AX, respectivamente, prejudicando os mecanismos de detecção de danos no DNA e levando as células a permanecerem mais tempo nos pontos de checagem G1/S e/ou G2/M do ciclo celular. Esses fatores contribuíram de modo expressivo para a redução da proliferação e sobrevivência celular levando as células à morte. Por fim, ensaios celulares de reparo de danos de um DNA exógeno através de mecanismos de Recombinação Homóloga (HR) e Recombinação Não-Homóloga de extremidades (NHEJ), demonstraram que a inibição da atividade de RhoA reduz significativamente a eficiência de ambas vias de reparo. Desta maneira, este trabalho demonstra e reforça a existência de mais um viés de atuação das pequenas GTPases RhoA e Rac1, agora em células HeLa, nas respostas celulares aos danos induzidos por exposição a radiação gama, modulando a sobrevivência, proliferação e indiretamente modulando resposta ao reparo do DNA através da via de Recombinação Homóloga e Não-Homóloga

The mechanism by which a cell responds to DNA damage is extremely important. This occurs by a quick activation of the DNA damage repair machinery, which consists of an intricate protein signaling network culminating in DNA repair. But if the damages are irreparable occurs there is activation of cell death mechanisms. RhoA and Rac1 belong to family of small Rho GTPases, signaling proteins that act as molecular switches cycling between the active state (GTP-bound) and inactive state (GDP-bound). Members of this family are implicated in the control of diverse cellular process such as cytoskeletal remodeling, migration, adhesion, endocytosis, cell cycle progression, and oncogenesis. However, despite Rho proteins are involved in a broad spectrum of biological activities, there is just a few information about their roles in the maintenance of genomic integrity, that is, when the cells are subjected to some kinf of genotoxic agent. To investigate the involvement of the GTPases RhoA and Rac1 in cellular responses to gamma radiation, we generated from human cervix carcinoma cells - HeLa, clonal sublines of RhoA and Rac1 mutants, exogenous and stably expressing the constitutively active RhoA (HeLa-RhoA V14), the dominant negative RhoA (HeLa-RhoA N19), the constitutively active Rac1 (HeLa-Rac1 V12) and the dominant negative Rac1 (HeLa-Rac1 N17). After all these cell lines have been exposed to different doses of gamma radiation, we found that both GTPases, RhoA and Rac1, are activated in response to the radiation effects. Furthermore, the modulation of two enzymes activity, by using the mutant clones, led to a change in cellular responses to the DNA damage, as the reduction in the capacity of repairing DNA single and double strand breaksr. On the other hand, the deficiency of RhoA or Rac1 GTPase led to a reduction of Chk1 and Chk2 activation, or on the phosphorylation of histone H2AX, respectively, hindering the mechanisms of DNA damage detection and arresting cells in the G1/S and/or G2/M checkpoints of cell cycle. These factors significantly contributed to the reduction of cell proliferation and survival, leading cells to death. Finally, cellular assays of DNA damage repair of exogenous DNA by Homologous Recombination (HR) and Non-Homologous End Joining (NHEJ), demonstrated that RhoA inhibition significantly reduced the repair efficiency of both pathways. Thus, this work demonstrates and reinforces the existence of other biological functions of small GTPases RhoA and Rac1 in HeLa cells, by regulating cellular responses to DNA damage induced by exposure to gamma radiation, modulating the survival, proliferation and indirectly modulating the response to DNA damage repair pathway through the Homologous Recombination and Non-Homologous Recombination

G protein signaling in the parasite Entamoeba histolytica

The parasite Entamoeba histolytica causes amebic colitis and systemic amebiasis. Among the known amebic factors contributing to pathogenesis are signaling pathways involving heterotrimeric and Ras superfamily G proteins. Here, we review the current knowledge of the roles of heterotrimeric G protein subunits, Ras, Rho and Rab GTPase families in E. histolytica pathogenesis, as well as of their downstream signaling effectors and nucleotide cycle regulators. Heterotrimeric G protein signaling likely modulates amebic motility and attachment to and killing of host cells, in part through activation of an RGS-RhoGEF (regulator of G protein signaling-Rho guanine nucleotide exchange factor) effector. Rho family GTPases, as well as RhoGEFs and Rho effectors (formins and p21-activated kinases) regulate the dynamic actin cytoskeleton of E. histolytica and associated pathogenesis-related cellular processes, such as migration, invasion, phagocytosis and evasion of the host immune response by surface receptor capping. A remarkably large family of 91 Rab GTPases has multiple roles in a complex amebic vesicular trafficking system required for phagocytosis and pinocytosis and secretion of known virulence factors, such as amebapores and cysteine proteases. Although much remains to be discovered, recent studies of G protein signaling in E. histolytica have enhanced our understanding of parasitic pathogenesis and have also highlighted possible targets for pharmacological manipulation.

Expression of Rho GTPaes signaling pathway in non-small cell lung carcinoma and its clinical significance / 肿瘤

Objective:To investigate the expression of Rho GTPases signaling pathway in non-small cell lung carcinoma (NSCLC)and its clinical significance.Methods:Molecules of Rho GTPases signaling pathway including RhoC, E-cadherin, MMP-2, and MMP-9 were detected by RT-PCR and immunohistochemistry in 36 specimens of non-small cell lung carcinoma (NSCLC). The relationship between RhoC mRNA and prognosis of patients was evaluated by using Kaplan-Meier survival curve analysis.Results:There was a significant difference in the expression of RhoC mRNA between NSCLC tissues and para-cancerous tissues (P0.05). Conclusion:Over-expression of RhoC mRNA is closely correlated with the tumorigenesis and progression of NSCLC, and may be related with invasion and metastasis of NSCLC early to middle stage.

Shear stress-regulated vascular endothelial permeability is mediated by Rho GTPases / 国际生物医学工程杂志

Dysfunctions of vascular endothelial permeability are related to a number of human diseases such as atherosclerosis, high blood pressure, stroke, inflammation, cancer, diabetes-induced retinopathy, macular edema and so on. Shear stress is an important mechanical force that affects vascular endothelial cells. It plays a particular role in permeability regulation. Rho GTPases is a family of small G proteins which act as cell signal molecules. They are assumed to mediate the regulation of the permeability of vascular endothelial cells. In this paper review is given on how shear stress regulates the permeability of vascular endothehal cells as well as the in-fluence of Rho GTPases on the role in molecular mechanism. It is suggested that shear stress-regulated vascular endothelial permeability is mediated by Rho GTPases.

Brain-derived neurotrophic factors inhibit phenylalanine-induced down-regulation of Cdc42, Rac1, and RhoA protein expression in cultured cortical neurons / 临床儿科杂志

Objective To explore whether phenylalanine affect Cdc42, Racl, and RhoA expression and disturb dendritic development. To determine the effects of brain-derived neurotrophic factor (BDNF) on this process. Methods Neurons were cultivated up to 3 days and then treated with 0.9 mmol/L phenylalanine or 100 ng/ml BDNF. Dendritic number were determined by morphologic analysis. Cdc42, Racl, and RhoA protein expression were examined by Western blotting analysis. ResultsThe number of dendrites in cultured neurons reduced two days after being treated with phenylalanine,while BDNF could rescue this change(P < 0.01), furthermore, BDNF was found to inhibit phenylalanineinduced down-regulation of Cdc42, Racl, and RhoA protein expression(P < 0.01). Conclusions Our study indicated that the protective effect of BDNF against phenylalanine-induced neuronal injury is probably mediated by expression of Cdc42, Racl,and RhoA. It suggested a potential neuroprotective action of BDNF in prevention and treatment of brain injury in the patients with phenylketonuria.

A Novel Human Rab26 cDNA Coloning,Expression and Its Endocytosis Enhancing Function / 生物化学与生物物理进展

Rab GTPases serve as master regulators of vesicular membrane transport on both the exo-and endocytic pathways. Though there are many reports on Rab proteins, the function of these small proteins still remain in speculation. And no report has ever clarified the character of human Rab26. Here it was reported that a novel Rab protein Rab26 is membranous organelle related and in volved inendocytosis of HeLa cells. By using RT-PCR method a novel Rab26 cDNA full-length cDNA of Rab26 that is 1656 bp was identified.The cDNA sequence that at 1197 is 'A' other than 'G', while 'C' at 956 substitutes for 'T', and has 'GCC' insertion at 48 to 50 compared with published sequences. The complete open reading frame (ORF) is 771 bp in length encoding 256-residue protein with a calculated molecular mass of 27.9 ku (GenBank accession No.AY646153), rather than a shorter one with 190-amino acid residue as reported previously. GFP labeled full-length Rab26 expression showed that Rab26 was mainly sublocated in membranous organelles and could enhance endocytosis which means could took PE labeled protein as an endocytic tracer. RT-PCR analysis showed Rab26 was detected to express in several kinds of adenocarcinoma cell lines such as Acc2, AccM, SPC-A1 and HeLa cell lines, which indicated that Rab26 expression might be associated with some carcinomas.