Rab25 is involved in hypospadias via the β1 integrin/EGFR pathway

BACKGROUND

Hypospadias is a common congenital abnormality of the penile. Abnormal regulation of critical genes involved in urethral development leads to hypospadias. We used the Rab25-/- mice and foreskin fibroblasts transfected with lentivirus in vitro and in vivo to investigate the role of Rab25 in hypospadias.

METHODS

The expression levels of various molecules in tissue samples and foreskin fibroblasts were confirmed using molecular biology methods (western blotting, PCR, immunohistochemistry, etc.). A scanning electron microscope (SEM) was used to visualize the external morphology of genital tubercles (GTs) of gestation day (GD) 18.5 male wild-type (WT) and Rab25-/- mice.

RESULTS

An expanded distal cleft and V-shaped urethral opening were observed in GD 18.5 Rab25-/- mice. We demonstrated that Rab25 mediated hypospadias through the β1 integrin/EGFR pathway. In addition, silencing Rab25 inhibited cell proliferation and migration and promoted apoptosis in the foreskin fibroblasts; Ki-67- and TUNEL-positive cells were mainly concentrated near the urethral seam.

CONCLUSION

These findings suggest that Rab25 plays an essential role in hypospadias by activation of β1 integrin/EGFR pathway, and Rab25 is a critical mediator of urethral seam formation in GD18.5 male fetal mice.

Expression of Rab25 is down-regulated in the foreskin of children with hypospadias

BACKGROUND

Hypospadias, a congenital malformation of the penis, is one of the newborns' most common developmental defects. The incidence of hypospadias is increasing yearly, and its pathogenesis is closely related to genetic susceptibility and environmental exposure to endocrine disruptors. Exploring the hypospadias' key molecular regulatory mechanism is crucial to reducing its incidence.

OBJECTIVE

To examine the differential expression of Rab25 in hypospadias and normal penile tissue and to identify whether it is a candidate gene for exploring the mechanism of hypospadias.

STUDY DESIGN

This study included 18 children aged 1-6 years undergoing hypospadias repair surgery at the Children's Hospital of Chongqing Medical University, and foreskin samples were collected. Children diagnosed with cryptorchidism, intersex status, or endocrine abnormalities were excluded from this study. Another 18 children aged 3-8 years with phimosis were included in the control group. The specimens were used for immunohistochemistry, western blotting, immunofluorescence, and polymerase chain reaction to assess the expression of Rab25.

RESULTS

Rab25 protein expression was lower in the hypospadias group than in the control group [ (2.101 ± 0.1845), (0.7506 ± 0.1779), p = 0.0008 < 0.05). The hypospadias group showed decreased expression of Rab25 protein in the epithelial cell layer. Rab25 mRNA levels were downregulated in the foreskin of children with hypospadias compared with controls [(1.697 ± 0.2005), (0.7687 ± 0.2130), p = 0.0053 < 0.05)].

DISCUSSION

Rab25 mRNA and protein expressions in the hypospadias group were significantly downregulated compared with the control group. This was consistent with the results of single-cell sequencing of fetal mice reproductive nodules at 15.5 days of gestation (Zhang Z, Liu Z, Zhang Q, et al., unpublished observations). Our study represents the first report of abnormal Rab25 expression in the foreskin tissue of patients with hypospadias. More detailed research on the relationship between Rab25 and urethral development could be conducted to reveal the molecular mechanism of hypospadias.

CONCLUSION

The expression of Rab25 in foreskin tissue was lower in the hypospadias group than in the control group. Rab25 is involved in the formation of the urethral seam and the occurrence of hypospadias. The potential mechanism by which Rab25 affects the canalization of the urethral plate needs to be further investigated.

Altered endosomal-lysosomal biogenesis in melanoma

Cutaneous melanoma is the deadliest form of skin neoplasm and its high mortality rates could be averted by early accurate detection. While the detection of melanoma is currently reliant upon melanin visualisation, research into melanosome biogenesis, as a key driver of pathogenesis, has not yielded technology that can reliably distinguish between atypical benign, amelanotic and melanotic lesions. The endosomal-lysosomal system has important regulatory roles in cancer cell biology, including a specific functional role in melanosome biogenesis. Herein, the involvement of the endosomal-lysosomal system in melanoma was examined by pooled secondary analysis of existing gene expression datasets. A set of differentially expressed endosomal-lysosomal genes was identified in melanoma, which were interconnected by biological function. To illustrate the protein expression of the dysregulated genes, immunohistochemistry was performed on samples from patients with cutaneous melanoma to reveal candidate markers. This study demonstrated the dysregulation of Syntenin-1, Sortilin and Rab25 may provide a differentiating feature between cutaneous melanoma and squamous cell carcinoma, while IGF2R may indicate malignant propensity in these skin cancers.

Proximity labelling identifies pro-migratory endocytic recycling cargo and machinery of the Rab4 and Rab11 families

Endocytic recycling controls the return of internalised cargoes to the plasma membrane to coordinate their positioning, availability and downstream signalling. The Rab4 and Rab11 small GTPase families regulate distinct recycling routes, broadly classified as fast recycling from early endosomes (Rab4) and slow recycling from perinuclear recycling endosomes (Rab11), and both routes handle a broad range of overlapping cargoes to regulate cell behaviour. We adopted a proximity labelling approach, BioID, to identify and compare the protein complexes recruited by Rab4a, Rab11a and Rab25 (a Rab11 family member implicated in cancer aggressiveness), revealing statistically robust protein-protein interaction networks of both new and well-characterised cargoes and trafficking machinery in migratory cancer cells. Gene ontological analysis of these interconnected networks revealed that these endocytic recycling pathways are intrinsically connected to cell motility and cell adhesion. Using a knock-sideways relocalisation approach, we were further able to confirm novel links between Rab11, Rab25 and the ESCPE-1 and retromer multiprotein sorting complexes, and identify new endocytic recycling machinery associated with Rab4, Rab11 and Rab25 that regulates cancer cell migration in the 3D matrix.

On demand expression control of endogenous genes with DExCon, DExogron and LUXon reveals differential dynamics of Rab11 family members

CRISPR technology has made generation of gene knock-outs widely achievable in cells. However, once inactivated, their re-activation remains difficult, especially in diploid cells. Here, we present DExCon (Doxycycline-mediated endogenous gene Expression Control), DExogron (DExCon combined with auxin-mediated targeted protein degradation), and LUXon (light responsive DExCon) approaches which combine one-step CRISPR-Cas9-mediated targeted knockin of fluorescent proteins with an advanced Tet-inducible TRE3GS promoter. These approaches combine blockade of active gene expression with the ability to re-activate expression on demand, including activation of silenced genes. Systematic control can be exerted using doxycycline or spatiotemporally by light, and we demonstrate functional knock-out/rescue in the closely related Rab11 family of vesicle trafficking regulators. Fluorescent protein knock-in results in bright signals compatible with low-light live microscopy from monoallelic modification, the potential to simultaneously image different alleles of the same gene, and bypasses the need to work with clones. Protein levels are easily tunable to correspond with endogenous expression through cell sorting (DExCon), timing of light illumination (LUXon), or by exposing cells to different levels of auxin (DExogron). Furthermore, our approach allowed us to quantify previously unforeseen differences in vesicle dynamics, transferrin receptor recycling, expression kinetics, and protein stability among highly similar endogenous Rab11 family members and their colocalization in triple knock-in ovarian cancer cell lines.

Notch regulates vascular collagen IV basement membrane through modulation of lysyl hydroxylase 3 trafficking

Collagen type IV (Col IV) is a basement membrane protein associated with early blood vessel morphogenesis and is essential for blood vessel stability. Defects in vascular Col IV deposition are the basis of heritable disorders, such as small vessel disease, marked by cerebral hemorrhage and drastically shorten lifespan. To date, little is known about how endothelial cells regulate the intracellular transport and selective secretion of Col IV in response to angiogenic cues, leaving a void in our understanding of this critical process. Our aim was to identify trafficking pathways that regulate Col IV deposition during angiogenic blood vessel development. We have identified the GTPase Rab10 as a major regulator of Col IV vesicular trafficking during vascular development using both in vitro imaging and biochemistry as well as in vivo models. Knockdown of Rab10 reduced de novo Col IV secretion in vivo and in vitro. Mechanistically, we determined that Rab10 is an indirect mediator of Col IV secretion, partnering with atypical Rab25 to deliver the enzyme lysyl hydroxylase 3 (LH3) to Col IV-containing vesicles staged for secretion. Loss of Rab10 or Rab25 results in depletion of LH3 from Col IV-containing vesicles and rapid lysosomal degradation of Col IV. Furthermore, we demonstrate that Rab10 is Notch responsive, indicating a novel connection between permissive Notch-based vessel maturation programs and vesicle trafficking. Our results illustrate both a new trafficking-based component in the regulated secretion of Col IV and how this vesicle trafficking program interfaces with Notch signaling to fine-tune basement membrane secretion during blood vessel development.

MiR-140 inhibits classical swine fever virus replication by targeting Rab25 in swine umbilical vein endothelial cells

Classical swine fever virus (CSFV) is one of the most important viral pathogens leading worldwide threats to pig industry. MicroRNAs (miRNAs) play important roles in regulating virus replication, but whether miRNAs affect CSFV infection is still poorly understood. In previous study, we identified four miRNAs that were down-regulated by CSFV in swine umbilical vein endothelial cells (SUVEC). In this study, miR-140, one of the most potently down-regulated genes was investigated. We found that the miRNA expression was significantly inhibited by CSFV infection. Subsequent studies revealed that miR-140 mimics significantly inhibited CSFV replication, while the inhibition of endogenous miR-140 enhanced CSFV replication. By using bioinformatics prediction, luciferase reporter system, real-time fluorescence quantitative PCR (RT-qPCR) and Western blot assays, we further demonstrated that miR-140 bind to the 3' UTR of Rab25 mRNA to regulate its expression. We also analyzed the expression pattern of Rab25 in SUVECs after CSFV infection. The results showed that CSFV infection induced Rab25 expression. Finally, Rab25 was found to promote CSFV replication. In conclusion, this study demonstrated that CSFV inhibits miR-140 expression and miR-140 inhibits replication by binding to host factor Rab25.

Let-7d and miR-185 Impede Epithelial-Mesenchymal Transition by Downregulating Rab25 in Breast Cancer

Objective:

MicroRNAs (miRNAs) expression has deregulated in several cancer types including breast cancer (BC). The present study aims at investigating the role, mechanism, clinical value of let-7d and miR-185 in BC, and the possible correlation these miRNAs with Rab25.

Materials and Methods:

Tumor samples as well adjacent normal tissues (ANT) were acquired from fresh surgical specimens from 110 patients and the expression levels of let-7d, miR-185, Rab25, and snail were evaluated using real-time PCR. The immunohistochemical (IHC) process and western blot were done to detect the level of Rab25 and Snail protein expression in BC samples.

Results:

By comparing miRNAs expression profiles in clinical tissues of 110 patients using real-time PCR, let-7d, and miR-185 expression were dramatically downregulated in BC tissues (P < 0.05). Tumor size, stage, and lymph node metastasis were significantly related to miRNAs expression. Based on qRT-PCR and bioinformatics database analyses, we also recognized Rab25 as a possible target of miR-185 and let-7d. Rab25 expression was enhanced in BC cells and associated inversely with the expression level of mentioned miRNAs. qRT-PCR, immunohistochemistry, and western blot studies verified that Rab25 upregulation increased the levels of the snail, that key transcription factor of epithelial-mesenchymal transition (EMT).

Conclusion:

These findings demonstrated that let-7d and miR-185 inhibited EMT by targeting Rab25 expression in BC. Therefore, targeting the let-7d and miR-185/Rab25 interaction may offer new therapeutic opportunities for treating BC patients.

Rab25 Deficiency Perturbs Epidermal Differentiation and Skin Barrier Function in Mice

Rab25, a member of the Rab11 small GTPase family, is central to achieving cellular polarity in epithelial tissues. Rab25 is highly expressed in epithelial cells of various tissues including breast, vagina, cervix, the gastrointestinal tract, and skin. Rab25 plays key roles in tumorigenesis, mainly by regulating epithelial differentiation and proliferation. However, its role in skin physiology is relatively unknown. In this study, we demonstrated that Rab25 knock-out (KO) mice show a skin barrier dysfunction with high trans-epidermal water loss and low cutaneous hydration. To examine this observation, we investigated the histology and epidermal differentiation markers of the skin in Rab25 KO mice. Rab25 KO increased cell proliferation at the basal layer of epidermis, whereas the supra-basal layer remained unaffected. Ceramide, which is a critical lipid component for skin barrier function, was not altered by Rab25 KO in its distribution or amount, as determined by immunohistochemistry. Notably, levels of epidermal differentiation markers, including loricrin, involucrin, and keratins (5, 14, 1, and 10) increased prominently in Rab25 KO mice. In line with this, depletion of Rab25 with single hairpin RNA increased the expression of differentiation markers in a human keratinocyte cell line, HaCaT. Transcriptomic analysis of the skin revealed increased expression of genes associated with skin development, epidermal development, and keratinocyte differentiation in Rab25 KO mice. Collectively, these results suggested that Rab25 is involved in the regulation of epidermal differentiation and proliferation.

Loss of Rab25 promotes the development of skin squamous cell carcinoma through the dysregulation of integrin trafficking

Rab25 can function as both a tumor suppressor and a tumor promoter across different tissues. This study sought to clarify the role of Rab25 as a tumor suppressor in skin squamous cell carcinoma (SCC). Rab25 loss was closely associated with neoplastic transition in both humans and mice. Rab25 loss was well correlated with increased cell proliferation and poor differentiation in human SCC. While Rab25 knockout (KO) in mice did not induce spontaneous tumor formation, it did significantly accelerate tumor generation and promote malignant transformation in a mouse two-stage skin carcinogenesis model. Xenografting of a Rab25-deficient human keratinocyte cell line, HaCaT, also elicited neoplastic transformation. Notably, Rab25 deficiency led to dysregulation of integrins β1, β4, and α6, which matched well with increased epidermal proliferation and impaired desmosome-tight junction formation. Rab25 deficiency induced impairment of integrin recycling, leading to the improper expression of integrins. In line with this, significant attenuation of integrin β1, β4, and α6 expression was identified in human SCCs where Rab25 was deficient. Collectively, these results suggest that loss of Rab25 promotes the development and neoplastic transition of SCC through dysregulation of integrin trafficking. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Rab25 promotes erlotinib resistance by activating the β1 integrin/AKT/β-catenin pathway in NSCLC

Objectives

Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI) has significant therapeutic efficacy in non‐small‐cell lung cancer (NSCLC) patients. However, acquired resistance is inevitable and limits the long‐term efficacy of EGFR‐TKI. Our study aimed to investigate the role of ras‐associated binding protein 25 (Rab25) in mediating EGFR‐TKI resistance in NSCLC.

Materials and Methods

Rab25 expression in NSCLC patients was measured by immunohistochemical staining. Western blotting was used to analyse the expression of molecules in the Rab25, EGFR and Wnt signalling pathways. Lentiviral vectors were constructed to knock in and knock out Rab25. The biological function of Rab25 was demonstrated by cell‐counting kit‐8 and flow cytometry. The interaction between Rab25 and β1 integrin was confirmed by co‐immunoprecipitation.

Results

Rab25 overexpression induced erlotinib resistance, whereas Rab25 knockdown reversed this refractoriness in vitro and in vivo. Moreover, Rab25 interacts with β1 integrin and promotes its trafficking to the cytoplasmic membrane. The membrane‐β1 integrin induced protein kinase B (AKT) phosphorylation and subsequently activated the Wnt/β‐catenin signalling pathway, promoting cell proliferation. Furthermore, high Rab25 expression was associated with poor response to EGFR‐TKI treatment in NSCLC patients.

Conclusions

Rab25 mediates erlotinib resistance by activating the β1 integrin/AKT/β‐catenin signalling pathway. Rab25 may be a predictive biomarker and has potential therapeutic value in NSCLC patients with acquired resistance to EGFR‐TKI.

MiR-577 suppresses epithelial-mesenchymal transition and metastasis of breast cancer by targeting Rab25

Background

MicroRNAs can act as both tumor suppressor genes and oncogenes and participate in cell proliferation, metastasis, and apoptosis. Low levels of miR‐577 are found in several cancers, for example, thyroid carcinoma, glioblastoma, and hepatocellular carcinoma. The aim of this study was to investigate the effect of miR‐577 on breast cancer (BC).

Methods

The relative level of miR‐577 in 120 BC tissues and cells was detected by real‐time PCR. MDA‐MB‐231 cells with upregulated miR‐577 and MCF‐7 cells with downregulated miR‐577 were established. Transwell invasion assays were used to examine the invasiveness of cells. Epithelial‐mesenchymal transition (EMT) markers were evaluated by immunofluorescence and Western blot. Targeted combinations of miR‐577 and Rab25 were analyzed by luciferase assays. Xenograft models were used to examine the effect of miR‐577 on BC metastasis.

Results

MiR‐577 expression was significantly suppressed in BC tissues. Tumor size, tumor stage, and lymphatic metastasis were attributed to miR‐577 expression. Moreover, miR‐577 overexpression strongly inhibited the invasiveness and EMT of BC cells in vitro. MiR‐577 directly regulated Rab25 in BC. Rab25 upregulation by miR‐577 decreased the levels of E‐cadherin and increased the levels of Vimentin. Notably, Rab25 knockdown inhibited BC invasion; however, an increase in Rab25 counteracted the invasive effect of miR‐577 in BC.

Conclusion

Results indicated that miR‐577 suppressed EMT by inhibiting Rab25 expression in BC. MiR‐577 and Rab25 are considered potential targets of BC treatment.

Epidermal growth factor-mediated Rab25 pathway regulates integrin β1 trafficking in colon cancer

Background

Integrins play a critical role in carcinogenesis. Integrin β1 localization is regulated by the guanosine-5′-triphosphate hydrolase Rab25 and integrin β1 levels are elevated in the serum of colon cancer patients; thus, the present study examined the effects of epidermal growth factor (EGF) and Rab25 on integrin β1 localization in colon cancer cells.

Methods

HCT116 human colon cancer cells were treated with increasing concentrations of EGF, and cell proliferation and protein expression were monitored by MTT and western blot analyses, respectively. Cell fractionation was performed to determine integrin β1 localization in the membrane and cytosol. Integrin β1 extracellular shedding was monitored by enzyme-linked immunosorbent assays (ELISAs) with culture supernatants from stimulated cells. HCT116 cells were transfected with Rab25-specific siRNA to determine the significance of Rab25 in integrin β1 trafficking in the presence of EGF.

Results

Total integrin β1 expression increased in response to EGF and subsequently decreased at 24 h post-stimulation. A similar decrease was observed in purified membrane fractions, whereas no changes were observed in cytosolic levels. ELISAs using media from stimulated cell cultures demonstrated increased integrin β1 levels corresponding to the decrease observed in membrane fractions, suggesting that EGF induces integrin receptor shedding. EGF stimulation in Rab25-knockdown cells resulted in integrin β1 accumulation in the membrane, suggesting that Rab25 promotes integrin endocytosis.

Conclusions

Integrin β1 is shed from colon cancer cells in response to EGF stimulation in a Rab25-dependent manner. These results further the present understanding of the role of integrin β1 in colon cancer progression.

Rab25 acts as an oncogene in luminal B breast cancer and is causally associated with Snail driven EMT

The Rab GTPases regulate vesicular trafficking machinery that transports and delivers a diverse pool of cargo, including growth factor receptors, integrins, nutrient receptors and junction proteins to specific intracellular sites. The trafficking machinery is indeed a major posttranslational modifier and is critical for cellular homeostasis. Deregulation of this stringently controlled system leads to a wide spectrum of disorders including cancer. Herein we demonstrate that Rab25, a key GTPase, mostly decorating the apical recycling endosome, is a dichotomous variable in breast cancer cell lines with higher mRNA and protein expression in Estrogen Receptor positive (ER+ve) lines. Rab25 and its effector, Rab Coupling Protein (RCP) are frequently coamplified and coordinately elevated in ER+ve breast cancers. In contrast, Rab25 levels are decreased in basal-like and almost completely lost in claudin-low tumors. This dichotomy exists despite the presence of the 1q amplicon that hosts Rab25 across breast cancer subtypes and is likely due to differential methylation of the Rab25 promoter. Functionally, elevated levels of Rab25 drive major hallmarks of cancer including indefinite growth and metastasis but in case of luminal B breast cancer only. Importantly, in such ER+ve tumors, coexpression of Rab25 and its effector, RCP is significantly associated with a markedly worsened clinical outcome. Importantly, in claudin-low cell lines, exogenous Rab25 markedly inhibits cell migration. Similarly, during Snail-induced epithelial to mesenchymal transition (EMT) exogenous Rab25 potently reverses Snail-driven invasion. Overall, this study substantiates a striking context dependent role of Rab25 in breast cancer where Rab25 is amplified and enhances aggressiveness in luminal B cancers while in claudin-low tumors, Rab25 is lost indicating possible anti-tumor functions.

Hypoxia-inducible factor 1 alpha is required for the tumourigenic and aggressive phenotype associated with Rab25 expression in ovarian cancer

The small GTPase Rab25 has been functionally linked to tumour progression and aggressiveness in ovarian cancer and promotes invasion in three-dimensional environments. This type of migration has been shown to require the expression of the hypoxia-inducible factor 1 alpha (HIF-1α). In this report we demonstrate that Rab25 regulates HIF-1α protein expression in an oxygen independent manner in a panel of cancer cell lines. Regulation of HIF-1α protein expression by Rab25 did not require transcriptional upregulation, but was dependent on de novo protein synthesis through the Erbb2/ERK1/2 and p70S6K/mTOR pathways. Rab25 expression induced HIF-1 transcriptional activity, increased cisplatin resistance, and conferred intraperitoneal growth to the A2780 cell line in immunocompromised mice. Targeting HIF1 activity by silencing HIF-1β re-sensitised cells to cisplatin in vitro and reduced tumour formation of A2780-Rab25 expressing cells in vivo in a mouse ovarian peritoneal carcinomatosis model. Similar effects on cisplatin resistance in vitro and intraperitoneal tumourigenesis in vivo were obtained after HIF1b knockdown in the ovarian cancer cell line SKOV3, which expresses endogenous Rab25 and HIF-1α at atmospheric oxygen concentrations. Our results suggest that Rab25 tumourigenic potential and chemoresistance relies on HIF1 activity in aggressive and metastatic ovarian cancer. Targeting HIF-1 activity may potentially be effective either alone or in combination with standard chemotherapy for aggressive metastatic ovarian cancer.

Rab25 GTPase: Functional roles in cancer

Rab25, a small GTPase belongs to the Rab protein family, has a pivotal role in cancer pathophysiology. Rab25 governs cell-surface receptors recycling and cellular signaling pathways activation, allowing it to control a diverse range of cellular functions, including cell proliferation, cell motility and cell death. Aberrant expression of Rab25 was linked to cancer development. Majority of research findings revealed that Rab25 is an oncogene. Elevated expression of Rab25 was correlated with poor prognosis and aggressiveness of renal, lung, breast, ovarian and other cancers. However, tumor suppressor function of Rab25 was reported in several cancers, such as colorectal cancer, indicating the tumor type-specific function of Rab25. In this review, we recapitulate the current knowledge of Rab25 in cancer development and therapy.

RIN1 promotes renal cell carcinoma malignancy by activating EGFR signaling through Rab25

We previously identified the important role of RIN1 expression in the prognosis of clear cell renal cell carcinoma (ccRCC). The role of RIN1 in ccRCC malignancy and underlying molecular mechanisms remain unclear. Here we report that ccRCC cells and tissues expressed more RIN1 than normal controls. Gain‐of‐function and loss‐of‐function studies demonstrated that RIN1 enhanced ccRCC cell growth, migration and invasion abilities in vitro and promoted tumor growth and metastasis in vivo. Mechanistic studies revealed that RIN1 has an activating effect on EGFR signaling in ccRCC. In addition, we unveil Rab25, a critical GTPase in ccRCC malignancy, as a functional RIN1 interacting partner. Knockdown of Rab25 eliminated the augmentation of carcinoma cell proliferation, migration and invasion by ectopic RIN1. We also confirmed that RIN1 and Rab25 expression correlates with the overall‐survival of ccRCC patients from TCGA. These findings suggest that RIN1 plays an important oncogenic role in ccRCC malignancy by activation of EGFR signaling through interacting with Rab25, and RIN1 could be employed as an effective therapeutic target for ccRCC.

High Rab25 expression associates with Ki67/TP53/CD133/VEGFR expression predicts poor prognosis in gastric cancer

Rab25 belongs to Rab GTPases which regulating vesicle trafficking of various extracellular and intracellular resources. Aberrant high Rab25 expression is closely linked to cancer development including gastric cancer. However, the underlying mechanism of Ras25 in gastric cancer is still unclear. In this study, we determined to investigate the potential association between Rab25 and four tumor markers, including Ki67 (a well-known hallmarker of tumor proliferation), TP53 (tumor p53, a master tumor regulator associated with cell apoptosis), CD133 (a common cancer stem cell marker) and VEGFR (Vascular endothelial growth factor receptor, an efficient therapy target for gastric cancer). The results indicated that Rab25 expression in both cytoplasm and nucleus was significantly higher in gastric cancer tissues than para-carcinoma tissues. High Rab25 nucleus expression was positively associated with distant metastasis (M stage) and clinical (cTNM) stage, while Rab25 nucleus expression correlated with M stage, cTNM stage and regional lymph metastasis stage (N stage). Survival analysis revealed that high Rab25 cytoplasm/nucleus expression predicted shorter overall survival time of patients with gastric cancer. Rab25 expression was significantly associated with Ki67 expression, TP53 expression, CD133 expressionand VEGFR expression in gastric cancer. In conclusion, our results indicated that Rab25 behaved as an oncogene in gastric cancer related to Ki67/TP53/CD133/VEGFR expression and suggested Rab25 to be a prognostic marker.

Autophagy regulates turnover of lipid droplets via ROS-dependent Rab25 activation in hepatic stellate cell

Activation of hepatic stellate cells (HSCs) is a pivotal event in liver fibrosis, characterized by dramatic disappearance of lipid droplets (LDs). Although LD disappearance has long been considered one of the hallmarks of HSC activation, the underlying molecular mechanisms are largely unknown. In this study, we sought to investigate the role of autophagy in the process of LD disappearance, and to further examine the underlying mechanisms in this molecular context. We found that LD disappearance during HSC activation was associated with a coordinate increase in autophagy. Inhibition or depletion of autophagy by Atg5 siRNA impaired LD disappearance of quiescent HSCs, and also restored lipocyte phenotype of activated HSCs. In contrast, induction of autophagy by Atg5 plasmid accelerated LD loss of quiescent HSCs. Importantly, our study also identified a crucial role for reactive oxygen species (ROS) in the facilitation of autophagy activation. Antioxidants, such as glutathione and N-acetyl cysteine, significantly abrogated ROS production, and in turn, prevented autophagosome generation and autophagic flux during HSC activation. Besides, we found that HSC activation triggered Rab25 overexpression, and promoted the combination of Rab25 and PI3KCIII, which direct autophagy to recognize, wrap and degrade LDs. Down-regulation of Rab25 activity, using Rab25 siRNA, blocked the target recognition of autophagy on LDs, and inhibited LD disappearance of quiescent HSCs. Moreover, the scavenging of excessive ROS could disrupt the interaction between autophagy and Rab25, and increase intracellular lipid content. Overall, these results provide novel implications to reveal the molecular mechanism of LD disappearance during HSC activation, and also identify ROS-Rab25-dependent autophagy as a potential target for the treatment of liver fibrosis.

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Autophagosome generation and autophagic flux are increased during HSC activation.

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The inhibition of autophagy blocks LD disappearance of quiescent HSCs.

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The induction of autophagy accelerates LD disappearance of quiescent HSCs.

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Rab25 activation is required for autophagy to degrade LDs during HSC activation.

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Mitochondrial H₂O₂ production triggers autophagy activation during HSC activation.

Overexpression of Rab25 promotes hepatocellular carcinoma cell proliferation and invasion

Rab25 was reported to be associated with several human cancers and malignant biological behavior of cancer cells. The goal of the present study was to determine its expression pattern and biological function in human hepatocellular carcinoma (HCC). We examined Rab25 protein in 92 cases of HCC tissues and 3 HCC cell lines. The results showed that Rab25 was upregulated in HCC tissues and cells compared with normal liver tissues and cell line. Rab25 overexpression correlated with advanced tumor stage and nodal metastasis. Rab25 small interfering RNA (siRNA) was employed in Bel7402 and SK-Hep-1 cell lines. Cell Counting Kit-8 (CCK-8) assay and colony formation assay showed that Rab25 depletion blocked cell growth rate and inhibited colony formation ability. Transwell assay showed that Rab25 depletion negatively regulated the invading ability of HCC cells. To explore the possible mechanisms, we checked several signaling pathways and found that Rab25 depletion downregulated AKT phosphorylation. In addition, luciferase reporter assay showed that Rab25 depletion inhibited the Wnt signaling pathway and its target genes such as cyclin D1, c-myc, and MMP7. In conclusion, Rab25 is overexpressed in human HCC and contributes to cancer cell proliferation and invasion possibly through regulation of the Wnt signaling pathway.

Rab25 upregulation correlates with the proliferation, migration, and invasion of renal cell carcinoma

Renal cell carcinoma (RCC) is a common urological cancer with a poor prognosis. A recent cohort study revealed that the median survival of RCC patients was only 1.5 years and that <10% of the patients in the study survived up to 5 years. In tumor development, Rab GTPase are known to play potential roles such as regulation of cell proliferation, migration, invasion, communication, and drug resistance in multiple tumors. However, the correlation between Rabs expression and the occurrence, development, and metastasis of RCC remains unclear. In this study, we analyzed the transcriptional levels of 52 Rab GTPases in RCC patients. Our results showed that high levels of Rab25 expression were significantly correlated with RCC invasion classification (P < 0.01), lymph-node metastasis (P < 0.001), and pathological stage (P < 0.01). Conversely, in 786-O and A-498 cells, knocking down Rab25 protein expression inhibited cell proliferation, migration, and invasion. Our results also demonstrated that Rab25 is a target gene of let-7d, and further suggested that Rab25 upregulation in RCC is due to diminished expression of let-7d. These findings indicate that Rab25 might be a novel candidate molecule involved in RCC development, thus identifying a potential biological therapeutic target for RCC.

Rab25 expression predicts poor prognosis in clear cell renal cell carcinoma

Rab25 has been implicated in a number of types of cancer. However, its expression status and clinical implications in clear cell renal cell carcinoma (ccRCC) remain to be investigated. The purpose of this study was to investigate the significance of Rab25 status in patients with ccRCC. Rab25 expression was determined by western blot analysis in 30 fresh ccRCC samples. Immunohistochemistry was performed on the ccRCC samples and paired adjacent noncancerous tissues from 107 patients with ccRCC who had undergone surgery. The prognostic role and correlations with other clinicopathological factors were evaluated. Rab25 expression was upregulated in ccRCC tissues compared with that in paired adjacent noncancerous tissues. A high expression of Rab25 protein was significantly correlated with the primary tumor stage; lymph node metastasis; distant metastasis; tumor, node and metastasis stage and histological grade. A Kaplan-Meier survival analysis by log-rank test demonstrated that elevated Rab25 expression predicted lower overall survival time in patients with ccRCC. Notably, multivariate analyses revealed that expression of Rab25 was an independent prognostic factor in ccRCC (hazard ratio, 3.43; 95% confidence interval, 1.13–10.38; P=0.023). In conclusion, Rab25 is a potential prognostic biomarker in ccRCC.

GRAB is a binding partner for the Rab11a and Rab11b GTPases

Co-ordination of Rab GTPase function has emerged as a crucial mechanism in the control of intracellular trafficking processes in eukaryotic cells. Here, we show that GRAB/Rab3IL1 [guanine nucleotide exchange factor for Rab3A; RAB3A interacting protein (rabin3)-like 1], a protein that has previously be shown to act as a GEF (guanine nucleotide exchange factor) for Rab3a, Rab8a and Rab8b, is also a binding partner for Rab11a and Rab11b, but not the closely related Rab25 GTPase. We demonstrate that exogenous expression of Rab11a and Rab11b shift GRAB's distribution from the cytoplasm onto membranes. We find that the Rab11a/Rab11b-binding region of GRAB lies within its carboxy-terminus, a region distinct from its GEF domain and Rab3a-binding region. Finally, we describe a GRAB deletion mutant (GRABΔ223-228) that is deficient in Rab11-binding ability. These data identify GRAB as a dual Rab-binding protein that could potentially link Rab3 and Rab11 and/or Rab8 and Rab11-mediated intracellular trafficking processes.

Structural and functional analysis of FIP2 binding to the endosome-localised Rab25 GTPase

Rab small GTPases are the master regulators of intracellular trafficking in eukaryotes. They mediate spatial and temporal recruitment of effector proteins to distinct cellular compartments through GTP-induced changes in their conformation. Despite numerous structural studies, the molecular basis for Rab/effector specificity and subsequent biological activity remains poorly understood. Rab25, also known as Rab11c, which is epithelial-specific, has been heavily implicated in ovarian cancer development and independently appears to act as a tumour suppressor in the context of a distinct subset of carcinomas. Here, we show that Rab25 associates with FIP2 and can recruit this effector protein to endosomal membranes. We report the crystal structure of Rab25 in complex with the C-terminal region of FIP2, which consists of a central dimeric FIP2 coiled-coil that mediates a heterotetrameric Rab25-(FIP2)2-Rab25 complex. Thermodynamic analyses show that, despite a relatively conserved interface, FIP2 binds to Rab25 with an approximate 3-fold weaker affinity than to Rab11a. Reduced affinity is mainly associated with lower enthalpic gains for Rab25:FIP2 complex formation, and can be attributed to subtle differences in the conformations of switch 1 and switch 2. These cellular, structural and thermodynamic studies provide insight into the Rab11/Rab25 subfamily of small GTPases that regulate endosomal trafficking pathways in eukaryotes.

Expression of Rab25 correlates with the invasion and metastasis of gastric cancer

The objective of this study was to determine the expression of the important vesicle trafficking-regulating factor Rab25 in human gastric cancer tissues, to analyze the correlation between Rab25 protein expression with gastric cancer occurrence and development, and to discuss the correlation of Rab25 protein expression with gastric cancer cell metastasis. The overall aim was to provide experimental evidence that can be used to design future biological treatments of human gastric cancer. Human gastric cancer tissue and the adjacent normal gastric tissue were surgically removed, and immunohistochemistry and Western blotting were used to detect Rab25 protein expression. The correlation between Rab25 protein expression with the development and pathological characteristics of gastric cancer was analyzed. Using RNAi, Rab25 expression was reduced in the gastric cancer cell line MGC80-3, and the changes in MGC80-3 cell invasiveness were then monitored. Immunohistochemistry showed that the Rab25 protein expression rates were 78.21% and 23.08% in gastric carcinoma and the adjacent normal gastric tissue, respectively. Immunohistochemistry and Western blot results showed that Rab25 protein expression in gastric cancer was significantly higher than in adjacent normal gastric tissues (P<0.01). Less differentiated gastric cancer cells had higher expression of Rab25 protein (P<0.01). Gastric carcinomas from patients with a late pathological stage (III-IV) had significantly higher Rab25 protein expression than early stage (I-II) patients (P<0.01). Gastric carcinomas from patients with lymph node metastasis had significantly higher Rab25 protein expression than lymph node metastasis-free patients (P<0.01). Gastric carcinomas from patients with distant metastases had significantly higher Rab25 protein expression than the distant metastasis-negative patients (P<0.01). Rab25 protein expression in gastric cancer was not affected by the patients(,) sex, age, or tumor size (P>0.05). MGC80-3 cells transfected with Rab25 siRNA had significantly lower Rab25 protein expression (P<0.01) and a significantly lower number of cells that passed through a Transwell chamber compared with non-transfected controls and the transfected control group (P<0.01). Rab25 protein expression is associated with the development of gastric cancer. siRNA knockdown of Rab25 protein expression in MGC80-3 gastric cancer cells reduced MGC80-3 cell invasiveness and provided experimental evidence for potential future biological treatment strategies of human gastric cancer.