lncRNA MAGI2-AS3 suppresses castration-resistant prostate cancer proliferation and migration via the miR-106a-5p/RAB31 axis.

Prostate cancer (PCa) is a common malignant cancer in elderly males in Western countries. Whole-genome sequencing confirmed that long non-coding RNAs (lncRNAs) are frequently altered in castration-resistant prostate cancer (CRPC) and promote drug resistance to cancer therapy. Therefore, elucidating the prospective role of lncRNAs in PCa oncogenesis and progression is of remarkable clinical significance. In this study, gene expression in prostate tissues was determined using RNA-sequencing datasets, and the gene diagnostic and prognostic values of CRPC were analyzed using bioinformatics. Further, the expression levels and clinical significance of MAGI2 Antisense RNA 3 (MAGI2-AS3) in PCa clinical specimens were evaluated. The tumor-suppressive activity of MAGI2-AS3 was functionally explored in PCa cell lines and animal xenograft models. MAGI2-AS3 was found to be aberrantly decreased in CRPC and was negatively correlated with Gleason score and lymph node status. Notably, low MAGI2-AS3 expression positively correlated with poorer survival in patients with PCa. The overexpression of MAGI2-AS3 significantly inhibited the proliferation and migration of PCa in vitro and in vivo. Mechanistically, MAGI2-AS3 could play a tumor suppressor function in CRPC through a novel miR-106a-5p/RAB31 regulatory network and could be a target for future cancer therapy.

A novel membrane targeting domain mediates the endosomal or Golgi localization specificity of small GTPases Rab22 and Rab31.

Rab22 and Rab31 belong to the Rab5 subfamily of GTPases that regulates endocytic traffic and endosomal sorting. Rab22 and Rab31 (a.k.a. Rab22b) are closely related and share 87% amino acid sequence similarity, but they show distinct intracellular localization and function in the cell. Rab22 is localized to early endosomes and regulates early endosomal recycling, while Rab31 is mostly localized to the Golgi complex with only a small fraction in the endosomes at steady state. The specific determinants that affect this differential localization, however, are unclear. In this study, we identify a novel membrane targeting domain (MTD) consisting of the C-terminal hypervariable domain (HVD), interswitch loop (ISL), and N-terminal domain as a major determinant of endosomal localization for Rab22 and Rab31, as well as Rab5. Rab22 and Rab31 share the same N-terminal domain, but we find Rab22 chimeras with Rab31 HVD exhibit phenotypic Rab31 localization to the Golgi complex, while Rab31 chimeras with the Rab22 HVD localize to early endosomes, similar to wildtype Rab22. We also find that the Rab22 HVD favors interaction with the early endosomal effector protein Rabenosyn-5, which may stabilize the Rab localization to the endosomes. The importance of effector interaction in endosomal localization is further demonstrated by the disruption of Rab22 endosomal localization in Rabenosyn-5 knockout cells and by the shift of Rab31 to the endosomes in Rabenosyn-5-overexpressing cells. Taken together, we have identified a novel MTD that mediates localization of Rab5 subfamily members to early endosomes via interaction with an effector such as Rabenosyn-5.

Bacillus anthracis spores are internalized in human lung epithelial cells by Rab GTPase-supported macropinocytosis.

Inhalation anthrax, the deadliest form of the disease, requires inhaled B. anthracis spores to escape from the alveolar space and travel to the mediastinal lymph nodes, from where the vegetative form of the pathogen disseminates, resulting in a rapidly fatal outcome. The role of epithelia in alveolar escape is unclear, but previous work suggests these epithelial cells are involved in this process. Using confocal microscopy, we found that B. anthracis spores are internalized more rapidly by A549 type II alveolar epithelial cells compared to hAELVi type I alveolar epithelial cells. Internalization of spores by alveolar epithelial cells requires cytoskeletal rearrangement evidenced by significant inhibition by cytochalasin D, an actin inhibitor. Chemical inhibitors of macropinocytosis significantly downregulated B. anthracis spore internalization in human alveolar cells, while inhibitors of other endocytosis pathways had minimal effects. Additional studies using a macropinosome marker and electron microscopy confirmed the role of macropinocytosis in spore uptake. By colocalization of B. anthracis spores with four endocytic Rab proteins, we demonstrated that Rab31 played a role in B. anthracis spore macropinocytosis. Finally, we confirmed that Rab31 is involved in B. anthracis spore internalization by enhanced spore uptake in Rab31-overexpressing A549 cells. This is the first report that shows B. anthracis spore internalization by macropinocytosis in human epithelial cells. Several Rab GTPases are involved in the process.

Lysosome-related exosome secretion mediated by miR-26b / Rab31 pathway was associated with the proliferation and migration of MCF-7 cells treated with BPA.

Bisphenol A (BPA), one of the typical environmental endocrine disruptors (EEDs), can promote the proliferation and migration of cancer cells, but the mechanism of which remains largely unclear. Exosome secretion plays an important role in the stress response of cells to environmental stimuli. This study was designed to explore whether exosome secretion was involved in the toxic effect of BPA on the proliferation and migration of MCF-7 cells, and the related mechanism. Our data shows that the IC50 value of MCF-7 exposure to BPA was about 65.82 µM. The exposure of MCF-7 to 10 µM BPA resulted in a decreased miR-26b expression and the activation of miR-26b/Rab-31 pathway, consequently, the number and activity of lysosomes decreased, the secretion of exosomes increased, cell proliferation and migration were enhanced obviously. Interestingly, miR-26b mimic up-regulated the number and activity of lysosomes via miR-26b/miR-31 pathway, exosome secretion was down-regulated, cell proliferation and migration decreased. Further, when GW4869 was used to directly inhibit the exosome secretion of MCF-7 treated with BPA, their proliferation and migration were down-regulated. Herein, we concluded that the stimulating effect of BPA on the proliferation and migration of MCF-7 cells was associated with the lysosome - related exosome secretion via miR-26b / Rab31 pathway.

LRG-1 promotes fat graft survival through the RAB31-mediated inhibition of hypoxia-induced apoptosis.

Autologous adipose tissue is an ideal soft tissue filling material, and its biocompatibility is better than that of artificial tissue substitutes, foreign bodies and heterogeneous materials. Although autologous fat transplantation has many advantages, the low retention rate of adipose tissue limits its clinical application. Here, we identified a secretory glycoprotein, leucine-rich-alpha-2-glycoprotein 1 (LRG-1), that could promote fat graft survival through RAB31-mediated inhibition of hypoxia-induced apoptosis. We showed that LRG-1 injection significantly increased the maintenance of fat volume and weight compared with the control. In addition, higher fat integrity, more viable adipocytes and fewer apoptotic cells were observed in the LRG-1-treated groups. Furthermore, we discovered that LRG-1 could reduce the ADSC apoptosis induced by hypoxic conditions. The mechanism underlying the LRG-1-mediated suppression of the ADSC apoptosis induced by hypoxia was mediated by the upregulation of RAB31 expression. Using LRG-1 for fat grafts may prove to be clinically successful for increasing the retention rate of transplanted fat.

Rab31, a receptor of advanced glycation end products (RAGE) interacting protein, inhibits AGE induced pancreatic ß-cell apoptosis through the pAKT/BCL2 pathway.

Receptor of advanced glycation end products (RAGE) mediates diverse signal transduction following ligand stimulation and plays an important role in diabetes complications and aging associated disease. We have previously verified that advanced glycation end products (AGE) bind to RAGE to cause pancreatic ß-cell apoptosis through the mitochondrial pathway. However, the direct interacting protein(s) of RAGE in ß cells has never been appreciated. In the present study, we utilized GST pull-down assay combined with mass spectrometry to identify the interacting proteins of the RAGE intracellular domain (C-terminal 43 amino acid of RAGE). Overall four RAGE interacting proteins, including Rab31, were identified with scores over 160. Rab31 was detected in three ß-cell lines and confirmed to have interacted with RAGE via co-immunoprecipitation and immunostaining assays. This interaction was further enhanced by glycation-serum (GS) stimulation due to membrane distribution of Rab31 following treatment with GS. We further confirmed that Rab31 promoted RAGE endocytosis and inhibited GS-induced ß-cell apoptosis through the pAKT/BCL2 pathway. These findings reveal a new RAGE interaction protein Rab31 that prevents AGE/RAGE-induced pancreatic ß-cell apoptosis. Rab31 is therefore a promising therapeutic target for preserving functional ß cells under diabetes conditions.

Rab31-dependent regulation of transforming growth factor ß expression in breast cancer cells.

BACKGROUND: The small GTP-binding protein Rab31 plays an important role in the modulation of tumor biological-relevant processes, including cell proliferation, adhesion, and invasion. As an underlying mechanism, Rab31 is presumed to act as a molecular switch between a more proliferative and an invasive phenotype. This prompted us to analyze whether Rab31 overexpression in breast cancer cells affects expression of genes involved in epithelial-to-mesenchymal transition (EMT)-like processes when compared to Rab31 low-expressing cells. METHODS: Commercially available profiler PCR arrays were applied to search for differentially expressed genes in Rab31 high- and low-expressing CAMA-1 breast cancer cells. Differential expression of selected candidate genes in response to Rab31 overexpression in CAMA-1 cells was validated by independent qPCR and protein assays. RESULTS: Gene expression profiling of key genes involved in EMT, or its reciprocal process MET, identified 9 genes being significantly up- or down-regulated in Rab31 overexpressing CAMA-1 cells, with the strongest effects seen for TGFB1, encoding TGF-ß1 (> 25-fold down-regulation in Rab31 overexpressing cells). Subsequent validation analyses by qPCR revealed a strong down-regulation of TGFB1 mRNA levels in response to increased Rab31 expression not only in CAMA-1 cells, but also in another breast cancer cell line, MDA-MB-231. Using ELISA and Western blot analysis, a considerable reduction of both intracellular and secreted TGF-ß1 antigen levels was determined in Rab31 overexpressing cells compared to vector control cells. Furthermore, reduced TGF-ß activity was observed upon Rab31 overexpression in CAMA-1 cells using a sensitive TGF-ß bioassay. Finally, the relationship between Rab31 expression and the TGF-ß axis was analyzed by another profiler PCR array focusing on genes involved in TGF-ß signaling. We found 12 out of 84 mRNAs significantly reduced and 7 mRNAs significantly increased upon Rab31 overexpression. CONCLUSIONS: Our results demonstrate that Rab31 is a potent modulator of the expression of TGF-ß and other components of the TGF-ß signaling pathway in breast cancer cells.

Effect of RAB31 silencing on osteosarcoma cell proliferation and migration through the Hedgehog signaling pathway.

Osteosarcoma (OS) is a prevalent cancer that plagues people worldwide. Identifying prognostic markers would be useful in treating human OS. In this study, we aimed to explore the functions of Ras-related protein Rab-31 (RAB31) in OS-cell proliferation, migration, and invasion as well as its roles in the Hedgehog signaling pathway for better understanding of the mechanism. To assess the detailed regulatory mechanism of RAB31 silencing on OS, both RT-qPCR and Western blot analysis were employed to evaluate the expressions of RAB31 as well as the Hedgehog signaling pathway-related genes. Besides, we also investigated the effects of silenced RAB31 both in vitro and in vivo. First, we found that in OS tissues, both mRNA and protein expressions of RAB31 and PCNA had a significant increase. Second, the Hedgehog signaling pathway was detected to play an integral role in OS progression. Finally, after transfection of RAB31-siRNA to reduce the expression of RAB31, the Hedgehog signaling pathway was suppressed, along with cell proliferation, invasion, and migration. Therefore, we conclude that RAB31 plays an important role in OS development and its silencing delays the OS progression via suppression of the Hedgehog signaling pathway.

Oncogenic Effect of the Novel Fusion Gene VAPA-Rab31 in Lung Adenocarcinoma.

Fusion genes have been identified as oncogenes in several solid tumors including lung, colorectal, and stomach cancers. Here, we characterized the fusion gene, VAPA-Rab31, discovered from RNA-sequencing data of a patient with lung adenocarcinoma who did not harbor activating mutations in EGFR, KRAS and ALK. This fusion gene encodes a protein comprising the N-terminal region of vesicle-associated membrane protein (VAMP)-associated protein A (VAPA) fused to the C-terminal region of Ras-related protein 31 (Rab31). Exogenous expression of VAPA-Rab31 in immortalized normal bronchial epithelial cells demonstrated the potential transforming effects of this fusion gene, including increased colony formation and cell proliferation in vitro. Also, enhanced tumorigenicity upon VAPA-Rab31 was confirmed in vivo using a mouse xenograft model. Metastatic tumors were also detected in the liver and lungs of xenografted mice. Overexpression of VAPA-Rab31 upregulated anti-apoptotic protein Bcl-2 and phosphorylated CREB both in cells and xenograft tumors. Reduced apoptosis and increased phosphorylation of CREB and Erk were observed in VAPA-Rab31-overexpressing cells after bortezomib treatment. Elevated Bcl-2 level via activated CREB contributed to the resistance to the bortezomib-induced apoptosis. Our data suggest the oncogenic function of the novel fusion gene VAPA-Rab31 via upregulated Bcl-2 and activated CREB in lung cancer.

The role of the small GTPase Rab31 in cancer.

Members of the small GTPase family Rab are emerging as potentially important factors in cancer development and progression. A good number of Rabs have been implicated or associated with various human cancers, and much recent excitement has been associated with the roles of the Rab11 subfamily member Rab25 and its effector, the Rab coupling protein (RCP), in tumourigenesis and metastasis. In this review, we focus on a Rab5 subfamily member, Rab31, and its implicated role in cancer. Well recognized as a breast cancer marker with good prognostic value, recent findings have provided some insights as to the mechanism underlying Rab31's influence on oncogenesis. Levels of Oestrogen Receptor α (ERα)- responsive Rab31 could be elevated through stabilization of its transcript by the RNA binding protein HuR, or though activation by the oncoprotein mucin1-C (MUC1-C), which forms a transcriptional complex with ERα. Elevated Rab31 stabilizes MUC1-C levels in an auto-inductive loop that could lead to aberrant signalling and gene expression associated with cancer progression. Rab31 and its guanine nucleotide exchange factor GAPex-5 have, however, also been shown to enhance early endosome-late endosome transport and degradation of the epidermal growth factor receptor (EGFR). The multifaceted action and influences of Rab31 in cancer is discussed in the light of its new interacting partners and pathways.

Rab31 promoted hepatocellular carcinoma (HCC) progression via inhibition of cell apoptosis induced by PI3K/AKT/Bcl-2/BAX pathway.

Rab31 belongs to the Ras superfamily of small GTP-binding proteins, which has been found to regulate the vesicle transport from the Golgi apparatus to early and late endosomes. The investigation here detected the expression of Rab31 in 96 patients with hepatocellular carcinoma (HCC) and tried to identify its significance on outcome of HCCs after liver resection. By immunohistochemistry staining, it was found that Rab31 expression in HCC tissues was remarkably higher than that in adjacent liver tissues. Aberrant Rab31 overexpression in HCC tissues was identified to be associated with worse prognosis after liver resection. Univariate analysis showed that advanced tumor-nodes-metastasis (TNM) staging of HCC, intrahepatic metastases, portal vein invasion, and higher Rab31 were the predictive factors of poor prognosis. Multivariate analysis demonstrated that intrahepatic metastases and higher Rab31 were the independent prognostic factors. Furthermore, forced expression of Rab31 in Huh7 cells was found to promote cell growth via upregulation of Bcl-2/BAX ratio induced by PI3K/AKT. Correspondingly, silencing Rab31 induced cell apoptosis and in turn suppressed the growth capacity of MHCC97 cells in vitro. Taken together, this study provides the evidence of Rab31 overexpression in HCC, and Rab31 is potentially used as a novel biomarker of poor prognosis in patients with HCC. PI3K/AKT/Bcl-2/BAX axis was involved in Rab31-promoting HCC progression.

RAB31 in glioma-derived endothelial cells promotes glioma cell invasion via extracellular vesicle-mediated enrichment of MYO1C.

Extracellular vesicles (EV), important messengers in intercellular communication, can load and transport various bioactive components and participate in different biological processes. We previously isolated glioma human endothelial cells (GhECs) and found that GhECs, rather than normal human brain endothelial cells (NhECs), exhibit specific enrichment of MYO1C into EVs and promote the migration of glioma cells. In this study, we explored the mechanism by which MYO1C is secreted into EVs. We report that such secretion is dependent on RAB31, RAB27B, and FAS. When expression of RAB31 increases, MYO1C is enriched in secretory EVs. Finally, we identified an EV export mechanism for MYO1C that promotes glioma cell invasion and is dependent on RAB31 in GhECs. In summary, our data indicate that the knockdown of RAB31 can reduce enrichment of MYO1C in extracellular vesicles, thereby attenuating the promotion of glioma cell invasion by GhEC-EVs.

RAB31 drives extracellular vesicle fusion and cancer-associated fibroblast formation leading to oxaliplatin resistance in colorectal cancer.

Epithelial-mesenchymal transition (EMT) is associated with tumorigenesis and drug resistance. The Rab superfamily of small G-proteins plays a role in regulating cell cytoskeleton and vesicle transport. However, it is not yet clear how the Rab family contributes to cancer progression by participating in EMT. By analysing various in silico datasets, we identified a statistically significant increase in RAB31 expression in the oxaliplatin-resistant group compared to that in the parental or other chemotherapy drug groups. Our findings highlight RAB31's powerful effect on colorectal cancer cell lines when compared with other family members. In a study that analysed multiple online meta-databases, RAB31 RNA levels were continually detected in colorectal tissue arrays. Additionally, RAB31 protein levels were correlated with various clinical parameters in clinical databases and were associated with negative prognoses for patients. RAB31 expression levels in all three probes were calculated using a computer algorithm and were found to be positively correlated with EMT scores. The expression of the epithelial-type marker CDH1 was suppressed in RAB31 overexpression models, whereas the expression of the mesenchymal-type markers SNAI1 and SNAI2 increased. Notably, RAB31-induced EMT and drug resistance are dependent on extracellular vesicle (EV) secretion. Interactome analysis confirmed that RAB31/AGR2 axis-mediated exocytosis was responsible for maintaining colorectal cell resistance to oxaliplatin. Our study concluded that RAB31 alters the sensitivity of oxaliplatin, a supplementary chemotherapy approach, and is an independent prognostic factor that can be used in the treatment of colorectal cancer.

Overexpression of RAB31 in gastric cancer is associated with released exosomes and increased tumor cell invasion and metastasis.

BACKGROUND: Gastric cancer (GC) is one of most common cancers worldwide. Several studies have suggested that Rab31 functions as a membrane vesicle transport regulator; however, the mechanism by which RAB31 regulates exosome secretion and promotes metastasis remains to be clarified. METHODS: We examined the expression of RAB31 protein and mRNA in GC tissue samples via immunohistochemistry and reverse transcription-polymerase chain reaction assays, respectively. We elucidated the function of RAB31 in GC cells by constructing a cell model and a pulmonary metastatic model of GC with overexpression of RAB31. Protein mass spectrometry was used to identify the exosomal protein. RESULTS: RAB31 expression increased at both the protein and mRNA levels with the development of GC. Cells overexpressing RAB31 showed an enhanced ability to migrate in both the in vitro cell model and the pulmonary metastatic model of GC. Exosome nanoparticle tracking analysis and electron microscopy revealed that the both the number and size of the exosomes secreted by GC cells were reduced when RAB31 expression was depleted. Injection of exosomes derived from RAB31 overexpressing cells promoted pulmonary metastasis in vivo. Analysis of the exosomal proteins revealed that PSMA1 was overexpressed in GC tissue in accordance with RAB31 expression. PSMA1 overexpression was highly associated with poor prognosis of GC patients. CONCLUSION: Our findings revealed a key role for RAB31 in GC metastasis through regulation of exosome secretion.

Rab31 promotes the invasion and metastasis of cervical cancer cells by inhibiting MAPK6 degradation.

Persistent infection with high-risk human papillomavirus (HPV) is the main risk factor for cervical cancer. Our mass spectrometry data showed that the Ras-associated binding protein Rab31 was upregulated by HPV; however, little is known regarding the role of Rab31 in the metastasis of cervical cancer cells. In this study, we showed that Rab31 was highly expressed in cervical cancer tissues and cells, and both HPV E6 and E7 promoted the expression of Rab31. Rab31 knockdown inhibited while Rab31 overexpression promoted the migration and invasion capabilities of cervical cancer cells. Additionally, Rab31 knockdown inhibited the epithelial-mesenchymal transition (EMT) and cytoskeletal rearrangement in cervical cancer cells. Furthermore, Rab31 interacted with mitogen-activated protein kinase 6 (MAPK6), and Rab31 knockdown inhibited the expression of MAPK6, which was mainly localized in the cytoplasm. More importantly, Rab31 knockdown promoted and Rab31 overexpression inhibited MAPK6 degradation. Accordingly, MAPK6 overexpression restored the decreased migration potential caused by Rab31 knockdown. Finally, a xenograft mouse model showed that Rab31 knockdown in cervical cancer cells led to reduced tumor growth and impaired lung and liver metastasis in vivo. In conclusion, Rab31 plays a crucial role in cervical cancer metastasis by inhibiting MAPK6 degradation. Thus, Rab31 may serve as a novel therapeutic target to manage cervical cancer.

MiR-378a-3p acts as a tumor suppressor in gastric cancer via directly targeting RAB31 and inhibiting the Hedgehog pathway proteins GLI1/2.

OBJECTIVE: To improve the prognosis of patients with gastric cancer (GC), more effective therapeutic targets are urgently needed. Increasing evidence indicates that miRNAs are involved in the progression of various tumors, and RAS-associated protein in the brain 31 (RAB31) is upregulated and promotes the progression of multiple malignant tumors. Here, we focused on identifying RAB31-targeted miRNAs and elucidating their potential mechanism in the progression of GC. METHODS: RAB31 and miR-378a-3p expression levels were detected in paired fresh GC tissues and GC cell lines. Bioinformatics analysis was used to predict the miRNAs targeting RAB31 and the relationships between RAB31 and other genes. Dual-luciferase reporter assays were applied to verify the targeted interaction relationship. CCK-8, colony formation, flow cytometry, wound healing, and Transwell assays were performed to assess the proliferation, apoptosis, migration, and invasion of GC cells. Tumorsphere formation assays were performed to assess the stemness of gastric cancer stem cells. Related proteins were detected by Western blot. Xenograft assays in nude mice were performed to explore the effect of miR-378a-3p in vivo. RESULTS: We report the first evidence that miR-378a-3p is downregulated in GC, whereas its overexpression inhibits proliferation, invasion, and migration as well as promotes apoptosis in GC cells. Mechanistically, miR-378a-3p inhibits the progression of GC by directly targeting RAB31. Restoring RAB31 expression partially offsets the inhibitory effect of miR-378a-3p. Further research revealed that miR-378a-3p inhibits GLI1/2 in the Hedgehog signaling pathway and attenuates the stemness of gastric cancer stem cells. Finally, xenograft assays showed that miR-378a-3p inhibits GC tumorigenesis in vivo. CONCLUSIONS: MiR-378a-3p inhibits GC progression by directly targeting RAB31 and inhibiting the Hedgehog signaling pathway proteins GLI1/2.

LncRNA HOXA10-AS Activated by E2F1 Facilitates Proliferation and Migration of Nasopharyngeal Carcinoma Cells Through Sponging miR-582-3p to Upregulate RAB31.

Nasopharyngeal carcinoma (NPC) is a kind of head and neck cancer with a characteristic regional distribution. Increasing evidence has illustrated that long noncoding RNAs (lncRNAs) exert the regulatory function in tumor development. Nevertheless, the specific functions of lncRNA HOXA10 antisense RNA (HOXA10-AS) in NPC remain to be clarified. In this research, quantitative reverse transcription polymerase chain reaction detected HOXA10-AS expression in NPC cells. Cell counting kit-8, colony formation, and transwell assays were utilized to measure the proliferation and migration of NPC cells. Moreover, mechanism assays detected the interaction of different genes. Briefly, HOXA10-AS was highly expressed in NPC cells. HOXA10-AS down-regulation restrained NPC cell proliferation and migration. Further, HOXA10-AS could bind to miR-582-3p by acting as a competing endogenous RNA. Besides, Ras-related protein Rab-31 (RAB31) was proven as the target gene of miR-582-3p. Additionally, E2F transcription factor 1 (E2F1) acted as a transcription factor to activate HOXA10-AS expression. In the final rescue assays, we observed that the effect of HOXA10-AS depletion on NPC cell growth could be fully reversed by RAB31 overexpression or miR-582-3p inhibition. In short, our research proved that HOXA10-AS activated by E2F1 facilitated proliferation and migration of NPC cells through sponging miR-582-3p to upregulate RAB31.

Rab31 promotes activation of hepatic stellate cells by accelerating TGF-ß receptor II complex endocytosis.

BACKGROUND & AIMS: Hepatic stellate cells activation is the key process of liver fibrosis, revealing the molecular mechanism of which is helpful to provide an effective target for inhibiting liver fibrosis. Rab31, a small GTPase, regulates the specificity of intracellular vesicular transport system, and is crucial for signal transduction. However, whether Rab31 is involved in hepatic stellate cells activation is unknown. METHODS & RESULTS: Analysis of the differences in gene expression between human healthy and fibrotic liver tissues by sequencing revealed that Rab31 was significantly upregulated in fibrotic tissues. Immunohistochemistry and immunofluorescence analysis confirmed that Rab31 positively correlated with hepatic fibrosis. Next, mouse primary hepatic stellate cells were prepared, and their continuous activation was accompanied by Rab31 expression increased. Interestingly, knockdown of Rab31 by lentivirus can significantly restrict those cell activation. Subsequently, the vary of signal transduction after Rab31 knockdown was detected, its presented that the TGF-ß/Smads signaling was obviously affected. Following experiments identified that Rab31 knockdown significantly inhibited the TGF-ß activation and led to the failure of hepatic stellate cells activation. Importantly, we revealed that Rab31 knockdown could inhibit TGF-ß receptor II complex endocytosis, a prerequisite for the activation of TGF-ß signaling. Finally, in a mouse CCl4 fibrosis model, we proved that Rab31 knockdown markedly inhibited hepatic fibrosis. CONCLUSIONS: Our study demonstrated that Rab31 could promote hepatic stellate cells activation by accelerating TGF-ß Receptor II complex endocytosis, suggesting that interfering with Rab31 could be an effectively strategy to inhibit hepatic fibrosis progression.

Association between Rab31/rs9965664 polymorphism and immunoglobulin therapy resistance in patients with Kawasaki disease.

Background: Kawasaki disease (KD) is an acute febrile systemic vasculitis affecting infants and young children. A high dose of intravenous immunoglobulin (IVIG) is the first-line strategy for patients with KD to reduce persistent inflammation and the risk of coronary artery aneurysm (CAA) formation. Unfortunately, 10-20% of the patients showed no response to the treatment and were defined as resistant to IVIG. Rab31 has been reported to regulate innate immunity in several human diseases. However, whether single nucleotide polymorphism (SNP) in Rab31 gene could predispose to IVIG therapy response in KD was uncovered. Methods: Rab31/rs9965664 polymorphism was genotyped in 1,024 Chinese patients with KD through TaqMan assay. The odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of association between Rab31/rs9965664 polymorphism and IVIG therapeutic effects. Results: Our results showed that Rab31/rs9965664 AA/GA genotype was significantly associated with an increased risk of IVIG resistance compared to GG genotype (GA vs. GG: p = 0.0249; AA vs. GG: p = 0.0016; AA/GA vs. GG: p = 0.0039; and AA vs. GG/GA: p = 0.0072). Moreover, the KD individuals carrying the rs9965664 A allele displayed lower Rab31 protein levels, and the expression level of Rab31 in the IVIG-resistant group was decreased significantly when compared to that observed in the response group. A mechanical study demonstrated that Rab31 modulated IVIG response through NLRP3 and p38 pathways. Conclusion: These results suggested that Rab31/rs9965664 polymorphism might be associated with an increased risk of IVIG resistance in southern Chinese patients with KD. The possible mechanism is that Rab31 regulates the NLRP3 pathway negatively to inhibit IVIG response.

Shigella escapes lysosomal degradation through inactivation of Rab31 by IpaH4.5.

Introduction. Shigella flexneri is an intracellular bacterial pathogen that utilizes a type III secretion apparatus to inject effector proteins into host cells.Hypothesis/Gap Statement. The T3SS effector IpaH4.5 is important for the virulence of Shigella.Aim. This study aimed to elucidate the molecular mechanism and host target of the IpaH4.5 as well as its roles in S. flexneri infection.Methodology. The GAP assay was used to identify substrate Rab GTPases of IpaH4.5. A coimmunoprecipitation assay was applied to identify the interaction of Rab GTPases with IpaH4.5. A confocal microscopy analysis was used to assess the effects of IpaH4.5 on mannose 6-phosphate receptor (MPR) trafficking. To identify the effects of IpaH4.5 GAP activity on the activity of lysosomal cathepsin B, the Magic Red-RR assay was used. Finally, the intracellular persistence assay was used to identify IpaH4.5 GAP activity in S. flexneri intracellular growth.Results. We found that the effector IpaH4.5 disrupts MPR trafficking and lysosomal function, thereby counteracting host lysosomal degradation. IpaH4.5 harbours TBC-like dual-finger motifs and exhibits potent RabGAP activities towards Rab31. IpaH4.5 disrupts the transport of the cation-dependent mannose 6-phosphate receptor (CD-MPR) from the Golgi to the endosome by targeting Rab31, thereby attenuating lysosomal function. As a result, the intracellular persistence of S. flexneri requires IpaH4.5 TBC-like GAP activity to mediate bacterial escape from host lysosome-mediated elimination.Conclusion. We identified an unknown function of IpaH4.5 and its potential role in S. flexneri infection.