Rab5 activation promotes focal adhesion disassembly, migration and invasiveness in tumor cells

A comparative analysis of paxillin and Hic-5 proximity interactomes

Focal adhesions serve as structural and signaling hubs, facilitating bidirectional communication at the cell-extracellular matrix interface. Paxillin and the related Hic-5 (TGFβ1i1) are adaptor/scaffold proteins that recruit numerous structural and regulatory proteins to focal adhesions, where they perform both overlapping and discrete functions. In this study, paxillin and Hic-5 were expressed in U2OS osteosarcoma cells as biotin ligase (BioID2) fusion proteins and used as bait proteins for proximity-dependent biotinylation in order to directly compare their respective interactomes. The fusion proteins localized to both focal adhesions and the centrosome, resulting in biotinylation of components of each of these structures. Biotinylated proteins were purified and analyzed by mass spectrometry. The list of proximity interactors for paxillin and Hic-5 comprised numerous shared core focal adhesion proteins that likely contribute to their similar functions in cell adhesion and migration, as well as proteins unique to paxillin and Hic-5 that have been previously localized to focal adhesions, the centrosome, or the nucleus. Western blotting confirmed biotinylation and enrichment of FAK and vinculin, known interactors of Hic-5 and paxillin, as well as several potentially unique proximity interactors of Hic-5 and paxillin, including septin 7 and ponsin, respectively. Further investigation into the functional relationship between the unique interactors and Hic-5 or paxillin may yield novel insights into their distinct roles in cell migration.

TTC7B is a new prognostic biomarker in head and neck squamous cell carcinoma linked to immune infiltration and ferroptosis

OBJECTIVE

To investigate the expression of TTC7B and its prognostic significance, biological roles, and impact on the immune system in patients with head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

Clinical and genomic data were obtained from TCGA (The Cancer Genome Atlas), GEO (Gene Expression Omnibus), GEPIA2 (Gene Expression Profiling Interactive Analysis 2.0), and TIMER2.0 (Tumor Immune Estimation Resource 2.0) databases. R software was utilized to process the retrieved data. qPCR and immunohistochemical assays were performed to validate the findings obtained from the databases.

RESULTS

High expression of TTC7B was observed in HNSCC, and this heightened expression is significantly associated with reduced overall survival (OS) in patients, making it an independent risk factor impacting OS. TTC7B is correlated with focal adhesions and cell migration pathways based on functional enrichment analysis. CIBERSORT analysis and TIMER2.0 show a positive link between TTC7B and multiple immune cells, particularly macrophages. Pearson's analysis reveals a significant correlation between TTC7B and ferroptosis-related genes.

CONCLUSION

In all, TTC7B could serve as a promising prognostic indicator of HNSCC, and is closely associated with focal adhesions, immune infiltration, and ferroptosis.

Distinct role of TGN-resident clathrin adaptors for Vps21p activation in the TGN-endosome trafficking pathway

Clathrin-mediated vesicle trafficking plays central roles in post-Golgi transport. In yeast (Saccharomyces cerevisiae), the AP-1 complex and GGA adaptors are predicted to generate distinct transport vesicles at the trans-Golgi network (TGN), and the epsin-related proteins Ent3p and Ent5p (collectively Ent3p/5p) act as accessories for these adaptors. Recently, we showed that vesicle transport from the TGN is crucial for yeast Rab5 (Vps21p)-mediated endosome formation, and that Ent3p/5p are crucial for this process, whereas AP-1 and GGA adaptors are dispensable. However, these observations were incompatible with previous studies showing that these adaptors are required for Ent3p/5p recruitment to the TGN, and thus the overall mechanism responsible for regulation of Vps21p activity remains ambiguous. Here, we investigated the functional relationships between clathrin adaptors in post-Golgi-mediated Vps21p activation. We show that AP-1 disruption in the ent3Δ5Δ mutant impaired transport of the Vps21p guanine nucleotide exchange factor Vps9p transport to the Vps21p compartment and severely reduced Vps21p activity. Additionally, GGA adaptors, the phosphatidylinositol-4-kinase Pik1p and Rab11 GTPases Ypt31p and Ypt32p were found to have partially overlapping functions for recruitment of AP-1 and Ent3p/5p to the TGN. These findings suggest a distinct role of clathrin adaptors for Vps21p activation in the TGN-endosome trafficking pathway.

Paxillin regulates Rab5-mediated vesicle motility through modulating microtubule acetylation

Rab GTPase-mediated vesicle trafficking of cell surface proteins, including integrins, through endocytic and recycling pathways is important in controlling cell-extracellular matrix interactions during cell migration. The focal adhesion adaptor protein, paxillin, plays a central role in regulating adhesion dynamics and was previously shown to promote anterograde vesicle trafficking through modulation of microtubule acetylation via its inhibition of the deacetylase HDAC6. The role of paxillin in retrograde trafficking is unknown. Herein, we identified a role for paxillin in the modulation of the Rab5 GTPase, which is necessary for regulating early endosome dynamics and focal adhesion turnover. Using MDA-MB-231 breast cancer cells and paxillin (-/-) fibroblasts, paxillin was shown to impact Rab5-associated vesicle size and distribution, as well as Rab5 GTPase activity, through its modulation of HDAC6. Using a combination of real-time imaging and particle tracking analysis, paxillin was shown to promote Rab5-associated vesicle motility through inhibition of HDAC6-mediated micro-tubule deacetylation, along with the localization of active integrin to focal adhesions.

The expression of Rab5 and its effect on invasion, migration and exosome secretion in triple negative breast cancer

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer and current therapeutic strategies are limited in their effectiveness. The expressions of Rab5 and the M2 tumor-associated macrophage marker CD163 in tissues were detected by Western blot. The migration and invasion of cells were determined using a Transwell assay. The expressions of the exosome markers were evaluated by Western blot. The polarization of human macrophages (THP-1) was determined by incubation of THP-1 cells with conditioned medium or exosomes collected from MDA-MB-231 cells with indicated transfections or by a coculture system of THP-1 and MDA-MB-231 cells. The M1 and M2 macrophage markers were evaluated by qRT-PCR. The expression of Rab5 in TNBC was significantly higher than that in normal breast tissue. Rab5 expressions in triple-negative and luminal A breast cancer were higher than those in other molecular subtypes. Higher CD163 expression was observed in triple-negative breast cancer and in triple-negative and luminal B subtypes. Rab5 knockdown suppressed but Rab5 overexpression promoted the migration and invasion capacity of MDA-MB-231 cells. The levels of CD63 and CD9 in the medium of Rab5 knockdown cells were lower than those in control cells, whereas higher levels of CD63 and CD9 were observed in Rab5 overexpression cells. Rab5 knockdown decreased the excretion but did not alter the diameter of the exosomes. Knockdown of Rab5 facilitated the anti-tumor polarization of macrophages, which was partially reversed by Rab5 overexpression. Therefore, Rab5 is expected to be a potential therapeutic target for triple-negative breast cancer.

The Sall2 transcription factor promotes cell migration regulating focal adhesion turnover and integrin β1 expression

SALL2/Sall2 is a transcription factor associated with development, neuronal differentiation, and cancer. Interestingly, SALL2/Sall2 deficiency leads to failure of the optic fissure closure and neurite outgrowth, suggesting a positive role for SALL2/Sall2 in cell migration. However, in some cancer cells, SALL2 deficiency is associated with increased cell migration. To further investigate the role of Sall2 in the cell migration process, we used immortalized Sall2 knockout (Sall2−/−) and Sall2 wild-type (Sall2+/+) mouse embryonic fibroblasts (iMEFs). Our results indicated that Sall2 positively regulates cell migration, promoting cell detachment and focal adhesions turnover. Sall2 deficiency decreased cell motility and altered focal adhesion dynamics. Accordingly, restoring Sall2 expression in the Sall2−/− iMEFs by using a doxycycline-inducible Tet-On system recovered cell migratory capabilities and focal adhesion dynamics. In addition, Sall2 promoted the autophosphorylation of Focal Adhesion Kinase (FAK) at Y397 and increased integrin β1 mRNA and its protein expression at the cell surface. We demonstrated that SALL2 increases ITGB1 promoter activity and binds to conserved SALL2-binding sites at the proximal region of the ITGB1 promoter, validated by ChIP experiments. Furthermore, the overexpression of integrin β1 or its blockade generates a cell migration phenotype similar to that of Sall2+/+ or Sall2−/− cells, respectively. Altogether, our data showed that Sall2 promotes cell migration by modulating focal adhesion dynamics, and this phenotype is associated with SALL2/Sall2-transcriptional regulation of integrin β1 expression and FAK autophosphorylation. Since deregulation of cell migration promotes congenital abnormalities, tumor formation, and spread to other tissues, our findings suggest that the SALL2/Sall2-integrin β1 axis could be relevant for those processes.

Dynamic regulation of KIF15 phosphorylation and acetylation promotes focal adhesions disassembly in pancreatic cancer

Pancreatic cancer (PC) is prone to distant metastasis in the early stage, which is attributed to the strong migration ability of tumor cells. Focal adhesion turnover is essential for cancer cell metastasis, and the integrin recycling process is a key activation pathway for focal adhesion depolymerization. To identify the key motor protein involving in the integrin β1 recycling, we screened kinesin proteins involved in integrin β1 recycling using a kinesin family siRNA library and identified kinesin family 15 (KIF15) as a key regulator. KIF15 was upregulated in metastasis PC tissues and promoted PC cell migration and invasion. We identified KIF15 as a key component mediating integrin β1/FAK signaling that accelerated FA disassembly in a FAK-Y397-dependent manner. KIF15 recruited PI3K-C2α to promote integrin β1/FAK signaling and FA disassembly in a RAB11A-dependent manner. The C-terminal tail of KIF15 is required for the PI3K-C2α interaction and RAB11A activation. In addition, we also found that SIRT1-mediated acetylation of KIF15 is essential for KIF15 phosphorylation, which is the key activation event in motor protein function. Together, these findings indicate that KIF15 interacts with PI3K-C2α to promote FA turnover in PC cells by controlling the endosome recycling of integrin β1 in a SIRT1 acetylation modification-dependent manner, eventually promoting focal adhesions turnover and distant metastasis in PC.

Host Cell Signatures of the Envelopment Site within Beta-Herpes Virions

Beta-herpesvirus infection completely reorganizes the membrane system of the cell. This system is maintained by the spatiotemporal arrangement of more than 3000 cellular proteins that continuously adapt the configuration of membrane organelles according to cellular needs. Beta-herpesvirus infection establishes a new configuration known as the assembly compartment (AC). The AC membranes are loaded with virus-encoded proteins during the long replication cycle and used for the final envelopment of the newly formed capsids to form infectious virions. The identity of the envelopment membranes is still largely unknown. Electron microscopy and immunofluorescence studies suggest that the envelopment occurs as a membrane wrapping around the capsids, similar to the growth of phagophores, in the area of the AC with the membrane identities of early/recycling endosomes and the trans-Golgi network. During wrapping, host cell proteins that define the identity and shape of these membranes are captured along with the capsids and incorporated into the virions as host cell signatures. In this report, we reviewed the existing information on host cell signatures in human cytomegalovirus (HCMV) virions. We analyzed the published proteomes of the HCMV virion preparations that identified a large number of host cell proteins. Virion purification methods are not yet advanced enough to separate all of the components of the rich extracellular material, including the large amounts of non-vesicular extracellular particles (NVEPs). Therefore, we used the proteomic data from large and small extracellular vesicles (lEVs and sEVs) and NVEPs to filter out the host cell proteins identified in the viral proteomes. Using these filters, we were able to narrow down the analysis of the host cell signatures within the virions and determine that envelopment likely occurs at the membranes derived from the tubular recycling endosomes. Many of these signatures were also found at the autophagosomes, suggesting that the CMV-infected cell forms membrane organelles with phagophore growth properties using early endosomal host cell machinery that coordinates endosomal recycling.

Focal adhesion-mediated cell anchoring and migration: from in vitro to in vivo

Cell-extracellular matrix interactions have been studied extensively using cells cultured in vitro. These studies indicate that focal adhesion (FA)-based cell-extracellular matrix interactions are essential for cell anchoring and cell migration. Whether FAs play a similarly important role in vivo is less clear. Here, we summarize the formation and function of FAs in cultured cells and review how FAs transmit and sense force in vitro. Using examples from animal studies, we also describe the role of FAs in cell anchoring during morphogenetic movements and cell migration in vivo. Finally, we conclude by discussing similarities and differences in how FAs function in vitro and in vivo.

Piezo1 promoted hepatocellular carcinoma progression and EMT through activating TGF-β signaling by recruiting Rab5c

BACKGROUND

Piezo1 has been revealed to play a regulatory role in vascular development and progression of variety tumors. However, whether and how the progression of hepatocellular carcinoma (HCC) regulated by Piezo1 remains elusive. This study aimed to elucidate the effect and mechanisms of Piezo1 in HCC.

METHODS

The mRNA and protein expression level of Piezo1 in HCC samples and cell lines was determined by qRT-PCR, western blot and immunohistochemistry analyses. Two independent study cohorts containing 280 patients were analyzed to reveal the association between Piezo1 expression and clinicopathological characteristics. Series of in vitro and in vivo experiments were used to validate the function of Piezo1 in HCC. Gene set enrichment analysis (GSEA) was performed to explore the signaling pathway of Piezo1. Immunoprecipitation, immunofluorescence and in vitro and in vivo experiments were used to explore the molecular mechanism of Piezo1 in HCC progression.

RESULTS

Our results demonstrated the Piezo1 expression was significantly upregulated in HCC tissues and cell lines, and upregulation of Piezo1 closely correlated with aggressive clinicopathological features and poor prognosis. Knockdown of Piezo1 in HCCLM3 and Hep3B cells significantly restrained proliferation, migration, invasion and epithelial-mesenchymal transition (EMT) of HCC cells in vitro, and tumor growth, metastasis, EMT in vivo. TGF-β signaling pathway was most significant enriched pathway in GSEA. Finally, tumor promotion effect of Piezo1 was found to exerted through recruiting and combining Rab5c to activating TGF-β signaling pathway.

CONCLUSIONS

Piezo1 significantly related to poor prognosis and promotes progression of hepatocellular carcinoma via activating TGF-β signaling, which suggesting that Piezo1 may serve as a novel prognostic predictor and the potential therapeutic target for HCC patients.

Histatin-1 is a novel osteogenic factor that promotes bone cell adhesion, migration, and differentiation

Histatin-1 is a salivary antimicrobial peptide involved in the maintenance of enamel and oral mucosal homeostasis. Moreover, Histatin-1 has been shown to promote re-epithelialization in soft tissues, by stimulating cell adhesion and migration in oral and dermal keratinocytes, gingival and skin fibroblasts, endothelial cells and corneal epithelial cells. The broad-spectrum activity of Histatin-1 suggests that it behaves as a universal wound healing promoter, although this is far from being clear yet. Here, we report that Histatin-1 is a novel osteogenic factor that promotes bone cell adhesion, migration, and differentiation. Specifically, Histatin-1 promoted cell adhesion, spreading, and migration of SAOS-2 cells and MC3T3-E1 preosteoblasts in vitro, when placed on a fibronectin matrix. Besides, Histatin-1 induced the expression of osteogenic genes, including osteocalcin, osteopontin, and Runx2, and increased both activity and protein levels of alkaline phosphatase. Furthermore, Histatin-1 promoted mineralization in vitro, as it augmented the formation of calcium deposits in both SAOS-2 and MC3T3-E1 cells. Mechanistically, although Histatin-1 failed to activate ERK1/2, FAK, and Akt, which are signaling proteins associated with osteogenic differentiation or cell migration, it triggered nuclear relocalization of β-catenin. Strikingly, the effects of Histatin-1 were recapitulated in cells that are nonosteogenically committed, since it promoted surface adhesion, migration, and the acquisition of osteogenic markers in primary mesenchymal cells derived from the apical papilla and dental pulp. Collectively, these observations indicate that Histatin-1 is a novel osteogenic factor that promotes bone cell differentiation, surface adhesion and migration, as crucial events required for bone tissue regeneration.

Functional Interaction among lncRNA HOTAIR and MicroRNAs in Cancer and Other Human Diseases

Simple Summary

This review aimed to describe the contribution of functional interaction between the lncRNA HOTAIR and microRNAs in human diseases, including cancer. HOTAIR/miRNAs complexes interfere with different cellular processes during carcinogenesis, mainly deregulating a series of oncogenic signaling pathways. A great number of ncRNAs-related databases have been established, supported by bioinformatics technologies, to identify the ncRNA-mediated sponge regulatory network. These approaches need experimental validation through cells and animal models studies. The optimization of systems to interfere with HOTAIR/miRNAs interplay could represent a new tool for the definition of diagnostic therapeutics in cancer patients.

Abstract

LncRNAs are a class of non-coding RNAs mostly involved in regulation of cancer initiation, metastatic progression, and drug resistance, through participation in post-transcription regulatory processes by interacting with different miRNAs. LncRNAs are able to compete with endogenous RNAs by binding and sequestering miRNAs and thereby regulating the expression of their target genes, often represented by oncogenes. The lncRNA HOX transcript antisense RNA (HOTAIR) represents a diagnostic, prognostic, and predictive biomarker in many human cancers, and its functional interaction with miRNAs has been described as crucial in the modulation of different cellular processes during cancer development. The aim of this review is to highlight the relation between lncRNA HOTAIR and different microRNAs in human diseases, discussing the contribution of these functional interactions, especially in cancer development and progression.

Endocytosis: a pivotal pathway for regulating metastasis

A potentially important aspect in the regulation of tumour metastasis is endocytosis. This process consists of internalisation of cell-surface receptors via pinocytosis, phagocytosis or receptor-mediated endocytosis, the latter of which includes clathrin-, caveolae- and non-clathrin or caveolae-mediated mechanisms. Endocytosis then progresses through several intracellular compartments for sorting and routing of cargo, ending in lysosomal degradation, recycling back to the cell surface or secretion. Multiple endocytic proteins are dysregulated in cancer and regulate tumour metastasis, particularly migration and invasion. Importantly, four metastasis suppressor genes function in part by regulating endocytosis, namely, the NME, KAI, MTSS1 and KISS1 pathways. Data on metastasis suppressors identify a new point of dysregulation operative in tumour metastasis, alterations in signalling through endocytosis. This review will focus on the multicomponent process of endocytosis affecting different steps of metastasis and how metastatic-suppressor genes use endocytosis to suppress metastasis.

Structure-based discovery of neoandrographolide as a novel inhibitor of Rab5 to suppress cancer growth

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It is the first study to identify neoandrographolide as a novel inhibitor of Rab5.

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Neoandrographolide can occupy the surface groove of Rab5 for inhibiting its activity.

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Neoandrographolide exhibits anticancer effect on lung cancer by targeting Rab5.

Rab5 is a small GTPase that plays a crucial role in oncogenic signal transduction, which was considered as an attractive target for cancer therapy. Rapid GDP/GTP exchange in the packet of Rab5 sustains its high activity for promoting cancer progression. However, Rab5 currently remains undruggable due to the lack of specific inhibitor. Herein, we reported the discovery of a novel Rab5 inhibitor, neoandrographolide (NAP), by using high-throughput virtual screening with a natural product library containing 7459 compounds, which can occupy the surface groove of Rab5, competing with GDP/GTP for the binding. Ser34 is the most important residue in the groove of Rab5, as it forms most hydrogen-bond interactions with GDP/GTP or NAP, and in silico mutation of Ser34 decreased the stabilization of Rab5. Moreover, fluorescence titration experiment and isothermal titration calorimetry (ITC) assay revealed a direct binding between NAP and Rab5. Biochemical and cell-based assays showed that NAP treatment not only diminished the activity of Rab5, but also suppressed cell growth of cancer cell. This finding firstly identifies NAP as a novel inhibitor of Rab5, which directly binds with Rab5 by occupying the GDP/GTP binding groove to suppress its functions, highlighting a great potential of NAP to be developed as a chemotherapeutic agent in cancer therapy.

The RabGEF ALS2 is a hypoxia inducible target associated with the acquisition of aggressive traits in tumor cells

Tumor hypoxia and the hypoxia inducible factor-1, HIF-1, play critical roles in cancer progression and metastasis. We previously showed that hypoxia activates the endosomal GTPase Rab5, leading to tumor cell migration and invasion, and that these events do not involve changes in Rab protein expression, suggesting the participation of intermediate activators. Here, we identified ALS2, a guanine nucleotide exchange factor that is upregulated in cancer, as responsible for increased Rab5-GTP loading, cell migration and metastasis in hypoxia. Specifically, hypoxia augmented ALS2 mRNA and protein levels, and these events involved HIF-1α-dependent transcription, as shown by RNAi, pharmacological inhibition, chromatin immunoprecipitation and bioinformatics analyses, which identified a functional HIF-1α-binding site in the proximal promoter region of ALS2. Moreover, ALS2 and Rab5 activity were elevated both in a model of endogenous HIF-1α stabilization (renal cell carcinoma) and by following expression of stable non-hydroxylatable HIF-1α. Strikingly, ALS2 upregulation in hypoxia was required for Rab5 activation, tumor cell migration and invasion, as well as experimental metastasis in C57BL/6 mice. Finally, immunohistochemical analyses in patient biopsies with renal cell carcinoma showed that elevated HIF-1α correlates with increased ALS2 expression. Hence, this study identifies ALS2 as a novel hypoxia-inducible gene associated with tumor progression and metastasis.

A semi-supervised Bayesian approach for simultaneous protein sub-cellular localisation assignment and novelty detection

The cell is compartmentalised into complex micro-environments allowing an array of specialised biological processes to be carried out in synchrony. Determining a protein's sub-cellular localisation to one or more of these compartments can therefore be a first step in determining its function. High-throughput and high-accuracy mass spectrometry-based sub-cellular proteomic methods can now shed light on the localisation of thousands of proteins at once. Machine learning algorithms are then typically employed to make protein-organelle assignments. However, these algorithms are limited by insufficient and incomplete annotation. We propose a semi-supervised Bayesian approach to novelty detection, allowing the discovery of additional, previously unannotated sub-cellular niches. Inference in our model is performed in a Bayesian framework, allowing us to quantify uncertainty in the allocation of proteins to new sub-cellular niches, as well as in the number of newly discovered compartments. We apply our approach across 10 mass spectrometry based spatial proteomic datasets, representing a diverse range of experimental protocols. Application of our approach to hyperLOPIT datasets validates its utility by recovering enrichment with chromatin-associated proteins without annotation and uncovers sub-nuclear compartmentalisation which was not identified in the original analysis. Moreover, using sub-cellular proteomics data from Saccharomyces cerevisiae, we uncover a novel group of proteins trafficking from the ER to the early Golgi apparatus. Overall, we demonstrate the potential for novelty detection to yield biologically relevant niches that are missed by current approaches.

Syndecan-4/PAR-3 signaling regulates focal adhesion dynamics in mesenchymal cells

Background

Syndecans regulate cell migration thus having key roles in scarring and wound healing processes. Our previous results have shown that Thy-1/CD90 can engage both αvβ3 integrin and Syndecan-4 expressed on the surface of astrocytes to induce cell migration. Despite a well-described role of Syndecan-4 during cell movement, information is scarce regarding specific Syndecan-4 partners involved in Thy-1/CD90-stimulated cell migration.

Methods

Mass spectrometry (MS) analysis of complexes precipitated with the Syndecan-4 cytoplasmic tail peptide was used to identify potential Syndecan-4-binding partners. The interactions found by MS were validated by immunoprecipitation and proximity ligation assays. The conducted research employed an array of genetic, biochemical and pharmacological approaches, including: PAR-3, Syndecan-4 and Tiam1 silencing, active Rac1 GEFs affinity precipitation, and video microscopy.

Results

We identified PAR-3 as a Syndecan-4-binding protein. Its interaction depended on the carboxy-terminal EFYA sequence present on Syndecan-4. In astrocytes where PAR-3 expression was reduced, Thy-1-induced cell migration and focal adhesion disassembly was impaired. This effect was associated with a sustained Focal Adhesion Kinase activation in the siRNA-PAR-3 treated cells. Our data also show that Thy-1/CD90 activates Tiam1, a PAR-3 effector. Additionally, we found that after Syndecan-4 silencing, Tiam1 activation was decreased and it was no longer recruited to the membrane. Syndecan-4/PAR-3 interaction and the alteration in focal adhesion dynamics were validated in mouse embryonic fibroblast (MEF) cells, thereby identifying this novel Syndecan-4/PAR-3 signaling complex as a general mechanism for mesenchymal cell migration involved in Thy-1/CD90 stimulation.

Conclusions

The newly identified Syndecan-4/PAR-3 signaling complex participates in Thy-1/CD90-induced focal adhesion disassembly in mesenchymal cells. The mechanism involves focal adhesion kinase dephosphorylation and Tiam1 activation downstream of Syndecan-4/PAR-3 signaling complex formation. Additionally, PAR-3 is defined here as a novel adhesome-associated component with an essential role in focal adhesion disassembly during polarized cell migration. These novel findings uncover signaling mechanisms regulating cell migration, thereby opening up new avenues for future research on Syndecan-4/PAR-3 signaling in processes such as wound healing and scarring.

Graphical abstract

Rab18 regulates focal adhesion dynamics by interacting with kinectin-1 at the endoplasmic reticulum

The members of the Rab family of small GTPases are molecular switches that regulate distinct steps in different membrane traffic pathways. In addition to this canonical function, Rabs can play a role in other processes, such as cell adhesion and motility. Here, we reveal the role of the small GTPase Rab18 as a positive regulator of directional migration in chemotaxis, and the underlying mechanism. We show that knockdown of Rab18 reduces the size of focal adhesions (FAs) and influences their dynamics. Furthermore, we found that Rab18, by directly interacting with the endoplasmic reticulum (ER)-resident protein kinectin-1, controls the anterograde kinesin-1–dependent transport of the ER required for the maturation of nascent FAs and protrusion orientation toward a chemoattractant. Altogether, our data support a model in which Rab18 regulates kinectin-1 transport toward the cell surface to form ER–FA contacts, thus promoting FA growth and cell migration during chemotaxis.

Wnt/β-Catenin Signaling in Oral Carcinogenesis

Oral carcinogenesis is a complex and multifactorial process that involves cumulative genetic and molecular alterations, leading to uncontrolled cell proliferation, impaired DNA repair and defective cell death. At the early stages, the onset of potentially malignant lesions in the oral mucosa, or oral dysplasia, is associated with higher rates of malignant progression towards carcinoma in situ and invasive carcinoma. Efforts have been made to get insights about signaling pathways that are deregulated in oral dysplasia, as these could be translated into novel markers and might represent promising therapeutic targets. In this context, recent evidence underscored the relevance of the Wnt/β-catenin signaling pathway in oral dysplasia, as this pathway is progressively "switched on" through the different grades of dysplasia (mild, moderate and severe dysplasia), with the consequent nuclear translocation of β-catenin and expression of target genes associated with the maintenance of representative traits of oral dysplasia, namely cell proliferation and viability. Intriguingly, recent studies provide an unanticipated connection between active β-catenin signaling and deregulated endosome trafficking in oral dysplasia, highlighting the relevance of endocytic components in oral carcinogenesis. This review summarizes evidence about the role of the Wnt/β-catenin signaling pathway and the underlying mechanisms that account for its aberrant activation in oral carcinogenesis.

Nuclear accumulation of β-catenin is associated with endosomal sequestration of the destruction complex and increased activation of Rab5 in oral dysplasia

Potentially malignant lesions, commonly referred to as dysplasia, are associated with malignant transformation by mechanisms that remain unclear. We recently reported that increased Wnt secretion promotes the nuclear accumulation of β-catenin and expression of target genes in oral dysplasia. However, the mechanisms accounting for nuclear re-localization of β-catenin in oral dysplasia remain unclear. In this study, we show that endosomal sequestration of the β-catenin destruction complex allows nuclear accumulation of β-catenin in oral dysplasia, and that these events depended on the endocytic protein Rab5. Tissue immunofluorescence analysis showed aberrant accumulation of enlarged early endosomes in oral dysplasia biopsies, when compared with healthy oral mucosa. These observations were confirmed in cell culture models, by comparing dysplastic oral keratinocytes (DOK) and non-dysplastic oral keratinocytes (OKF6). Intriguingly, DOK depicted higher levels of active Rab5, a critical regulator of early endosomes, when compared with OKF6. Increased Rab5 activity in DOK was necessary for nuclear localization of β-catenin and Tcf/Lef-dependent transcription, as shown by expression of dominant negative and constitutively active mutants of Rab5, along with immunofluorescence, subcellular fractionation, transcription, and protease protection assays. Mechanistically, elevated Rab5 activity in DOK accounted for endosomal sequestration of components of the destruction complex, including GSK3β, Axin, and adenomatous polyposis coli (APC), as observed in Rab5 dominant negative experiments. In agreement with these in vitro observations, tissue immunofluorescence analysis showed increased co-localization of GSK3β, APC, and Axin, with early endosome antigen 1- and Rab5-positive early endosomes in clinical samples of oral dysplasia. Collectively, these data indicate that increased Rab5 activity and endosomal sequestration of the β-catenin destruction complex leads to stabilization and nuclear accumulation of β-catenin in oral dysplasia.

TUFT1 promotes metastasis and chemoresistance in triple negative breast cancer through the TUFT1/Rab5/Rac1 pathway

Background

Triple negative breast cancer (TNBC) is a breast cancer (BC) subtype that is characterized by its strong invasion and a high risk of metastasis. However, the specific mechanisms underlying these phenotypes are unclear. TUFT1 plays an important role in BC and impacts the proliferation and survival of BC cells. Recent studies have shown that TUFT1 mediates intracellular lysosome localization and vesicle transport by regulating Rab GTPase, but the relevance of this activity in TNBC is unknown. Therefore, our aim was to systematically study the role of TUFT1 in the metastasis and chemoresistance of TNBC.

Methods

We measured TUFT1, Rab5-GTP, and Rac1-GTP expression levels in samples of human TNBC by immunohistochemistry (IHC) and conducted univariate and multivariate analyses. shRNA-mediated knockdown and overexpression, combined with transwell assays, co-immunoprecipitation, a nude mouse xenograft tumor model, and GTP activity assays were used for further mechanistic studies.

Results

TUFT1 expression was positively correlated with Rab5-GTP and Rac1-GTP in the TNBC samples, and co-expression of TUFT1 and Rab5-GTP predicted poor prognosis in TNBC patients who were treated with chemotherapy. Mechanism studies showed that TUFT1 could activate Rab5 by binding to p85α, leading to activation of Rac1 through recruitment of Tiam1, and concurrent down-regulation of the NF-κB pathway and proapoptotic factors, ultimately promoting metastasis and chemoresistance in TNBC cells.

Conclusions

Our findings suggest that the TUFT1/Rab5/Rac1 pathway may be a potential target for the effective treatment of TNBC.

Rab GTPases: Switching to Human Diseases

Rab proteins compose the largest family of small GTPases and control the different steps of intracellular membrane traffic. More recently, they have been shown to also regulate cell signaling, division, survival, and migration. The regulation of these processes generally occurs through recruitment of effectors and regulatory proteins, which control the association of Rab proteins to membranes and their activation state. Alterations in Rab proteins and their effectors are associated with multiple human diseases, including neurodegeneration, cancer, and infections. This review provides an overview of how the dysregulation of Rab-mediated functions and membrane trafficking contributes to these disorders. Understanding the altered dynamics of Rabs and intracellular transport defects might thus shed new light on potential therapeutic strategies.

TFEB-driven autophagy potentiates TGF-β induced migration in pancreatic cancer cells

Background

Pancreatic ductal adenocarcinoma is one of the most aggressive cancers, with a 5-year survival rate of less than 8%. The complicated tumor microenvironment, particularly TGF-β, provides possible convenience for the progression of PC cells. TGF-β regulates critical cellular processes, including autophagy. However, the mechanism and effects of TGF-β-mediated autophagy are still poorly understood.

Methods

Bioinformatics analysis, western blot, transmission electron microscopy and confocal microscopy were used to identify that TFEB is the key factors in TGF-β-induced autophagy. The biological effects of TFEB-driven autophagy were investigated in vitro using transwell and wound healing assays and in vivo using liver metastasis and LSL-KrasG12D/Pdx1-Cre mice models. Luciferase assays and motif analysis were used to assess regulation of RAB5A gene promoter activity by TGF-β-induced TFEB. TFEB levels were measured by real-time PCR, western blot and immunohistochemical staining in clinical pancreatic ductal adenocarcinoma tissues.

Results

We demonstrated that TGF-β induces TFEB expression via the canonical smad pathway in Smad4-positive PC cells and facilitates TFEB-mediated autophagic activation. TFEB-driven autophagy caused by TGF-β regulates RAB5A-dependent endocytosis of Itgα5 and promotes progression of PC cells. We further showed that enhanced TFEB expression and its direct target RAB5A both predict poor prognosis in PC patients.

Conclusions

Our findings reveal TFEB-driven autophagy is required for TGF-β induced migration and metastasis of PC cells by promoting endocytosis of Itgα5β1 and focal adhesion disassembly through the TGF-β-TFEB-RAB5A axis. Our results highlight the potential utility of suppressing TFEB-driven autophagy to block PC metastasis.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1343-4) contains supplementary material, which is available to authorized users.

The exocyst complex and Rab5 are required for abscission by localizing ESCRT III subunits to the cytokinetic bridge

Cytokinesis is the final step of cell division following chromosome segregation that generates two daughter cells. The conserved exocyst complex is required for scission of the intercellular cytokinetic bridge, although the molecular mechanisms it employs in this process are unclear. We identify and validate the early endocytic GTPase Rab5 as interacting with the exocyst complex in mammalian cells. Rab5 localizes in the cytokinetic bridge and on the midbody ring in a manner similar to the exocyst complex. Depletion of Rab5 led to delayed abscission. Caenorhabditis elegans orthologs of both exocyst complex subunits and Rab5 localize along the cleavage furrow and are required for cytokinesis in early embryos. Cytokinetic cells depleted of either Rab5 or the exocyst subunits Exoc3 and Exoc4 showed impaired deposition of the endosomal sorting complexes required for transport (ESCRT) III subunits CHMP2B and/or CHMP4B near the midbody ring. The study reveals an evolutionarily conserved role for the early endocytic marker Rab5 in cytokinetic abscission. In addition, it uncovers a key requirement of the exocyst and Rab5 for the delivery of components of the membrane-severing ESCRT III machinery to complete cytokinesis.

Summary: The conserved exocytic vesicle-tethering exocyst complex and the endocytic master regulator Rab5 mutually interact and are required to deliver the ESCRT III membrane scission apparatus for completion of cytokinesis.

Focal adhesion kinase-dependent activation of the early endocytic protein Rab5 is associated with cell migration

Focal adhesion kinase (FAK) is a central regulator of integrin-dependent cell adhesion and migration and has recently been shown to co-localize with endosomal proteins. The early endocytic protein Rab5 controls integrin trafficking, focal adhesion disassembly, and cell migration and has been shown to be activated upon integrin engagement by mechanisms that remain unclear. Because FAK is a critical regulator of integrin-dependent signaling and Rab5 recapitulates FAK-mediated effects, we evaluated the possibility that FAK activates Rab5 and contributes to cell migration. Pulldown assays revealed that Rab5-GTP levels are decreased upon treatment with a pharmacological inhibitor of FAK, PF562,271, in resting A549 cells. These events were associated with decreased peripheral Rab5 puncta and a reduced number of early endosome antigen 1 (EEA1)-positive early endosomes. Accordingly, as indicated by FAK inhibition experiments and in FAK-null fibroblasts, adhesion-induced FAK activity increased Rab5-GTP levels. In fact, expression of WT FAK and FAK/Y180A/M183A (open conformation), but not FAK/Arg⁴⁵⁴ (kinase-dead), augmented Rab5-GTP levels in FAK-null fibroblasts and A549 cells. Moreover, expression of a GDP-bound Rab5 mutant (Rab5/S34N) or shRNA-mediated knockdown of endogenous Rab5 prevented FAK-induced A549 cell migration, whereas expression of WT or GTP-bound Rab5 (Rab5/Q79L), but not Rab5/S34N, promoted cell migration in FAK-null fibroblasts. Mechanistically, FAK co-immunoprecipitated with the GTPase-activating protein p85α in a phosphorylation (Tyr³⁹⁷)-dependent manner, preventing Rab5-GTP loading, as shown by knockdown and transfection recovery experiments. Taken together, these results reveal that FAK activates Rab5, leading to cell migration.

The knocking down of the oncoprotein Golgi phosphoprotein 3 in T98G cells of glioblastoma multiforme disrupts cell migration by affecting focal adhesion dynamics in a focal adhesion kinase-dependent manner

Golgi phosphoprotein 3 (GOLPH3) is a conserved protein of the Golgi apparatus that in humans has been implicated in tumorigenesis. However, the precise function of GOLPH3 in malignant transformation is still unknown. Nevertheless, clinicopathological data shows that in more than a dozen kinds of cancer, including gliomas, GOLPH3 could be found overexpressed, which correlates with poor prognosis. Experimental data shows that overexpression of GOLPH3 leads to transformation of primary cells and to tumor growth enhancement. Conversely, the knocking down of GOLPH3 in GOLPH3-overexpressing tumor cells reduces tumorigenic features, such as cell proliferation and cell migration and invasion. The cumulative evidence indicate that GOLPH3 is an oncoprotein that promotes tumorigenicity by a mechanism that impact at different levels in different types of cells, including the sorting of Golgi glycosyltransferases, signaling pathways, and the actin cytoskeleton. How GOLPH3 connects mechanistically these processes has not been determined yet. Further studies are important to have a more complete understanding of the role of GOLPH3 as oncoprotein. Given the genetic diversity in cancer, a still outstanding aspect is how in this inherent heterogeneity GOLPH3 could possibly exert its oncogenic function. We have aimed to evaluate the contribution of GOLPH3 overexpression in the malignant phenotype of different types of tumor cells. Here, we analyzed the effect on cell migration that resulted from stable, RNAi-mediated knocking down of GOLPH3 in T98G cells of glioblastoma multiforme, a human glioma cell line with unique features. We found that the reduction of GOLPH3 levels produced dramatic changes in cell morphology, involving rearrangements of the actin cytoskeleton and reduction in the number and dynamics of focal adhesions. These effects correlated with decreased cell migration and invasion due to affected persistence and directionality of cell motility. Moreover, the knocking down of GOLPH3 also caused a reduction in autoactivation of focal adhesion kinase (FAK), a cytoplasmic tyrosine kinase that regulates focal adhesions. Our data support a model in which GOLPH3 in T98G cells promotes cell migration by stimulating the activity of FAK.

Impact of p85α Alterations in Cancer

The phosphatidylinositol 3-kinase (PI3K) pathway plays a central role in the regulation of cell signaling, proliferation, survival, migration and vesicle trafficking in normal cells and is frequently deregulated in many cancers. The p85α protein is the most characterized regulatory subunit of the class IA PI3Ks, best known for its regulation of the p110-PI3K catalytic subunit. In this review, we will discuss the impact of p85α mutations or alterations in expression levels on the proteins p85α is known to bind and regulate. We will focus on alterations within the N-terminal half of p85α that primarily regulate Rab5 and some members of the Rho-family of GTPases, as well as those that regulate PTEN (phosphatase and tensin homologue deleted on chromosome 10), the enzyme that directly counteracts PI3K signaling. We highlight recent data, mapping the interaction surfaces of the PTEN⁻p85α breakpoint cluster region homology (BH) domain, which sheds new light on key residues in both proteins. As a multifunctional protein that binds and regulates many different proteins, p85α mutations at different sites have different impacts in cancer and would necessarily require distinct treatment strategies to be effective.

MiRNA-575 suppresses angiogenesis by targeting Rab5-MEK-ERK pathway in endothelial cells

Hypertension is a major risk factor for the development of atherosclerosis. Increased carotid intima-media thickness (CIMT) is generally considered as an early marker of atherosclerosis. Recently, circulating miRNAs have been implicated both as sensitive biomarkers and key regulators in the development of atherosclerosis. However, the biological functions and molecular regulatory mechanisms for miR-575 on angiogenesis remain unknown. In our study, we first identified up-regulation of circulating miR-575 in plasma of essential hypertensive patients with increased CIMT (iCIMT) compared with those patients with normal CIMT (nCIMT). Furthermore, the overexpression of miR-575 in human umbilical vein endothelial cells (HUVECs) by its mimics significantly inhibited migration and proliferation as well as induction of apoptosis of HUVECs. Inhibition of miR-575 performed the reverse effects of HUVECs. We further suggested Rab5B was the downstream target of miR-575 and knockdown of Rab5B significantly inhibited migration and proliferation of HUVECs. Overexpression of Rab5B largely rescued the miR-575-mediated impairment of angiogenesis processes including: cell proliferation, migration, and apoptosis as well as activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK-ERK) signaling. Therefore, our results uncover a novel role of miR-575 in endothelial cells, implying a potential biomarker and clinical target for atherosclerosis in hypertensive patients.

Fabrication of Silver Nanoparticles Using a Gas Phase Nanocluster Device and Preliminary Biological Uses

Nanoparticles can be used in a large variety of applications, including magnetic sensing, biological, superconductivity, tissue engineering, and other fields. In this study, we explore the fabrication of gas phase silver nanoparticles using a sputtering evaporation source. This setup composed of a dual magnetron cluster source holds several advantages over other techniques. The system has independent control over the cluster concentration and a wide range of cluster size and materials that can be used for the clusters and for the matrix where it can be embedded. Characterization of these silver nanoparticles was done using transmission electron microscopy (TEM). We obtain a lateral width of 10.6 nm with a dispersion of 0.24 nm. With atomic force microscopy (AFM) a Gaussian fit of this distribution yields and average height of 6.3 nm with a standard deviation of 1.4 nm. We confirm that the deposited silver nanoparticles have a homogenous area distribution, that they have a defined shape and size distribution, and that they are single standing nanoparticles. Given that the scientific literature is not precise regarding the toxic concentration of the nanoparticles, devices such as ours can help clarify these questions. In order to explore further biological applications, we have done preliminary experiments of cell spreading (myoblast adhesion), obtaining interesting morphological changes correlated with the silver concentration on the surface. With a deposited silver concentration ranging from 100–620 ng/cm², the cells showed morphological changes in a short time of 2 h. We conclude that this high precision nanoparticle fabrication technique is adequate for further biological research.

Filopodia and focal adhesions: An integrated system driving branching morphogenesis in neuronal pathfinding and angiogenesis

Single cell branching during development in vertebrates is typified by neuronal branching to form neurites and vascular branches formed by sprouting angiogenesis. Neurons and endothelial tip cells possess subcellular protrusions that share many common features from the morphological to the molecular level. Both systems utilize filopodia as their cellular protrusion organelles and depend on specific integrin-mediated adhesions to the local extracellular matrix for guidance in their pathfinding. We discuss the similar molecular machineries involved in these two types of cell branch formation and use their analogy to propose a new mechanism for angiogenic filopodia function, namely as adhesion assembly sites. In support of this model we provide primary data of angiogenesis in zebrafish in vivo showing that the actin assembly factor VASP participates in both filopodia formation and adhesion assembly at the base of the filopodia, enabling forward progress of the tip cell. The use of filopodia and their associated adhesions provide a common mechanism for neuronal and endothelial pathfinding during development in response to extracellular matrix cues.

Intracellular Ca2+ Increases and Connexin 43 Hemichannel Opening Are Necessary but Not Sufficient for Thy-1-Induced Astrocyte Migration

Under pro-inflammatory conditions, astrocytes become reactive and acquire a migratory phenotype. Our results show that hemichannels formed by connexin 43 (Cx43) play an important role in Thy-1-induced astrocyte migration. The neuronal protein Thy-1 binds to αvβ3 integrin in astrocytes, thereby leading to intricate signaling pathways that include calcium (Ca2+) release from intracellular stores, opening of Cx43 hemichannels, release of ATP, activation of P2X7 receptor, and Ca2+ influx. However, because these Thy-1 effects occur exclusively in reactive astrocytes, we wondered whether by elevating calcium levels and promoting hemichannel opening we could prompt non-reactive astrocytes to respond to Thy-1. Cx43 immunoreactivity increased at juxta-membrane sites, where hemichannels (not gap junctions) participate in astrocyte polarization and migration stimulated by Thy-1. Also, intracellular Ca2+ increase, due to ionomycin treatment, induced hemichannel opening, but activated astrocyte migration only partially, and this limitation was overcome by pre-treatment with tumor necrosis factor (TNF) and Thy-1. Finally, αvβ3 integrin formed membrane clusters after TNF stimulation or overexpression of β3 integrin. We suggest that these microclusters are required for cells to respond to Thy-1 stimulation. Therefore, the large increase in intracellular Ca2+ and hemichannel opening induced by ionomycin are required, but not sufficient, to permit Thy-1-induced astrocyte migration. Thus, we suggest that proinflammatory stimuli prompt astrocytes to respond to migratory signals of neuronal cells.

The role of the oncogenic Rab35 in cancer invasion, metastasis, and immune evasion, especially in leukemia

The study of cancer has allowed researchers to describe some biological characteristics that tumor cells acquire during their development, known as the “hallmarks of cancer” but more research is needed to expand our knowledge about cancer biology and to generate new strategies of treatment. The role that RabGTPases might play in some hallmarks of cancer represents interesting areas of study since these proteins are frequently altered in cancer. However, their participation is not well known. Recently, Rab35was recognized as an oncogenic RabGTPase and and because of its association with different cellular functions, distinctly important in immune cells, a possible role of Rab35 in leukemia can be suggested. Nevertheless, the involvement of Rab35 in cancer remains poorly understood and its possible specific role in leukemia remains unknown. In this review, we analyze general aspects of the participation of RabGTPases in cancer, and especially, the plausible role of Rab35 in leukemia.

SNORD126 promotes HCC and CRC cell growth by activating the PI3K-AKT pathway through FGFR2

Small nucleolar RNA (snoRNA) dysfunctions have been associated with cancer development. SNORD126 is an orphan C/D box snoRNA that is encoded within introns 5-6 of its host gene, cyclin B1-interacting protein 1 (CCNB1IP1). The cancer-associated molecular mechanisms triggered by SNORD126 are not fully understood. Here, we demonstrate that SNORD126 is highly expressed in hepatocellular carcinoma (HCC) and colorectal cancer (CRC) patient samples. SNORD126 increased Huh-7 and SW480 cell growth and tumorigenicity in nude mice. Knockdown of SNORD126 inhibited HepG2 and LS174T cell growth. We verified that SNORD126 was not processed into small RNAs with miRNA activity. Moreover, SNORD126 did not show a significant expression correlation with CCNB1IP1 in HCC samples or regulate CCNB1IP1 expression. Our gene expression profile analysis indicated that SNORD126-upregulated genes frequently mapped to the PI3K-AKT pathway. SNORD126 overexpression increased the levels of phosphorylated AKT, GSK-3β, and p70S6K and elevated fibroblast growth factor receptor 2 (FGFR2) expression. siRNA-mediated knockdown or AZD4547-mediated inactivation of FGFR2 in SNORD126-overexpressing Huh-7 cells inhibited AKT phosphorylation and suppressed cell growth. These findings indicate an oncogenic role for SNORD126 in cancer and suggest its potential as a therapeutic target.

Exploring the key genes and pathways in enchondromas using a gene expression microarray

Enchondromas are the most common primary benign osseous neoplasms that occur in the medullary bone; they can undergo malignant transformation into chondrosarcoma. However, enchondromas are always undetected in patients, and the molecular mechanism is unclear. To identify key genes and pathways associated with the occurrence and development of enchondromas, we downloaded the gene expression dataset GSE22855 and obtained the differentially expressed genes (DEGs) by analyzing high-throughput gene expression in enchondromas. In total, 635 genes were identified as DEGs. Of these, 225 genes (35.43%) were up-regulated, and the remaining 410 genes (64.57%) were down-regulated. We identified the predominant gene ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways that were significantly over-represented in the enchondromas samples compared with the control samples. Subsequently the top 10 core genes were identified from the protein-protein interaction (PPI) network. The enrichment analyses of the genes mainly involved in two significant modules showed that the DEGs were principally related to ribosomes, protein digestion and absorption, ECM-receptor interaction, focal adhesion, amoebiasis and the PI3K-Akt signaling pathway.Together, these data elucidate the molecular mechanisms underlying the occurrence and development of enchondromas and provide promising candidates for therapeutic intervention and prognostic evaluation. However, further experimental studies are needed to confirm these results.

Endosomal sorting and c-Cbl targeting of paxillin to autophagosomes regulate cell-matrix adhesion turnover in human breast cancer cells

Post-translational mechanisms regulating cell-matrix adhesion turnover during cell locomotion are not fully elucidated. In this study, we uncovered an essential role of Y118 site-specific tyrosine phosphorylation of paxillin, an adapter protein of focal adhesion complexes, in paxillin recruitment to autophagosomes to trigger turnover of peripheral focal adhesions in human breast cancer cells. We demonstrate that the Rab-7 GTPase is a key upstream regulator of late endosomal sorting of tyrosine118-phosphorylated paxillin, which is subsequently recruited to autophagosomes via the cargo receptor c-Cbl. Essentially, this recruitment involves a direct and selective interaction between Y118-phospho-paxillin, c-Cbl, and LC3 and is independent from c-Cbl E3 ubiquitin ligase activity. Interference with the Rab7-paxillin-autophagy regulatory network using genetic and pharmacological approaches greatly impacted focal adhesion stability, cell locomotion and progression to metastasis using a panel of human breast cancer cells. Together, these results provide novel insights into the requirement of phospho-site specific post-translational mechanism of paxillin for autophagy targeting to regulate cell-matrix adhesion turnover and cell locomotion in breast cancer cells.

Histatins, wound healing, and cell migration

Wounds in the oral mucosa heal faster and more efficiently than those in the skin, although the mechanisms underlying these differences are not completely clear. In the last 10 years, a group of salivary peptides, the histatins, has gained attention on behalf of their ability to improve several phases of the wound-healing process. In addition to their roles as anti-microbial agents and in enamel maintenance, histatins elicit other biological effects, namely by promoting the migration of different cell types contained in the oral mucosa and in non-oral tissues. Histatins, and specifically histatin-1, promote cell adhesion and migration in oral keratinocytes, gingival and dermal fibroblasts, non-oral epithelial cells, and endothelial cells. This is particularly relevant, as histatin-1 promotes the re-epithelialization phase and the angiogenic responses by increasing epithelial and endothelial cell migration. Although the molecular mechanisms associated with histatin-dependent cell migration remain poorly understood, recent studies have pointed to the control of signaling endosomes and the balance of small GTPases. This review aimed to update the literature on the effects of histatins in cell migration, with a focus on wound healing. We will also discuss the consequences that this increasing field will have in disease and therapy design.

α5β1 integrin trafficking and Rac activation are regulated by APPL1 in a Rab5-dependent manner to inhibit cell migration

Cell migration is a tightly coordinated process that requires the spatiotemporal regulation of many molecular components. Because adaptor proteins can serve as integrators of cellular events, they are being increasingly studied as regulators of cell migration. The adaptor protein containing a pleckstrin-homology (PH) domain, phosphotyrosine binding (PTB) domain, and leucine zipper motif 1 (APPL1) is a 709 amino acid endosomal protein that plays a role in cell proliferation and survival as well as endosomal trafficking and signaling. However, its function in regulating cell migration is poorly understood. Here, we show that APPL1 hinders cell migration by modulating both trafficking and signaling events controlled by Rab5 in cancer cells. APPL1 decreases internalization and increases recycling of α5β1 integrin, leading to higher levels of α5β1 integrin at the cell surface that hinder adhesion dynamics. Furthermore, APPL1 decreases the activity of the GTPase Rac and its effector PAK, which in turn regulate cell migration. Thus, we demonstrate a novel role for the interaction between APPL1 and Rab5 in governing crosstalk between signaling and trafficking pathways on endosomes to affect cancer cell migration.This article has an associated First Person interview with the first author of the paper.

Hypoxia promotes Rab5 activation, leading to tumor cell migration, invasion and metastasis

Hypoxia, a common condition of the tumor microenvironment, is associated with poor patient prognosis, tumor cell migration, invasion and metastasis. Recent evidence suggests that hypoxia alters endosome dynamics in tumor cells, leading to augmented cell proliferation and migration and this is particularly relevant, because endosomal components have been shown to be deregulated in cancer. The early endosome protein Rab5 is a small GTPase that promotes integrin trafficking, focal adhesion turnover, Rac1 activation, tumor cell migration and invasion. However, the role of Rab5 and downstream events in hypoxia remain unknown. Here, we identify Rab5 as a critical player in hypoxia-driven tumor cell migration, invasion and metastasis. Exposure of A549 human lung carcinoma, ZR-75, MDA-MB-231 and MCF-7 human breast cancer and B16-F10 mouse melanoma cells to hypoxia increased Rab5 activation, followed by its re-localization to the leading edge and association with focal adhesions. Importantly, Rab5 was required for hypoxia-driven cell migration, FAK phosphorylation and Rac1 activation, as shown by shRNA-targeting and transfection assays with Rab5 mutants. Intriguingly, the effect of hypoxia on both Rab5 activity and migration was substantially higher in metastatic B16-F10 cells than in poorly invasive B16-F0 cells. Furthermore, exogenous expression of Rab5 in B16-F0 cells predisposed to hypoxia-induced migration, whereas expression of the inactive mutant Rab5/S34N prevented the migration of B16-F10 cells induced by hypoxia. Finally, using an in vivo syngenic C57BL/6 mouse model, Rab5 expression was shown to be required for hypoxia-induced metastasis. In summary, these findings identify Rab5 as a key mediator of hypoxia-induced tumor cell migration, invasion and metastasis.

Potential microRNA-related Targets for Therapeutic Intervention with Ovarian Cancer Metastasis

Treatment of disseminated epithelial ovarian cancer (EOC) is an unmet medical need. Therefore, the identification along with preclinical and clinical validation of new targets is an issue of high importance. In this review we focus on microRNAs that mediate metastasis of EOC. We summarize up-regulated metastasis-promoting and down-regulated metastasis-suppressing microRNAs. We focus on preclinical in vitro and in vivo functions as well as their metastasis-related clinical correlations. Finally, we outline modalities for therapeutic intervention and critical issues of microRNA-based therapeutics in the context of metastatic EOC.

Calpain2 mediates Rab5-driven focal adhesion disassembly and cell migration

The early endosome protein Rab5 was recently shown to promote cell migration by enhancing focal adhesion disassembly through mechanisms that remain elusive. Focal adhesion disassembly is associated to proteolysis of talin, in a process that requires calpain2. Since calpain2 has been found at vesicles and endosomal compartments, we hypothesized that Rab5 stimulates calpain2 activity, leading to enhanced focal adhesion disassembly in migrating cells. We observed that calpain2 co-localizes with EEA1-positive early endosomes and co-immunoprecipitates with EEA1 and Rab5 in A549 lung carcinoma cells undergoing spreading, whereas Rab5 knock-down decreased the accumulation of calpain2 at early endosomal-enriched fractions. In addition, Rab5 silencing decreased calpain2 activity, as shown by cleavage of the fluorogenic substrate tBOC-LM-CMAC and the endogenous substrate talin. Accordingly, Rab5 promoted focal adhesion disassembly in a calpain2-dependent manner, as expression of GFP-Rab5 accelerated focal adhesion disassembly in nocodazole-synchronized cells, whereas pharmacological inhibition of calpain2 with N-acetyl-Leu-Leu-Met prevented both focal adhesion disassembly and cell migration induced by Rab5. In summary, these data uncover Rab5 as a novel regulator of calpain2 activity and focal adhesion proteolysis leading to cell migration.

Exploring the key genes and pathways of osteosarcoma with pulmonary metastasis using a gene expression microarray

Osteosarcoma is a common and highly malignant tumour in children and teenagers that is characterized by drug resistance and high metastatic potential. Patients often develop pulmonary metastasis and have a low survival rate. However, the mechanistic basis for pulmonary metastasis remains unclear. To identify key gene and pathways associated with pulmonary metastasis of osteosarcoma, the authors downloaded the gene expression dataset GSE85537 and obtained the differentially expressed genes (DEGs) by analyzing high-throughput gene expression in primary tumours and lung metastases. Subsequently, the authors performed gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway (KEGG) enrichment analyses and a protein-protein interaction (PPI) network was constructed and analyzed by Cytoscape software. In total, 2,493 genes were identified as DEGs. Of these, 485 genes (19.45%) were upregulated, and the remaining 2,008 genes (80.55%) were downregulated. The authors identified the predominant GO categories and KEGG pathways that were significantly over-represented in the metastatic OS samples compared with the non-metastatic OS samples. A PPI network was constructed, and the results indicated that ALB, EGFR, INS, IL6, CDH1, FYN, ERBB2, IL8, CXCL12 and RAC2 were the top 10 core genes. The enrichment analyses of the genes involved in the top three significant modules demonstrated that the DEGs were principally related to neuroactive ligand-receptor interaction, the Rap1 signaling pathway, and protein digestion and absorption. Together, these data elucidated the molecular mechanisms of OS patients with pulmonary metastasis and provide potential therapeutic targets. However, further experimental studies are needed to confirm these results.

Pro-migratory and TGF-β-activating functions of αvβ6 integrin in pancreatic cancer are differentially regulated via an Eps8-dependent GTPase switch

The integrin αvβ6 is up-regulated in numerous carcinomas, where expression commonly correlates with poor prognosis. αvβ6 promotes tumour invasion, partly through regulation of proteases and cell migration, and is also the principal mechanism by which epithelial cells activate TGF-β1; this latter function complicates therapeutic targeting of αvβ6, since TGF-β1 has both tumour-promoting and -suppressive effects. It is unclear how these different αvβ6 functions are linked; both require actin cytoskeletal reorganization, and it is suggested that tractive forces generated during cell migration activate TGF-β1 by exerting mechanical tension on the ECM-bound latent complex. We examined the functional relationship between cell invasion and TGF-β1 activation in pancreatic ductal adenocarcinoma (PDAC) cells, and confirmed that both processes are αvβ6-dependent. Surprisingly, we found that cellular functions could be biased towards either motility or TGF-β1 activation depending on the presence or absence of epidermal growth factor receptor pathway substrate 8 (Eps8), a regulator of actin remodelling, endocytosis, and GTPase activation. Similar to αvβ6, we found that Eps8 was up-regulated in >70% of PDACs. In complex with Abi1/Sos1, Eps8 regulated αvβ6-dependent cell migration through activation of Rac1. Down-regulation of Eps8, Sos1 or Rac1 suppressed cell movement, while simultaneously increasing αvβ6-dependent TGF-β1 activation. This latter effect was modulated through increased cell tension, regulated by Rho activation. Thus, the Eps8/Abi1/Sos1 tricomplex acts as a key molecular switch altering the balance between Rac1 and Rho activation; its presence or absence in PDAC cells modulates αvβ6-dependent functions, resulting in a pro-migratory (Rac1-dependent) or a pro-TGF-β1 activation (Rho-dependent) functional phenotype, respectively. © 2017 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Association of RAB5 overexpression in pancreatic cancer with cancer progression and poor prognosis via E-cadherin suppression

Pancreatic cancer is a common type of cancer with poor prognosis worldwide. Postoperative survival depends on the existence of metastasis. Elucidation of the mechanism underlying cancer progression is important to improve prognosis. The RAS-associated protein RAB5 activates intracellular membrane trafficking, and RAB5 expression is correlated to progression and epithelial mesenchymal transition in various cancers.

The expression of RAB5 and E-cadherin in 111 pancreatic cancer samples was investigated by immunohistochemical staining, and the relationship among RAB5 expression, clinicopathological factors, and E-cadherin expression was assessed. Furthermore, RAB5 suppression analysis by siRNA was performed to determine the roles of RAB5 in morphological change, proliferation potency, cell migration ability, and invasiveness of the pancreatic cancer cell line.

High RAB5 expression correlated with the presence of lymphatic invasion and venous invasion and low E-cadherin expression. Patients with high RAB5 expression had a poorer prognosis than those with low RAB5 expression. RAB5 suppression in pancreatic cancer cells enhanced E-cadherin expression; changed cell morphology from spindle to round; and inhibited proliferation, invasion, and cell migration.

RAB5 contributes to poor prognosis and progression in pancreatic cancer patients. It may be a promising candidate for individualized therapy in refractory pancreatic cancer.

APPL1 is a multifunctional endosomal signaling adaptor protein

Endosomal adaptor proteins are important regulators of signaling pathways underlying many biological processes. These adaptors can integrate signals from multiple pathways via localization to specific endosomal compartments, as well as through multiple protein-protein interactions. One such adaptor protein that has been implicated in regulating signaling pathways is the adaptor protein containing a pleckstrin homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif 1 (APPL1). APPL1 localizes to a subset of Rab5-positive endosomes through its Bin-Amphiphysin-Rvs and PH domains, and it coordinates signaling pathways through its interaction with many signaling receptors and proteins through its PTB domain. This review discusses our current understanding of the role of APPL1 in signaling and trafficking, as well as highlights recent work into the function of APPL1 in cell migration and adhesion.

The salivary peptide histatin-1 promotes endothelial cell adhesion, migration, and angiogenesis

Saliva is a key factor that contributes to the high efficiency of wound healing in the oral mucosa. This is not only attributed to physical cues but also to the presence of specific peptides in the saliva, such as histatins. Histatin-1 is a 38 aa antimicrobial peptide, highly enriched in human saliva, which has been previously reported to promote the migration of oral keratinocytes and fibroblasts in vitro However, the participation of histatin-1 in other crucial events required for wound healing, such as angiogenesis, is unknown. Here we demonstrate that histatin-1 promotes angiogenesis, as shown in vivo, using the chick chorioallantoic membrane model, and by an in vitro tube formation assay, using both human primary cultured endothelial cells (HUVECs) and the EA.hy926 cell line. Specifically, histatin-1 promoted endothelial cell adhesion and spreading onto fibronectin, as well as endothelial cell migration in the wound closure and Boyden chamber assays. These actions required the activation of the Ras and Rab interactor 2 (RIN2)/Rab5/Rac1 signaling axis, as histatin-1 increased the recruitment of RIN2, a Rab5-guanine nucleotide exchange factor (GEF) to early endosomes, leading to sequential Rab5/Rac1 activation. Accordingly, interfering with either Rab5 or Rac1 activities prevented histatin-1-dependent endothelial cell migration. Finally, by immunodepletion assays, we showed that salivary histatin-1 is required for the promigratory effects of saliva on endothelial cells. In conclusion, we report that salivary histatin-1 is a novel proangiogenic factor that may contribute to oral wound healing.-Torres, P., Díaz, J., Arce, M., Silva, P., Mendoza, P., Lois, P., Molina-Berríos, A., Owen, G. I., Palma, V., Torres, V. A. The salivary peptide histatin-1 promotes endothelial cell adhesion, migration, and angiogenesis.

Low-intensity pulsed ultrasound promotes cell motility through vinculin-controlled Rac1 GTPase activity

Low-intensity pulsed ultrasound (LIPUS) is a therapy used clinically to promote healing. Using live-cell imaging we show that LIPUS stimulation, acting through integrin-mediated cell-matrix adhesions, rapidly induces Rac1 activation associated with dramatic actin cytoskeleton rearrangements. Our study demonstrates that the mechanosensitive focal adhesion (FA) protein vinculin, and both focal adhesion kinase (FAK, also known as PTK2) and Rab5 (both the Rab5a and Rab5b isoforms) have key roles in regulating these effects. Inhibiting the link of vinculin to the actin-cytoskeleton abolished LIPUS sensing. We show that this vinculin-mediated link was not only critical for Rac1 induction and actin rearrangements, but was also important for the induction of a Rab5-dependent increase in the number of early endosomes. Expression of dominant-negative Rab5, or inhibition of endocytosis with dynasore, also blocked LIPUS-induced Rac1 signalling events. Taken together, our data show that LIPUS is sensed by cell matrix adhesions through vinculin, which in turn modulates a Rab5-Rac1 pathway to control ultrasound-mediated endocytosis and cell motility. Finally, we demonstrate that a similar FAK-Rab5-Rac1 pathway acts to control cell spreading upon fibronectin.

Characterization of the role of RILP in cell migration

Rab-interacting lysosomal protein (RILP) is a regulator of late stages of endocytosis. Recent work proved that depletion of RILP promotes migration of breast cancer cells in wound healing assay, whereas its overexpression influences re-arrangements of actin cytoskeleton. Here, we further characterized the role of RILP in cell migration by analyzing several aspects of this process. We showed that RILP is fundamental also for migration of lung cancer cells regulating cell velocity. RILP silencing did not affect Golgi apparatus nor microtubules reorientation during migration. However, both RILP over-expression and expression of its mutated form, RILPC33, impair cell adhesion and spreading. In conclusion, our results demonstrate that RILP has important regulatory roles in cell motility affecting migration velocity but also in cell adhesion and cell spreading.

Rab5-regulated endocytosis plays a crucial role in apical extrusion of transformed cells

Newly emerging transformed cells are often eliminated from epithelial tissues. Recent studies have revealed that this cancer-preventive process involves the interaction with the surrounding normal epithelial cells; however, the molecular mechanisms underlying this phenomenon remain largely unknown. In this study, using mammalian cell culture and zebrafish embryo systems, we have elucidated the functional involvement of endocytosis in the elimination of RasV12-transformed cells. First, we show that Rab5, a crucial regulator of endocytosis, is accumulated in RasV12-transformed cells that are surrounded by normal epithelial cells, which is accompanied by up-regulation of clathrin-dependent endocytosis. Addition of chlorpromazine or coexpression of a dominant-negative mutant of Rab5 suppresses apical extrusion of RasV12 cells from the epithelium. We also show in zebrafish embryos that Rab5 plays an important role in the elimination of transformed cells from the enveloping layer epithelium. In addition, Rab5-mediated endocytosis of E-cadherin is enhanced at the boundary between normal and RasV12 cells. Rab5 functions upstream of epithelial protein lost in neoplasm (EPLIN), which plays a positive role in apical extrusion of RasV12 cells by regulating protein kinase A. Furthermore, we have revealed that epithelial defense against cancer (EDAC) from normal epithelial cells substantially impacts on Rab5 accumulation in the neighboring transformed cells. This report demonstrates that Rab5-mediated endocytosis is a crucial regulator for the competitive interaction between normal and transformed epithelial cells in mammals.