A central role for vesicle trafficking in epithelial neoplasia: intracellular highways to carcinogenesis

Differentially expressed tRFs in CD5 positive relapsed & refractory diffuse large B cell lymphoma and the bioinformatic analysis for their potential clinical use

Background

Patients diagnosed as diffuse large B cell lymphoma (DLBCL) with CD5 positive normally have a worse outcome and poorly respond to the regulatory treatment strategy.

Results

We recently reported differently expressed tRFs and their potential target-genes of tRFs in patients with CD5+ R/R DLBCL. Differently expressed tRFs were detected by Illumina NextSeq instrument and the results were verified by quantitative real-time reverse transcription-PCR. tRF2Cancer database was searched to compared with the results. Further research was performed through bio-informatic analysis including gene ontology (GO) and pathway enrichment analyses, etc. A total of 308 tRFs were identified. Two sequences (AS-tDR-008946, AS-tDR-013492) were chosen for further investigated.

Conclusions

The results of Bioinformatics analysis revealed that the target genes including NEDD4L and UBA52 and several associated pathways including PI3K/AKT and MAPK/ERK might be involved in the development of CD5+ R/R DLBCL. Our preliminary study on the associated tRFs might provide a valuable measure to explore the pathogenesis and progression of CD5+ R/R DLBCL.

Reviewers

This article was reviewed by Zhen Qing Ye, Nagarajan Raju and Jin Zhuang Dou.

Spatiotemporal Control of Intracellular Membrane Trafficking by Rho GTPases

As membrane-associated master regulators of cytoskeletal remodeling, Rho GTPases coordinate a wide range of biological processes such as cell adhesion, motility, and polarity. In the last years, Rho GTPases have also been recognized to control intracellular membrane sorting and trafficking steps directly; however, how Rho GTPase signaling is regulated at endomembranes is still poorly understood. In this review, we will specifically address the local Rho GTPase pools coordinating intracellular membrane trafficking with a focus on the endo- and exocytic pathways. We will further highlight the spatiotemporal molecular regulation of Rho signaling at endomembrane sites through Rho regulatory proteins, the GEFs and GAPs. Finally, we will discuss the contribution of dysregulated Rho signaling emanating from endomembranes to the development and progression of cancer.

Quantitative phase microscopy with enhanced contrast and improved resolution through ultra-oblique illumination (UO-QPM)

Recent developments in phase contrast microscopy have enabled the label-free visualization of certain organelles due to their distinct morphological features, making this method an attractive alternative in the study of cellular dynamics. However tubular structures such as endoplasmic reticulum (ER) networks and complex dynamics such as the fusion and fission of mitochondria, due to their low phase contrast, still need fluorescent labeling to be adequately imaged. In this article, we report a quantitative phase microscope with ultra-oblique illumination that enables us to see those structures and their dynamics with high contrast for the first time without labeling. The imaging capability was validated through comparison to the fluorescence images with the same field-of-view. The high image resolution (~270 nm) was validated using both beads and cellular structures. Furthermore, we were able to record the vibration of ER networks at a frame rate of 250 Hz. We additionally show complex cellular processes such as remodeling of the mitochondria networks through fusion and fission and vesicle transportation along the ER without labels. Our high spatial and temporal resolution allowed us to observe mitochondria "spinning", which has not been reported before, further demonstrating the advantages of the proposed method.

Biochemical pathways mediated by KLK6 protease in breast cancer

Kallikrein-related peptidase 6 (KLK6) is a serine protease normally expressed in mammary tissue and aberrantly regulated in breast cancer. At physiological levels, KLK6 functions as a suppressor of breast cancer, while its aberrant overexpression (> 50-fold higher than normal) is characteristic of a subset of breast cancers and has been linked to accelerated growth of primary breast tumors in severe combined immunodeficiency mice (Pampalakis et al. Cancer Res 2009, 69, 3779). Here, we investigated the molecular mechanisms underlying the concentration-dependent functions of KLK6 by comparing MDA-MB-231 stable transfectants expressing increasing levels of KLK6 in in vitro and in vivo tumorigenicity assays (soft agar, xenograft growth, tail vein metastasis). Quantitative proteomics was applied to identify proteins that are altered upon re-expression of KLK6 in MDA-MB-231 at normal or constitutive levels. Overexpression of KLK6 is associated with increased metastatic ability of breast cancer cells into lungs, increased expression of certain S100 proteins (S100A4, S100A11) and keratins (KRT), and downregulation of the apoptosis-related proteases CASP7 and CASP8, and RABs. On the other hand, KLK6 re-expression at physiological levels leads to inhibition of lung metastases associated with suppression of S100 proteins (S100A4, S100A10, S100A13, S100A16) and induced CASP7 and CASP8 expression. As this is the first report that KLK6 expression is associated with S100 proteins, caspases, RABs, and KRTs, we validated this finding in clinical datasets. By integrating proteomics and microarray data from breast cancer patients, we generated two composite scores, KLK6 + S100B-S100A7 and KLK6 + S100B-S100A14-S100A16, to predict long-term survival of breast cancer patients. We present previously unknown pathways implicating KLK6 in breast cancer. The findings promise to aid our understanding of the functional roles of KLK6 in breast cancer and may yield new biomarkers for the cancer types in which KLK6 is known to be aberrantly upregulated.

Inhibition of UCH-L1 Deubiquitinating Activity with Two Forms of LDN-57444 Has Anti-Invasive Effects in Metastatic Carcinoma Cells

Normally ubiquitin C-terminal hydrolase L1 (UCH-L1) is expressed in the central nervous and reproductive systems of adults, but its de novo expression has been detected in many human cancers. There is a growing body of evidence that UCH-L1 de-ubiquitinating (DUB) activity plays a major pro-metastatic role in certain carcinomas. Here we tested anti-metastatic effects of the small-molecule inhibitor of UCH-L1 DUB activity, LDN-57444, in cell lines from advanced oral squamous cell carcinoma (OSCC) as well as invasive nasopharyngeal (NP) cell lines expressing the major pro-metastatic gene product of Epstein–Barr virus (EBV) tumor virus, LMP1. To overcome the limited aqueous solubility of LDN-57444 we developed a nanoparticle formulation of LDN-57444 by incorporation of the compound in polyoxazoline micellear nanoparticles (LDN-POx). LDN-POx nanoparticles were equal in effects as the native compound in vitro. Our results demonstrate that inhibition of UCH-L1 DUB activity with LDN or LDN-POx inhibits secretion of exosomes and reduces levels of the pro-metastatic factor in exosomal fractions. Both forms of UCH-L1 DUB inhibitor suppress motility of metastatic squamous carcinoma cells as well as nasopharyngeal cells expressing EBV pro-metastatic Latent membrane protein 1 (LMP1) in physiological assays. Moreover, treatment with LDN and LDN-POx resulted in reduced levels of pro-metastatic markers, a decrease of carcinoma cell adhesion, as well as inhibition of extra-cellular vesicle (ECV)-mediated transfer of viral invasive factor LMP1. We suggest that soluble inhibitors of UCH-L1 such as LDN-POx offer potential forms of treatment for invasive carcinomas including EBV-positive malignancies.

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

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

Recycling Endosomes in Mature Epithelia Restrain Tumorigenic Signaling

The effects of polarized membrane trafficking in mature epithelial tissue on cell growth and cancer progression have not been fully explored in vivo. A majority of colorectal cancers have reduced and mislocalized Rab11, a small GTPase dedicated to trafficking of recycling endosomes. Patients with low Rab11 protein expression have poor survival rates. Using genetic models across species, we show that intact recycling endosome function restrains aberrant epithelial growth elicited by APC or RAS mutations. Loss of Rab11 protein led to epithelial dysplasia in early animal development and synergized with oncogenic pathways to accelerate tumor progression initiated by carcinogen, genetic mutation, or aging. Transcriptomic analysis uncovered an immediate expansion of the intestinal stem cell pool along with cell-autonomous Yki/Yap activation following disruption of Rab11a-mediated recycling endosomes. Intestinal tumors lacking Rab11a traffic exhibited marked elevation of nuclear Yap, upd3/IL6-Stat3, and amphiregulin-MAPK signaling, whereas suppression of Yki/Yap or upd3/IL6 reduced gut epithelial dysplasia and hyperplasia. Examination of Rab11a function in enteroids or cultured cell lines suggested that this endosome unit is required for suppression of the Yap pathway by Hippo kinases. Thus, recycling endosomes in mature epithelia constitute key tumor suppressors, loss of which accelerates carcinogenesis. SIGNIFICANCE: Recycling endosome traffic in mature epithelia constitutes a novel tumor suppressing mechanism.

YIPF2 is a novel Rab-GDF that enhances HCC malignant phenotypes by facilitating CD147 endocytic recycle

An increased surface level of CIE (clathrin-independent endocytosis) proteins is a new feature of malignant neoplasms. CD147 is a CIE glycoprotein highly up-regulated in hepatocellular carcinoma (HCC). The ability to sort out the early endosome and directly target the recycling pathway confers on CD147 a prolonged surface half-life. However, current knowledge on CD147 trafficking to and from the cell-surface is limited. In this study, an MSP (membrane and secreted protein)-cDNA library was screened against EpoR/LR-F3/CD147EP-expressed cells by MAPPIT (mammalian protein–protein interaction trap). CD147 co-expressing with the new binder was investigated by GEPIA (gene expression profiling interactive analysis). The endocytosis, ER-Golgi trafficking and recycling of CD147 were measured by confocal imaging, flow cytometry, and biotin-labeled chase assays, respectively. Rab GTPase activation was checked by GST-RBD pull-down and MMP activity was measured by gelatin zymography. HCC malignant phenotypes were determined by cell adhesion, proliferation, migration, Transwell motility, and invasion assays. An ER-Golgi-resident transmembrane protein YIPF2 was identified as an intracellular binder to CD147. YIPF2 correlated and co-expressed with CD147, which is a survival predictor for HCC patients. YIPF2 is critical for CD147 glycosylation and trafficking functions in HCC cells. YIPF2 acts as a Rab-GDF (GDI-displacement factor) regulating three independent trafficking steps. First, YIPF2 recruits and activates Rab5 and Rab22a GTPases to the endomembrane structures. Second, YIPF2 modulates the endocytic recycling of CD147 through distinctive regulation on Rab5 and Rab22a. Third, YIPF2 mediates the mature processing of CD147 via the ER-Golgi trafficking route. Decreased YIPF2 expression induced a CD147 efficient delivery to the cell-surface, promoted MMP secretion, and enhanced the adhesion, motility, migration, and invasion behaviors of HCC cells. Thus, YIPF2 is a new trafficking determinant essential for CD147 glycosylation and transport. Our findings revealed a novel YIPF2-controlled ER-Golgi trafficking signature that promotes CD147-medated malignant phenotypes in HCC.

Transferrin Functionization Elevates Transcytosis of Nanogranules across Epithelium by Triggering Polarity-Associated Transport Flow and Positive Cellular Feedback Loop

Overcoming the epithelial barriers to enhance drug transport is a focused topic for gastrointestinal, intratracheal, intranasal, vaginal, and intrauterine delivery. Nanomedicines with targeting functionization promote such a process owing to specific ligand-receptor interaction. However, compared to the cell uptake of targeting nanotherapies, currently few studies concentrate on their transcytosis including endocytosis for "in" and exocytosis for "out". In fact, the cellular regulatory mechanism for these pathways as well as the principle of ligand's effect on the transcytosis are almost ignored. Here, we fabricated transferrin (Tf) functionalized nanogranules (Tf-NG) as the nanomedicine model and confirmed the difference in polar distributions of Tf receptors (TfRs) between two epithelium models (bipolarity for Caco-2 and unipolarity for MDCK cells). Compared to the nonspecific reference, Tf-conjugation boosted the endocytosis by different pathways in two cell models and transformed the intracellular route of Tf-NG in both cells differently, affecting exocytosis, recycling, and degradation but not the secretion pathway. Only bipolar cells could establish a complete transport flow from "in" to "out", leading to the enhanced transcytosis of Tf-NG. Importantly, epithelia could make responses to Tf-NG transcytosis. Based on the quantitative proteomics, the intracellular trafficking of Tf-NG altered the protein expression profiles, in which the endocytosis- and transcytosis-related proteins were specifically upregulated. Particularly, only bipolar cells could positively feed back to such trafficking via accelerating the subsequent Tf-NG transcytosis. Here, all the cell transport of Tf-NG was polarity associated. In summary, Tf modification elevated the transcytosis of Tf-NG across the epithelium by triggering the polarity-associated transport flow and positive cell feedback loop. These findings provided an insight into the targeting nanodelivery for efficient transport through epithelial barriers.

The lncRNA HOXA11-AS regulates Rab3D expression by sponging miR-125a-5p promoting metastasis of osteosarcoma

Objective: Many studies have shown that long non-coding RNAs (lncRNAs) are closely related to various cancers. This study aims to explore the roles of lncRNA HOXA11-AS in the development and progression of osteosarcoma (OS).

Methods: The expression levels of HOXA11-AS and miR-125a-5p in tumor tissues and the adjacent tissues were detected by RT-PCR method. The proliferation, migration and invasion of MG-63 and KHOS cells were determined.

Results: It was found that HOXA11-AS expression levels in OS tissues and OS cell lines were higher than those in OS adjacent tissues and normal human osteoblast cell lines. The higher expression level of HOXA11-AS was positively correlated with more severe clinical stage, distant metastasis and poor prognosis of OS. Inhibition of HOXA11-AS expression could reduce metastasis and invasion of OS cell lines. In addition, HOXA11-AS was found to be an endogenous inhibitor of miR-125a-5p, it down regulated the expression level of miR-125a-5p, and this process could promote the expression of Rab3D, the target gene of miR-125a-5p.

Conclusion: Our study elucidated the role of a new HOXA11-AS/miR-125a-5p/Rab3D regulatory pathway in promoting OS metastasis.

Rab-dependent cellular trafficking and amyotrophic lateral sclerosis

Rab GTPases are becoming increasingly implicated in neurodegenerative disorders, although their role in amyotrophic lateral sclerosis (ALS) has been somewhat overlooked. However, dysfunction of intracellular transport is gaining increasing attention as a pathogenic mechanism in ALS. Many previous studies have focused axonal trafficking, and the extreme length of axons in motor neurons may contribute to their unique susceptibility in this disorder. In contrast, the role of transport defects within the cell body has been relatively neglected. Similarly, whilst Rab GTPases control all intracellular membrane trafficking events, their role in ALS is poorly understood. Emerging evidence now highlights this family of proteins in ALS, particularly the discovery that C9orf72 functions in intra transport in conjunction with several Rab GTPases. Here, we summarize recent updates on cellular transport defects in ALS, with a focus on Rab GTPases and how their dysfunction may specifically target neurons and contribute to pathophysiology. We discuss the molecular mechanisms associated with dysfunction of Rab proteins in ALS. Finally, we also discuss dysfunction in other modes of transport recently implicated in ALS, including nucleocytoplasmic transport and the ER-mitochondrial contact regions (MAM compartment), and speculate whether these may also involve Rab GTPases.

Non-canonical role of cancer-associated mutant SEC23B in the ribosome biogenesis pathway

SEC23B is a component of coat protein complex II (COPII) vesicles that transport secretory proteins from the endoplasmic reticulum (ER) to the Golgi apparatus. Loss-of-function SEC23B mutations cause a rare form of anemia, resulting from decreased SEC23B levels. We recently identified germline heterozygous SEC23B variants as potentially cancer-predisposing. Mutant SEC23B associated with ER stress-mediated tumorigenesis, without decreased SEC23B expression. However, our understanding of the processes behind these observations remain limited. Here, we show mutant SEC23B exists within nucleoli, in addition to classical distribution at the ER/Golgi. This occurs independent of other COPII proteins and does not compromise secretory function. Mutant cells have increased ribosomal protein and translation-related gene expression, and enhanced translational capacity, in the presence of ER stress. We show that mutant SEC23B binds to UBF transcription factor, with increased UBF transcription factor binding at the ribosomal DNA promoter. Our data indicate SEC23B has potential non-canonical COPII-independent function, particularly within the ribosome biogenesis pathway, and that may contribute to the pathogenesis of cancer-predisposition.

A Novel Truncated Form of Nephronectin Is Present in Small Extracellular Vesicles Isolated from 66cl4 Cells

Extracellular vesicles are emerging as biomarkers in breast cancer. Our recent report suggested that an intracellular granular staining pattern of the extracellular matrix protein nephronectin (NPNT) in breast tumor sections correlated with a poor prognosis. Furthermore, the results showed that NPNT is localized in extracellular vesicles derived from mouse breast cancer cells. In this study, we performed proteomic analysis that revealed that several proteins, including tumor-promoting molecules, are differentially expressed in the cargo of small extracellular vesicles (sEVs) derived from NPNT-expressing mouse breast cancer cells. We also identified three different forms of NPNT at 80, 60, and 20 kDa. We report that the native form of NPNT at 60 kDa becomes further glycosylated and is detected as the 80 kDa NPNT, which may be processed by matrix metalloproteinases to a shorter form of around 20 kDa, which has not previously been described. Although both 80 and 20 kDa NPNT are detected in sEVs derived from breast cancer cells, the 20 kDa form of NPNT is concentrated in sEVs. In summary, we show that a novel truncated form of NPNT is found in sEVs derived from breast cancer cells.

Golgi Structure and Function in Health, Stress, and Diseases

The Golgi apparatus is a central intracellular membrane-bound organelle with key functions in trafficking, processing, and sorting of newly synthesized membrane and secretory proteins and lipids. To best perform these functions, Golgi membranes form a unique stacked structure. The Golgi structure is dynamic but tightly regulated; it undergoes rapid disassembly and reassembly during the cell cycle of mammalian cells and is disrupted under certain stress and pathological conditions. In the past decade, significant amount of effort has been made to reveal the molecular mechanisms that regulate the Golgi membrane architecture and function. Here we review the major discoveries in the mechanisms of Golgi structure formation, regulation, and alteration in relation to its functions in physiological and pathological conditions to further our understanding of Golgi structure and function in health and diseases.

The Autophagy-Lysosomal Pathways and Their Emerging Roles in Modulating Proteostasis in Tumors

In normal physiological condition, the maintenance of cellular proteostasis is a prerequisite for cell growth, functioning, adapting to changing micro-environments, and responding to extracellular stress. Cellular proteostasis is maintained by specific proteostasis networks (PNs) to prevent protein misfolding, aggregating, and accumulating in subcellular compartments. Commonly, the PNs are composed of protein synthesis, molecular chaperones, endoplasmic reticulum (ER), unfolded protein response (UPR), stress response pathways (SRPs), secretions, ubiquitin proteasome system (UPS), and autophagy-lysosomal pathways (ALPs). Although great efforts have been made to explore the underlying detailed mechanisms of proteostasis, there are many questions remain to explore, especially in proteostasis regulated by the ALPs. Proteostasis out-off-balance is correlated with various human diseases such as diabetes, stroke, inflammation, hypertension, pulmonary fibrosis, and Alzheimer’s disease. Enhanced regulation of PNs is observed in tumors, thereby indicating that proteostasis may play a pivotal role in tumorigenesis and cancer development. Recently, inhibitors targeting the UPS have shown to be failed in solid tumor treatment. However, there is growing evidence showing that the ALPs play important roles in regulation of proteostasis alone or with a crosstalk with other PNs in tumors. In this review, we provide insights into the proteostatic process and how it is regulated by the ALPs, such as macroautophagy, aggrephagy, chaperone-mediated autophagy, microautophagy, as well as mitophagy during tumor development.

Inorganic semiconductor biointerfaces

Biological systems respond to and communicate through biophysical cues, such as electrical, thermal, mechanical and topographical signals. However, precise tools for introducing localized physical stimuli and/or for sensing biological responses to biophysical signals with high spatiotemporal resolution are limited. Inorganic semiconductors display many relevant electrical and optical properties, and they can be fabricated into a broad spectrum of electronic and photonic devices. Inorganic semiconductor devices enable the formation of functional interfaces with biological material, ranging from proteins to whole organs. In this Review, we discuss fundamental semiconductor physics and operation principles, with a focus on their behaviour in physiological conditions, and highlight the advantages of inorganic semiconductors for the establishment of biointerfaces. We examine semiconductor device design and synthesis and discuss typical signal transduction mechanisms at bioelectronic and biophotonic interfaces for electronic and optoelectronic sensing, optoelectronic and photothermal stimulation and photoluminescent in vivo imaging of cells and tissues. Finally, we evaluate cytotoxicity and highlight possible new material components and biological targets of inorganic semiconductor devices.

Generation and characterization of monoclonal antibodies that recognize human and murine supervillin protein isoforms

Supervillin isoforms have been implicated in cell proliferation, actin filament-based motile processes, vesicle trafficking, and signal transduction. However, an understanding of the roles of these proteins in cancer metastasis and physiological processes has been limited by the difficulty of obtaining specific antibodies against these highly conserved membrane-associated proteins. To facilitate research into the biological functions of supervillin, monoclonal antibodies were generated against the bacterially expressed human supervillin N-terminus. Two chimeric monoclonal antibodies with rabbit Fc domains (clones 1E2/CPTC-SVIL-1; 4A8/CPTC-SVIL-2) and two mouse monoclonal antibodies (clones 5A8/CPTC-SVIL-3; 5G3/CPTC-SVIL-4) were characterized with respect to their binding sites, affinities, and for efficacy in immunoblotting, immunoprecipitation, immunofluorescence microscopy and immunohistochemical staining. Two antibodies (1E2, 5G3) recognize a sequence found only in primate supervillins, whereas the other two antibodies (4A8, 5A8) are specific for a more broadly conserved conformational epitope(s). All antibodies function in immunoblotting, immunoprecipitation and in immunofluorescence microscopy under the fixation conditions identified here. We also show that the 5A8 antibody works on immunohistological sections. These antibodies should provide useful tools for the study of mammalian supervillins.

Human rhomboid family-1 modulates clathrin coated vesicle-dependent pro-transforming growth factor α membrane trafficking to promote breast cancer progression

BACKGROUND

Epidermal growth factor receptor (EGFR) signalling is critical in epithelial cancer development. Human rhomboid family-1 (RHBDF1) facilitates the secretion of TGFα, an EGFR ligand, in breast cancer; however, the underlying mechanism remains unclear. We evaluated the role for RHBDF1 in clathrin-coated vesicle (CCV)-dependent pro-TGFα membrane trafficking in breast cancer cells upon stimulation by G-protein coupled receptor (GPCR) agonists.

METHODS

RHBDF1 was silenced in various breast cancer cells using shRNA. TGFα levels, subcellular localization, and secretion were evaluated using ELISA, immunofluorescent staining, and coimmunoprecipitation. Phosphorylation and expression of relevant proteins were measured by western blotting. RHBDF1-dependent cell viability and invasion were measured.

FINDINGS

RHBDF1 mediates GPCR agonist-induced EGFR phosphorylation by promoting TGFα secretion in various types of breast cancer cells. RHBDF1 not only mediates ADAM17-dependent shedding of TGFα, but is essential in membrane trafficking of pro-TGFα. RHBDF1 silencing results in blocking of clathrin uncoating from CCV, a crucial step for the plasma membrane release of pro-TGFα. Interaction of RHBDF1 with auxilin-2, a CCV protein, determines the recruitment of HSC70 to CCV to facilitate clathrin uncoating. RHBDF1 function is required for the proliferation and mobility of breast cancer cells upon stimulation by Sphingosine 1 Phosphate (S1P), a GPCR agonist. We demonstrate a significant correlation between RHBDF1 overexpression and EGFR activation in breast cancer tissues.

INTERPRETATION

RHBDF1 is an indispensable component of the protein trafficking machinery involved in GPCR-mediated EGFR transactivation, and is an attractive therapeutic target for cancer. FUND: National Natural Science Foundation of China (81,672,740 to ZSZ, 81,272,356 and 81,330,029 to LYL).

O-GlcNAcylation on Rab3A attenuates its effects on mitochondrial oxidative phosphorylation and metastasis in hepatocellular carcinoma

Rab3A is a small Ras-like GTPase critical for membrane traffic. Although the functions of Rab3A have been reported in several cancers, the roles of Rab3A in hepatocellular carcinoma (HCC) have never been determined. To investigate the potential roles of Rab3A in HCC progression, we first determined Rab3A levels in HCC tissues and observed upregulated mRNA and protein levels of Rab3A in most tumor tissues. However, in vitro data showed that decreasing Rab3A in most HCC cell lines conferred no significant effects and overexpressing Rab3A in PLC/PRF/5 cells even inhibited migration and invasion. Meanwhile, the upregulation of Rab3A in HCC patients did not correlate with metastasis or overall survival of HCC patients. These contradict data suggested that Rab3A might act as metastatic suppressor and its effects might be attenuated in most HCC cells. Further experiments revealed that O-GlcNAcylation on Rab3A was key for attenuating Rab3A-mediated effects by regulating its GTP-binding activity, and verified the effects of Rab3A and its aberrant O-GlcNAcylation on HCC metastasis in vitro and in vivo. We also found that Rab3A and its O-GlcNAcylation had opposite roles in mitochondria oxidative phosphorylation (mtOXPHOS), and their functions on HCC metastasis were partially depended on their effects on metabolic reprogramming.

Papillomaviruses and Endocytic Trafficking

Endocytic trafficking plays a major role in transport of incoming human papillomavirus (HPVs) from plasma membrane to the trans Golgi network (TGN) and ultimately into the nucleus. During this infectious entry, several cellular sorting factors are recruited by the viral capsid protein L2, which plays a critical role in ensuring successful transport of the L2/viral DNA complex to the nucleus. Later in the infection cycle, two viral oncoproteins, E5 and E6, have also been shown to modulate different aspects of endocytic transport pathways. In this review, we highlight how HPV makes use of and perturbs normal endocytic transport pathways, firstly to achieve infectious virus entry, secondly to produce productive infection and the completion of the viral life cycle and, finally, on rare occasions, to bring about the development of malignancy.

LRRK2 deficiency impairs trans-Golgi to lysosome trafficking and endocytic cargo degradation in human renal proximal tubule epithelial cells

Defects in vesicular trafficking underlie a wide variety of human diseases. Genetic disruption of leucine-rich repeat kinase 2 (LRRK2) in rodents results in epithelial vesicular trafficking errors that can also be induced by treatment of animals with LRRK2 kinase inhibitors. Here we demonstrate that defects in human renal cells lacking LRRK2 phenocopy those seen in the kidneys of Lrrk2 knockout mice, characterized by accumulation of intracellular waste vesicles and fragmentation of the Golgi apparatus. This phenotype can be recapitulated by knockdown of N-ethylmaleimide-sensitive factor, which physically associates with LRRK2 in renal cells. Deficiency in either protein leads to a defect in trans-Golgi to lysosome protein trafficking, which compromises the capacity of lysosomes to degrade endocytic and autophagic cargo. In contrast, neither bulk endocytosis nor autophagic flux are impaired when LRRK2 is acutely knocked down in normal immortalized human kidney (HK2) cells. These data collectively suggest that the primary renal defect caused by LRRK2 deficiency is in protein trafficking between the Golgi apparatus and late endosome/lysosome, which leads to progressive impairments in lysosomal function.

Receptor mediated transcytosis in biological barrier: The influence of receptor character and their ligand density on the transmembrane pathway of active-targeting nanocarriers

Active-targeting nanocarriers can significantly improve the transcytosis of poorly water-soluble or bio-macromolecular drugs across biological barrier. However, reasons for the improvement are not understood enough, which hampered the reasonable design of active targeting nanocarriers. To illustrate how different factors influence the transport of active-targeting nanocarriers, we established ligand-decorated micelles targeting different receptors to study how the decorations influence the transcytosis of the micelles by comparing the endocytosis, transport pathway and exocytosis process. Three different kinds of receptors, Neonatal Fc receptor (FcRn), transferrin receptor (TfR) and αvβ3 integrin were selected. They presented three different transport pathways, mainly mediating transcytosis, recycling pathway and cell binding, respectively. Their corresponding ligand FcBP, 7pep and c(RGDfK) decorated micelles with different ligand densities were prepared first. Then the effects of receptor and ligand density on the transcytosis across biological barrier were investigated. The results showed that the uptake rate of active micelles was higher than passive micelles and an optimum ligand density with most endocytosis appeared in all functional micelles. Transport pathway study showed 7pep decorated micelles were transferred into apical recycling endosome (ARE) and exocytosed to apical plasma membrane in a ligand depended way. c(RGDfK) decorated micelles were transferred through common recycling endosome (CRE) and Golgi complex to basolateral plasma membrane instead of ARE. While FcBP decorated micelles took both the recycling pathway and transcytosis through CRE, but not Golgi complex. Proper ligand density, not the higher the better, led the most uptake. Also the apical to basolateral transcytosis ratio may not be in accordance with the uptake. Among all the itineraries, transcytosis through CRE is the best itinerary for transcytosis. So, in the design of active targeting nanocarriers to overcome biological barrier, receptor character should be considered priorly, and then ligand density should be optimized.

Associations of single nucleotide polymorphisms with mucinous colorectal cancer: genome-wide common variant and gene-based rare variant analyses

Background

Colorectal cancer has significant impact on individuals and healthcare systems. Many genes have been identified to influence its pathogenesis. However, the genetic basis of mucinous tumor histology, an aggressive subtype of colorectal cancer, is currently not well-known. This study aimed to identify common and rare genetic variations that are associated with the mucinous tumor phenotype.

Methods

Genome-wide single nucleotide polymorphism (SNP) data was investigated in a colorectal cancer patient cohort (n = 505). Association analyses were performed for 729,373 common SNPs and 275,645 rare SNPs. Common SNP association analysis was performed using univariable and multivariable logistic regression under different genetic models. Rare-variant association analysis was performed using a multi-marker test.

Results

No associations reached the traditional genome-wide significance. However, promising genetic associations were identified. The identified common SNPs significantly improved the discriminatory accuracy of the model for mucinous tumor phenotype. Specifically, the area under the receiver operating characteristic curve increased from 0.703 (95% CI: 0.634–0.773) to 0.916 (95% CI: 0.873–0.960) when considering the most significant SNPs. Additionally, the rare variant analysis identified a number of genetic regions that potentially contain causal rare variants associated with the mucinous tumor phenotype.

Conclusions

This is the first study applying both common and rare variant analyses to identify genetic associations with mucinous tumor phenotype using a genome-wide genotype data. Our results suggested novel associations with mucinous tumors. Once confirmed, these results will not only help us understand the biological basis of mucinous histology, but may also help develop targeted treatment options for mucinous tumors.

Electronic supplementary material

The online version of this article (10.1186/s40364-018-0133-z) contains supplementary material, which is available to authorized users.

Prostate tumor cell exosomes containing hyaluronidase Hyal1 stimulate prostate stromal cell motility by engagement of FAK-mediated integrin signaling

The hyaluronidase Hyal1 is clinically and functionally implicated in prostate cancer progression and metastasis. Elevated Hyal1 accelerates vesicular trafficking in prostate tumor cells, thereby enhancing their metastatic potential in an autocrine manner through increased motility and proliferation. In this report, we found Hyal1 protein is a component of exosomes produced by prostate tumor cell lines overexpressing Hyal1. We investigated the role of exosomally shed Hyal1 in modulating tumor cell autonomous functions and in modifying the behavior of prostate stromal cells. Catalytic activity of Hyal1 was necessary for enrichment of Hyal1 in the exosome fraction, which was associated with increased presence of LC3BII, an autophagic marker, in the exosomes. Hyal1-positive exosome contents were internalized from the culture medium by WPMY-1 prostate stromal fibroblasts. Treatment of prostate stromal cells with tumor exosomes did not affect proliferation, but robustly stimulated their migration in a manner dependent on Hyal1 catalytic activity. Increased motility of exosome-treated stromal cells was accompanied by enhanced adhesion to a type IV collagen matrix, as well as increased FAK phosphorylation and integrin engagement through dynamic membrane residence of β1 integrins. The presence of Hyal1 in tumor-derived exosomes and its ability to impact the behavior of stromal cells suggests cell-cell communication via exosomes is a novel mechanism by which elevated Hyal1 promotes prostate cancer progression.

The multifaceted role of exosomes in cancer progression: diagnostic and therapeutic implications [corrected]

BACKGROUND

Recent advances in cancer biology have highlighted the relevance of exosomes and nanovesicles as carriers of genetic and biological messages between cancer cells and their immediate and/or distant environments. It has been found that these molecular cues may play significant roles in cancer progression and metastasis. Cancer cells secrete exosomes containing diverse molecules that can be transferred to recipient cells and/or vice versa to induce a plethora of biological processes, including angiogenesis, metastasis formation, therapeutic resistance, epithelial-mesenchymal transition and epigenetic/stemness (re)programming. While exosomes interact with cells within the tumour microenvironment to promote tumour growth, these vesicles can also facilitate the process of distant metastasis by mediating the formation of pre-metastatic niches. Next to their tumour promoting effects, exosomes have been found to serve as potential tools for cancer diagnosis and therapy. The ease of isolating exosomes and their content from different body fluids has led to the identification of diagnostic and prognostic biomarker signatures, as well as to predictive biomarker signatures for therapeutic responses. Exosomes can also be used as cargos to deliver therapeutic anti-cancer drugs, and they can be engineered to serve as vaccines for immunotherapy. Additionally, it has been found that inhibition of exosome secretion, and thus the transfer of oncogenic molecules, holds promise for inhibiting tumour growth. Here we provide recent information on the diverse roles of exosomes in various cellular and systemic processes governing cancer progression, and discuss novel strategies to halt this progression using exosome-based targeted therapies and methods to inhibit exosome secretion and the transfer of pro-tumorigenic molecules.

CONCLUSIONS

This review highlights the important role of exosomes in cancer progression and its implications for (non-invasive) diagnostics and the development of novel therapeutic strategies, as well as its current and future applications in clinical trials.

Integrated genomics and functional validation identifies malignant cell specific dependencies in triple negative breast cancer

Triple negative breast cancers (TNBCs) lack recurrent targetable driver mutations but demonstrate frequent copy number aberrations (CNAs). Here, we describe an integrative genomic and RNAi-based approach that identifies and validates gene addictions in TNBCs. CNAs and gene expression alterations are integrated and genes scored for pre-specified target features revealing 130 candidate genes. We test functional dependence on each of these genes using RNAi in breast cancer and non-malignant cells, validating malignant cell selective dependence upon 37 of 130 genes. Further analysis reveals a cluster of 13 TNBC addiction genes frequently co-upregulated that includes genes regulating cell cycle checkpoints, DNA damage response, and malignant cell selective mitotic genes. We validate the mechanism of addiction to a potential drug target: the mitotic kinesin family member C1 (KIFC1/HSET), essential for successful bipolar division of centrosome-amplified malignant cells and develop a potential selection biomarker to identify patients with tumors exhibiting centrosome amplification.

MTSS1 and SCAMP1 cooperate to prevent invasion in breast cancer

Cell-cell adhesions constitute the structural "glue" that retains cells together and contributes to tissue organisation and physiological function. The integrity of these structures is regulated by extracellular and intracellular signals and pathways that act on the functional units of cell adhesion such as the cell adhesion molecules/adhesion receptors, the extracellular matrix (ECM) proteins and the cytoplasmic plaque/peripheral membrane proteins. In advanced cancer, these regulatory pathways are dysregulated and lead to cell-cell adhesion disassembly, increased invasion and metastasis. The Metastasis suppressor protein 1 (MTSS1) plays a key role in the maintenance of cell-cell adhesions and its loss correlates with tumour progression in a variety of cancers. However, the mechanisms that regulate its function are not well-known. Using a system biology approach, we unravelled potential interacting partners of MTSS1. We found that the secretory carrier-associated membrane protein 1 (SCAMP1), a molecule involved in post-Golgi recycling pathways and in endosome cell membrane recycling, enhances Mtss1 anti-invasive function in HER2+/ER-/PR- breast cancer, by promoting its protein trafficking leading to elevated levels of RAC1-GTP and increased cell-cell adhesions. This was clinically tested in HER2 breast cancer tissue and shown that loss of MTSS1 and SCAMP1 correlates with reduced disease-specific survival. In summary, we provide evidence of the cooperative roles of MTSS1 and SCAMP1 in preventing HER2+/ER-/PR- breast cancer invasion and we show that the loss of Mtss1 and Scamp1 results in a more aggressive cancer cell phenotype.

TUFT1 interacts with RABGAP1 and regulates mTORC1 signaling

The mammalian target of rapamycin (mTOR) pathway is commonly activated in human cancers. The activity of mTOR complex 1 (mTORC1) signaling is supported by the intracellular positioning of cellular compartments and vesicle trafficking, regulated by Rab GTPases. Here we showed that tuftelin 1 (TUFT1) was involved in the activation of mTORC1 through modulating the Rab GTPase-regulated process. TUFT1 promoted tumor growth and metastasis. Consistently, the expression of TUFT1 correlated with poor prognosis in lung, breast and gastric cancers. Mechanistically, TUFT1 physically interacted with RABGAP1, thereby modulating intracellular lysosomal positioning and vesicular trafficking, and promoted mTORC1 signaling. In addition, expression of TUFT1 predicted sensitivity to perifosine, an alkylphospholipid that alters the composition of lipid rafts. Perifosine treatment altered the positioning and trafficking of cellular compartments to inhibit mTORC1. Our observations indicate that TUFT1 is a key regulator of the mTORC1 pathway and suggest that it is a promising therapeutic target or a biomarker for tumor progression.

Small change, big effect: Taking RAS by the tail through suppression of post-prenylation carboxylmethylation

Mutant RAS isoforms are the most common oncogenes affecting human cancers. After decades of effort in developing drugs targeting oncogenic RAS-driven cancers, we are still charting an unclear path. Despite recent developments exemplified by KRAS (G12C) inhibitors, direct targeting of mutant RAS remains a difficult endeavor. Inhibiting RAS function by targeting its post-translational prenylation processing has remained an important approach, especially with recent progress on the study of isoprenylcysteine carboxylmethyltransferase (ICMT), the unique enzyme for the last step of prenylation processing of RAS isoforms and other substrates. Inhibition of ICMT has shown efficacy both in vitro and in vivo in RAS-mutant cancer models. We will discuss the roles of RAS family of proteins in human cancers and the impact of post-prenylation carboxylmethylation on RAS driven tumorigenesis. In addition, we will review what is known of the molecular and cellular impact of ICMT inhibition on cancer cells that underlie its anti-proliferative and pro-apoptosis efficacy.

Glutaminolysis drives membrane trafficking to promote invasiveness of breast cancer cells

The role of glutaminolysis in providing metabolites to support tumour growth is well-established, but the involvement of glutamine metabolism in invasive processes is yet to be elucidated. Here we show that normal mammary epithelial cells consume glutamine, but do not secrete glutamate. Indeed, low levels of extracellular glutamate are necessary to maintain epithelial homoeostasis, and provision of glutamate drives disruption of epithelial morphology and promotes key characteristics of the invasive phenotype such as lumen-filling and basement membrane disruption. By contrast, primary cultures of invasive breast cancer cells convert glutamine to glutamate which is released from the cell through the system Xc- antiporter to activate a metabotropic glutamate receptor. This contributes to the intrinsic aggressiveness of these cells by upregulating Rab27-dependent recycling of the transmembrane matrix metalloprotease, MT1-MMP to promote invasive behaviour leading to basement membrane disruption. These data indicate that acquisition of the ability to release glutamate is a key watershed in disease aggressiveness.

Knockdown of Rab21 inhibits proliferation and induces apoptosis in human glioma cells

Background

Gliomas are commonly malignant tumors that arise in the human central nervous system and have a low overall five-year survival rate. Previous studies reported that several members of Rab GTPase family are involved in the development of glioma, and abnormal expression of Rab small GTPases is known to cause aberrant tumor cell behavior. In this study, we characterized the roles of Rab21 (Rab GTPase 21), a member of Rab GTPase family, in glioma cells.

Methods

The study involved downregulation of Rab21 in two glioma cell lines (T98G and U87) through transfection with specific-siRNA. Experiments using the MTT assay, cell cycle analysis, apoptosis assay, real-time PCR and western blot were performed to establish the expression levels of related genes.

Results

The results show that downregulation of Rab21 can significantly inhibit cell growth and remarkably induce cell apoptosis in T98G and U87 cell lines. Silencing Rab21 resulted in significantly increased expression of apoptosis-related proteins (caspase7, Bim and Bax) in glioma cells.

Conclusions

We inferred that Rab21 silencing can induce apoptosis and inhibit proliferation in human glioma cells, indicating that Rab21 might act as an oncogene and serve as a novel target for glioma therapy.

Decreased MALL expression negatively impacts colorectal cancer patient survival

The aim of the present study was to determine whether MALL expression is associated with colon cancer progression and patient survival. MALL mRNA expression was reduced in the tumor tissues of 70% of the colon cancer patients and 75% of the rectal cancer patients as compared to their normal tissues. MALL protein was also significantly reduced in the tumor tissues of colon cancer patients (P < 0.001). Increased LOH and methylation of MALL was observed in tumor tissues as compared to normal tissues. Reduced MALL expression was associated with vessin invasion, disease recurrence and metastasis or death (P ≤ 0.027). Furthermore, patients with MALL-negative tumors had significantly decreased overall survival (OS) and disease-free survival (DFS) (P < 0.008 and P < 0.011, respectively). Univariate analysis indicated that MALL expression was significantly associated with OS and DFS. Finally, overexpression of MALL suppressed HCT116 and SW480 cell proliferation and inhibited HCT116 migration. MALL may play a role in colorectal cancer progression as suppression of its expression in tumor tissues negatively impacts colorectal cancer patient survival. Further analyses are required to determine if reduced MALL expression is due to LOH and/or methylation.

A new role for human dyskerin in vesicular trafficking

Dyskerin is an essential, conserved, multifunctional protein found in the nucleolus, whose loss of function causes the rare genetic diseases X‐linked dyskeratosis congenita and Hoyeraal‐Hreidarsson syndrome. To further investigate the wide range of dyskerin's biological roles, we set up stable cell lines able to trigger inducible protein knockdown and allow a detailed analysis of the cascade of events occurring within a short time frame. We report that dyskerin depletion quickly induces cytoskeleton remodeling and significant alterations in endocytic Ras‐related protein Rab‐5A/Rab11 trafficking. These effects arise in different cell lines well before the onset of telomere shortening, which is widely considered the main cause of dyskerin‐related diseases. Given that vesicular trafficking affects many homeostatic and differentiative processes, these findings add novel insights into the molecular mechanisms underlining the pleiotropic manifestation of the dyskerin loss‐of‐function phenotype.

Rab GTPases in Immunity and Inflammation

Strict spatiotemporal control of trafficking events between organelles is critical for maintaining homeostasis and directing cellular responses. This regulation is particularly important in immune cells for mounting specialized immune defenses. By controlling the formation, transport and fusion of intracellular organelles, Rab GTPases serve as master regulators of membrane trafficking. In this review, we discuss the cellular and molecular mechanisms by which Rab GTPases regulate immunity and inflammation.

Phosphorylation of Rab37 by protein kinase C alpha inhibits the exocytosis function and metastasis suppression activity of Rab37

We previously identified a novel Rab small GTPase protein, Rab37, which plays a critical role in regulating exocytosis of secreted glycoproteins, tissue inhibitor of metalloproteinases 1 (TIMP1) to suppress lung cancer metastasis. Patients with preserved Rab37 protein expression were associated with better prognosis. However, a significant number of the patients with preserved Rab37 expression showed poor survival. In addition, the molecular mechanism for the regulation of Rab37-mediated exocytosis remained to be further identified. Therefore, we investigated the molecular mechanism underlying the dysregulation of Rab37-mediated exocytosis and metastasis suppression. Here, we report a novel mechanism for Rab37 inactivation by phosphorylation. Lung cancer patients with preserved Rab37, low TIMP1, and high PKCα expression profile correlate with worse progression-free survival examined by Kaplan-Meier survival, suggesting that PKCα overexpression leads to dysfunction of Rab37. This PKCα-Rab37-TIMP1 expression profile predicts the poor outcome by multivariate Cox regression analysis. We also show that Rab37 is phosphorylated by protein kinase Cα (PKCα) at threonine 172 (T172), leading to attenuation of its GTP-bound state, and impairment of the Rab37-mediated exocytosis of TIMP1, and thus reduces its suppression activity on lung cancer cell motility. We further demonstrate that PKCα reduces vesicle colocalization of Rab37 and TIMP1, and therefore inhibits Rab37-mediated TIMP1 trafficking. Moreover, Phospho-mimetic aspartate substitution mutant T172D of Rab37 significantly promotes tumor metastasis in vivo. Our findings reveal a novel regulation of Rab37 activity by PKCα-mediated phosphorylation which inhibits exocytic transport of TIMP1 and thereby enhances lung tumor metastasis.

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.

Rab25 GTPase: Functional roles in cancer

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

Cytoplasmic fragment of CD147 generated by regulated intramembrane proteolysis contributes to HCC by promoting autophagy

Hepatocellular carcinoma (HCC) is one of the most lethal and prevalent cancers worldwide. CD147 (EMMPRIN or basigin) is a leading gene relating to hepatocarcinogenesis and metastasis, and is detected in transmembrane, exosome or circulating forms in HCC patients. The endosome recycling of CD147 further enhances the function of this oncoprotein from a dynamic perspective. However, previous studies about CD147 mainly focused on one separate form, and little attention has been paid to how the different forms of tumor-derived CD147 changes. Moreover, uncovering the roles of the residual C-terminal portion of CD147 after shedding is inevitable to fully understand CD147 promoting tumor progression. In this study, we discovered that under low-cholesterol condition, CD147 endocytosis is inhibited but its shedding mediated by ADAM10 is enhanced. Further procession of residual CD147 in the lysosome produces nuclear-localized CD147-ICD (intracellular domain of CD147), which contributes to autophagy through NF-κB–TRAIL–caspase8–ATG3 axis. As autophagy endows cancer cells with increased adaptability to chemotherapy, and HAb 18 (a specific antibody targeting CD147) inhibits CD147 shedding and sequential CD147-ICD enhances autophagy, we found the combination of HAb 18 and cisplatin exhibited marked antitumor efficiency.

Autophagy-Dependent Shuttling of TBC1D5 Controls Plasma Membrane Translocation of GLUT1 and Glucose Uptake

Autophagy traditionally sustains metabolism in stressed cells by promoting intracellular catabolism and nutrient recycling. Here, we demonstrate that in response to stresses requiring increased glycolytic demand, the core autophagy machinery also facilitates glucose uptake and glycolytic flux by promoting cell surface expression of the glucose transporter GLUT1/Slc2a1. During metabolic stress, LC3⁺ autophagic compartments bind and sequester the RabGAP protein TBC1D5 away from its inhibitory interactions with the retromer complex, thereby enabling retromer recruitment to endosome membranes and GLUT1 plasma membrane translocation. In contrast, TBC1D5 inhibitory interactions with the retromer are maintained in autophagy-deficient cells, leading to GLUT1 mis-sorting into endolysosomal compartments. Furthermore, TBC1D5 depletion in autophagy-deficient cells rescues retromer recruitment to endosomal membranes and GLUT1 surface recycling. Hence, TBC1D5 shuttling to autophagosomes during metabolic stress facilitates retromer-dependent GLUT1 trafficking. Overall, our results illuminate key interconnections between the autophagy and endosomal pathways dictating GLUT1 trafficking and extracellular nutrient uptake.

Characterization of Laminin Binding Integrin Internalization in Prostate Cancer Cells

Laminin binding integrins α6 (CD49f) and α3 (CD49c) are persistently but differentially expressed in prostate cancer (PCa). Integrin internalization is an important determinant of their cell surface expression and function. Using flow cytometry, and first order kinetic modeling, we quantitated the intrinsic internalization rates of integrin subunits in a single cycle of internalization. In PCa cell line DU145, α6 integrin internalized with a rate constant (kactual ) of 3.25 min-1 , threefold faster than α3 integrin (1.0 min-1 ), 1.5-fold faster than the vitronectin binding αv integrin (CD51) (2.2 min-1 ), and significantly slower than the unrelated transferrin receptor (CD71) (15 min-1 ). Silencing of α3 integrin protein expression in DU145, PC3, and PC3B1 cells resulted in up to a 1.71-fold increase in kactual for α6 integrin. The internalized α6 integrin was targeted to early endosomes but not to lamp1 vesicles. Depletion of α3 integrin expression resulted in redistribution of α6β4 integrin to an observed cell-cell staining pattern that is consistent with a suprabasal distribution observed in epidermis and early PIN lesions in PCa. Depletion of α3 integrin increased cell migration by 1.8-fold, which was dependent on α6β1 integrin. Silencing of α6 integrin expression however, had no significant effect on the kactual of α3 integrin or its distribution in early endosomes. These results indicate that α3 and α6 integrins have significantly different internalization kinetics and that coordination exists between them for internalization. J. Cell. Biochem. 118: 1038-1049, 2017. © 2016 Wiley Periodicals, Inc.

Rab22a enhances CD147 recycling and is required for lung cancer cell migration and invasion

Rab22a is a member of the Ras-related small GTPase family, which plays a key role in regulating the recycling of cargo proteins entering cells through clathrin-independent endocytosis (CIE). Rab22a is overexpressed in different cancer types, including liver cancer, malignant melanoma, ovarian cancer and osteosarcoma. However, its oncogenic role remains unknown. In this study, we found that silencing of Rab22a suppressed the migration and invasion of lung cancer cells. Furthermore, Rab22a interacts with CD147, and knockdown of Rab22a blocks CD147 recycling and promotes CD147 degradation. Taken together, our findings indicate that Rab22a enhances recycling of CD147, which is required for lung cancer cell migration and invasion,and targeting CD147 recycling may be a rational strategy for lung cancer therapy.

Phosphorylation of Rab-coupling protein by LMTK3 controls Rab14-dependent EphA2 trafficking to promote cell:cell repulsion

The Rab GTPase effector, Rab-coupling protein (RCP) is known to promote invasive behaviour in vitro by controlling integrin and receptor tyrosine kinase (RTK) trafficking, but how RCP influences metastasis in vivo is unclear. Here we identify an RTK of the Eph family, EphA2, to be a cargo of an RCP-regulated endocytic pathway which controls cell:cell repulsion and metastasis in vivo. Phosphorylation of RCP at Ser435 by Lemur tyrosine kinase-3 (LMTK3) and of EphA2 at Ser897 by Akt are both necessary to promote Rab14-dependent (and Rab11-independent) trafficking of EphA2 which generates cell:cell repulsion events that drive tumour cells apart. Genetic disruption of RCP or EphA2 opposes cell:cell repulsion and metastasis in an autochthonous mouse model of pancreatic adenocarcinoma-whereas conditional knockout of another RCP cargo, α5 integrin, does not suppress pancreatic cancer metastasis-indicating a role for RCP-dependent trafficking of an Eph receptor to drive tumour dissemination in vivo.

A proteomic approach to identify endosomal cargoes controlling cancer invasiveness

We have previously shown that Rab17, a small GTPase associated with epithelial polarity, is specifically suppressed by ERK2 (also known as MAPK1) signalling to promote an invasive phenotype. However, the mechanisms through which Rab17 loss permits invasiveness, and the endosomal cargoes that are responsible for mediating this, are unknown. Using quantitative mass spectrometry-based proteomics, we have found that knockdown of Rab17 leads to a highly selective reduction in the cellular levels of a v-SNARE (Vamp8). Moreover, proteomics and immunofluorescence indicate that Vamp8 is associated with Rab17 at late endosomes. Reduced levels of Vamp8 promote transition between ductal carcinoma in situ (DCIS) and a more invasive phenotype. We developed an unbiased proteomic approach to elucidate the complement of receptors that redistributes between endosomes and the plasma membrane, and have pin-pointed neuropilin-2 (NRP2) as a key pro-invasive cargo of Rab17- and Vamp8-regulated trafficking. Indeed, reduced Rab17 or Vamp8 levels lead to increased mobilisation of NRP2-containing late endosomes and upregulated cell surface expression of NRP2. Finally, we show that NRP2 is required for the basement membrane disruption that accompanies the transition between DCIS and a more invasive phenotype.

Epithelial-to-mesenchymal transition drives a pro-metastatic Golgi compaction process through scaffolding protein PAQR11

Tumor cells gain metastatic capacity through a Golgi phosphoprotein 3-dependent (GOLPH3-dependent) Golgi membrane dispersal process that drives the budding and transport of secretory vesicles. Whether Golgi dispersal underlies the pro-metastatic vesicular trafficking that is associated with epithelial-to-mesenchymal transition (EMT) remains unclear. Here, we have shown that, rather than causing Golgi dispersal, EMT led to the formation of compact Golgi organelles with improved ribbon linking and cisternal stacking. Ectopic expression of the EMT-activating transcription factor ZEB1 stimulated Golgi compaction and relieved microRNA-mediated repression of the Golgi scaffolding protein PAQR11. Depletion of PAQR11 dispersed Golgi organelles and impaired anterograde vesicle transport to the plasma membrane as well as retrograde vesicle tethering to the Golgi. The N-terminal scaffolding domain of PAQR11 was associated with key regulators of Golgi compaction and vesicle transport in pull-down assays and was required to reconstitute Golgi compaction in PAQR11-deficient tumor cells. Finally, high PAQR11 levels were correlated with EMT and shorter survival in human cancers, and PAQR11 was found to be essential for tumor cell migration and metastasis in EMT-driven lung adenocarcinoma models. We conclude that EMT initiates a PAQR11-mediated Golgi compaction process that drives metastasis.

Adapt, Recycle, and Move on: Proteostasis and Trafficking Mechanisms in Melanoma

Melanoma has emerged as a paradigm of a highly aggressive and plastic cancer, capable to co-opt the tumor stroma in order to adapt to the hostile microenvironment, suppress immunosurveillance mechanisms, and disseminate. In particular, oncogene- and aneuploidy-driven dysregulations of proteostasis in melanoma cells impose a rewiring of central proteostatic processes, such as the heat shock and unfolded protein responses, autophagy, and the endo-lysosomal system, to avoid proteotoxicity. Research over the past decade has indicated that alterations in key nodes of these proteostasis pathways act in conjunction with crucial oncogenic drivers to increase intrinsic adaptations of melanoma cells against proteotoxic stress, modulate the high metabolic demand of these cancer cells and the interface with other stromal cells, through the heightened release of soluble factors or exosomes. Here, we overview and discuss how key proteostasis pathways and vesicular trafficking mechanisms are turned into vital conduits of melanoma progression, by supporting cancer cell's adaptation to the microenvironment, limiting or modulating the ability to respond to therapy and fueling melanoma dissemination.

Dominant Suppression of β1 Integrin by Ectopic CD98-ICD Inhibits Hepatocellular Carcinoma Progression

Hepatocellular carcinoma (HCC) is currently the third most common cause of cancer-related death in the Asia-Pacific region. Our previous work showed that knockdown of CD98 significantly inhibits malignant HCC cell phenotypes in vitro and in vivo. The level of CD98 in the membrane is tightly regulated to mediate complex processes associated with cell–cell communication and intracellular signaling. In addition, the intracellular domain of CD98 (CD98-ICD) seems to be of vital importance for recycling CD98 to the membrane after it is endocytosed. The intracellular and transmembrane domains of CD98 associate with β-integrins (primarily β1 but also β3), and this association is essential for CD98 mediation of integrin-like signaling and complements dominant suppression of β1-integrin. We speculated that isolated CD98-ICD would similarly suppress β1-integrin activation and inhibit the malignant behaviors of cancer cells. In particular, the exact role of CD98-ICD has not been studied independently in HCC. In this study, we found that ectopic expression of CD98-ICD inhibited the malignant phenotypes of HCC cells, and the mechanism possibly involves β1-integrin suppression. Moreover, the expression levels of CD98, β1-integrin-A (the activated form of β1-integrin) and Ki-67 were significantly increased in HCC tissues relative to those of normal liver tissues. Therefore, our preliminary study indicates that ectopic CD98-ICD has an inhibitory role in the malignant development of HCC, and shows that CD98-ICD acts as a dominant negative mutant of CD98 that attenuates β1-integrin activation. CD98-ICD may emerge as a promising candidate for antitumor treatment.