Transmembrane Domain-containing Protein Research Articles

Current advancements in PD-L1 modulation by CMTM6 in malignant tumors

Abstract The CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6), a member of the chemokine-like factor superfamily, binds to programmed death-ligand 1 (PD-L1) on the cell membrane, thereby impeding PD-L1’s lysosomal degradation and sustaining its expression. In recent years, extensive studies on PD-L1 have provided insights into its function as an immunepoint inhibitor involved in tumor cell immune evasion. The specific interaction between CMTM6 and PD-L1 suggests a potential role in tumor cell immune evasion and suppression, potentially offering a novel therapeutic target for cancer immunotherapy. Currently, the research on CMTM6 and PD-L1 in diverse tumors and diseases is limited, but their significant roles are indicated. This article provides an overview of the impact of CMTM6 on the immune microenvironment in different types of cancer (such as lung cancer, breast cancer, and liver cancer), and summarizes the effects of CMTM6 on the occurrence and development of various tumors.

CMTM6 mediates the Warburg effect and promotes the liver metastasis of colorectal cancer

Liver metastasis of colorectal cancer (CRC) is a leading cause of death among cancer patients. The overexpression of glucose transporter 1 (Glut1) and enhanced glucose uptake that are associated with the Warburg effect are frequently observed in CRC liver metastases, but the underlying mechanisms remain poorly understood. CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6) regulates the intracellular trafficking of programmed death-ligand-1 (PD-L1); therefore, we investigated whether CMTM6 regulates Glut1 trafficking and the Warburg effect in CRC cells. We found that knocking down of CMTM6 by shRNA induced the lysosomal degradation of Glut1, decreased glucose uptake and glycolysis in CRC cells, and suppressed subcutaneous CRC growth in nude mice and liver metastasis in C57BL/6 mice. Mechanistically, CMTM6 forms a complex with Glut1 and Rab11 in the endosomes of CRC cells, and this complex is required for the Rab11-dependent transport of Glut1 to the plasma membrane and for the protection of Glut1 from lysosomal degradation. Multiomics revealed global transcriptomic changes in CMTM6-knockdown CRC cells that affected the transcriptomes of adjacent cancer-associated fibroblasts from CRC liver metastases. As a result of these transcriptomic changes, CMTM6-knockdown CRC cells exhibited a defect in the G2-to-M phase transition, reduced secretion of 60 cytokines/chemokines, and inability to recruit cancer-associated fibroblasts to support an immunosuppressive CRC liver metastasis microenvironment. Analysis of TCGA data confirmed that CMTM6 expression was increased in CRC patients and that elevated CMTM6 expression was associated with worse patient survival. Together, our data suggest that CMTM6 plays multiple roles in regulating the Warburg effect, transcriptome, and liver metastasis of CRC.

MIF-Modulated Spinal Proteins Associated with Persistent Bladder Pain: A Proteomics Study.

Bladder pain is a prominent symptom in Interstitial Cystitis/Bladder Pain Syndrome (IC/BPS). We studied spinal mechanisms of bladder pain in mice using a model where repeated activation of intravesical Protease Activated Receptor-4 (PAR4) results in persistent bladder hyperalgesia (BHA) with little or no bladder inflammation. Persistent BHA is mediated by spinal macrophage migration inhibitory factor (MIF), and is associated with changes in lumbosacral proteomics. We investigated the contribution of individual spinal MIF receptors to persistent bladder pain as well as the spinal proteomics changes associated with relief of persistent BHA by spinal MIF antagonism. Female mice with persistent BHA received either intrathecal (i.t.) MIF monoclonal antibodies (mAb) or mouse IgG1 (isotype control antibody). MIF antagonism temporarily reversed persistent BHA (peak effect: 2 h), while control IgG1 had no effect. Moreover, i.t. antagonism of the MIF receptors CD74 and C-X-C chemokine receptor type 4 (CXCR4) partially reversed persistent BHA. For proteomics experiments, four separate groups of mice received either repeated intravesical scrambled peptide and sham i.t. injection (control, no pain group) or repeated intravesical PAR4 and: sham i.t.; isotype IgG1 i.t. (15 μg); or MIF mAb (15 μg). L6-S1 spinal segments were excised 2 h post-injection and examined for proteomics changes using LC-MS/MS. Unbiased proteomics analysis identified and relatively quantified 6739 proteins. We selected proteins that showed significant changes compared to control (no pain group) after intravesical PAR4 (sham or IgG i.t. treatment) and showed no significant change after i.t. MIF antagonism. Six proteins decreased during persistent BHA (V-set transmembrane domain-containing protein 2-like confirmed by immunohistochemistry), while two proteins increased. Spinal MIF antagonism reversed protein changes. Therefore, spinal MIF and MIF receptors mediate persistent BHA and changes in specific spinal proteins. These novel MIF-modulated spinal proteins represent possible new targets to disrupt spinal mechanisms that mediate persistent bladder pain.

Differential Expression of CKLF-like MARVEL Transmembrane Domain-Containing Protein 6 and Programmed Cell Death Ligand 1 as Prognostic Biomarkers in Upper Tract Urothelial Carcinoma.

Upper tract urothelial carcinoma (UTUC) accounts for 5-10% of all UCs. Immune checkpoint inhibitors (ICIs) have been established for UCs. The prognostic and predictive potential of programmed cell death ligand 1 (PD-L1) expression to stratify patients benefiting from ICIs is not fully understood, and additional markers influencing the impact of PD-L1-mediated ICI response are needed. Previously, the chemokine-like MARVEL transmembrane domain-containing protein 6 (CMTM6) was identified as a positive regulator of PD-L1. Our aim was to investigate the expression profiles and impact of PD-L1 and CMTM6 protein status on the prognostic parameters and survival of UTUC patients. In this retrospective study, the combined positive score (CPS), tumor proportion score (TPS), and immune cell score (ICS) for PD-L1 and CMTM6 were determined. High PD-L1 CPS, ICS, and TPS were found in 77.4%, 58.3%, and 45.2% of cases, and high CMTM6 CPS, ICS, and TPS were seen in 52.5%, 51.5%, and 55.5% of cases, respectively. The scores of both markers had a significant positive correlation. High PD-L1 and CMTM6 expression was coupled with higher pT status, WHO grade, necrosis, and metastasis (p < 0.05, respectively). In the univariate survival analysis, patients with a PD-L1 ICS high and higher degree of intratumoral inflammation showed significantly longer overall survival. Compared to other studies on UC, our study shows a substantially higher rate of PD-L1-positive tumors. CMTM6 was associated with more aggressive tumors.

A CUG-initiated CATSPERθ functions in the CatSper channel assembly and serves as a checkpoint for flagellar trafficking

Calcium signaling is critical for successful fertilization. In spermatozoa, calcium influx into the sperm flagella mediated by the sperm-specific CatSper calcium channel is necessary for hyperactivated motility and male fertility. CatSper is a macromolecular complex and is repeatedly arranged in zigzag rows within four linear nanodomains along the sperm flagella. Here, we report that the Tmem249-encoded transmembrane (TM) domain-containing protein, CATSPERθ is essential for the CatSper channel assembly during sperm tail formation. CATSPERθ facilitates the channel assembly by serving as a scaffold for a pore-forming subunit CATSPER4. CATSPERθ is specifically localized at the interface of a CatSper dimer and can self-interact, suggesting its potential role in CatSper dimer formation. Male mice lacking CATSPERθ are infertile because the sperm lack the entire CatSper channel from sperm flagella, rendering sperm unable to hyperactivate, regardless of their normal expression in the testis. In contrast, genetic abrogation of any of the other CatSper TM subunits results in loss of CATSPERθ protein in the spermatid cells during spermatogenesis. CATSPERθ might act as a checkpoint for the properly assembled CatSper channel complex to traffic to sperm flagella. This study provides insights into the CatSper channel assembly and elucidates the physiological role of CATSPERθ in sperm motility and male fertility.

Decreased TMIGD1 aggravates colitis and intestinal barrier dysfunction via the BANF1-NF-κB pathway in Crohn’s disease

BackgroundDisrupted intestinal epithelial barrier is one of the major causes of Crohn’s disease (CD). Novel molecular targets for intestinal epithelial barrier are essential to treatment of CD. Transmembrane and immunoglobulin domain-containing protein 1 (TMIGD1) is an adhesion molecule that regulates cell adhesion, migration, and enterocyte differentiation. However, the function and mechanism of TMIGD1 in CD and intestinal epithelial barrier has rarely been studied. Furthermore, the association between TMIGD1 and the clinical features of CD remains unclear.MethodsTranscriptome analysis on colonic mucosa from CD patients and healthy individuals were performed to identify dysregulated genes. Multi-omics integration of the 1000IBD cohort including genomics, transcriptomics of intestinal biopsies, and serum proteomics identified the association between genes and characteristics of CD. Inflammation was assessed by cytokine production in cell lines, organoids and intestinal-specific Tmigd1 knockout (Tmigd1INT-KO) mice. Epithelial barrier integrity was evaluated by trans-epithelium electrical resistance (TEER), paracellular permeability, and apical junction complex (AJC) expression. Co-immunoprecipitation, GST pull-down assays, mass spectrometry, proteomics, and transcriptome analysis were used to explore downstream mechanisms.ResultsMulti-omics integration suggested that TMIGD1 was negatively associated with inflammatory characteristics of CD. TMIGD1 was downregulated in inflamed intestinal mucosa of patients with CD and mice colitis models. Tmigd1INT-KO mice were more susceptible to chemically induced colitis. In epithelial cell lines and colonic organoids, TMIGD1 knockdown caused impaired intestinal barrier integrity evidenced by increased paracellular permeability and reduced TEER and AJC expression. TMIGD1 knockdown in intestinal epithelial cells also induced pro-inflammatory cytokine production. Mechanistically, TMIGD1 directly interacted with cytoplasmic BAF nuclear assembly factor 1 (BANF1) to inhibit NF-κB activation. Exogenous expression of TMIGD1 and BANF1 restored intestinal barrier function and inhibited inflammation in vitro and in vivo. TMIGD1 expression predicted response to anti-TNF treatment in patients with CD.ConclusionsOur study demonstrated that TMIGD1 maintained intestinal barrier integrity and inactivated inflammation, and was therefore a potential therapeutic target for CD.

Proteomic characterization of acute kidney injury in patients hospitalized with SARS-CoV2 infection

BackgroundAcute kidney injury (AKI) is a known complication of COVID-19 and is associated with an increased risk of in-hospital mortality. Unbiased proteomics using biological specimens can lead to improved risk stratification and discover pathophysiological mechanisms.MethodsUsing measurements of ~4000 plasma proteins in two cohorts of patients hospitalized with COVID-19, we discovered and validated markers of COVID-associated AKI (stage 2 or 3) and long-term kidney dysfunction. In the discovery cohort (N = 437), we identified 413 higher plasma abundances of protein targets and 30 lower plasma abundances of protein targets associated with COVID-AKI (adjusted p < 0.05). Of these, 62 proteins were validated in an external cohort (p < 0.05, N = 261).ResultsWe demonstrate that COVID-AKI is associated with increased markers of tubular injury (NGAL) and myocardial injury. Using estimated glomerular filtration (eGFR) measurements taken after discharge, we also find that 25 of the 62 AKI-associated proteins are significantly associated with decreased post-discharge eGFR (adjusted p < 0.05). Proteins most strongly associated with decreased post-discharge eGFR included desmocollin-2, trefoil factor 3, transmembrane emp24 domain-containing protein 10, and cystatin-C indicating tubular dysfunction and injury.ConclusionsUsing clinical and proteomic data, our results suggest that while both acute and long-term COVID-associated kidney dysfunction are associated with markers of tubular dysfunction, AKI is driven by a largely multifactorial process involving hemodynamic instability and myocardial damage.

VSTM2L contributes to anoikis resistance and acts as a novel biomarker for metastasis and clinical outcome in ovarian cancer

The majority of patients are diagnosed when ovarian cancer (OC) has metastasized, making surgery and chemotherapy less effective. Thus, there is an urgent need to elucidate the mechanisms underlying metastasis and to further explore novel diagnostic biomarkers of OC metastasis. Here, we conducted a genome-wide CRISPR-Cas9 screen for anoikis resistance to identify key genes associated with OC metastasis. Further, bioinformatic analysis was performed using TCGA and GTEx datasets to explore the genes associated with OC progression and prognosis. After integrated analysis, the V-set and transmembrane domain-containing protein 2-like (VSTM2L) was identified as a crucial gene closely associated with OC metastasis, progression, and prognosis. Further validation using a patient-based cohort suggested that VSTM2L expression was significantly higher in metastatic lesions than in primary lesions. Subsequently, an in vitro assay showed that VSTM2L silencing increased SKOV3 cell death and hampered spheroid formation. Mechanistically, GSEA highlighted that epithelial-mesenchymal transition (EMT)-related pathways was positively associated with VSTM2L expression. Consistently, the validation based on the VSTM2L silence suggested the involvement of VSTM2L in EMT-related TGF-β and NF-κB signaling. Meanwhile, the addition of VSTM2L-containing medium did not provoke those signaling, indicating VSTM2L functions as an intracellular protein to activate TGF-β and NF-κB signaling. In summary, our study revealed that VSTM2L is a novel player involved in anoikis resistance and is a promising biomarker of OC metastasis and prognosis.

ELTD1 Review: New Regulator of Angiogenesis in Glioma.

Glioblastoma (GBM) is a severe brain cancer in which angiogenesis is controlled by G protein-coupled receptors (GPCRs), such as Epidermal Growth Factor Latrophilin and seven transmembrane domain-containing protein 1 (ELTD1), which are crucial for tumor progression. ELTD1 is an understudied GPCR with a broad expression profile in various tissues, including the human brain, especially in the cerebral cortex. It plays a significant role in angiogenesis and tumorigenesis and is regulated by interconnected VEGF and DLL4/Notch pathways. ELTD1 also modulates the JAK/STAT3/HIF-1α signaling axis, affecting the response of cells to low-oxygen conditions and promoting cell proliferation. However, their specific ligands and functional mechanisms remain unclear. ELTD1 expression is associated with different outcomes in various cancers. For example, in GBM, higher ELTD1 levels are linked to more mature and less leaky blood vessels, potentially enhancing drug delivery and therapeutic success. It also has divergent prognostic implications in renal, ovarian, and colorectal cancer. Additionally, ELTD1 overexpression in central nervous system endothelial cells suggests that it is a potential biomarker for multiple sclerosis. Therapeutically, blocking ELTD1 inhibits vessel formation, possibly slowing tumor growth. Initial therapies used polyclonal antibodies, but the shift has been towards more targeted monoclonal antibodies, particularly in preclinical glioma models. This review aimed to translate these insights into effective clinical treatments. However, several gaps remain in our knowledge regarding ELTD1 ligands and their potential involvement in other physiological or pathological processes that future research can address to elucidate the role of ELTD1 in cancer, through angiogenesis and other intracellular pathways.

An LRR domain-containing membrane protein gene in rotifer Brachionus plicatilis: Sequence feature, expression pattern, and ligands binding activity

Leucine-rich repeat (LRR) domains mediate multiple innate immune responses via protein-ligand and protein-protein interactions, but their exact roles in invertebrates are poorly understood. Herein, an LRR domain-containing transmembrane protein (BpLRRm) was identified in the rotifer Brachionus plicatilis. The 1069 bp BpLRRm nucleotide sequence contains a 942 bp open reading frame (ORF) encoding a 313 amino acid polypeptide with four LRR motifs harbouring the LXXLXXLXLXXNXLXXL motif, and a transmembrane domain. Treatment with 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) decreased BpLRRm mRNA levels at 3 h, but they increased thereafter and peaked at 12 h. Lipopolysaccharide (LPS) treatment first increased BpLRRm mRNA levels at 3 h, but levels returned to normal at 12 h, then increased and peaked at 24 h. Recombinant BpLRRm protein bound pathogen-related molecular patterns (PAMPs), including LPS, peptidoglycan (PGN), glucan (GLU) and polyinosinic-polycytidylic acid (poly IC), in a dose-dependent manner. Thus, BpLRRm might function as a pattern recognition receptor (PRR) in the innate immunity of B. plicatilis, and mediate responses to environmental pollution.

Suppression of Tumor or Host Intrinsic CMTM6 Drives Antitumor Cytotoxicity in a PD-L1-Independent Manner.

CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6) is known to be a regulator of membranal programmed death ligand 1 (PD-L1) stability and a factor associated with malignancy progression, but the effects and mechanisms of CMTM6 on tumor growth, as well as its potential as a target for therapy, are still largely unknown. Here, we show that CMTM6 expression increased with tumor progression in both patients and mice. Ablation of CMTM6 significantly reduced human and murine tumor growth in a manner dependent on T-cell immunity. Tumor CMTM6 suppression broke resistance to immune-checkpoint inhibitors and remodeled the tumor immune microenvironment, as specific antitumor cytotoxicity was enhanced and contributed primarily to tumor inhibition. Without the PD-1/PD-L1 axis, CMTM6 suppression still significantly dampened tumor growth dependent on cytotoxic cells. Furthermore, we identified that CMTM6 was widely expressed on immune cells. T-cell CMTM6 levels increased with sustained immune activation and intratumoral immune exhaustion and affected T cell-intrinsic PD-L1 levels. Host CMTM6 knockout significantly restrained tumor growth in a manner dependent on CD8+ T cells and not entirely dependent on PD-L1. Thus, we developed and evaluated the antitumor efficacy of CMTM6-targeting adeno-associated virus (AAV), which effectively mobilized antitumor immunity and could be combined with various antitumor drugs. Our findings reveal that both tumor and host CMTM6 are involved in antitumor immunity with or without the PD-1/PD-L1 axis and that gene therapy targeting CMTM6 is a promising strategy for cancer immunotherapy.

Promoting anti-tumor immunity by targeting TMUB1 to modulate PD-L1 polyubiquitination and glycosylation

Immune checkpoint blockade therapies targeting the PD-L1/PD-1 axis have demonstrated clear clinical benefits. Improved understanding of the underlying regulatory mechanisms might contribute new insights into immunotherapy. Here, we identify transmembrane and ubiquitin-like domain-containing protein 1 (TMUB1) as a modulator of PD-L1 post-translational modifications in tumor cells. Mechanistically, TMUB1 competes with HECT, UBA and WWE domain-containing protein 1 (HUWE1), a E3 ubiquitin ligase, to interact with PD-L1 and inhibit its polyubiquitination at K281 in the endoplasmic reticulum. Moreover, TMUB1 enhances PD-L1 N-glycosylation and stability by recruiting STT3A, thereby promoting PD-L1 maturation and tumor immune evasion. TMUB1 protein levels correlate with PD-L1 expression in human tumor tissue, with high expression being associated with poor patient survival rates. A synthetic peptide engineered to compete with TMUB1 significantly promotes antitumor immunity and suppresses tumor growth in mice. These findings identify TMUB1 as a promising immunotherapeutic target.

Abstract 10273: Proteomic Analysis of Chronic Kidney Disease (CKD) in Heart Failure With Preserved Ejection Fraction (HFpEF)

Introduction: CKD is highly prevalent in HFpEF and is associated with increased morbidity and mortality. The biologic correlates of CKD in HFpEF are not well understood. We conducted a plasma proteomics analysis to assess biologic pathways associated with CKD in HFpEF. Methods: We utilized biosamples from TOPCAT for de novo measurements of 4776 plasma proteins using the SomaScan (version 4) proteomic assay, among 218 participants enrolled in the Americas. Linear regression and pathway analyses were used to study the relationship of proteins and pathways to the estimated glomerular filtration rate (eGFR). All regression estimates are standardized (per unit increase in z score) to facilitate comparisons. Results: After correction for multiple comparisons, we identified 73 proteins associated with eGFR. The strongest positively associated proteins were contactin-4, contactin-1, laminin-2, tenascin-X, and neuropilin-2. Proteins with the strongest negative association were transmembrane emp24 domain-containing protein 10, desmocollin-2, beta-2-microglobulin, neutrophil gelatinase-associated lipocalin, and cystatin C ( Figure 1 ). Biologic pathways associated with eGFR included complement system, acute phase response signaling, apoptosis, lysosomal expression and regulation, inflammation, fibrosis, chondroitin and dermatan sulfate degradation, notch signaling, and gluconeogenesis ( Figure 2 ). Conclusions: Using a broad proteomics approach, we identified novel biomarkers and pathways associated with renal dysfunction in HFpEF. Further research is required to assess whether targeting these pathways can ameliorate renal dysfunction in HFpEF patients.

VSTM5 is a novel immune checkpoint that promotes oral tolerance of cell-mediated and antibody responses

The V-set and transmembrane domain-containing protein (VSTM) family is a newly discovered immunoglobulin (Ig) superfamily that shares structural similarities with the B7-like transmembrane proteins. Although most VSTM5 members have been reported to exert immune-related functions, VSTM5 has been described as a regulator of neuronal morphogenesis and migration in the brain. Based on its close phylogenetic relationship with two immune checkpoints, VISTA and TIGIT, we investigated the potential role of VSTM5 in T-cell immune responses. VSTM5.Ig inhibits T-cell proliferation and cytokine production, induces T-cell apoptosis, and promotes the generation of regulatory T cells (Tregs) in in vitro T-cell assays. VSTM5 also contributes to the maintenance of T-cell anergy in vitro. Similarly, serum VSTM5.Ig produced using a recombinant plasmid in ovalbumin (OVA)-immunized mice inhibits both naive and effector T-cell immune responses. In addition, VSTM5.Ig enhances oral tolerance of cell-mediated and antibody responses in OVA-fed mice by inducing Tregs and T-cell clonal deletion. Consequently, our findings suggest that VSTM5 is a novel immune checkpoint that could be used to improve the therapeutic efficacy of tolerance-based therapies for autoimmune diseases.

TMUB1 Correlated with Immune Infiltration Is a Prognostic Marker for Colorectal Cancer.

Background Transmembrane and ubiquitin-like domain-containing protein 1 (TMUB1) is overexpressed in a large number of liver and esophageal tumors. However, only a few reports on the clinical significance of TMUB1 in colorectal cancer (CRC) exist. Methods Here, we evaluated the clinical significance and potential biological role of TMUB1 using bioinformatics analysis. Univariate and multivariate analyses were performed to evaluate the relationship of TMUB1 with clinicopathological features. Gene set enrichment analysis (GSEA) was performed to identify the biological function of TMUB1, while any associations between the expression of TMUB1 and the infiltration of 24 immune cells were analyzed using simple-sample GSEA. Results TMUB1 was significantly overexpressed in CRC tissues compared with normal controls. The high expression of TMUB1 in CRC was associated with T stage, neotype, and residual tumor. Moreover, TMUB1 was identified as an independent factor of poor disease-free survival (DFS) and short overall survival (OS). GSEA demonstrated that TMUB1 was related to hypoxia, angiogenesis, adipogenesis, inflammatory response, IL6-JAK-STAT3 signaling, apoptosis, mitotic spindle, and IL2-STAT5 signaling. The expression of TMUB1 negatively correlated with the abundance of T helper cells, Tcm cells, macrophages, and Th2 cells, whereas it positively correlated with the abundance of several immune cell types, including CD56bright and CD56dim NK cells. Conclusions The high expression of TMUB1 is closely related to a poor prognosis in patients with CRC. TMUB1 may be a potential prognostic biomarker and be used for therapeutic approaches in CRC.

The mitosome of the anaerobic parasitic protist Entamoeba histolytica: A peculiar and minimalist mitochondrion-related organelle.

The simplest class of mitochondrion-related organelles (MROs) is the mitosome, an organelle present in a few anaerobic protozoan parasites such as Entamoeba histolytica, Giardia intestinalis, and Cryptosporidium parvum. E. histolytica causes amoebiasis in humans, deemed as one of the important, yet neglected tropical infections in the world. Much of the enigma of the E. histolytica mitosome circles around the obvious lack of a majority of known mitochondrial components and functions exhibited in other organisms. The identification of enzymes responsible for sulfate activation (AS, IPP, and APSK) and a number of lineage-specific proteins such as the outer membrane beta-barrel protein (MBOMP30), and transmembrane domain-containing proteins that bind to various organellar proteins (ETMP1, ETMP30, EHI_170120, and EHI_099350) showcased the remarkable divergence of this organelle compared to the other MROs of anaerobic protozoa. Here, we summarize the findings regarding the biology of the mitosomes in E. histolytica, from their discovery up to the present understanding of its roles and interactions. We also include current advances and future perspectives on the biology, biochemistry, and evolution of the mitosomes of E. histolytica.

The Role of TMIGD1 as a Tumor Suppressor in Colorectal Cancer.

Background: Colorectal cancer (CRC) is one of the leading causes of cancer-related death, and up to 50% of individuals will suffer relapse. Although transmembrane and immunoglobulin domain-containing protein 1 (TMIGD1) was found to be a protective factor in several renal and intestinal diseases, the specific role of TMIGD1 in CRC remains unclear. Objective: To determine the tumor suppressor TMIGD1 expression and its function in inhibiting CRC. Methods: We analyzed three Gene Expression Omnibus (GEO) datasets through the GEO2R online tool to obtain the set of differentially expressed genes (DEGs) between CRC and normal tissues, and further analyzed the TMIGD1 gene's expression in databases. Real-time quantitative polymerase chain reaction and western blot assays were used to investigate expression of TMIGD1. Transwell and wound healing assays were performed to detect the migration and invasion ability. Cell Counting Kit-8 (CCK-8) and colony formation assays were used to evaluate cell proliferation. In vivo studies were conducted to illustrate the tumorigenicity. Results: We found that the TMIGD1 gene is one of the highly downregulated genes in CRC through bioinformatic analysis. We also showed that downregulation of TMIGD1 is associated with poor overall survival rate of CRC based on The Cancer Genome Atlas (TCGA) databases. In addition, we showed that overexpression of TMIGD1 protein significantly impaired the metastasis and proliferation ability of the CRC cells. Finally, TMIGD1 also repressed subcutaneous tumorigenesis of CRC cells in vivo. Conclusion: Our findings indicate that downregulation of TMIGD1 may promote CRC progression and invasion. Therefore, TMIGD1 may serve as a biomarker for CRC prognoses.

A gold revision of the Golgi Dynamics (GOLD) domain structure and associated cell functionalities.

The classical secretory pathway is the key membrane-based delivery system in eukaryotic cells. Several families of proteins involved in the secretory pathway, with functionalities going from cargo sorting receptors to the maintenance and dynamics of secretory organelles, share soluble globular domains predicted to mediate protein-protein interactions. One of them is the 'Golgi Dynamics' (GOLD) domain, named after its strong association with the Golgi apparatus. There are many GOLD-containing protein families, such as the transmembrane emp24 domain-containing proteins (TMED/p24 family), animal SEC14-like proteins, human Golgi resident protein ACBD3, a splice variant of TICAM2 called TRAM with GOLD domain, and FYCO1. Here, we critically review the state-of-the-art knowledge of the structures and functions of the main representatives of GOLD-containing proteins in vertebrates. We provide the first unified description of the GOLD domain structure across different families since the first high-resolution structure was determined. With a brand-new update on the definition of the GOLD domain, we also discuss how its tertiary structure fits the β-sandwich-like fold map and give exciting new directions for forthcoming studies.

PD-L1 promotes myofibroblastic activation of hepatic stellate cells by distinct mechanisms selective for TGF-β receptor I versus II.

SUMMARYIntrahepatic cholangiocarcinoma (ICC) contains abundant myofibroblasts derived from hepatic stellate cells (HSCs) through an activation process mediated by TGF-β. To determine the role of programmed death-ligand 1 (PD-L1) in myofibroblastic activation of HSCs, we disrupted PD-L1 of HSCs by shRNA or anti-PD-L1 antibody. We find that PD-L1, produced by HSCs, is required for HSC activation by stabilizing TGF-β receptors I (TβRI) and II (TβRII). While the extracellular domain of PD-L1 (amino acids 19–238) targets TβRII protein to the plasma membrane and protects it from lysosomal degradation, a C-terminal 260-RLRKGR-265 motif on PD-L1 protects TβRI mRNA from degradation by the RNA exosome complex. PD-L1 is required for HSC expression of tumor-promoting factors, and targeting HSC PD-L1 by shRNA or Cre/loxP recombination suppresses HSC activation and ICC growth in mice. Thus, myofibroblast PD-L1 can modulate the tumor microenvironment and tumor growth by a mechanism independent of immune suppression.

CMTM6, a potential immunotherapy target.

The CKLF-like MARVEL transmembrane domain-containing protein 6 (CMTM6), which binds to the programmed death ligand 1 (PD-L1) and stabilizes the expression of PD-L1 on the cell surface, has been recently discovered as a novel regulator of PD-L1 expression in cancer. PD-L1 is an immune checkpoint inhibitory molecule that can mediate the immune escape of tumor cells in various tumors and has been studied intensively in recent years. In 2017, two articles simultaneously reported that CMTM6 can stabilize the expression of PD-L1 on the plasma membrane and prevent PD-L1 from being degraded by lysosomes; therefore, CMTM6 may play an important role in tumor cell immune escape and immunosuppression. At present, there are few studies on the relationship between the expression of CMTM6 and PD-L1 in different tumors and diseases. These studies together suggested that CMTM6 may be a potential novel immunotherapy target. In this review, we briefly describe the latest research progresses of CMTM6 in various cancers and other diseases.