Transmembrane BAX Inhibitor Motif-6 (TMBIM6) protects against cisplatin-induced testicular toxicity.

STUDY QUESTION: Is the Transmembrane BAX Inhibitor Motif-6 (TMBIM6) involved in the molecular mechanism by which cisplatin causes reproductive toxicity? SUMMARY ANSWER: TMBIM6 protects against cisplatin-induced testicular toxicity through up-regulation of heme oxygenase-1 (HO-1),-which maintains the levels of steroidogenic enzymes by decreaseing oxidative stress in the endoplasmic reticulum (ER). WHAT IS KNOWN ALREADY: Testosterone production is highly suppressed as a main complication of cisplatin (cis-diamminedichloroplatinum) anticancer therapy. STUDY DESIGN, SIZE, DURATION: Groups of seven wild type or Tmbim6 KO C57BL/6J mice were given a single i.p., injection of cisplatin (30 mg/kg body wt) and testis and serum were collected 3 days later. Tmbim6-lentivirus-mediated testicular expression-rescued KO mice were analyzed to confirm function was restored. Tmbim6-over expressing TM3 mouse Leydig cells were exposed to cisplatin in vitro. PARTICIPANTS/MATERIALS, SETTING, METHODS: After collection of the specimens serum testosterone level and testicular weight and structure were compared between the groups. Quantitative PCR, immunoblot, and assays for ROS, HO-1 activity and protein disulfide isomerase (PDI) carbonylation were performed. MAIN RESULTS AND THE ROLE OF CHANCE: Phospho protein kinase B (p-Akt), nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2), and its downstream gene product HO-1 and the levels of testosterone synthesis-associated enzymes, including steroidogenic acute regulatory protein (StAR), a rate limiting enzyme for testosterone production, were significantly expressed in the presence of Tmbim6 and maintained after cisplatin treament. Excessive post-translational oxidation of protein disulfide isomerase (PDI), altered folding capacitance and ROS accumulation, and ER stress were also decreased in the presence of Tmbim6. Higher levels of ER stress and protein hypercarbonylation were consistently observed in KO testis, compared with WT testis. In the Tmbim6 KO mice, lentivirus-mediated testicular expression of Tmbim6 rescued the above phenotypes. Furthermore, the protective role of Tmbim6 against testicular toxicity was consistently shown in Tmbim6-overexpressing TM3 Leydig cells (testosterone producing cells). We conclude that TMBIM6 protects against cisplatin-induced testicular toxicity by inducing HO-1 and enhancing ER folding capacitance. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: This study was performed using a short, 3-day cisplatin treatment condition. Therefore, the results need to be cautiously interpreted with regard to cisplatin-associated chronic toxicity. Moreover, to determine the clinical relevance of the role of TMBIM6, further studies in testicular cancer are needed. WIDER IMPLICATIONS OF THE FINDINGS: Cisplatin-associated ER stress and redox imbalance might be implicated as toxicity mechanisms associated with anticancer therapy. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the National Research Foundation of Korea (2015R1A2A1A13001849). The authors have no competing interests to disclose.

Compliance with Saliva Collection Protocol in Healthy Volunteers: Strategies for Managing Risk and Errors.

Salivary bioscience technologies such as electrophoresis are widely applied for diagnosing systemic health status. Diagnosis using a saliva sample has emerged as a preferred technique since the sample is easy to collect and the method is inexpensive and non-invasive. Salivary diagnostics have even been identified as potential substitutes for serum protein biomarkers. However, the optimal protocol for collecting saliva has not yet been established. In many scientific settings, such as randomized controlled trials, sampling and statistical errors often occur when handling samples from healthy volunteers. These errors can be due to the psychological behavior of the volunteers, subject nonadherence, questionnaire characteristics, collection methods, and/or sample processing. The purpose of the review presented here is to outline the strategies for managing the risk factors and to minimize the sampling errors during saliva collection in healthy volunteers.

Ixeris dentata Extract Increases Salivary Secretion through the Regulation of Endoplasmic Reticulum Stress in a Diabetes-Induced Xerostomia Rat Model.

This study aimed to investigate the molecular mechanism of diabetes mellitus (DM)-induced dry mouth and an application of natural products from Ixeris dentata (IXD), a recently suggested regulator of amylase secretion in salivary cells. Vehicle-treated or diabetic rats were orally treated with either water or an IXD extract for 10 days to observe the effect on salivary flow. We found that the IXD extract increased aquaporin 5 (AQP5) and alpha-amylase protein expression in the submandibular gland along with salivary flow rate. Similarly, the IXD extract and its purified compound increased amylase secretion in high glucose-exposed human salivary gland cells. Furthermore, increased endoplasmic reticulum stress response in the submandibular gland of diabetic rats was inhibited by treatment with the IXD extract, suggesting that IXD extract treatment improves the ER environment by increasing the protein folding capacity. Thus, pharmacological treatment with the IXD extract is suggested to relieve DM-induced dry mouth symptoms.

ß-Cell protection and antidiabetic activities of Crassocephalum crepidioides (Asteraceae) Benth. S. Moore extract against alloxan-induced oxidative stress via regulation of apoptosis and reactive oxygen species (ROS).

BACKGROUND: Medicinal plants are becoming more popular in the treatment of various diseases because of the adverse effects of the current therapy, especially antioxidant plant components such as phenols and flavonoids have a protective role against oxidative stress-induced degenerative diseases like diabetes. Thus, the purpose of this study was to investigate ß-cell protection and antidiabetic activities of Crassocephalum crepidioides (Asteraceae) Benth. S. Moore. METHOD: The in-vitro study was conducted by the pancreatic ß-cell culture and α-amylase inhibition technique which includes two methods, namely starch-iodine method and 3,5-dinitrosalicylic acid (DNSA) method. On the other hand, the in-vivo study was performed by oral glucose tolerance test (OGTT) method and alloxan-induced diabetes method by using Wistar albino rat. At the end pancreatic specimens were removed and processed for histopathological study. RESULT: The plant extract showed significant (*p < 0.05, **p < 0.01) effect on hyperglycemia as compared to standard (Gliclazide) in OGTT. The plant extract showed efficient protection activity of pancreatic ß-cell from cell death in INS-1 cell line by significantly reduced (*p < 0.05, **p < 0.01) the levels alloxan-induced apoptosis and intracellular reactive oxygen species (ROS) accumulation. In addition, the plant extract showed a significant (*p < 0.05, **p < 0.01) effect on hyperglycemia by increases in percent of ß-cells present in each islet (45% - 60%) compared to the diabetic group. CONCLUSION: The result showed that C. crepidioides had ß-cell protection and antidiabetic activities in pancreatic ß-cell culture and Wistar albino rat.

Polyphenolic Extract of Euphorbia supina Attenuates Manganese-Induced Neurotoxicity by Enhancing Antioxidant Activity through Regulation of ER Stress and ER Stress-Mediated Apoptosis.

Manganese (Mn) is an important trace element present in human body, which acts as an enzyme co-factor or activator in various metabolic reactions. While essential in trace amounts, excess levels of Mn in human brain can produce neurotoxicity, including idiopathic Parkinson's disease (PD)-like extrapyramidal manganism symptoms. This study aimed to investigate the protective role of polyphenolic extract of Euphorbia supina (PPEES) on Mn-induced neurotoxicity and the underlying mechanism in human neuroblastoma SKNMC cells and Sprague-Dawley (SD) male rat brain. PPEES possessed significant amount of total phenolic and flavonoid contents. PPEES also showed significant antioxidant activity in 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and reducing power capacity (RPC) assays. Our results showed that Mn treatment significantly reduced cell viability and increased lactate dehydrogenase (LDH) level, which was attenuated by PPEES pretreatment at 100 and 200 µg/mL. Additionally, PPEES pretreatment markedly attenuated Mn-induced antioxidant status alteration by resolving the ROS, MDA and GSH levels and SOD and CAT activities. PPEES pretreatment also significantly attenuated Mn-induced mitochondrial membrane potential (ΔΨm) and apoptosis. Meanwhile, PPEES pretreatment significantly reversed the Mn-induced alteration in the GRP78, GADD34, XBP-1, CHOP, Bcl-2, Bax and caspase-3 activities. Furthermore, administration of PPEES (100 and 200 mg/kg) to Mn exposed rats showed improvement of histopathological alteration in comparison to Mn-treated rats. Moreover, administration of PPEES to Mn exposed rats showed significant reduction of 8-OHdG and Bax immunoreactivity. The results suggest that PPEES treatment reduces Mn-induced oxidative stress and neuronal cell loss in SKNMC cells and in the rat brain. Therefore, PPEES may be considered as potential treat-ment in Mn-intoxicated patients.

Investigation of inherited noncoding genetic variation impacting the pharmacogenomics of childhood acute lymphoblastic leukemia treatment.

Defining genetic factors impacting chemotherapy failure can help to better predict response and identify drug resistance mechanisms. However, there is limited understanding of the contribution of inherited noncoding genetic variation on inter-individual differences in chemotherapy response in childhood acute lymphoblastic leukemia (ALL). Here we map inherited noncoding variants associated with treatment outcome and/or chemotherapeutic drug resistance to ALL cis-regulatory elements and investigate their gene regulatory potential and target gene connectivity using massively parallel reporter assays and three-dimensional chromatin looping assays, respectively. We identify 54 variants with transcriptional effects and high-confidence gene connectivity. Additionally, functional interrogation of the top variant, rs1247117, reveals changes in chromatin accessibility, PU.1 binding affinity and gene expression, and deletion of the genomic interval containing rs1247117 sensitizes cells to vincristine. Together, these data demonstrate that noncoding regulatory variants associated with diverse pharmacological traits harbor significant effects on allele-specific transcriptional activity and impact sensitivity to antileukemic agents.

Mutual antagonism between glucocorticoid and canonical Wnt signaling pathways in B-cell acute lymphoblastic leukemia.

Glucocorticoids (GCs; i.e., steroids) are important chemotherapeutic agents in the treatment of B-cell precursor acute lymphoblastic leukemia (B-ALL) and de novo GC resistance predicts relapse and poor clinical outcome in patients. Glucocorticoids induce B-ALL cell apoptosis through activation of glucocorticoid receptor (GR), a ligand-induced nuclear receptor transcription factor (TF). We previously identified disruptions to glucocorticoid receptor (GR)-bound cis -regulatory elements controlling TLE1 expression in GC-resistant primary B-ALL cells from patients. TLE1 is a GC-response gene up-regulated by steroids and functions as a canonical Wnt signaling repressor. To better understand the mechanistic relationship between GC signaling and canonical Wnt signaling, we performed diverse functional analyses that identified extensive crosstalk and mutual antagonism between these two signaling pathways in B-ALL. We determined that crosstalk and antagonism was driven by the binding of GR and the canonical Wnt signaling TFs LEF1 and TCF7L2 to overlapping sets of cis -regulatory elements associated with genes impacting cell death and cell proliferation, and was further accompanied by overlapping and opposing transcriptional programs. Our data additionally suggest that cis -regulatory disruptions at TLE1 are linked to GC resistance through a dampening of the GC response and GC-mediated apoptosis via enhanced canonical Wnt signaling. As a result of the extensive genomic and gene regulatory connectivity between these two signaling pathways, our data supports the importance of canonical Wnt signaling in mediating GC resistance in B-ALL.

Epigenomic mapping in B-cell acute lymphoblastic leukemia identifies transcriptional regulators and noncoding variants promoting distinct chromatin architectures.

B-cell lineage acute lymphoblastic leukemia (B-ALL) is comprised of diverse molecular subtypes and while transcriptional and DNA methylation profiling of B-ALL subtypes has been extensively examined, the accompanying chromatin landscape is not well characterized for many subtypes. We therefore mapped chromatin accessibility using ATAC-seq for 10 B-ALL molecular subtypes in primary ALL cells from 154 patients. Comparisons with B-cell progenitors identified candidate B-ALL cell-of-origin and AP-1-associated cis-regulatory rewiring in B-ALL. Cis-regulatory rewiring promoted B-ALL-specific gene regulatory networks impacting oncogenic signaling pathways that perturb normal B-cell development. We also identified that over 20% of B-ALL accessible chromatin sites exhibit strong subtype enrichment, with transcription factor (TF) footprint profiling identifying candidate TFs that maintain subtype-specific chromatin architectures. Over 9000 inherited genetic variants were further uncovered that contribute to variability in chromatin accessibility among individual patient samples. Overall, our data suggest that distinct chromatin architectures are driven by diverse TFs and inherited genetic variants which promote unique gene regulatory networks that contribute to transcriptional differences among B-ALL subtypes.

Functional investigation of inherited noncoding genetic variation impacting the pharmacogenomics of childhood acute lymphoblastic leukemia treatment.

Although acute lymphoblastic leukemia (ALL) is the most common childhood cancer, there is limited understanding of the contribution of inherited genetic variation on inter-individual differences in chemotherapy response. Defining genetic factors impacting therapy failure can help better predict response and identify drug resistance mechanisms. We therefore mapped inherited noncoding variants associated with chemotherapeutic drug resistance and/or treatment outcome to ALL cis-regulatory elements and investigated their gene regulatory potential and genomic connectivity using massively parallel reporter assays and promoter capture Hi-C, respectively. We identified 53 variants with reproducible allele-specific effects on transcription and high-confidence gene targets. Subsequent functional interrogation of the top variant (rs1247117) determined that it disrupted a PU.1 consensus motif and PU.1 binding affinity. Importantly, deletion of the genomic interval containing rs1247117 sensitized ALL cells to vincristine. Together, these data demonstrate that noncoding regulatory variation associated with diverse pharmacological traits harbor significant effects on allele-specific transcriptional activity and impact sensitivity to chemotherapeutic agents in ALL.

Epigenomic mapping reveals distinct B cell acute lymphoblastic leukemia chromatin architectures and regulators.

B cell lineage acute lymphoblastic leukemia (B-ALL) is composed of diverse molecular subtypes, and while transcriptional and DNA methylation profiling has been extensively examined, the chromatin landscape is not well characterized for many subtypes. We therefore mapped chromatin accessibility using ATAC-seq in primary B-ALL cells from 156 patients spanning ten molecular subtypes and present this dataset as a resource. Differential chromatin accessibility and transcription factor (TF) footprint profiling were employed and identified B-ALL cell of origin, TF-target gene interactions enriched in B-ALL, and key TFs associated with accessible chromatin sites preferentially active in B-ALL. We further identified over 20% of accessible chromatin sites exhibiting strong subtype enrichment and candidate TFs that maintain subtype-specific chromatin architectures. Over 9,000 genetic variants were uncovered, contributing to variability in chromatin accessibility among patient samples. Our data suggest that distinct chromatin architectures are driven by diverse TFs and inherited genetic variants that promote unique gene-regulatory networks.

Amino acid stress response genes promote L-asparaginase resistance in pediatric acute lymphoblastic leukemia.

Understanding the genomic and epigenetic mechanisms of drug resistance in pediatric acute lymphoblastic leukemia (ALL) is critical for further improvements in treatment outcomes. The role of transcriptomic response in conferring resistance to l-asparaginase (LASP) is poorly understood beyond asparagine synthetase (ASNS). We defined reproducible LASP response genes in LASP-resistant and LASP-sensitive ALL cell lines as well as primary leukemia samples from newly diagnosed patients. Defining target genes of the amino acid stress response-related transcription factor activating transcription factor 4 (ATF4) in ALL cell lines using chromatin immunoprecipitation sequencing (ChIP-seq) revealed 45% of genes that changed expression after LASP treatment were direct targets of the ATF4 transcription factor, and 34% of these genes harbored LASP-responsive ATF4 promoter binding events. SLC7A11 was found to be a response gene in cell lines and patient samples as well as a direct target of ATF4. SLC7A11 was also one of only 2.4% of LASP response genes with basal level gene expression that also correlated with LASP ex vivo resistance in primary leukemia cells. Experiments using chemical inhibition of SLC7A11 with sulfasalazine, gene overexpression, and partial gene knockout recapitulated LASP resistance or sensitivity in ALL cell lines. These findings show the importance of assessing changes in gene expression following treatment with an antileukemic agent for its association with drug resistance and highlight that many response genes may not differ in their basal expression in drug-resistant leukemia cells.

The aftermath of the interplay between the endoplasmic reticulum stress response and redox signaling.

The endoplasmic reticulum (ER) is an essential organelle of eukaryotic cells. Its main functions include protein synthesis, proper protein folding, protein modification, and the transportation of synthesized proteins. Any perturbations in ER function, such as increased demand for protein folding or the accumulation of unfolded or misfolded proteins in the ER lumen, lead to a stress response called the unfolded protein response (UPR). The primary aim of the UPR is to restore cellular homeostasis; however, it triggers apoptotic signaling during prolonged stress. The core mechanisms of the ER stress response, the failure to respond to cellular stress, and the final fate of the cell are not yet clear. Here, we discuss cellular fate during ER stress, cross talk between the ER and mitochondria and its significance, and conditions that can trigger ER stress response failure. We also describe how the redox environment affects the ER stress response, and vice versa, and the aftermath of the ER stress response, integrating a discussion on redox imbalance-induced ER stress response failure progressing to cell death and dynamic pathophysiological changes.

Isolation of amylase regulators from the leaves of Ixeridium dentatum.

Two new compounds, one sesquiterpene lactone (1) and one phenylethanoid tautomer (2), together with eleven known compounds (3-13) were isolated from the leaves of Ixeridium dentatum. Their structures were determined by extensive spectroscopic methods, including 1D-, 2D-NMR, and mass spectrometry. All compounds were evaluated for their amylase secretion activity in human salivary gland cells after treatment in 40 mM of high glucose. All compounds showed increased amylase secretion activity. Moreover, previously undescribed compounds (1-2), luteolin 7-O-ß-D-glucopyranoside (10), quercimeritrin (11), and quercetin 3-O-ß-D-xylopyranoside (13) exhibited significant amylase activity, which is comparable to the positive control.

TMBIM6 (transmembrane BAX inhibitor motif containing 6) enhances autophagy through regulation of lysosomal calcium.

Lysosomal Ca2+ contributes to macroautophagy/autophagy, an intracellular process for the degradation of cytoplasmic material and organelles in the lysosomes to protect cells against stress responses. TMBIM6 (transmembrane BAX inhibitor motif containing 6) is a Ca2+ channel-like protein known to regulate ER stress response and apoptosis. In this study, we examined the as yet unknown role of TMBIM6 in regulating lysosomal Ca2+ levels. The Ca2+ efflux from the ER through TMBIM6 was found to increase the resting lysosomal Ca2+ level, in which ITPR-independent regulation of Ca2+ status was observed. Further, TMBIM6 regulated the local release of Ca2+ through lysosomal MCOLN1/TRPML1 channels under nutrient starvation or MTOR inhibition. The local Ca2+ efflux through MCOLN1 channels was found to activate PPP3/calcineurin, triggering TFEB (transcription factor EB) nuclear translocation, autophagy induction, and lysosome biogenesis. Upon genetic inactivation of TMBIM6, lysosomal Ca2+ and the associated TFEB nuclear translocation were decreased. Furthermore, autophagy flux was significantly enhanced in the liver or kidney from starved Tmbim6+/+ mice compared with that in the counter tmbim6-/- mice. Together, our observations indicated that under stress conditions, TMBIM6 increases lysosomal Ca2+ release, leading to PPP3/calcineurin-mediated TFEB activation and subsequently enhanced autophagy. Thus, TMBIM6, an ER membrane protein, is suggested to be a lysosomal Ca2+ modulator that coordinates with autophagy to alleviate metabolism stress.Abbreviations: AVs: autophagic vacuoles; CEPIA: calcium-measuring organelle-entrapped protein indicator; ER: endoplasmic reticulum; GPN: glycyl-L-phenylalanine-beta-naphthylamide; ITPR/IP3R: inositol 1,4,5-trisphosphate receptor; LAMP1: lysosomal associated membrane protein 1; MCOLN/TRPML: mucolipin; MEF: mouse embryonic fibroblast; ML-SA1: mucolipin synthetic agonist 1; MTORC1: mechanistic target of rapamycin kinase complex 1; RPS6KB1: ribosomal protein S6 kinase B1; SQSTM1: sequestosome 1; TFEB: transcription factor EB; TKO: triple knockout; TMBIM6/BI-1: transmembrane BAX inhibitor motif containing 6.

TMBIM6 regulates redox-associated posttranslational modifications of IRE1α and ER stress response failure in aging mice and humans.

Age-associated persistent ER stress is the result of declining chaperone systems of the ER that reduces cellular functions, induces apoptosis, and leads to age-related diseases. This study investigated the previously unknown regulatory mechanism of TMBIM6 during age-associated hepatic abnormalities. Wild-type (WT) and the TMBIM6 knockout (TMBIM6-/-) mice liver, human liver samples from different age groups were used to demonstrate the effect of physiological aging on liver. For TMBIM6 rescue experiments, TMBIM6-/- old mice and stable human hepatic cell lines expressing TMBIM 6 were used to study the functional role of TMBIM6 on aging-associated steatosis and its associated mechanisms. In aging humans and mice, we observed declined expression of TMBIM6 and aberrant UPR expression, which were associated with high hepatic lipid accumulation. During aging, TMBIM6-deficient mice had increased senescence than their WT counterparts. We identified redox-mediated posttranslational modifications of IRE1α such as S-nitrosylation and sulfonation were higher in TMBIM6-deficient aging mice and humans, which impaired the ER stress response signaling. Sulfonation of IRE1α enhanced regulated IRE1α-dependent decay (RIDD) activity inducing TMBIM6 decay, whereas S-nitrosylation of IRE1α inhibited XBP1 splicing enhancing the cell death. Moreover, the degradation of miR-338-3p by strong IRE1α cleavage activity enhanced the expression of PTP1B, resulting in diminishing phosphorylation of PERK. The re-expression of TMBIM6 reduced IRE1α modifications, preserved ER homeostasis, reduced senescence and senescence-associated lipid accumulation in human hepatic cells and TMBIM6-depleted mice. S-nitrosylation or sulfonation of IRE1α and its controller, the TMBIM6, might be the potential therapeutic targets for maintaining ER homeostasis in aging and aging-associated liver diseases.

Chalcone suppresses tumor growth through NOX4-IRE1α sulfonation-RIDD-miR-23b axis.

Chalcone is a polyphenolic compound found abundantly in natural plant components. They have been acclaimed as potential antitumor compounds in multiple tumor cells. However, not much attention has been paid to elucidate its antitumor mechanism of action. Here, chalcone was demonstrated to trigger endoplasmic reticulum (ER) stress-induced apoptosis through sulfonation of IRE1α by ER-localized NADPH oxidase 4 (NOX4). IRE1α-sulfonation at a cysteine residue was shown to induce "regulated IRE1α-dependent decay" (RIDD) of mRNA rather than specific splicing of XBP1. The IRE1α sulfonation-induced RIDD degraded miR-23b, enhancing the expression of NOX4. The expression of NOX4 was also upregulated in breast, and prostate cancer tissue. In chalcone-administered mice in vivo, tumor growth was regressed by the consistent mechanisms "NOX4-IRE1α sulfonation-RIDD". Similarly, NOX4 activation and IRE1α sulfonation were also highly increased under severe ER stress conditions. Together, these findings suggest chalcone as a lead anticancer compound where it acts through NOX4-IRE1α-RIDD-miR-23b axis providing a promising vision of chalcone derivatives' anticancer mechanism.

Endoplasmic Reticulum (ER) Stress Response Failure in Diseases.

Recent work provides evidence for the new terminology, 'endoplasmic reticulum (ER) stress response or sensing failure', in relation to metabolic disease. We seek to identify and amass possible conditions of ER stress response failure in various metabolic and age-related pathogenesis, including obesity and diabetes.

TMBIM6/BI-1 contributes to cancer progression through assembly with mTORC2 and AKT activation.

Transmembrane B cell lymphoma 2-associated X protein inhibitor motif-containing (TMBIM) 6, a Ca2+ channel-like protein, is highly up-regulated in several cancer types. Here, we show that TMBIM6 is closely associated with survival in patients with cervical, breast, lung, and prostate cancer. TMBIM6 deletion or knockdown suppresses primary tumor growth. Further, mTORC2 activation is up-regulated by TMBIM6 and stimulates glycolysis, protein synthesis, and the expression of lipid synthesis genes and glycosylated proteins. Moreover, ER-leaky Ca2+ from TMBIM6, a unique characteristic, is shown to affect mTORC2 assembly and its association with ribosomes. In addition, we identify that the BIA compound, a potentialTMBIM6 antagonist, prevents TMBIM6 binding to mTORC2, decreases mTORC2 activity, and also regulates TMBIM6-leaky Ca2+, further suppressing tumor formation and progression in cancer xenograft models. This previously unknown signaling cascade in which mTORC2 activity is enhanced via the interaction with TMBIM6 provides potential therapeutic targets for various malignancies.

Expression of TMBIM6 in Cancers: The Involvement of Sp1 and PKC.

Transmembrane Bax Inhibitor Motif-containing 6 (TMBIM6) is upregulated in several cancer types and involved in the metastasis. Specific downregulation of TMBIM6 results in cancer cell death. However, the TMBIM6 gene transcriptional regulation in normal and cancer cells is least studied. Here, we identified the core promoter region (-133/+30 bp) sufficient for promoter activity of TMBIM6 gene. Reporter gene expression with mutations at transcription factor binding sites, EMSA, supershift, and ChIP assays demonstrated that Sp1 is an essential transcription factor for basal promoter activity of TMBIM6. The TMBIM6 mRNA expression was increased with Sp1 levels in a concentration dependent manner. Ablation of Sp1 through siRNA or inhibition with mithramycin-A reduced the TMBIM6 mRNA expression. We also found that the protein kinase-C activation stimulates promoter activity and endogenous TMBIM6 mRNA by 2- to 2.5-fold. Additionally, overexpression of active mutants of PKCι, PKCε, and PKCδ increased TMBIM6 expression by enhancing nuclear translocation of Sp1. Immunohistochemistry analyses confirmed that the expression levels of PKCι, Sp1, and TMBIM6 were correlated with one another in samples from human breast, prostate, and liver cancer patients. Altogether, this study suggests the involvement of Sp1 in basal transcription and PKC in the enhanced expression of TMBIM6 in cancer.

The imprint of salivary secretion in autoimmune disorders and related pathological conditions.

Xerostomia is a state of oral dryness associated with salivary gland dysfunction and is induced by stress, radiation and chemical therapy, various systemic and autoimmune diseases, and specific medications. Fluid secretion is interrupted by the stimulation of neurotransmitter-induced increase in cytosolic calcium ([Ca2+]i) in salivary gland acinar cells, prompting the mobilization of ion channels and their transporters. Salivary fluid and protein secretion are principally dependent on parasympathetic and sympathetic nerves. Various inflammatory cytokines allied with lymphocytic infiltration cause glandular damage and Sjogren's syndrome, an autoimmune exocrinopathy associated with hyposalivation. A defect in IP3Rs, a major calcium release channel, prompts inadequate agonist-induced [Ca2+]i in acinar cells and deters salivary flow. The store-operated calcium entry-mediated Ca2+ movement into the acini activates K+ and Cl- channels, which further opens a water channel protein, aquaporin-5, and triggers the release of fluid secretion from the salivary glands. The cellular mechanism of salivary gland dysfunction and hyposalivation has not yet been elucidated. In this review, we focused mainly on the proteins responsible for deficient saliva, the correlation between inflammation and salivation, autoimmune disorders and other ailments or complications associated with hyposalivation.