Displaying all 19 publications

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  1. Calreticulin and cancer
    Zamanian M, Veerakumarasivam A, Abdullah S, Rosli R
    Pathol Oncol Res, 2013 Apr;19(2):149-54.
    PMID: 23392843 DOI: 10.1007/s12253-012-9600-2
    Calreticulin (CRT) as a multi-functional endoplasmic reticulum protein is involved in a spectrum of cellular processes which ranges from calcium homeostasis and chaperoning to cell adhesion and finally malignant formation and progression. Previous studies have shown a contributing role for CRT in a range of different cancers. This present review will focus on the possible roles of CRT in the progression of malignant proliferation and the mechanisms involved in its contribution to cancer invasion.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  2. Use of control analysis to study the regulation of plant lipid biosynthesis
    Ramli US, Baker DS, Quant PA, Harwood JL
    Biochem Soc Trans, 2002 Nov;30(Pt 6):1043-6.
    PMID: 12440968
    Control analysis is a powerful method to quantify the regulation of metabolic pathways. We have applied it to lipid biosynthesis for the first time by using model tissue culture systems from the important oil crops, olive ( Olea europaea L.) and oil palm ( Elaeis guineensis Jacq.). By the use of top-down control analysis, fatty acid biosynthesis has been shown to exert more control than lipid assembly under different experimental conditions. However, both parts of the lipid biosynthetic pathway are important, so that attempts to alter oil yield by manipulating the activity of a single enzyme step are very unlikely to produce significant increases.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  3. Pregnenolone metabolites in rat testis: endogenous concentrations, and intracellular distribution in whole testes during incubation in vitro
    Pertiwi AK, Kwan TK, Gower DB
    J Steroid Biochem Mol Biol, 2002 Aug;81(4-5):363-7.
    PMID: 12361726
    The intracellular movements of pregnenolone in rat testes were investigated. Whole testes were incubated in the presence or absence of pregnenolone (2.5mM) in the medium for 120 min (in some studies 30, 60, and 90 min). The testes were homogenised, subcellular fractions prepared and analysed in quadruplicate for steroid content by gas chromatography-mass spectrometry with selected ion monitoring. Quantification of pregnenolone and 11 of its metabolites, obtained from non-incubated whole testes, provided values for endogenous amounts. Pregnenolone was the only steroid of quantitative importance found initially in the mitochondrial fraction but was subsequently found in the microsomal fraction, where metabolism occurred. Identification and quantification of metabolites indicated that both classical pathways for testosterone production were operating, with the 4-en-3-oxosteroid pathway predominating. By 120 min, virtually all pregnenolone metabolites, including pregnenolone itself, were found in the cytosol, consistent with an overall movement from mitochondria to endoplasmic reticulum to cytosol.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  4. Signal grass (Brachiaria decumbens) toxicity in sheep: changes in motility and pH of reticulo-rumen
    Abdullah AS, Nordin MM, Rajion MA
    Vet Hum Toxicol, 1988 Jun;30(3):256-8.
    PMID: 3388753
    In addition to generalized icterus, enlargement of the liver and severe photosensitization, signal grass (Brachiaria decumbens) toxicity also caused ruminal stasis and a decreased rumen pH in sheep. Ruminal stasis, which occurred within 3 weeks of grazing on this grass, may be the effect of the toxin produced in the rumen rather than a sequele of a decreased rumen pH. Animals were anorexic and the volume of their rumen content was very much reduced.
    Matched MeSH terms: Reticulum/metabolism
  5. Fulltext Ubiquitylation of the ER-Shaping Protein Lunapark via the CRL3KLHL12 Ubiquitin Ligase Complex
    Yuniati L, Lauriola A, Gerritsen M, Abreu S, Ni E, Tesoriero C, et al.
    Cell Rep, 2020 05 19;31(7):107664.
    PMID: 32433973 DOI: 10.1016/j.celrep.2020.107664
    Cullin-RING ligases (CRLs) control key cellular processes by promoting ubiquitylation of a multitude of soluble cytosolic and nuclear proteins. Subsets of CRL complexes are recruited and activated locally at cellular membranes; however, few CRL functions and substrates at these distinct cellular compartments are known. Here, we use a proteomic screen to identify proteins that are ubiquitylated at cellular membranes and found that Lunapark, an endoplasmic reticulum (ER)-shaping protein localized to ER three-way junctions, is ubiquitylated by the CRL3KLHL12 ubiquitin ligase. We demonstrate that Lunapark interacts with mechanistic target of rapamycin complex-1 (mTORC1), a central cellular regulator that coordinates growth and metabolism with environmental conditions. We show that mTORC1 binds Lunapark specifically at three-way junctions, and lysosomes, where mTORC1 is activated, make contact with three-way junctions where Lunapark resides. Inhibition of Lunapark ubiquitylation results in neurodevelopmental defects indicating that KLHL12-dependent ubiquitylation of Lunapark is required for normal growth and development.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism*
  6. The anterior gradient-2 interactome
    Delom F, Mohtar MA, Hupp T, Fessart D
    Am. J. Physiol., Cell Physiol., 2020 01 01;318(1):C40-C47.
    PMID: 31644305 DOI: 10.1152/ajpcell.00532.2018
    The anterior gradient-2 (AGR2) is an endoplasmic reticulum (ER)-resident protein belonging to the protein disulfide isomerase family that mediates the formation of disulfide bonds and assists the protein quality control in the ER. In addition to its role in proteostasis, extracellular AGR2 is responsible for various cellular effects in many types of cancer, including cell proliferation, survival, and metastasis. Various OMICs approaches have been used to identify AGR2 binding partners and to investigate the functions of AGR2 in the ER and outside the cell. Emerging data showed that AGR2 exists not only as monomer, but it can also form homodimeric structure and thus interact with different partners, yielding different biological outcomes. In this review, we summarize the AGR2 "interactome" and discuss the pathological and physiological role of such AGR2 interactions.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism*
  7. Fulltext JMJD8 is a novel endoplasmic reticulum protein with a JmjC domain
    Yeo KS, Tan MC, Lim YY, Ea CK
    Sci Rep, 2017 11 13;7(1):15407.
    PMID: 29133832 DOI: 10.1038/s41598-017-15676-z
    Jumonji C (JmjC) domain-containing proteins have been shown to regulate cellular processes by hydroxylating or demethylating histone and non-histone targets. JMJD8 belongs to the JmjC domain-only family that was recently shown to be involved in angiogenesis and TNF-induced NF-κB signaling. Here, we employed bioinformatic analysis and immunofluorescence microscopy to examine the physiological properties of JMJD8. We demonstrated that JMJD8 localizes to the lumen of endoplasmic reticulum and that JMJD8 forms dimers or oligomers in vivo. Furthermore, we identified potential JMJD8-interacting proteins that are known to regulate protein complex assembly and protein folding. Taken together, this work demonstrates that JMJD8 is the first JmjC domain-containing protein found in the lumen of the endoplasmic reticulum that may function in protein complex assembly and protein folding.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism*
  8. Fulltext NKX3.1 Expression and Molecular Characterization of Secretory Myoepithelial Carcinoma (SMCA): Advancing the Case for a Salivary Mucous Acinar Phenotype
    Patel S, Wald AI, Bastaki JM, Chiosea SI, Singhi AD, Seethala RR
    Head Neck Pathol, 2023 Jun;17(2):467-478.
    PMID: 36746884 DOI: 10.1007/s12105-023-01524-2
    BACKGROUND: Secretory myoepithelial carcinomas (SMCA) are rare, mucinous, signet ring predominant tumors with primitive myoepithelial features. While many mucinous salivary gland tumors have now been molecularly characterized, key drivers in SMCA have yet to be elucidated. Recently, NKX3.1, a homeodomain transcription factor implicated in salivary mucous acinar development was also shown in a subset of salivary mucinous neoplasms, salivary intraductal papillary mucinous neoplasms (SG-IPMN). To date, NKX3.1 expression has not been characterized in other mucinous salivary lesions. Here, we report molecular and extended immunophenotypic findings in SMCA and NKX3.1 expression in the context of other head and neck lesions.

    METHODS: We retrieved 4 previously reported SMCA, performed additional immunohistochemical and targeted next-generation sequencing (NGS). We also investigated the use of NKX3.1 as a marker for SMCA in the context of its prevalence and extent (using H-score) in a mixed cohort of retrospectively and prospectively tested head and neck lesions (n = 223) and non-neoplastic tissues (n = 66).

    RESULTS: NKX3.1 positivity was confirmed in normal mucous acini as well as in mucous acinar class of lesions (5/6, mean H-score: 136.7), including mucinous adenocarcinomas (3/4), SG-IPMN (1/1), and microsecretory adenocarcinoma (MSA) (1/1). All SMCA were positive. Fluorescence in situ hybridization for SS18 rearrangements were negative in all successfully tested cases (0/3). NGS was successful in two cases (cases 3 and 4). Case 3 demonstrated a PTEN c.655C>T p.Q219* mutation and a SEC16A::NOTCH1 fusion while case 4 (clinically aggressive) showed a PTEN c.1026+1G>A p.K342 splice site variant, aTP53 c.524G>A p.R175H mutation and a higher tumor mutation burden (29 per Mb). PTEN immunohistochemical loss was confirmed in both cases and a subset of tumor cells showed strong (extreme) staining for P53 in Case 4.

    CONCLUSION: Despite a partial myoepithelial phenotype, SMCA, along with mucinous adenocarcinomas/SG-IPMN and MSA, provisionally constitute a mucous acinar class of tumors based on morphology and NKX3.1 expression. Like salivary mucinous adenocarcinomas/SG-IPMN, SMCA also show alterations of the PTEN/PI3K/AKT pathway and may show progressive molecular alterations. We document the first extramammary tumor with a SEC16A::NOTCH1 fusion.

    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  9. The association between neuropsychiatric effects of substance use and occurrence of endoplasmic reticulum and unfolded protein response: A systematic review
    Yang B, Zhang R, Leong Bin Abdullah MFI
    Toxicol Lett, 2024 Jan;391:71-85.
    PMID: 38101493 DOI: 10.1016/j.toxlet.2023.12.008
    INTRODUCTION: This systematic review aimed to assess the association between neuropsychiatric effects of substance use and occurrence of ER stress and unfolded protein response (UPR) through comprehensive electronic search of existing literature and review of their findings.

    METHODS: A comprehensive electronic literature search was carried out on research articles published between 1950 to July 2023 through major databases, such as Scopus, Web of Science, Google Scholar, PubMed, PsycINFO, EMBASE, Medline and Cochrane Library.

    RESULTS: A total of 21 research articles were selected for review, which were comprised of sixteen animal studies, four human studies and one study on postmortem human brain samples. The selected studies revealed that alcohol, methamphetamine, cocaine, opioid and kratom exposures contributed to neuropsychiatric effects: such as decline in learning and memory function, executive dysfunction, alcohol, methamphetamine, opioid, and kratom dependence. These effects were associated with activation and persistent of ER stress and UPR with elevation of BiP and CHOP expression and the direction of ER stress is progressing towards the PERK-eIF2α-ATF4-CHOP pathway and neuronal apoptosis and neurodegeneration at various regions of the brain. In addition, regular kratom use in humans also contributed to elevation of p-JNK expression, denoting progress of ER stress towards the IRE1-ASK1-JNK-p-JNK pathway which was linked to kratom use disorder. However, treatment with certain compounds or biological agents could reverse the activation of ER stress.

    CONCLUSIONS: The neuropsychiatric effects of alcohol, methamphetamine, cocaine, opioid and kratom use may be associated with persistent ER stress and UPR.

    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  10. The influenza A virus matrix protein 2 undergoes retrograde transport from the endoplasmic reticulum into the cytoplasm and bypasses cytoplasmic proteasomal degradation
    Bhowmick S, Chakravarty C, Sellathamby S, Lal SK
    Arch Virol, 2017 Apr;162(4):919-929.
    PMID: 27942972 DOI: 10.1007/s00705-016-3153-8
    The matrix protein 2 (M2) is a spliced product of segment 7 genome of influenza A virus. Previous studies indicate its role in uncoating of the viral ribonucleoprotein complex during viral entry and in membrane scission while budding. Despite its crucial role in the viral life cycle, little is known about its subcellular distribution and dynamics. In this study, we have shown that the M2 protein is translocated from the membrane to the cytoplasm by a retrograde route via endosomes and the Golgi network. It utilizes retromer cargo while moving from the endosome to the trans-Golgi network and prevents endosome fusion with the lysosome. Further, M2 interacts with the endoplasmic-reticulum-resident AAA-ATPase p97 for its release into the cytoplasm. Our study also revealed that the M2 protein in the cellular milieu does not undergo ubiquitin-mediated proteasomal degradation. The migration of M2 through this pathway inside the infected cell suggests possible new roles that the M2 protein may have in the host cytoplasm, apart from its previously described functions.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism*
  11. Fulltext Geranylated 4-Phenylcoumarins Exhibit Anticancer Effects against Human Prostate Cancer Cells through Caspase-Independent Mechanism
    Suparji NS, Chan G, Sapili H, Arshad NM, In LL, Awang K, et al.
    PLoS One, 2016;11(3):e0151472.
    PMID: 26974436 DOI: 10.1371/journal.pone.0151472
    Geranylated 4-phenylcoumarins, DMDP-1 & -2 isolated from Mesua elegans were investigated for anticancer potential against human prostate cancer cells. Treatment with DMDP-1 & -2 resulted in cell death in a time and dose dependent manner in an MTT assay on all cancer cell lines tested with the exception of lung adenocarcinoma cells. DMDP-1 showed highest cytotoxic efficacy in PC-3 cells while DMDP-2 was most potent in DU 145 cells. Flow cytometry indicated that both coumarins were successful to induce programmed cell death after 24 h treatment. Elucidation on the mode-of-action via protein arrays and western blotting demonstrated death induced without any significant expressions of caspases, Bcl-2 family proteins and cleaved PARP, thus suggesting the involvement of caspase-independent pathways. In identifying autophagy, analysis of GFP-LC3 showed increased punctate in PC-3 cells pre-treated with CQ and treated with DMDP-1. In these cells decreased expression of autophagosome protein, p62 and cathepsin B further confirmed autophagy. In contrary, the DU 145 cells pre-treated with CQ and treated with DMDP-2 has reduced GFP-LC3 punctate although the number of cells with obvious GFP-LC3 puncta was significantly increased in the inhibitor-treated cells. The increase level of p62 suggested leakage of cathepsin B into the cytosol to trigger potential downstream death mediators. This correlated with increased expression of cathepsin B and reduced expression after treatment with its inhibitor, CA074. Also auto-degradation of calpain-2 upon treatment with DMDP-1 &-2 and its inhibitor alone, calpeptin compared with the combination treatment, further confirmed involvement of calpain-2 in PC-3 and DU 145 cells. Treatment with DMDP-1 & -2 also showed up-regulation of total and phosphorylated p53 levels in a time dependent manner. Hence, DMDP-1 & -2 showed ability to activate multiple death pathways involving autophagy, lysosomal and endoplasmic reticulum death proteins which could potentially be manipulated to develop anti-cancer therapy in apoptosis resistant cells.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  12. Resistance against apoptosis by the cellular prion protein is dependent on its glycosylation status in oral HSC-2 and colon LS 174T cancer cells
    Yap YH, Say YH
    Cancer Lett, 2011 Jul 1;306(1):111-9.
    PMID: 21439722 DOI: 10.1016/j.canlet.2011.02.040
    Most studies have focused on the role of the cellular prion protein (PrP(C)) in neurodegenerative diseases, whereas the function of this ubiquitous protein outside the nervous system remains elusive. Therefore, the anti-apoptotic property of PrP(C) in oral squamous cell carcinoma (HSC-2) and colon adenocarcinoma (LS 174T) was evaluated in this study, by stable shRNA knockdown and overexpression, respectively. PrP(C) confers resistance against oxidative stress-apoptosis as indicated by MTT assay, Annexin V-FITC/PI and DCFH-DA staining, but this property is abolished upon N-glycosylation inhibition by tunicamycin. Our results indicate that the inhibition of glycosylation in cancer cells overexpressing PrP(C) could represent a potential therapeutic target.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  13. Fulltext Subcellular localization and interactions among rubber particle proteins from Hevea brasiliensis
    Brown D, Feeney M, Ahmadi M, Lonoce C, Sajari R, Di Cola A, et al.
    J Exp Bot, 2017 Nov 02;68(18):5045-5055.
    PMID: 29036360 DOI: 10.1093/jxb/erx331
    Natural rubber (polyisoprene) from the rubber tree Hevea brasiliensis is synthesized by specialized cells called laticifers. It is not clear how rubber particles arise, although one hypothesis is that they derive from the endoplasmic reticulum (ER) membrane. Here we cloned the genes encoding four key proteins found in association with rubber particles and studied their intracellular localization by transient expression in Nicotiana benthamiana leaves. We show that, while the cis-prenyltransferase (CPT), responsible for the synthesis of long polyisoprene chains, is a soluble, cytosolic protein, other rubber particle proteins such as rubber elongation factor (REF), small rubber particle protein (SRPP) and Hevea rubber transferase 1-REF bridging protein (HRBP) are associated with the endoplasmic reticulum (ER). We also show that SRPP can recruit CPT to the ER and that interaction of CPT with HRBP leads to both proteins relocating to the plasma membrane. We discuss these results in the context of the biogenesis of rubber particles.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  14. Fulltext Stearoyl CoA Desaturase Is Essential for Regulation of Endoplasmic Reticulum Homeostasis and Tumor Growth in Glioblastoma Cancer Stem Cells
    Pinkham K, Park DJ, Hashemiaghdam A, Kirov AB, Adam I, Rosiak K, et al.
    Stem Cell Reports, 2019 04 09;12(4):712-727.
    PMID: 30930246 DOI: 10.1016/j.stemcr.2019.02.012
    Inherent plasticity and various survival cues allow glioblastoma stem-like cells (GSCs) to survive and proliferate under intrinsic and extrinsic stress conditions. Here, we report that GSCs depend on the adaptive activation of ER stress and subsequent activation of lipogenesis and particularly stearoyl CoA desaturase (SCD1), which promotes ER homeostasis, cytoprotection, and tumor initiation. Pharmacological targeting of SCD1 is particularly toxic due to the accumulation of saturated fatty acids, which exacerbates ER stress, triggers apoptosis, impairs RAD51-mediated DNA repair, and achieves a remarkable therapeutic outcome with 25%-100% cure rate in xenograft mouse models. Mechanistically, divergent cell fates under varying levels of ER stress are primarily controlled by the ER sensor IRE1, which either promotes SCD1 transcriptional activation or converts to apoptotic signaling when SCD1 activity is impaired. Taken together, the dependence of GSCs on fatty acid desaturation presents an exploitable vulnerability to target glioblastoma.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism*
  15. Anti-hypertensive and vasodilatory effects of amended Banxia Baizhu Tianma Tang
    Tan CS, Loh YC, Ng CH, Ch'ng YS, Asmawi MZ, Ahmad M, et al.
    Biomed Pharmacother, 2018 Jan;97:985-994.
    PMID: 29136777 DOI: 10.1016/j.biopha.2017.11.021
    Although Banxia Baizhu Tianma Tang (BBT) has been long administered for hypertensive treatment in Traditional Chinese Medicine (TCM), the ratio of the herbal components that makes up the formulation has not been optimized with respect to the anti-hypertensive effect that it inherently possesses. A newly amended BBT (ABBT) formulation was developed using the evidence-based approach of orthogonal stimulus-response compatibility model. The ABBT showed enhanced therapeutic effect while maintaining its traditional theoretical approach rooted in TCM. This study was designed to investigate the possible mechanism of actions involved in the vasodilatory activity of ABBT-50 by evaluating its vasodilative effect on isolated Sprague Dawley rats in the presence of absence of various antagonists. When pre-contracted with phenylephrine, relaxation was observed in endothelium intact (EC50=0.027±0.003mg/ml, Rmax=109.8±2.12%) and denuded aortic rings (EC50=0.409±0.073mg/ml, Rmax=63.15±1.78%), as well as in endothelium intact aortic rings pre-contracted with potassium chloride (EC50=32.7±12.16mg/ml, Rmax=34.02±3.82%). Significant decrease in the vasodilative effect of ABBT-50 was observed in the presence of Nω-nitro-l-arginine methyl ester (EC50=0.12±0.021mg/ml, Rmax=75.33±3.28%), 1H-[1,2,4] Oxadiazolo[4,3-a]quinoxalin-1-one (EC50=0.463±0.18mg/ml, Rmax=54.48±2.02%), methylene blue (EC50=0.19±0.037mg/ml, Rmax=83.69±3.19%), indomethacin (EC50=0.313±0.046mg/ml, Rmax=71.33±4.12%), atropine (EC50=0.146±0.013mg/ml, Rmax=77.2±3.41%), and 4-aminopyridine (EC50=0.045±0.008mg/ml, Rmax=95.55±2.36%). ABBT-50 was also suppressing Ca2+ release from sarcoplasmic reticulum and inhibiting calcium channels. Vasodilatory effects of ABBT-50 are mediated through NO/sGC/cGMP cascade and PGI2, followed by muscarinic pathways and calcium channels.
    Matched MeSH terms: Sarcoplasmic Reticulum/metabolism
  16. Fulltext Effect of flecainide derivatives on sarcoplasmic reticulum calcium release suggests a lack of direct action on the cardiac ryanodine receptor
    Bannister ML, Alvarez-Laviada A, Thomas NL, Mason SA, Coleman S, du Plessis CL, et al.
    Br J Pharmacol, 2016 08;173(15):2446-59.
    PMID: 27237957 DOI: 10.1111/bph.13521
    BACKGROUND AND PURPOSE: Flecainide is a use-dependent blocker of cardiac Na(+) channels. Mechanistic analysis of this block showed that the cationic form of flecainide enters the cytosolic vestibule of the open Na(+) channel. Flecainide is also effective in the treatment of catecholaminergic polymorphic ventricular tachycardia but, in this condition, its mechanism of action is contentious. We investigated how flecainide derivatives influence Ca(2) (+) -release from the sarcoplasmic reticulum through the ryanodine receptor channel (RyR2) and whether this correlates with their effectiveness as blockers of Na(+) and/or RyR2 channels.

    EXPERIMENTAL APPROACH: We compared the ability of fully charged (QX-FL) and neutral (NU-FL) derivatives of flecainide to block individual recombinant human RyR2 channels incorporated into planar phospholipid bilayers, and their effects on the properties of Ca(2) (+) sparks in intact adult rat cardiac myocytes.

    KEY RESULTS: Both QX-FL and NU-FL were partial blockers of the non-physiological cytosolic to luminal flux of cations through RyR2 channels but were significantly less effective than flecainide. None of the compounds influenced the physiologically relevant luminal to cytosol cation flux through RyR2 channels. Intracellular flecainide or QX-FL, but not NU-FL, reduced Ca(2) (+) spark frequency.

    CONCLUSIONS AND IMPLICATIONS: Given its inability to block physiologically relevant cation flux through RyR2 channels, and its lack of efficacy in blocking the cytosolic-to-luminal current, the effect of QX-FL on Ca(2) (+) sparks is likely, by analogy with flecainide, to result from Na(+) channel block. Our data reveal important differences in the interaction of flecainide with sites in the cytosolic vestibules of Na(+) and RyR2 channels.

    Matched MeSH terms: Sarcoplasmic Reticulum/metabolism*
  17. Fulltext Induction of Endoplasmic Reticulum Stress Pathway by Green Tea Epigallocatechin-3-Gallate (EGCG) in Colorectal Cancer Cells: Activation of PERK/p-eIF2α/ATF4 and IRE1α
    Md Nesran ZN, Shafie NH, Ishak AH, Mohd Esa N, Ismail A, Md Tohid SF
    Biomed Res Int, 2019;2019:3480569.
    PMID: 31930117 DOI: 10.1155/2019/3480569
    Epigallocatechin-3-gallate (EGCG) is the most abundant bioactive polyphenolic compound among the green tea constituents and has been identified as a potential anticancer agent in colorectal cancer (CRC) studies. This study was aimed to determine the mechanism of actions of EGCG when targeting the endoplasmic reticulum (ER) stress pathway in CRC. The MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay was performed on HT-29 cell line and normal cell line (3T3) to determine the EGCG toxicity. Next, western blot was done to observe the expression of the related proteins for the ER stress pathway. The Caspase 3/7 assay was performed to determine the apoptosis induced by EGCG. The results demonstrated that EGCG treatment was toxic to the HT-29 cell line. EGCG induced ER stress in HT-29 by upregulating immunoglobulin-binding (BiP), PKR-like endoplasmic reticulum kinase (PERK), phosphorylation of eukaryotic initiation factor 2 alpha subunit (eIF2α), activating transcription 4 (ATF4), and inositol-requiring kinase 1 alpha (IRE1α). Apoptosis was induced in HT-29 cells after the EGCG treatment, as shown by the Caspase 3/7 activity. This study indicates that green tea EGCG has the potential to inhibit colorectal cancer cells through the induction of ER stress.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
  18. Vasorelaxant Action of the Chloroform Fraction of Orthosiphon stamineus via NO/cGMP Pathway, Potassium and Calcium Channels
    Yam MF, Tan CS, Ahmad M, Ruan S
    Am J Chin Med, 2016;44(7):1413-1439.
    PMID: 27785939
    Orthosiphon stamineus Benth. (Lamiaceae) is an important plant in traditional folk medicine that is used to treat hypertension and kidney stones. In humans, this plant has been tested as an addition regiment for antihypertensive treatment. Among the treatments for hypertension, O. stamineus had been to have diuretic and vasorelaxant effects in animal models. There is still very little information regarding the vasorelaxant effect of O. stamineus. Therefore, the present study was designed to investigate the vasorelaxant activity and mechanism of action of the fractions of O. stamineus. The vasorelaxant activity and the underlying mechanisms of the chloroform fraction of the 50% methanolic extract of O. stamineus (CF) was evaluated on thoracic aortic rings isolated from Sprague Dawley rats. CF caused relaxation of the aortic ring pre-contracted with phenylephrine in the presence and absence of endothelium, and pre-contracted with potassium chloride in endothelium-intact aortic ring. In the presence of endothelium, both indomethacin (a nonselective cyclooxygenase inhibitor) and [Formula: see text]-[1,2,4]Oxadiazolo[4,3-[Formula: see text]]quinoxalin-1-one (ODQ, selective soluble guanylate cyclase inhibitor) had a small effect on the vasorelaxation response. On the other hand, in the presence of Nω-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), methylene blue (cyclic guanosine monophosphate lowering agent), tetraethylammonium ([Formula: see text], nonselective calcium activator [Formula: see text] channel blocker), 4-aminopyridine (4-AP, voltage-dependent [Formula: see text] channel blocker), barium chloride ([Formula: see text], inwardly rectifying [Formula: see text] channel blocker), glibenclamide (nonspecific ATP-sensitive [Formula: see text] channel blocker), atropine (muscarinic receptor blocker) and propranolol (β-adrenergic receptor blocker), the vasorelaxant effect significantly reduced the relaxation stimulated by CF. CF was also found to be active in reducing [Formula: see text] release from the sarcoplasmic reticulum and blocking calcium channels.
    Matched MeSH terms: Sarcoplasmic Reticulum/metabolism
  19. Mechanism of the induction of endoplasmic reticulum stress by the anti-cancer agent, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT): Activation of PERK/eIF2α, IRE1α, ATF6 and calmodulin kinase
    Merlot AM, Shafie NH, Yu Y, Richardson V, Jansson PJ, Sahni S, et al.
    Biochem Pharmacol, 2016 06 01;109:27-47.
    PMID: 27059255 DOI: 10.1016/j.bcp.2016.04.001
    The endoplasmic reticulum (ER) plays a major role in the synthesis, maturation and folding of proteins and is a critical calcium (Ca(2+)) reservoir. Cellular stresses lead to an overwhelming accumulation of misfolded proteins in the ER, leading to ER stress and the activation of the unfolded protein response (UPR). In the stressful tumor microenvironment, the UPR maintains ER homeostasis and enables tumor survival. Thus, a novel strategy for cancer therapeutics is to overcome chronically activated ER stress by triggering pro-apoptotic pathways of the UPR. Considering this, the mechanisms by which the novel anti-cancer agent, Dp44mT, can target the ER stress response pathways were investigated in multiple cell-types. Our results demonstrate that the cytotoxic chelator, Dp44mT, which forms redox-active metal complexes, significantly: (1) increased ER stress-associated pro-apoptotic signaling molecules (i.e., p-eIF2α, ATF4, CHOP); (2) increased IRE1α phosphorylation (p-IRE1α) and XBP1 mRNA splicing; (3) reduced expression of ER stress-associated cell survival signaling molecules (e.g., XBP1s and p58(IPK)); (4) increased cleavage of the transcription factor, ATF6, which enhances expression of its downstream targets (i.e., CHOP and BiP); and (5) increased phosphorylation of CaMKII that induces apoptosis. In contrast to Dp44mT, the iron chelator, DFO, which forms redox-inactive iron complexes, did not affect BiP, p-IRE1α, XBP1 or p58(IPK) levels. This study highlights the ability of a novel cancer therapeutic (i.e., Dp44mT) to target the pro-apoptotic functions of the UPR via cellular metal sequestration and redox stress. Assessment of ER stress-mediated apoptosis is fundamental to the understanding of the pharmacology of chelation for cancer treatment.
    Matched MeSH terms: Endoplasmic Reticulum/metabolism
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