scholarly journals The Protein Translocation Defect of MCT8L291R Is Rescued by Sodium Phenylbutyrate

2020 ◽  
Vol 9 (5) ◽  
pp. 269-280
Author(s):  
Doreen Braun ◽  
Ulrich Schweizer

Introduction: The monocarboxylate transporter 8 (MCT8; SLC16A2) is a specific transporter for thyroid hormones. MCT8 deficiency, formerly known as the Allan-Herndon-Dudley syndrome, is a rare genetic disease that leads to neurological impairments and muscle weakness. Current experimental treatment options rely on thyromimetic agonists that do not depend on MCT8 for cellular uptake. Another approach comes from studies with the chemical chaperone sodium phenylbutyrate (NaPB), which was able to stabilize MCT8 mutants having protein folding defects in vitro. In addition, NaPB is known as a compound that assists with plasma membrane translocation. Objective: The pathogenic MCT8L291R leads to the same severe neurological impairments found for other MCT8-deficient patients but, unexpectedly, lacks alterations in plasma 3,3′,5-triiodothyronine (T3) levels. Here we tried to unravel the underlying mechanism of MCT8 deficiency and tested whether the pathogenic MCT8L291R mutant responds to NaPB treatment. Therefore, we overexpressed the mutant in Madin-Darby canine kidney cells in the human choriocarcinoma cell line JEG1 and in COS7 cells of African green monkey origin. Results: In our recent study we describe that the MCT8L291R mutation most likely leads to a translocation defect. The pathogenic mutant is not located at the plasma membrane, but shows overlapping expression with a marker protein of the lysosome. Mutation of the corresponding amino acid in murine Mct8 (Mct8L223R) displays a similar effect on cell surface expression and transport function as seen before for MCT8L291R. NaPB was able to correct the translocation defect of MCT8L291R/Mct8L223R and restored protein function by increasing T3 transport activity. Furthermore, we detected enhanced mRNA levels of wild-type and mutant MCT8/Mct8 after NaPB treatment. The increase in mRNA levels could be an explanation for the positive effect on protein expression and function detected for wild-type MCT8. Conclusion: NaPB is not only suitable for the treatment of mutations leading to misfolding and protein degradation, but also for a mutant wrongly sorted inside a cell which is otherwise functional.

Genes ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1126
Author(s):  
Shengru Wang ◽  
Xiran Chai ◽  
Zihui Yan ◽  
Sen Zhao ◽  
Yang Yang ◽  
...  

FGFR1 encodes a transmembrane cytokine receptor, which is involved in the early development of the human embryo and plays an important role in gastrulation, organ specification and patterning of various tissues. Pathogenic FGFR1 variants have been associated with Kallmann syndrome and hypogonadotropic hypogonadism. In our congenital scoliosis (CS) patient series of 424 sporadic CS patients under the framework of the Deciphering disorders Involving Scoliosis and COmorbidities (DISCO) study, we identified four unrelated patients harboring FGFR1 variants, including one frameshift and three missense variants. These variants were predicted to be deleterious by in silico prediction and conservation analysis. Signaling activities and expression levels of the mutated protein were evaluated in vitro and compared to that of the wild type (WT) FGFR1. As a result, the overall protein expressions of c.2334dupC, c.2339T>C and c.1261A>G were reduced to 43.9%, 63.4% and 77.4%, respectively. By the reporter gene assay, we observed significantly reduced activity for c.2334dupC, c.2339T>C and c.1261A>G, indicating the diminished FGFR1 signaling pathway. In conclusion, FGFR1 variants identified in our patients led to only mild disruption to protein function, caused milder skeletal and cardiac phenotypes than those reported previously.


Endocrinology ◽  
2004 ◽  
Vol 145 (12) ◽  
pp. 5525-5531 ◽  
Author(s):  
Gary M. Leong ◽  
Sofia Moverare ◽  
Jesena Brce ◽  
Nathan Doyle ◽  
Klara Sjögren ◽  
...  

Abstract Suppressors of cytokine signaling (SOCS) are important negative regulators of cytokine action. We recently reported that estrogen stimulates SOCS-2 expression and inhibits GH signaling in kidney cells. The effects of estrogen on SOCS expression in other tissues are unclear. The aim of this study was to investigate in vivo and in vitro whether estrogen affected SOCS expression in the liver, a major target organ of GH. The in vivo hepatic effects of estrogen on ovariectomized mice lacking estrogen receptor (ER)-α, ERβ, or both and their wild-type littermates were examined by DNA microarray analysis. In vitro, the effects of estrogen on SOCS expression in human hepatoma cells were examined by reverse transcription quantitative PCR. Long-term (3 wk) estrogen treatment induced a 2- to 3-fold increase in hepatic expression of SOCS-2 and -3 in wild-type and ERβ knockout mice but not in those lacking ERα or both ER subtypes. Short-term treatment (at 24 h) increased the mRNA level of SOCS-3 but not SOCS-2. In cultured hepatoma cells, estrogen increased SOCS-2 and -3 mRNA levels by 2-fold in a time- and dose-dependent manner (P < 0.05). Estrogen induced murine SOCS-3 promoter activity by 2-fold (P < 0.05) in constructs containing a region between nucleotides −1862 and −855. Moreover, estrogen and GH had additive effects on the SOCS-3 promoter activity. In summary, estrogen, via ERα, up-regulated hepatic expression of SOCS-2 and -3, probably through transcriptional activation. This indicates a novel mechanism of estrogen regulation of cytokine action.


2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Michael Fiske ◽  
Michael White ◽  
Stephanie Valtierra ◽  
Sara Herrera ◽  
Keith Solvang ◽  
...  

In Parkinson’s disease (PD), midbrain dopaminergic neuronal death is linked to the accumulation of aggregated α-synuclein. The familial PD mutant form of α-synuclein, E46K, has not been thoroughly evaluated yet in an organismal model system. Here, we report that E46K resembled wild-type (WT) α-synuclein in Saccharomyces cerevisiae in that it predominantly localized to the plasma membrane, and it did not induce significant toxicity or accumulation. In contrast, in Schizosaccharomyces pombe, E46K did not associate with the plasma membrane. Instead, in one strain, it extensively aggregated in the cytoplasm and was as toxic as WT. Remarkably, in another strain, E46K extensively associated with the endomembrane system and was more toxic than WT. Our studies recapitulate and extend aggregation and phospholipid membrane association properties of E46K previously observed in vitro and cell culture. Furthermore, it supports the notion that E46K generates toxicity partly due to increased association with endomembrane systems within cells.


Blood ◽  
2012 ◽  
Vol 120 (16) ◽  
pp. 3336-3344 ◽  
Author(s):  
Anu Laitala ◽  
Ellinoora Aro ◽  
Gail Walkinshaw ◽  
Joni M. Mäki ◽  
Maarit Rossi ◽  
...  

AbstractAn endoplasmic reticulum transmembrane prolyl 4-hydroxylase (P4H-TM) is able to hydroxylate the α subunit of the hypoxia-inducible factor (HIF) in vitro and in cultured cells, but nothing is known about its roles in mammalian erythropoiesis. We studied such roles here by administering a HIF-P4H inhibitor, FG-4497, to P4h-tm−/− mice. This caused larger increases in serum Epo concentration and kidney but not liver Hif-1α and Hif-2α protein and Epo mRNA levels than in wild-type mice, while the liver Hepcidin mRNA level was lower in the P4h-tm−/− mice than in the wild-type. Similar, but not identical, differences were also seen between FG-4497–treated Hif-p4h-2 hypomorphic (Hif-p4h-2gt/gt) and Hif-p4h-3−/− mice versus wild-type mice. FG-4497 administration increased hemoglobin and hematocrit values similarly in the P4h-tm−/− and wild-type mice, but caused higher increases in both values in the Hif-p4h-2gt/gt mice and in hematocrit value in the Hif-p4h-3−/− mice than in the wild-type. Hif-p4h-2gt/gt/P4h-tm−/− double gene-modified mice nevertheless had increased hemoglobin and hematocrit values without any FG-4497 administration, although no such abnormalities were seen in the Hif-p4h-2gt/gt or P4h-tm−/− mice. Our data thus indicate that P4H-TM plays a role in the regulation of EPO production, hepcidin expression, and erythropoiesis.


2021 ◽  
Vol 22 (3) ◽  
pp. 1276
Author(s):  
Michihiro Hashimoto ◽  
Ayumi Goto ◽  
Yuki Endo ◽  
Masataka Sugimoto ◽  
Jun Ueda ◽  
...  

Cellular repressor of E1A-stimulated genes 1 (CREG1) is a secreted glycoprotein that accelerates p16-dependent cellular senescence in vitro. We recently reported the ability of CREG1 to stimulate brown adipogenesis using adipocyte P2-CREG1-transgenic (Tg) mice; however, little is known about the effect of CREG1 on aging-associated phenotypes. In this study, we investigated the effects of CREG1 on age-related obesity and renal dysfunction in Tg mice. Increased brown fat formation was detected in aged Tg mice, in which age-associated metabolic phenotypes such as body weight gain and increases in blood glucose were improved compared with those in wild-type (WT) mice. Blood CREG1 levels increased significantly in WT mice with age, whereas the age-related increase was suppressed, and its levels were reduced, in the livers and kidneys of Tg mice relative to those in WT mice at 25 months. Intriguingly, the mRNA levels of Ink4a, Arf, and senescence-associated secretory phenotype (SASP)-related genes and p38MAPK activity were significantly lowered in the aged kidneys of Tg mice, in which the morphological abnormalities of glomeruli as well as filtering function seen in WT kidneys were alleviated. These results suggest the involvement of CREG1 in kidney aging and its potential as a target for improving age-related renal dysfunction.


2001 ◽  
Vol 281 (4) ◽  
pp. G1004-G1013 ◽  
Author(s):  
Takashi Kojima ◽  
Alfredo Fort ◽  
Mingyuan Tao ◽  
Masao Yamamoto ◽  
David C. Spray

Primary cultures of adult mouse hepatocytes are shown here to reexpress differentiated hepatocyte features following treatment with 2% DMSO and 10−7 M glucagon. To examine the roles of gap junctional communication during hepatocyte growth and differentiation, we have compared treated and untreated hepatocytes from connexin (Cx)32-deficient [Cx32 knockout (KO)] and wild-type mice. In untreated cultures, DNA replication of Cx32 KO hepatocytes was markedly higher than of wild types. Although Cx26 mRNA levels remained high at all time points in wild-type and Cx32 KO hepatocytes, Cx32 mRNA and protein in wild-type hepatocytes underwent a marked decline, which recovered in 10-day treated cultures. Increased levels of Cx26 protein and junctional conductance were observed in Cx32 KO hepatocytes at 96 h in culture, a time when cell growth rate was high. Treatment with DMSO/glucagon highly reinduced Cx26 expression in Cx32 KO hepatocytes, and such treatment reinduced expression of both Cx32 and Cx26 expression in wild types. Dye transfer was not observed following Lucifer yellow injection into DMSO/glucagon-treated Cx32 KO hepatocytes, whereas the spread was extensive in wild types. Nevertheless, high junctional conductance values were observed in treated cells from both genotypes. These studies provide a method by which the differentiated phenotype can be obtained in cultured mouse hepatocytes and provide in vitro evidence that expression of gap junctions formed of Cx32 are involved in the regulation of growth of mouse hepatocytes.


2001 ◽  
Vol 69 (12) ◽  
pp. 7413-7418 ◽  
Author(s):  
Tahar van der Straaten ◽  
Angela van Diepen ◽  
Kitty Kwappenberg ◽  
Sjaak van Voorden ◽  
Kees Franken ◽  
...  

ABSTRACT Upon contact with host cells, the intracellular pathogenSalmonella enterica serovar Typhimurium promotes its uptake, targeting, and survival in intracellular niches. In this process, the bacterium evades the microbicidal effector mechanisms of the macrophage, including oxygen intermediates. This study reports the phenotypic and genotypic characterization of an S. enterica serovar Typhimurium mutant that is hypersusceptible to superoxide. The susceptible phenotype is due to a MudJ insertion-inactivation of a previously undescribedSalmonella gene designated sspJ that is located between 54.4 and 64 min of the Salmonellachromosome and encodes a 392-amino-acid protein. In vivo, upon intraperitoneal injection of 104 to 107bacteria in C3H/HeN and 101 to 104 bacteria in BALB/c mice, the mutant strain was less virulent than the wild type. Consistent with this finding, during the first hour after ingestion by macrophage-like J774 and RAW264.7 cells in vitro, the intracellular killing of the strain carrying sspJ::MudJ is enhanced fivefold over that of wild-type microorganisms. Wild-type salmonellae displayed significant intracellular replication during the first 24 h after uptake, but sspJ::MudJ mutants failed to do so. This phenotype could be restored to that of the wild type by sspJ complementation. The SspJ protein is found in the cytoplasmic membrane and periplasmic space. Amino acid sequence homology analysis did reveal a leader sequence and putative pyrroloquinoline quinone-binding domains, but no putative protein function. We excluded the possibility that SspJ is a scavenger of superoxide or has superoxide dismutase activity.


Blood ◽  
1996 ◽  
Vol 87 (5) ◽  
pp. 2020-2028 ◽  
Author(s):  
HY Huh ◽  
SF Pearce ◽  
LM Yesner ◽  
JL Schindler ◽  
RL Silverstein

Abstract CD36 is an 88-kD integral membrane glycoprotein expressed on monocytes, platelets, and certain microvascular endothelium serving distinct cellular functions both as an adhesive receptor for thrombospondin, collagen, and Plasmodium falciparum-infected erythrocytes, and as a scavenger receptor for oxidized low-density lipoprotein and apoptotic neutrophils. In this study, we examined the expression of CD36 during in vitro differentiation of peripheral blood monocytes into culture- derived macrophages. Steady-state mRNA levels of CD36 showed a transient eightfold increase during monocyte-to-macrophage differentiation, peaking at the early macrophage stage (days 3 or 4 in culture), following a gradual decrease back to baseline levels by the mature macrophage stage (days 7 or 8 in culture). Immunoblotting with monoclonal antibodies to CD36 supported this transient, yet significant (8- to 10-fold) increase in total protein levels of CD36. The increased CD36 protein was observed at the plasma membrane, whereas an intracellular pool of CD36 was also detected from day 2 to day 6 in culture through indirect immunofluorescence. A concomitant twofold increase in the cells' ability to bind 125I-thrombospondin at the early macrophage stage (day 4) verified the functional competency of the plasma membrane localized CD36, and supported the presence of an intracellular pool of CD36. The in vitro differentiated macrophages as well as alveolar macrophages remained responsive to macrophage colony- stimulating factor (M-CSF), a known transcriptional regulator of monocyte CD36. The M-CSF-induced macrophages resulted in enhanced foam cell formation, which was inhibitable with monoclonal antibodies to CD36. Thus, the transient expression of CD36 during monocyte-to- macrophage differentiation, and the ability of M-CSF to maintain macrophage CD36 at elevated levels, may serve as a critical process in dictating the functional activity of CD36 during inflammatory responses and atherogenesis.


1999 ◽  
Vol 277 (6) ◽  
pp. C1202-C1209 ◽  
Author(s):  
Robert S. Haworth ◽  
James Sinnett-Smith ◽  
Enrique Rozengurt ◽  
Metin Avkiran

The regulation of plasma membrane Na+/H+exchanger (NHE) activity by protein kinase D (PKD), a novel protein kinase C- and phorbol ester-regulated kinase, was investigated. To determine the effect of PKD on NHE activity in vivo, intracellular pH (pHi) measurements were made in COS-7 cells by microepifluorescence using the pH indicator cSNARF-1. Cells were transfected with empty vector (control), wild-type PKD, or its kinase-deficient mutant PKD-K618M, together with green fluorescent protein (GFP). NHE activity, as reflected by the rate of acid efflux ( J H), was determined in single GFP-positive cells following intracellular acidification. Overexpression of wild-type PKD had no significant effect on J H(3.48 ± 0.25 vs. 3.78 ± 0.24 mM/min in control at pHi 7.0). In contrast, overexpression of PKD-K618M increased J H (5.31 ± 0.57 mM/min at pHi 7.0; P < 0.05 vs. control). Transfection with these constructs produced similar effects also in A-10 cells, indicating that native PKD may have an inhibitory effect on NHE in both cell types, which is relieved by a dominant-negative action of PKD-K618M. Exposure of COS-7 cells to phorbol ester significantly increased J H in control cells but failed to do so in cells overexpressing either wild-type PKD (due to inhibition by the overexpressed PKD) or PKD-K618M (because basal J Hwas already near maximal). A fusion protein containing the cytosolic regulatory domain (amino acids 637–815) of NHE1 (the ubiquitous NHE isoform) was phosphorylated in vitro by wild-type PKD, but with low stoichiometry. These data suggest that PKD inhibits NHE activity, probably through an indirect mechanism, and represents a novel pathway in the regulation of the exchanger.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3481-3481
Author(s):  
Ajay Abraham ◽  
Savitha Varatharajan ◽  
Ashok kumar Jayavelu ◽  
Shaji R Velayudhan ◽  
Rayaz Ahmed ◽  
...  

Abstract Abstract 3481 Wide inter-individual variation in terms of treatment outcome and toxic side effects of treatment exist among patients with AML receiving chemotherapy with cytarabine (ara-C) and daunorubicin. The pre-requisite for the cytotoxic action of pro-drug Ara-C is the enzymatic conversion to its active tri-phosphorylated form ara-CTP. Many drug activating (Deoxycytidine kinase (dCK) and human Equilibrative Nucleoside Transporter 1 (hENT1) and deactivating (Cytidine deaminase (CDA), 5'nucleotidase (NT5C2) genes and ribonucleoside reductase (RRM1), which are involved in transport and biotransformation of cytarabine contribute to the variation in ara-C sensitivity in AML patients. FLT3-ITD and NPM1 mutations act as major poor and good prognostic markers respectively in cytogenetically normal AML. The effect of these mutations in ara-C metabolism remains to be elucidated. The present study aims to determine independent as well as the combined effect of ara-C metabolizing genes mRNA expression on in-vitro ara-C cytotoxicity and the role of FLT3-ITD and NPM mutations on mRNA expression of these genes. Diagnostic bone marrow sample (median blasts 65%; range 21 – 98%) from 98 adult patients with de novo AML (other than AML-M3) were included in this study. mRNA expression levels for each target gene relative to housekeeping gene GAPDH was analyzed using Taqman based gene expression assays. In vitro cytotoxicity was assessed using MTT cell viability assay and IC-50 was calculated. In vitro sensitivity or resistance was classified on the basis of the IC-50 values <6uM and >6uM ara-C respectively. FLT3 ITD and NPM mutation status at diagnosis were determined through PCR followed by Genescan analysis using genomic DNA samples. Type of NPM mutation was identified by sequencing. When ara-C IC-50 values were compared with the mRNA expression levels of these candidate genes, Ara-C sensitive samples (n= 30; IC-50 < 6uM) showed significantly higher mRNA expression of dCK and hENT1 compared to those with Ara-C resistance (n=51) IC50 >6uM (median 314 (61.56 – 1232) vs. 180 (31.87 – 749.2); p = 0.0004 and median 172.1 (44.12 – 657.6) vs. 96.19 (37.49 – 432.4), p= 0.0008 respectively. RRM1 and NT5C2 did not show any association with in vitro Ara-C cytotoxicity, while CDA showed a trend towards association with lower CDA expression in ara-C sensitive samples. Based on these findings we put forward Ara-C resistance index (RI). RI is calculated by the formula RI = ΔCT (dCK X ENT1)/ ΔCT CDA. (Smaller ΔCT value= higher mRNA expression). RI values were significantly higher in resistant (IC50 >6uM) compared to sensitive cells (median: 6.084; range 1.89–11.82) vs. 3.702 (1.89–9.80); p=<0.0001). This association should now be validated in an independent cohort. Effects of NPM and FLT3 mutation status on Ara-C metabolizing genes were then evaluated. No significant association was found between FLT3-ITD status and the mRNA expression of these candidate genes. Interestingly, dCK mRNA levels were significantly higher in samples with NPM mutation (n=39) compared to NPM wild type (n=59); median 272.3 (41.64–1232) vs. 188.6 (31.87–1030); p value= 0.01. When analysed separately, patients with NPM type A mutation (n=27) showed significantly higher dCK expression (median 347.4 (41.64–1232) vs. 188.6 (31.87–1030); p value= 0.003 compared to those with wild type NPM1. This first report showing an association between expression profiles of ara-C metabolizing genes and NPM mutation should form the basis for evaluating their clinical correlations. Disclosures: No relevant conflicts of interest to declare.


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