scholarly journals Statins and Downstream Inhibitors of the Isoprenylation Pathway Increase Type 2 Iodothyronine Deiodinase Activity

Endocrinology ◽  
2012 ◽  
Vol 153 (8) ◽  
pp. 4039-4048 ◽  
Author(s):  
B. T. Miller ◽  
C. B. Ueta ◽  
V. Lau ◽  
K. G. Jacomino ◽  
L. M. Wasserman ◽  
...  
Keyword(s):  
Active Form ◽  
Critical Determinant ◽  
Iodothyronine Deiodinase ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
Reductase Inhibitors ◽  
293 Cells ◽  
Brown Adipose ◽  
Prenyl Transferase

The type 2 iodothyronine selenodeiodinase (D2) is a critical determinant of local thyroid signaling, converting T4 to the active form T3 at the cytoplasmic face of the endoplasmic reticulum, thus supplying the nucleus with T3 without immediately affecting circulating thyroid hormone levels. Although inhibitors of the cholesterol synthesis/isoprenylation pathway, such as hydroxy-methyl-glutaryl-coenzyme A reductase inhibitors (statins) have been to shown to down-regulate selenoproteins via interruption of normal selenocysteine incorporation, little is known about the effect of statins on D2. Here, we report that statins and prenyl transferase inhibitors actually increase D2 activity in cells with endogenous D2 expression. Although we confirmed that lovastatin (LVS) decreases the activity of transiently expressed D2 in HEK-293 cells, the prenyl transferase inhibitors increase activity in this system as well. LVS treatment increases endogenous Dio2 mRNA in MSTO-211H cells but does not alter transiently expressed Dio2 mRNA in HEK-293 cells. The prenyl transferase inhibitors do not increase Dio2 mRNA in either system, indicating that a posttranscriptional mechanism must exist. Cotreatment with LVS or the prenyl transferase inhibitors with the proteasome inhibitor MG-132 did not lead to additive increases in D2 activity, indirectly implicating the ubiquitin-proteasomal system in the mechanism. Finally, C57BL/6J mice treated with LVS or farnesyl transferase inhibitor-277 for 24 h exhibited increased D2 activity in their brown adipose tissue. These data indicate that statins and downstream inhibitors of the isoprenylation pathway may increase thyroid signaling via stimulation of D2 activity.

scholarly journals The E3 Ubiquitin Ligase TEB4 Mediates Degradation of Type 2 Iodothyronine Deiodinase

2009 ◽  
Vol 29 (19) ◽  
pp. 5339-5347 ◽  
Author(s):  
Ann Marie Zavacki ◽  
Rafael Arrojo e Drigo ◽  
Beatriz C. G. Freitas ◽  
Mirra Chung ◽  
John W. Harney ◽  
...  
Keyword(s):  
Cell Types ◽  
Iodothyronine Deiodinase ◽  
Hek 293 ◽  
Protein Levels ◽  
Hematopoietic Lineage ◽  
293 Cells ◽  
Brown Adipose ◽  
Critical Instability ◽  
Proteasomal Inhibitor

ABSTRACT The endoplasmic reticulum resident thyroid hormone-activating type 2 deiodinase (D2) is inactivated by ubiquitination via the hedgehog-inducible WSB-1. Ubiquitinated D2 can then be subsequently taken up by the proteasomal system or be reactivated by USP-33/20-mediated deubiquitination. Given that heterologously expressed D2 accumulates in Saccharomyces cerevisiae lacking the E3 ligase Doa10, we tested whether the human Doa10 ortholog, TEB4, plays a role in D2 ubiquitination and degradation. In a setting of transient coexpression in HEK-293 cells, TEB4 and D2 could be coimmunoprecipitated, and additional TEB4 expression decreased D2 activity by ∼50% (P < 0.05). A highly efficient TEB4 knockdown (>90% reduction in mRNA and protein levels) decreased D2 ubiquitination and increased D2 activity and protein levels by about fourfold. The other activating deiodinase, D1, or a truncated D2 molecule (Δ18-D2) that lacks a critical instability domain was not affected by TEB4 knockdown. Furthermore, TEB4 knockdown prolonged D2 activity half-life at least fourfold, even under conditions known to promote D2 ubiquitination. Neither exposure to 1 μM of the proteasomal inhibitor MG132 for 24 h nor RNA interference WSB-1 knockdown resulted in additive effects on D2 expression when combined with TEB4 knockdown. Similar results were obtained with MSTO-211 cells, which endogenously express D2, after TEB4 knockdown using a lentivirus-based transduction strategy. While TEB4 expression predominates in the hematopoietic lineage, both WSB-1 and TEB4 are coexpressed with D2 in a number of tissues and cell types, except the thyroid and brown adipose tissue, where TEB4 expression is minimal. We conclude that TEB4 interacts with and mediates loss of D2 activity, indicating that D2 ubiquitination and degradation can be tissue specific, depending on WSB-1 and TEB4 expression levels.

Phosphoinositide 3-kinase-dependent phosphorylation of the dual adaptor for phosphotyrosine and 3-phosphoinositides by the Src family of tyrosine kinase

2000 ◽  
Vol 349 (2) ◽  
pp. 605-610 ◽  
Author(s):  
Simon DOWLER ◽  
Leire MONTALVO ◽  
Doreen CANTRELL ◽  
Nick MORRICE ◽  
Dario R. ALESSI
Keyword(s):  
Growth Factor ◽  
Tyrosine Kinase ◽  
Active Form ◽  
Adaptor Protein ◽  
Sh2 Domain ◽  
Ph Domain ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Phosphoinositide 3 Kinase

We recently identified a novel adaptor protein, termed dual adaptor for phosphotyrosine and 3-phosphoinositides (DAPP1), that possesses a Src homology (SH2) domain and a pleckstrin homology (PH) domain. DAPP1 exhibits a high-affinity interaction with PtdIns(3,4,5)P3 and PtdIns(3,4)P2, which bind to the PH domain. In the present study we show that when DAPP1 is expressed in HEK-293 cells, the agonists insulin, insulin-like growth factor-1 and epidermal growth factor induce the phosphorylation of DAPP1 at Tyr139. Treatment of cells with phosphoinositide 3-kinase (PI 3-kinase) inhibitors or expression of a dominant-negative PI 3-kinase prevent phosphorylation of DAPP1 at Tyr139, and a PH-domain mutant of DAPP1, which does not interact with PtdIns(3,4,5)P3 or PtdIns(3,4)P2, is not phosphorylated at Tyr139 following agonist stimulation of cells. Overexpression of a constitutively active form of PI 3-kinase induced the phosphorylation of DAPP1 in unstimulated cells. We demonstrated that Tyr139 of DAPP1 is likely to be phosphorylated in vivo by a Src-family tyrosine kinase, since the specific Src-family inhibitor, PP2, but not an inactive variant of this drug, PP3, prevented the agonist-induced tyrosine phosphorylation of DAPP1. Src, Lyn and Lck tyrosine kinases phosphorylate DAPP1 at Tyr139in vitro at similar rates in the presence or absence of PtdIns(3,4,5)P3, and overexpression of these kinases in HEK-293 cells induces the phosphorylation of Tyr139. These findings indicate that, following activation of PI 3-kinases, PtdIns(3,4,5)P3 or PtdIns(3,4)P2 bind to DAPP1, recruiting it to the plasma membrane where it becomes phosphorylated at Tyr139 by a Src-family tyrosine kinase.

Type 2 IP3 receptors are involved in uranyl acetate induced apoptosis in HEK 293 cells

Toxicology ◽  
2009 ◽  
Vol 262 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Juraj Kopacek ◽  
Karol Ondrias ◽  
Barbora Sedlakova ◽  
Jana Tomaskova ◽  
Lucia Zahradnikova ◽  
...  
Keyword(s):  
Uranyl Acetate ◽  
Ip3 Receptors ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Induced Apoptosis

scholarly journals Overexpression of the human 2-oxoglutarate carrier lowers mitochondrial membrane potential in HEK-293 cells: contrast with the unique cold-induced mitochondrial carrier CGI-69

2001 ◽  
Vol 353 (2) ◽  
pp. 369-375 ◽  
Author(s):  
Xing Xian YU ◽  
David A. LEWIN ◽  
Alan ZHONG ◽  
Jennifer BRUSH ◽  
Peter W. SCHOW ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Human Protein ◽  
Mitochondrial Carrier ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Brown Adipose ◽  
Oxoglutarate Carrier

Using differential mRNA expression analysis, a previously uncharacterized gene was found to be up-regulated 2-fold in brown adipose tissue (BAT) of mice exposed to cold (4°C) for 48h. Contig and homology analysis revealed that the gene represents the murine orthologue to a sequence from a public database encoding a putative human protein (CGI-69). The presence of mitochondrial carrier domains in the human protein, its transmembrane topology and cold-induction of the mouse CGI-69 gene in BAT prompted an analysis of the idea that CGI-69 may represent a new uncoupling protein (UCP) functional homologue. However, transfection of human CGI-69 isoforms in HEK-293 cells yielded no change in mitochondrial membrane potential (∆Ψm), despite localization of FLAG-tagged CGI-69 to mitochondria of MCF7 cells. Surprisingly, overexpression of the human 2-oxoglutarate carrier (OGC) protein (originally designed as a negative control) sparked a significant drop in ∆Ψm, possibly signalling a previously unappreciated uncoupling activity for the OGC.

Ablation of small conductance calcium-activated potassium type-2 channel (SK2) delays occurrence of bupivacaine-induced cardiotoxicity in isolated mouse hearts

2020 ◽  
pp. 096032712095810
Author(s):  
H Chen ◽  
F Xia ◽  
X Chen ◽  
Y Cai ◽  
Z Jin
Keyword(s):  
Rate Pressure Product ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
Severe Arrhythmia ◽  
293 Cells ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent ◽  
Small Conductance

Bupivacaine is frequently used for conducting regional anesthesia. When accidentally injected or excessively absorbed into circulation, bupivacaine can induce severe arrhythmia and potentially lead to cardiac arrest. The specific mechanisms underlying this cardiotoxicity, however, remain to be clarified. We transfected HEK-293 cells to express the small conductance calcium-activated potassium type-2 channel (SK2), and used a whole-cell patch clamp method in order to explore how bupivacaine affected these channels. We subsequently used SK2 knockout mice to explore the relevance of SK2 channels in bupivacaine-induced cardiotoxicity in isolating mouse hearts, mounting them on a Langendorff apparatus, and perfusing them with bupivacaine. Using this system, arrhythmia, asystole, and cardiac functions were monitored. We observed dose-dependent inhibition of SK2 channels by bupivacaine: half-maximal inhibitory concentration (IC50) value = 18.6 μM (95% CI 10.8–32.1). When SK2 knockout (SK2 −/−) or wild-type (WT) mice were perfused with Krebs-Henseleit buffer (KHB), we did not observe any instances of arrhythmia. When SK2 −/− mice or WT were perfused with KHB containing bupivacaine (40 μM), the time to arrhythmia (Tarrhythmia) and time to asystole (Tasystole) were both significantly longer in SK2 −/− mice relative to WT mice ( P < 0.001). Similarly, SK2 −/− mice exhibited a significantly longer time to 25%, 50%, and 75% reductions in heart rate (HR) and rate-pressure product (RPP) relative to WT mice following bupivacaine perfusion ( P < 0.001). These results reveal that bupivacaine was able to mediate a dose-dependent inhibition of SK2 channels in HEK-293 cells, and deletion of SK2 channels can delay bupivacaine-induced cardiotoxicity in isolated mouse hearts.

scholarly journals Bupivacaine inhibits a small conductance calcium-activated potassium type 2 channel (SK2) in HEK 293 cells

2019 ◽  
Author(s):  
Hongfei Chen ◽  
Fangfang Xia ◽  
Zhousheng Jin ◽  
Yuting He ◽  
Zhengjie Chen ◽  
...  
Keyword(s):  
Inhibitory Effect ◽  
Heart Cells ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Ic50 Value ◽  
Small Conductance

Abstract Background: Bupivacaine blocks many ion channels in the heart muscle, which could cause severe cardiotoxicity. Small conductance calcium-activated potassium type 2 channels (SK2 channels) are widely distributed in the heart cells and are involved in relevant physiological functions. However, whether bupivacaine can inhibit SK2 channels is still unknown. This study investigated the effect of bupivacaine on SK2 channels. Methods: The SK2 channel gene was transfected into human embryonic kidney 293 cells (HEK-293 cells) with Lipofectamine 2000. The whole-cell patch clamp technique was used to study the effect of bupivacaine on SK2 channels. The inhibitory effect of various concentrations of bupivacaine on SK2 currents exhibited a non-linear relation, and the half-maximal inhibitory concentration (IC50) value was determined. Results: Bupivacaine inhibited the SK2 channels reversibly in a dose-dependent manner. The IC50 value of bupivacaine, ropivacaine and lidocaine on the SK2 current was 133.7, 189.3, and 885.8 µM, respectively. The degree of SK2 current inhibition by bupivacaine was dependent on the intracellular concentration of free calcium. Conclusions: The results of this study suggested a new inhibitory effect of bupivacaine on SK2 channels. Future studies should be concerned with the effects of SK2 on bupivacaine cardiotoxicity. Keywords: Bupivacaine, SK2 channel, inhibition, cardiotoxicity, HEK 293.

Modulatory role of HMG-CoA reductase inhibitors and ezetimibe on LDL-AGEs-induced ROS generation and RAGE-associated signalling in HEK-293 Cells

Life Sciences ◽  
2019 ◽  
Vol 235 ◽  
pp. 116823
Author(s):  
Rabia Nabi ◽  
Sahir Sultan Alvi ◽  
Arunim Shah ◽  
Chandra P. Chaturvedi ◽  
Danish Iqbal ◽  
...  
Keyword(s):  
Ros Generation ◽  
Hmg Coa Reductase ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
Reductase Inhibitors ◽  
293 Cells ◽  
Hmg Coa Reductase Inhibitors ◽  
Coa Reductase

scholarly journals Increase of 5-HT levels is induced both in mouse brain and HEK-293 cells following their exposure to a non-viral tryptophan hydroxylase construct

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Emiliano Tesoro-Cruz ◽  
Leticia Manuel-Apolinar ◽  
Norma Oviedo ◽  
Sandra Orozco-Suárez ◽  
Minerva Crespo Ramírez ◽  
...  
Keyword(s):  
Brain Function ◽  
Tryptophan Hydroxylase ◽  
Impulsive Behavior ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Serotonin Deficiency ◽  
Rate Limiting ◽  
The Brain

AbstractTryptophan hydroxylase type 2 (Tph2) is the rate-limiting enzyme for serotonin (5-HT) biosynthesis in the brain. Dysfunctional Tph2 alters 5-HT biosynthesis, leading to a deficiency of 5-HT, which could have repercussions on human behavior. In the last decade, several studies have associated polymorphisms of the TPH2 gene with suicidal behavior. Additionally, a 5-HT deficiency has been implicated in various psychiatric pathologies, including alcoholism, impulsive behavior, anxiety, and depression. Therefore, the TPH2 gene could be an ideal target for analyzing the effects of a 5-HT deficiency on brain function. The aim of this study was to use the construct pIRES-hrGFP-1a-Tph2-FLAG to treat CD1-male mice and to transfect HEK-293-cells and then to evaluate whether this treatment increases 5-HT production. 5-HT levels were enhanced 48 h post-transfection, in HEK-293 cells. Three days after the ocular administration of pIRES-hrGFP-1a-Tph2-FLAG to mice, putative 5-HT production was significantly higher than in the control in both hypothalamus and amygdala, but not in the brainstem. Further research will be needed on the possible application of this treatment for psychiatric diseases involving a Tph2 dysfunction or serotonin deficiency.

scholarly journals Characteristics and requirements of basal autophagy in HEK 293 cells

Autophagy ◽  
2013 ◽  
Vol 9 (9) ◽  
pp. 1407-1417 ◽  
Author(s):  
Patience Musiwaro ◽  
Matthew Smith ◽  
Maria Manifava ◽  
Simon A. Walker ◽  
Nicholas T. Ktistakis
Keyword(s):  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells

Halothane Inhibition of Recombinant Cardiac L-type Ca2+ Channels Expressed in HEK-293 Cells

2005 ◽  
Vol 103 (6) ◽  
pp. 1156-1166 ◽  
Author(s):  
Kevin J. Gingrich ◽  
Son Tran ◽  
Igor M. Nikonorov ◽  
Thomas J. Blanck
Keyword(s):  
Charge Transfer ◽  
Calcium Channels ◽  
Dependent Manner ◽  
Current Time ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells ◽  
Dependent Inactivation ◽  
Voltage Dependent

Background Volatile anesthetics depress cardiac contractility, which involves inhibition of cardiac L-type calcium channels. To explore the role of voltage-dependent inactivation, the authors analyzed halothane effects on recombinant cardiac L-type calcium channels (alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1), which differ by the alpha2/delta1 subunit and consequently voltage-dependent inactivation. Methods HEK-293 cells were transiently cotransfected with complementary DNAs encoding alpha1C tagged with green fluorescent protein and beta2a, with and without alpha2/delta1. Halothane effects on macroscopic barium currents were recorded using patch clamp methodology from cells expressing alpha1Cbeta2a and alpha1Cbeta2aalpha2/delta1 as identified by fluorescence microscopy. Results Halothane inhibited peak current (I(peak)) and enhanced apparent inactivation (reported by end pulse current amplitude of 300-ms depolarizations [I300]) in a concentration-dependent manner in both channel types. alpha2/delta1 coexpression shifted relations leftward as reported by the 50% inhibitory concentration of I(peak) and I300/I(peak)for alpha1Cbeta2a (1.8 and 14.5 mm, respectively) and alpha1Cbeta2aalpha2/delta1 (0.74 and 1.36 mm, respectively). Halothane reduced transmembrane charge transfer primarily through I(peak) depression and not by enhancement of macroscopic inactivation for both channels. Conclusions The results indicate that phenotypic features arising from alpha2/delta1 coexpression play a key role in halothane inhibition of cardiac L-type calcium channels. These features included marked effects on I(peak) inhibition, which is the principal determinant of charge transfer reductions. I(peak) depression arises primarily from transitions to nonactivatable states at resting membrane potentials. The findings point to the importance of halothane interactions with states present at resting membrane potential and discount the role of inactivation apparent in current time courses in determining transmembrane charge transfer.

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