scholarly journals Mitochondrial potassium channels: A novel calcitriol target

2022 ◽  
Vol 27 (1) ◽  
Author(s):  
Anna M. Olszewska ◽  
Adam K. Sieradzan ◽  
Piotr Bednarczyk ◽  
Adam Szewczyk ◽  
Michał A. Żmijewski
Keyword(s):  
Vitamin D ◽  
Potassium Channels ◽  
Potassium Channel ◽  
Mitochondrial Membrane ◽  
Human Keratinocytes ◽  
Inner Mitochondrial Membrane ◽  
Open Probability ◽  
Expression Of Genes ◽  
High Calcium ◽  
Genes Encoding

Abstract Background Calcitriol (an active metabolite of vitamin D) modulates the expression of hundreds of human genes by activation of the vitamin D nuclear receptor (VDR). However, VDR-mediated transcriptional modulation does not fully explain various phenotypic effects of calcitriol. Recently a fast non-genomic response to vitamin D has been described, and it seems that mitochondria are one of the targets of calcitriol. These non-classical calcitriol targets open up a new area of research with potential clinical applications. The goal of our study was to ascertain whether calcitriol can modulate mitochondrial function through regulation of the potassium channels present in the inner mitochondrial membrane. Methods The effects of calcitriol on the potassium ion current were measured using the patch-clamp method modified for the inner mitochondrial membrane. Molecular docking experiments were conducted in the Autodock4 program. Additionally, changes in gene expression were investigated by qPCR, and transcription factor binding sites were analyzed in the CiiiDER program. Results For the first time, our results indicate that calcitriol directly affects the activity of the mitochondrial large-conductance Ca2+-regulated potassium channel (mitoBKCa) from the human astrocytoma (U-87 MG) cell line but not the mitochondrial calcium-independent two-pore domain potassium channel (mitoTASK-3) from human keratinocytes (HaCaT). The open probability of the mitoBKCa channel in high calcium conditions decreased after calcitriol treatment and the opposite effect was observed in low calcium conditions. Moreover, using the AutoDock4 program we predicted the binding poses of calcitriol to the calcium-bound BKCa channel and identified amino acids interacting with the calcitriol molecule. Additionally, we found that calcitriol influences the expression of genes encoding potassium channels. Such a dual, genomic and non-genomic action explains the pleiotropic activity of calcitriol. Conclusions Calcitriol can regulate the mitochondrial large-conductance calcium-regulated potassium channel. Our data open a new chapter in the study of non-genomic responses to vitamin D with potential implications for mitochondrial bioenergetics and cytoprotective mechanisms.

Large-conductance Ca2+-activated potassium channel in mitochondria of endothelial EA.hy926 cells

2013 ◽  
Vol 304 (11) ◽  
pp. H1415-H1427 ◽  
Author(s):  
Piotr Bednarczyk ◽  
Agnieszka Koziel ◽  
Wieslawa Jarmuszkiewicz ◽  
Adam Szewczyk
Keyword(s):  
Potassium Channel ◽  
Mitochondrial Membrane ◽  
Single Channel ◽  
Dependent Manner ◽  
Channel Activity ◽  
Inner Mitochondrial Membrane ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Α Subunit ◽  
Ea.Hy926 Cells

In the present study, we describe the existence of a large-conductance Ca2+-activated potassium (BKCa) channel in the mitochondria of the human endothelial cell line EA.hy926. A single-channel current was recorded from endothelial mitoplasts (i.e., inner mitochondrial membrane) using the patch-clamp technique in the mitoplast-attached mode. A potassium-selective current was recorded with a mean conductance equal to 270 ± 10 pS in a symmetrical 150/150 mM KCl isotonic solution. The channel activity, which was determined as the open probability, increased with the addition of calcium ions and the potassium channel opener NS1619. Conversely, the activity of the channel was irreversibly blocked by paxilline and iberiotoxin, BKCa channel inhibitors. The open-state probability was found to be voltage dependent. The substances known to modulate BKCa channel activity influenced the bioenergetics of mitochondria isolated from human endothelial EA.hy926 cells. In isolated mitochondria, 100 μM Ca2+, 10 μM NS1619, and 0.5 μM NS11021 depolarized the mitochondrial membrane potential and stimulated nonphosphorylating respiration. These effects were blocked by iberiotoxin and paxilline in a potassium-dependent manner. Under phosphorylating conditions, NS1619-induced, iberiotoxin-sensitive uncoupling diverted energy from ATP synthesis during the phosphorylating respiration of the endothelial mitochondria. Immunological analysis with antibodies raised against proteins of the plasma membrane BKCa channel identified a pore-forming α-subunit and an auxiliary β2-subunit of the channel in the endothelial mitochondrial inner membrane. In conclusion, we show for the first time that the inner mitochondrial membrane in human endothelial EA.hy926 cells contains a large-conductance calcium-dependent potassium channel with properties similar to those of the surface membrane BKCa channel.

Intermediate conductance Ca2+-activated potassium channel (KCa3.1) in the inner mitochondrial membrane of human colon cancer cells

Cell Calcium ◽  
2009 ◽  
Vol 45 (5) ◽  
pp. 509-516 ◽  
Author(s):  
Umberto De Marchi ◽  
Nicola Sassi ◽  
Bernard Fioretti ◽  
Luigi Catacuzzeno ◽  
Grazia M. Cereghetti ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Potassium Channel ◽  
Cancer Cells ◽  
Mitochondrial Membrane ◽  
Human Colon ◽  
Colon Cancer Cells ◽  
Inner Mitochondrial Membrane ◽  
Human Colon Cancer ◽  
Human Colon Cancer Cells

The calcium-sensitive large-conductance potassium channel (BK/MAXI K) is present in the inner mitochondrial membrane of rat brain

Neuroscience ◽  
2006 ◽  
Vol 139 (4) ◽  
pp. 1249-1261 ◽  
Author(s):  
R.M. Douglas ◽  
J.C.K. Lai ◽  
S. Bian ◽  
L. Cummins ◽  
E. Moczydlowski ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Rat Brain ◽  
Mitochondrial Membrane ◽  
Inner Mitochondrial Membrane

scholarly journals Revisiting the Large-Conductance Calcium-Activated Potassium (BKCa) Channels in the Pulmonary Circulation

Biomolecules ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1629
Author(s):  
Divya Guntur ◽  
Horst Olschewski ◽  
Péter Enyedi ◽  
Réka Csáki ◽  
Andrea Olschewski ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Potassium Channels ◽  
Pulmonary Circulation ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Free Calcium ◽  
Bkca Channel ◽  
Lung Pathology ◽  
Open Probability ◽  
Bkca Channels ◽  
Genes Encoding

Potassium ion concentrations, controlled by ion pumps and potassium channels, predominantly govern a cell′s membrane potential and the tone in the vessels. Calcium-activated potassium channels respond to two different stimuli-changes in voltage and/or changes in intracellular free calcium. Large conductance calcium-activated potassium (BKCa) channels assemble from pore forming and various modulatory and auxiliary subunits. They are of vital significance due to their very high unitary conductance and hence their ability to rapidly cause extreme changes in the membrane potential. The pathophysiology of lung diseases in general and pulmonary hypertension, in particular, show the implication of either decreased expression and partial inactivation of BKCa channel and its subunits or mutations in the genes encoding different subunits of the channel. Signaling molecules, circulating humoral molecules, vasorelaxant agents, etc., have an influence on the open probability of the channel in pulmonary arterial vascular cells. BKCa channel is a possible therapeutic target, aimed to cause vasodilation in constricted or chronically stiffened vessels, as shown in various animal models. This review is a comprehensive collation of studies on BKCa channels in the pulmonary circulation under hypoxia (hypoxic pulmonary vasoconstriction; HPV), lung pathology, and fetal to neonatal transition, emphasising pharmacological interventions as viable therapeutic options.

scholarly journals BK in Double-Membrane Organelles: A Biophysical, Pharmacological, and Functional Survey

2021 ◽  
Vol 12 ◽  
Author(s):  
Naileth González-Sanabria ◽  
Felipe Echeverría ◽  
Ignacio Segura ◽  
Rosangelina Alvarado-Sánchez ◽  
Ramon Latorre
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Potassium Channel ◽  
Lipid Bilayers ◽  
Bk Channels ◽  
Bk Channel ◽  
Inner Mitochondrial Membrane ◽  
Modular Architecture ◽  
Open Probability ◽  
Α Subunit

In the 1970s, calcium-activated potassium currents were recorded for the first time. In 10years, this Ca2+-activated potassium channel was identified in rat skeletal muscle, chromaffin cells and characterized in skeletal muscle membranes reconstituted in lipid bilayers. This calcium- and voltage-activated potassium channel, dubbed BK for “Big K” due to its large ionic conductance between 130 and 300 pS in symmetric K+. The BK channel is a tetramer where the pore-forming α subunit contains seven transmembrane segments. It has a modular architecture containing a pore domain with a highly potassium-selective filter, a voltage-sensor domain and two intracellular Ca2+ binding sites in the C-terminus. BK is found in the plasma membrane of different cell types, the inner mitochondrial membrane (mitoBK) and the nuclear envelope’s outer membrane (nBK). Like BK channels in the plasma membrane (pmBK), the open probability of mitoBK and nBK channels are regulated by Ca2+ and voltage and modulated by auxiliary subunits. BK channels share common pharmacology to toxins such as iberiotoxin, charybdotoxin, paxilline, and agonists of the benzimidazole family. However, the precise role of mitoBK and nBK remains largely unknown. To date, mitoBK has been reported to play a role in protecting the heart from ischemic injury. At the same time, pharmacology suggests that nBK has a role in regulating nuclear Ca2+, membrane potential and expression of eNOS. Here, we will discuss at the biophysical level the properties and differences of mitoBK and nBK compared to those of pmBK and their pharmacology and function.

A large-conductance calcium-regulated K+ channel in human dermal fibroblast mitochondria

2016 ◽  
Vol 473 (23) ◽  
pp. 4457-4471 ◽  
Author(s):  
Anna Kicinska ◽  
Bartlomiej Augustynek ◽  
Bogusz Kulawiak ◽  
Wieslawa Jarmuszkiewicz ◽  
Adam Szewczyk ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Potassium Channel ◽  
Mitochondrial Membrane Potential ◽  
Mitochondrial Membrane ◽  
Dermal Fibroblast ◽  
Human Dermal Fibroblast ◽  
Dermal Fibroblasts ◽  
K Channel ◽  
Inner Mitochondrial Membrane ◽  
Bkca Channels

Potassium channels have been found in the inner mitochondrial membrane of various cells. These channels regulate the mitochondrial membrane potential, respiration and production of reactive oxygen species. In the present study, we identified the activity of a mitochondrial large-conductance Ca2+-regulated potassium channel (mitoBKCa channel) in mitoplasts isolated from a primary human dermal fibroblast cell line. A potassium selective current was recorded with a mean conductance of 280 ± 2 pS in a symmetrical 150 mM KCl solution. The mitoBKCa channel was activated by the Ca2+ and by potassium channel opener NS1619. The channel activity was irreversibly inhibited by paxilline, a selective inhibitor of the BKCa channels. In isolated fibroblast mitochondria NS1619 depolarized the mitochondrial membrane potential, stimulated nonphosphorylating respiration and decreased superoxide formation. Additionally, the α- and β-subunits (predominantly the β3-form) of the BKCa channels were identified in fibroblast mitochondria. Our findings indicate, for the first time, the presence of a large-conductance Ca2+-regulated potassium channel in the inner mitochondrial membrane of human dermal fibroblasts.

scholarly journals Vitamin D Receptor Gene Expression in Adipose Tissue of Obese Individuals is Regulated by miRNA and Correlates with the Pro-Inflammatory Cytokine Level

2019 ◽  
Vol 20 (21) ◽  
pp. 5272 ◽  
Author(s):  
Marta Izabela Jonas ◽  
Alina Kuryłowicz ◽  
Zbigniew Bartoszewicz ◽  
Wojciech Lisik ◽  
Maurycy Jonas ◽  
...  
Keyword(s):  
Vitamin D ◽  
Adipose Tissue ◽  
Receptor Gene ◽  
Normal Weight ◽  
Mrna Levels ◽  
Adipose Tissues ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Obese Subjects ◽  
Inflammatory Milieu

Background: Given the role that vitamin D (VD) plays in the regulation of the inflammatory activity of adipocytes, we aimed to assess whether obesity changes the expression of VD-related genes in adipose tissue and, if so, to investigate whether this phenomenon depends on microRNA interference and how it may influence the local inflammatory milieu. Methods: The expression of genes encoding VD 1α-hydroxylase (CYP27B1), 24-hydroxylase (CYP24A1) and receptor (VDR), selected interleukins and microRNAs was evaluated by real-time PCR in visceral (VAT) and in subcutaneous (SAT) adipose tissues of 55 obese (BMI > 40 kg/m2) and 31 normal-weight (BMI 20–24.9 kg/m2) individuals. Results: VDR mRNA levels were higher, while CYP27B1 levels were lower in adipose tissues of obese patients than in those of normal-weight controls (VAT: P = 0.04, SAT: P < 0.0001 and VAT: P = 0.004, SAT: P = 0.016, respectively). The expression of VDR in VAT of obese subjects correlated negatively with levels of miR-125a-5p (P = 0.0006, rs = −0.525), miR-125b-5p (P = 0.001, rs = −0.495), and miR-214-3p (P = 0.009, rs = −0.379). Additionally, VDR mRNA concentrations in visceral adipose tissues of obese subjects correlated positively with mRNA levels of interleukins: 1β, 6 and 8. Conclusions: We observed obesity-associated up-regulation of VDR and down-regulation of CYP27B mRNA levels in adipose tissue. VDR expression correlates with the expression of pro-inflammatory cytokines and may be regulated by miRNAs.

scholarly journals Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization.

2000 ◽  
Vol 47 (2) ◽  
pp. 469-480 ◽  
Author(s):  
A Szkopińska
Keyword(s):  
Metabolic Pathways ◽  
Mitochondrial Membrane ◽  
Coenzyme Q ◽  
Intracellular Localization ◽  
Mitochondrial Respiratory Chain ◽  
Cellular Level ◽  
Reduced Form ◽  
Side Chain ◽  
Inner Mitochondrial Membrane ◽  
Genes Encoding

Ubiquinone, known as coenzyme Q, was shown to be the part of the metabolic pathways by Crane et al. in 1957. Its function as a component of the mitochondrial respiratory chain is well established. However, ubiquinone has recently attracted increasing attention with regard to its function, in the reduced form, as an antioxidant. In ubiquinone synthesis the para-hydroxybenzoate ring (which is the derivative of tyrosine or phenylalanine) is condensed with a hydrophobic polyisoprenoid side chain, whose length varies from 6 to 10 isoprene units depending on the organism. para-Hydroxybenzoate (PHB) polyprenyltransferase that catalyzes the condensation of PHB with polyprenyl diphosphate has a broad substrate specificity. Most of the genes encoding (all-E)-prenyltransferases which synthesize polyisoprenoid chains, have been cloned. Their structure is either homo- or heterodimeric. Genes that encode prenyltransferases catalysing the transfer of the isoprenoid chain to para-hydroxybenzoate were also cloned in bacteria and yeast. To form ubiquinone, prenylated PHB undergoes several modifications such as hydroxylations, O-methylations, methylations and decarboxylation. In eukaryotes ubiquinones were found in the inner mitochondrial membrane and in other membranes such as the endoplasmic reticulum, Golgi vesicles, lysosomes and peroxisomes. Still, the subcellular site of their biosynthesis remains unclear. Considering the diversity of functions of ubiquinones, and their multistep biosynthesis, identification of factors regulating their cellular level remains an elusive task.

scholarly journals Vitamin D-Related Genetics as Predictive Biomarker of Clinical Remission in Adalimumab-Treated Patients Affected by Crohn’s Disease: A Pilot Study

2021 ◽  
Vol 14 (12) ◽  
pp. 1230
Author(s):  
Jessica Cusato ◽  
Lorenzo Bertani ◽  
Miriam Antonucci ◽  
Cristina Tomasello ◽  
Gian Paolo Caviglia ◽  
...  
Keyword(s):  
Vitamin D ◽  
Crohn’S Disease ◽  
Crohn's Disease ◽  
Clinical Remission ◽  
Predictive Biomarker ◽  
Nucleotide Polymorphisms ◽  
Protein Levels ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Bowel Diseases

Adalimumab (ADA) is a human anti-tumor necrosis factor (TNF-α) monoclonal antibody used in inflammatory bowel diseases, such as Crohn’s disease (CD). Vitamin-D (VD) is important for biological functions, such as the modulation of expression of genes encoding enzymes and transporters involved in drug metabolism and transport. ADA trough levels were associated with VD concentrations in patients with IBD, but no data are present in the literature concerning VD pathway-related gene single-nucleotide polymorphisms (SNPs) in affecting clinical outcomes. For this reason, the aim of this study was to evaluate the ability of VD-related genetics to predict clinical remission at 3 and 12 months in patients affected by CD treated with ADA. Patients affected by CD were included in this study. SNPs in CYP27B1, CYP24A1, GC, and VDR genes were analyzed through real-time PCR. A total of 63 patients were enrolled. Calprotectin, hemoglobin, and C-reactive protein levels were influenced by SNPs in VDR, CYP27B1, and GC genes. After 3 months of therapy, clinical remission was predicted by smoke, systemic steroids, and VDR BsmI, whereas at 12 months by GC 1296AA/AC and VD supplementation. This study reports the association between VD pathway-related genetics and ADA treatment. Further studies are needed to confirm these promising data.

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