Expression Of Calcium-activated Potassium Channels Research Articles

A Detailed Study to Discover the Trade between Left Atrial Blood Flow, Expression of Calcium-Activated Potassium Channels and Valvular Atrial Fibrillation.

Background: The present study aimed to explore the correlation between calcium-activated potassium channels, left atrial flow field mechanics, valvular atrial fibrillation (VAF), and thrombosis. The process of transforming mechanical signals into biological signals has been revealed, which offers new insights into the study of VAF. Methods: Computational fluid dynamics simulations use numeric analysis and algorithms to compute flow parameters, including turbulent shear stress (TSS) and wall pressure in the left atrium (LA). Real-time PCR and western blotting were used to detect the mRNA and protein expression of IKCa2.3/3.1, ATK1, and P300 in the left atrial tissue of 90 patients. Results: In the valvular disease group, the TSS and wall ressure in the LA increased, the wall pressure increased in turn in all disease groups, mainly near the mitral valve and the posterior portion of the LA, the increase in TSS was the most significant in each group near the mitral valve, and the middle and lower part of the back of the LA and the mRNA expression and protein expression levels of IKCa2.3/3.1, AKT1, and P300 increased (p < 0.05) (n = 15). The present study was preliminarily conducted to elucidate whether there might be a certain correlation between IKCa2.3 and LA hemodynamic changes. Conclusions: The TSS and wall pressure changes in the LA are correlated with the upregulation of mRNA and protein expression of IKCa2.3/3.1, AKT1, and P300.

Characterization of the expression of calcium-activated potassium channels (BKCa and IKCa) in placenta of gestational diabetes mellitus

Characterization of the expression of calcium-activated potassium channels (BKCa and IKCa) in placenta of gestational diabetes mellitus

Pyk2 inhibition promotes contractile differentiation in arterial smooth muscle

Modulation from contractile to synthetic phenotype of vascular smooth muscle cells is a central process in disorders involving compromised integrity of the vascular wall. Phenotype modulation has been shown to include transition from voltage-dependent toward voltage-independent regulation of the intracellular calcium level, and inhibition of non-voltage dependent calcium influx contributes to maintenance of the contractile phenotype. One possible mediator of calcium-dependent signaling is the FAK-family non-receptor protein kinase Pyk2, which is activated by a number of stimuli in a calcium-dependent manner. We used the Pyk2 inhibitor PF-4594755 and Pyk2 siRNA to investigate the role of Pyk2 in phenotype modulation in rat carotid artery smooth muscle cells and in cultured intact arteries. Pyk2 inhibition promoted the expression of smooth muscle markers at the mRNA and protein levels under stimulation by FBS or PDGF-BB and counteracted phenotype shift in cultured intact carotid arteries and balloon injury ex vivo. During long-term (24-96 hr) treatment with PF-4594755, smooth muscle markers increased before cell proliferation was inhibited, correlating with decreased KLF4 expression and differing from effects of MEK inhibition. The Pyk2 inhibitor reduced Orai1 and preserved SERCA2a expression in carotid artery segments in organ culture, and eliminated the inhibitory effect of PDGF stimulation on L-type calcium channel and large-conductance calcium-activated potassium channel expression in carotid cells. Basal intracellular calcium level, calcium wave activity, and store-operated calcium influx were reduced after Pyk2 inhibition of growth-stimulated cells. Pyk2 inhibition may provide an interesting approach for preserving vascular smooth muscle differentiation under pathophysiological conditions.

Characterization and expression of calcium-activated potassium channels (Slo) in ovary of the mud crab, Scylla paramamosain

Large conductance calcium-activated potassium channels (Slo) play important roles in controlling neuronal excitability. At present, very little is known about the function of Slo channels on ovarian development. We cloned the SPSlo gene from the mud crab, Scylla paramamosain. This gene shows 91 and 93 % sequence identity to PISlo from the spiny lobster, Panulirus interruptus and CBSlo from the jonah crab, Cancer borealis, respectively. We isolated six variants of the SPSlo cDNA within S. paramamosain ovary tissue. Sequence analysis indicated that there were at least seven alternative sites in SPSlo, each with multiple alternative segments. Real-time PCR showed that the SPSlo gene was expressed in various tissues, and highly expressed in brain and ovary. In addition, the expression of SPSlo changed throughout ovarian development, highest at the early-developing stage (Stage II) followed by a slow decrease in subsequent stages. These results suggested that SPSlo channels may be implicated in the ovarian development of the mud crab.

Effects of botulinum toxin type A on digit abduction score and running wheel assays and assessment of diffusion using calcium-activated potassium channel expression

Effects of botulinum toxin type A on digit abduction score and running wheel assays and assessment of diffusion using calcium-activated potassium channel expression

Calcium activated potassium channel expression during human iPS cell-derived neurogenesis

The family of calcium activated potassium channels of low and intermediate conductance, known as SK channels, consists of four members (SK1-4). These channels are widely expressed throughout the organism and involved in various cellular processes, such as the afterhyperpolarization in excitable cells but also in differentiation processes of various tissues. To date, the role of SK channels in developmental processes has been merely a marginal focus of investigation, although it is well accepted that cell differentiation and maturation affect the expression patterns of certain ion channels. Recently, several studies from our laboratory delineated the influence of SK channel expression and their respective activity on cytoskeletal reorganization in neural and pluripotent stem cells and regulation of cell fate determination toward the cardiac lineage in human and mouse pluripotent stem cells. Herein, we have now analyzed SK channel expression patterns and distribution at various stages of human induced pluripotent stem cell-derived neurogenesis particularly focusing on undifferentiated iPS cells, neural progenitors and mature neurons. All family members could be detected starting at the iPS cell level and were differentially expressed during the subsequent maturation process. Intriguingly, we found obvious discrepancies between mRNA and protein expression pointing toward a complex regulatory mechanism. Inhibition of SK channels with either apamin or clotrimazol did not have any significant effects on the speed or amount of neurogenesis in vitro. The abundance and specific regulation of SK channel expression during iPS cell differentiation indicates distinct roles of these ion channels not only for the cardiac but also for neuronal cell differentiation and in vitro neurogenesis.

Distinct Acyl Protein Transferases and Thioesterases Control Surface Expression of Calcium-activated Potassium Channels

Protein palmitoylation is rapidly emerging as an important determinant in the regulation of ion channels, including large conductance calcium-activated potassium (BK) channels. However, the enzymes that control channel palmitoylation are largely unknown. Indeed, although palmitoylation is the only reversible lipid modification of proteins, acyl thioesterases that control ion channel depalmitoylation have not been identified. Here, we demonstrate that palmitoylation of the intracellular S0-S1 loop of BK channels is controlled by two of the 23 mammalian palmitoyl-transferases, zDHHC22 and zDHHC23. Palmitoylation by these acyl transferases is essential for efficient cell surface expression of BK channels. In contrast, depalmitoylation is controlled by the cytosolic thioesterase APT1 (LYPLA1), but not APT2 (LYPLA2). In addition, we identify a splice variant of LYPLAL1, a homolog with ∼30% identity to APT1, that also controls BK channel depalmitoylation. Thus, both palmitoyl acyltransferases and acyl thioesterases display discrete substrate specificity for BK channels. Because depalmitoylated BK channels are retarded in the trans-Golgi network, reversible protein palmitoylation provides a critical checkpoint to regulate exit from the trans-Golgi network and thus control BK channel cell surface expression.

Rapid Aldosterone Signaling and Vascular Reactivity: Relax or Don't Do It

Rapid Aldosterone Signaling and Vascular Reactivity: Relax or Don't Do It

Dexamethasone enhances calcium-activated potassium channel expression in blood-brain tumor barrier in a rat brain tumor model

This study was performed to determine whether dexamethasone (DEX) had an effect on calcium-activated potassium channels ( K Ca channels) in blood-brain tumor barrier (BTB). Using a rat brain glioma model, we found that the expression of K Ca channels protein was significantly increased in brain tumor tissue. And bradykinin-induced increase of K Ca channels protein was further enhanced after DEX pretreatment for 3 days. In addition, DEX pretreatment enhanced bradykinin-mediated up-regulation of the density of I KCa in the rat brain C6 cells in vitro BTB. Bradykinin markedly increased BTB permeability independent of DEX pretreatment. All of these results strongly suggest that DEX could regulate the target in the transcellular pathway of BTB- K Ca channels.

Calcium-activated potassium channel and connexin expression in small mesenteric arteries from eNOS-deficient (eNOS −/−) and eNOS-expressing (eNOS +/+) mice

Endothelium-derived hyperpolarizing factor (EDHF), notably in the microcirculation, plays an important role in the regulation of vascular tone. The cellular events that mediate EDHF are critically dependent, in a vessel dependent manner, on small conductance calcium-activated potassium channels (SK) and intermediate conductance calcium-activated potassium channels (IK) as well as the presence of the gap junction connexins 37, 40, and 43. We hypothesized that the expression levels of SK, IK, as well as vascular connexins, notably 37, 40 and 43 but, potentially, connexin 45, would show correlation with the contribution of EDHF to acetylcholine-mediated vasodilatation as well as, in the absence of endothelial-derived NO, higher expression levels in eNOS −/− mice. Wire myograph studies were performed to confirm the contribution of EDHF to endothelium-dependent relaxation in 1st, 2nd and 3rd order small mesenteric arteries from C57BL/6J eNOS-expressing (eNOS +/+) and eNOS-deficient C57BL/6J (eNOS −/−) mice. Small mesenteric arteries, as well as the branch points between 1st and 2nd and 2nd and 3rd order vessels, were analysed for the expression of mRNA for SK1, SK2, SK3, IK and large conductance calcium-activated potassium channels (BK) and comparable studies were performed for connexins 37, 40, 43 and 45. Although the contribution of EDHF to endothelium-dependent relaxation was significantly greater in the 3rd order vessels from the eNOS +/+ the real-time (RT) polymerase chain reaction (PCR) data showed no differences for the expression levels of mRNA for any of the channel subtypes or the connexins within the small mesenteric arteries from either the eNOS +/+ or eNOS −/− mice, nor, based on RT PCR analysis, were there differences in expression of the potassium channels studied in the branch points versus 1st, 2nd or 3rd order vessels. These data suggest that neither the gene expression of calcium-activated potassium channels nor vascular connexins are modulated by NO; however, their functional contribution to endothelium-dependent relaxation may be modulated by other physiological parameters.

721Alterations in calcium-activated potassium channel expression in human prostate cancer

Duk Yoon Kim, Eun Kyoung Yang, Jung Wook Kim Department of Urology, Catholic University of Daegu School of Medicine, Department of Physiology, Kyungpook National University School of Medicine, Daegu, Korea Purpose: Recent studies have shown that potassium (K) and sodium channels are involved in prostate cell growth. However, a great many of the studies have been done in prostate cancer cell lines and there are only scant studies on prostate cancer and benign prostatic hypertrophy (BPH) tissue. The present study was aimed to evaluate the alterations of the calcium-activated K channel (KCa) expression in prostate cancer, and to compare them with the expression profiles in human BPH tissue to understand their potential role in the progression of prostate cancer. Materials and Methods: The prostate tissues obtained from radical prostatectomy (n=10) and transurethral resection of the prostate (n=18) were quickly frozen in liquid nitrogen for the RNA measurements. The protein and mRNA levels of the KCa subtypes and connexins were measured by performing immunoblot analysis and reverse-transcription polymerase chain reaction, respectively. Results: The mRNA levels of type 2 (SK2) and type 3 (SK3) small-conductance and large-conductance (BK) KCas in the prostate cancer tissues were decreased more than 50% compared with those in the BPH samples. In addition, the BK and SK2 protein levels in prostate cancer were also significantly lower than those in the BPH. As reported previously, the connexin 26 and 43 transcript signals in the prostate cancer were significantly reduced compared with those in the BPH samples. Conclusions: These results suggest that the impaired expression of KCas may have a role in tumor progression via aberrant and uncontrolled prostate cell growth. (Korean J Urol 2006;47:548-552) ꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏꠏ