Plasticity of sarcolemmal KATP channel surface expression: relevance during ischemia and ischemic preconditioning

CL-705G: a novel chemical Kir6.2-specific KATP channel opener

Background: KATP channels have diverse roles, including regulation of insulin secretion and blood flow, and protection against biological stress responses and are excellent therapeutic targets. Different subclasses of KATP channels exist in various tissue types due to the unique assemblies of specific pore-forming (Kir6.x) and accessory (SURx) subunits. The majority of pharmacological openers and blockers act by binding to SURx and are poorly selective against the various KATP channel subclasses. Methods and Results: We used 3D models of the Kir6.2/SUR homotetramers based on existing cryo-EM structures of channels in both the open and closed states to identify a potential agonist binding pocket in a functionally critical area of the channel. Computational docking screens of this pocket with the Chembridge Core chemical library of 492,000 drug-like compounds yielded 15 top-ranked "hits", which were tested for activity against KATP channels using patch clamping and thallium (Tl+) flux assays with a Kir6.2/SUR2A HEK-293 stable cell line. Several of the compounds increased Tl+ fluxes. One of them (CL-705G) opened Kir6.2/SUR2A channels with a similar potency as pinacidil (EC50 of 9 µM and 11 μM, respectively). Remarkably, compound CL-705G had no or minimal effects on other Kir channels, including Kir6.1/SUR2B, Kir2.1, or Kir3.1/Kir3.4 channels, or Na+ currents of TE671 medulloblastoma cells. CL-705G activated Kir6.2Δ36 in the presence of SUR2A, but not when expressed by itself. CL-705G activated Kir6.2/SUR2A channels even after PIP2 depletion. The compound has cardioprotective effects in a cellular model of pharmacological preconditioning. It also partially rescued activity of the gating-defective Kir6.2-R301C mutant that is associated with congenital hyperinsulinism. Conclusion: CL-705G is a new Kir6.2 opener with little cross-reactivity with other channels tested, including the structurally similar Kir6.1. This, to our knowledge, is the first Kir-specific channel opener.

The cardioprotective role of sirtuins is mediated in part by regulating KATP channel surface expression

Sirtuins are NAD+-dependent deacetylases with beneficial roles in conditions relevant to human health, including metabolic disease, type II diabetes, obesity, cancer, aging, neurodegenerative diseases, and cardiac ischemia. Since ATP-sensitive K+ (KATP) channels have cardioprotective roles, we investigated whether they are regulated by sirtuins. Nicotinamide mononucleotide (NMN) was used to increase cytosolic NAD+ levels and to activate sirtuins in cell lines, isolated rat and mouse cardiomyocytes or insulin-secreting INS-1 cells. KATP channels were studied with patch clamping, biochemistry techniques, and antibody uptake experiments. NMN led to an increase in intracellular NAD+ levels and an increase in the KATP channel current, without significant changes in the unitary current amplitude or open probability. An increased surface expression was confirmed using surface biotinylation approaches. The rate of KATP channel internalization was diminished by NMN, which may be a partial explanation for the increased surface expression. We show that NMN acts via sirtuins since the increased KATP channel surface expression was prevented by blockers of SIRT1 and SIRT2 (Ex527 and AGK2) and mimicked by SIRT1 activation (SRT1720). The pathophysiological relevance of this finding was studied using a cardioprotection assay with isolated ventricular myocytes, in which NMN protected against simulated ischemia or hypoxia in a KATP channel-dependent manner. Overall, our data draw a link between intracellular NAD+, sirtuin activation, KATP channel surface expression, and cardiac protection against ischemic damage.

Rab35 GTPase positively regulates endocytic recycling of cardiac KATP channels

ATP-sensitive K⁺ (K_ATP) channel couples membrane excitability to intracellular energy metabolism. Maintaining K_ATP channel surface expression is key to normal insulin secretion, blood pressure and cardioprotection. However, the molecular mechanisms regulating K_ATP channel internalization and endocytic recycling, which directly affect the surface expression of K_ATP channels, are poorly understood. Here we used the cardiac K_ATP channel subtype, Kir6.2/SUR2A, and characterized Rab35 GTPase as a key regulator of K_ATP channel endocytic recycling. Electrophysiological recordings and surface biotinylation assays showed decreased K_ATP channel surface density with co-expression of a dominant negative Rab35 mutant (Rab35-DN), but not other recycling-related Rab GTPases, including Rab4, Rab11a and Rab11b. Immunofluorescence images revealed strong colocalization of Rab35-DN with recycling Kir6.2. Rab35-DN minimized the recycling rate of K_ATP channels. Rab35 also regulated K_ATP channel current amplitude in isolated adult cardiomyocytes by affecting its surface expression but not channel properties, which validated its physiologic relevance and the potential of pharmacologic target for treating the diseases with K_ATP channel trafficking defects.

Subcellular trafficking and endocytic recycling of KATP channels

Sarcolemmal/plasmalemmal ATP-sensitive K+ (KATP) channels have key roles in many cell types and tissues. Hundreds of studies have described how the KATP channel activity and ATP sensitivity can be regulated by changes in the cellular metabolic state, by receptor signaling pathways and by pharmacological interventions. These alterations in channel activity directly translate to alterations in cell or tissue function, that can range from modulating secretory responses, such as insulin release from pancreatic β-cells or neurotransmitters from neurons, to modulating contractile behavior of smooth muscle or cardiac cells to elicit alterations in blood flow or cardiac contractility. It is increasingly becoming apparent, however, that KATP channels are regulated beyond changes in their activity. Recent studies have highlighted that KATP channel surface expression is a tightly regulated process with similar implications in health and disease. The surface expression of KATP channels is finely balanced by several trafficking steps including synthesis, assembly, anterograde trafficking, membrane anchoring, endocytosis, endocytic recycling, and degradation. This review aims to summarize the physiological and pathophysiological implications of KATP channel trafficking and mechanisms that regulate KATP channel trafficking. A better understanding of this topic has potential to identify new approaches to develop therapeutically useful drugs to treat KATP channel-related diseases.

ROS‑associated mechanism of different concentrations of pinacidil postconditioning in the rat cardiac Nrf2‑ARE signaling pathway

Previous studies have confirmed that 50 µmol/l pinacidil postconditioning (PPC) activates the nuclear factor-E2 related factor 2 (Nrf2)-antioxidant responsive element (ARE) pathway, which protects the myocardium from ischemia-reperfusion (IR) injury; however, whether this is associated with reactive oxygen species (ROS) generation remains unclear. In the present study, a Langendorff rat model of isolated myocardial IR was established to investigate the mechanism of PPC at different concentrations, as well as the association between the rat myocardial Nrf2-ARE signaling pathway and ROS. A total of 48 rats were randomly divided into the following six groups (n=8 per group): i) Normal; ii) IR iii) 10 µmol/l PPC (P10); iv) 30 µmol/l PPC (P30); v) 50 µmol/l PPC (P50); and vi) N-(2-mercaptopropionyl)-glycine (MPG; a ROS scavenger) + 50 µmol/l pinacidil (P50 + MPG). At the end of reperfusion (T3), compared with the IR group, the P10, P30 and P50 groups exhibited improved cardiac function, such as left ventricular development pressure, heart rate, left ventricular end-diastolic pressure, +dp/dtmax, myocardial cell ultrastructure and mitochondrial Flameng score. Furthermore, the P10 and P50 groups demonstrated the weakest and most marked improvements, respectively. Additionally, in the P10, P30 and P50 groups, the residual ROS content at the end of reperfusion was highly negatively correlated with relative expression levels of Nrf2 gene and protein. Higher pinacidil concentration was associated with higher ROS generation at 5 min post-reperfusion (T2), although this was significantly lower compared with the IR group, as well as with increased expression levels of antioxidant proteins and phase II detoxification enzymes downstream of the Nrf2 and Nrf2-ARE pathways. This result was associated with a stronger ability to scavenge ROS during reperfusion, leading to lower levels of ROS at the end of reperfusion (T3) and less myocardial damage. The optimal myocardial protective effect was achieved by 50 mmol/l pinacidil. However, cardiac function of the P50 + MPG group was significantly decreased, ultrastructure of cardiomyocytes was significantly impaired and the relative expression levels of genes and proteins in the Nrf2-ARE pathway were decreased. The aforementioned results confirmed that different PPC concentrations promoted early generation of ROS and activated the Nrf2-ARE signaling pathway following reperfusion, regulated expression levels of downstream antioxidant proteins and alleviated myocardial IR injury in rats. Treatment with 50 mmol/l pinacidil resulted in the best myocardial protection.

Ions, the Movement of Water and the Apoptotic Volume Decrease

The movement of water across the cell membrane is a natural biological process that occurs during growth, cell division, and cell death. Many cells are known to regulate changes in their cell volume through inherent compensatory regulatory mechanisms. Cells can sense an increase or decrease in their cell volume, and compensate through mechanisms known as a regulatory volume increase (RVI) or decrease (RVD) response, respectively. The transport of sodium, potassium along with other ions and osmolytes allows the movement of water in and out of the cell. These compensatory volume regulatory mechanisms maintain a cell at near constant volume. A hallmark of the physiological cell death process known as apoptosis is the loss of cell volume or cell shrinkage. This loss of cell volume is in stark contrast to what occurs during the accidental cell death process known as necrosis. During necrosis, cells swell or gain water, eventually resulting in cell lysis. Thus, whether a cell gains or loses water after injury is a defining feature of the specific mode of cell death. Cell shrinkage or the loss of cell volume during apoptosis has been termed apoptotic volume decrease or AVD. Over the years, this distinguishing feature of apoptosis has been largely ignored and thought to be a passive occurrence or simply a consequence of the cell death process. However, studies on AVD have defined an underlying movement of ions that result in not only the loss of cell volume, but also the activation and execution of the apoptotic process. This review explores the role ions play in controlling not only the movement of water, but the regulation of apoptosis. We will focus on what is known about specific ion channels and transporters identified to be involved in AVD, and how the movement of ions and water change the intracellular environment leading to stages of cell shrinkage and associated apoptotic characteristics. Finally, we will discuss these concepts as they apply to different cell types such as neurons, cardiomyocytes, and corneal epithelial cells.

Atherogenic L5 LDL induces cardiomyocyte apoptosis and inhibits KATP channels through CaMKII activation

Background

Cardiac Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation plays a critical role in cardiomyocyte (CM) apoptosis and arrhythmia. Functional ATP-sensitive potassium (K_ATP) channels are essential for cardiac protection during ischemia. In cultured CMs, L5 low-density lipoprotein (LDL) induces apoptosis and QTc prolongation. L5 is a highly electronegative and atherogenic aberrant form of LDL, and its levels are significantly higher in patients with cardiovascular-related diseases. Here, the role of L5 in cardiac injury was studied by evaluating the effects of L5 on CaMKII activity and K_ATP channel physiology in CMs.

Methods

Cultured neonatal rat CMs (NRCMs) were treated with a moderate concentration (ie, 7.5 μg/mL) of L5 or L1 (the least electronegative LDL subfraction). NRCMs were examined for apoptosis and viability, CaMKII activity, and the expression of phosphorylated CaMKIIδ and NOX2/gp91^phox. The function of K_ATP and action potentials (APs) was analyzed by using the patch-clamp technique.

Results

In NRCMs, L5 but not L1 significantly induced cell apoptosis and reduced cell viability. Furthermore, L5 decreased Kir6.2 expression by more than 50%. Patch-clamp analysis showed that L5 reduced the K_ATP current (I_KATP) density induced by pinacidil, a K_ATP opener. The partial recovery of the inward potassium current during pinacidil washout was susceptible to subsequent inhibition by the I_KATP blocker glibenclamide. Suppression of I_KATP by L5 significantly prolonged the AP duration. L5 also significantly increased the activity of CaMKII, the phosphorylation of CaMKIIδ, and the expression of NOX2/gp91^phox. L5-induced apoptosis was prevented by the addition of the CaMKII inhibitor KN93 and the reactive oxygen species scavenger Mn (III)TBAP.

Conclusions

L5 but not L1 induces CM damage through the activation of the CaMKII pathway and increases arrhythmogenicity in CMs by modulating the AP duration. These results help to explain the harmful effects of L5 in cardiovascular-related disease.

Complex Effects of Putative DRP-1 Inhibitors on Stress Responses in Mouse Heart and Rat Cardiomyoblasts

Dynamin-related protein-1 (DRP-1)-dependent mitochondrial fission may influence cardiac tolerance to ischemic or oxidative stress, presenting a potential "cardioprotective" target. Effects of dynamin inhibitors [mitochondrial division inhibitor 1 (MDIVI-1) and dynasore] on injury, mitochondrial function, and signaling proteins were assessed in distinct models: ischemia-reperfusion (I-R) in mouse hearts and oxidative stress in rat H9c2 cardiomyoblasts. Hearts exhibited substantial cell death [approx. 40 IU lactate dehydrogenase (LDH) efflux] and dysfunction (approx. 40 mmHg diastolic pressure, approx. 40% contractile recovery) following 25 minutes' ischemia. Pretreatment with 1 μM MDIVI-1 reduced dysfunction (30 mmHg diastolic pressure, approx. 55% recovery) and delayed without reducing overall cell death, whereas 5 μM MDIVI-1 reduced overall death at the same time paradoxically exaggerating dysfunction. Postischemic expression of mitochondrial DRP-1 and phospho-activation of ERK1/2 were reduced by MDIVI-1. Conversely, 1 μM dynasore worsened cell death and reduced nonmitochondrial DRP-1. Postischemic respiratory fluxes were unaltered by MDIVI-1, although a 50% fall in complex-I flux control ratio was reversed. In H9c2 myoblasts stressed with 400 μM H₂O₂, treatment with 50 μM MDIVI-1 preserved metabolic (MTT assay) and mitochondrial (basal respiration) function without influencing survival. This was associated with differential signaling responses, including reduced early versus increased late phospho-activation of ERK1/2, increased phospho-activation of protein kinase B (AKT), and differential changes in determinants of autophagy [reduced microtubule-associated protein 1 light chain 3b (LC3B-II/I) vs. increased Parkinson juvenile disease protein 2 (Parkin)] and apoptosis [reduced poly-(ADP-ribose) polymerase (PARP) cleavage vs. increased BCL2-associated X (BAX)/B-cell lymphoma 2 (BCL2)]. These data show MDIVI-1 (not dynasore) confers some benefit during I-R/oxidative stress. However, despite mitochondrial and metabolic preservation, MDIVI-1 exerts mixed effects on cell death versus dysfunction, potentially reflecting differential changes in survival kinase, autophagy, and apoptosis pathways. SIGNIFICANCE STATEMENT: Inhibition of mitochondrial fission is a novel approach to still elusive cardioprotection. Assessing effects of fission inhibitors on responses to ischemic or oxidative stress in hearts and cardiomyoblasts reveals mitochondrial division inhibitor 1 (MDIVI-1) and dynasore induce complex effects and limited cardioprotection. This includes differential impacts on death and dysfunction, survival kinases, and determinants of autophagy and apoptosis. Although highlighting the interconnectedness of fission and these key processes, results suggest MDIVI-1 and dynasore may be of limited value in the quest for effective cardioprotection.

Myocardial death and dysfunction after ischemia-reperfusion injury require CaMKIIδ oxidation

Reactive oxygen species (ROS) contribute to myocardial death during ischemia-reperfusion (I/R) injury, but detailed knowledge of molecular pathways connecting ROS to cardiac injury is lacking. Activation of the Ca²⁺/calmodulin-dependent protein kinase II (CaMKIIδ) is implicated in myocardial death, and CaMKII can be activated by ROS (ox-CaMKII) through oxidation of regulatory domain methionines (Met281/282). We examined I/R injury in mice where CaMKIIδ was made resistant to ROS activation by knock-in replacement of regulatory domain methionines with valines (MMVV). We found reduced myocardial death, and improved left ventricular function 24 hours after I/R injury in MMVV in vivo and in vitro compared to WT controls. Loss of ATP sensitive K⁺ channel (KATP) current contributes to I/R injury, and CaMKII promotes sequestration of KATP from myocardial cell membranes. KATP current density was significantly reduced by H₂O₂ in WT ventricular myocytes, but not in MMVV, showing ox-CaMKII decreases KATP availability. Taken together, these findings support a view that ox-CaMKII and KATP are components of a signaling axis promoting I/R injury by ROS.

Rab8a is involved in membrane trafficking of Kir6.2 in the MIN6 insulinoma cell line

Although ATP-sensitive K⁺ (K_ATP) channels play an important role in the secretion of insulin by pancreatic beta cells, the mechanisms that regulate the intracellular transport of K_ATP channel subunit proteins (i.e., Kir6.2 and sulfonylurea receptor 1 (SUR1)) to the plasma membrane remain uncharacterized. We investigated the possibility that an interaction between K_ATP channel subunit proteins and Rab8a protein, a member of the RAS superfamily, may be involved in the membrane trafficking of K_ATP channels. Co-immunoprecipitation and immunostaining experiments using co-expression systems with fluorescent protein-tagged Kir6.2 were carried out to identify the coupling of K_ATP channels and Rab8a proteins in the insulin-secreting cell line, MIN6. Rab8a protein co-localized with Kir6.2 protein, a channel pore subunit (in a granular pattern), and with insulin. Knockdown of the Rab8a gene with RNA interference using small interfering RNA systems caused reductions in the amount of total K_ATP and plasma membrane surface K_ATP channels without decreasing the messenger RNA transcription of the K_ATP channel subunits. Rab8a gene knockdown also enhanced glucose-induced insulin secretion. These results suggest that Rab8a may be involved in membrane trafficking of K_ATP channels and the maintenance of normal insulin secretion in the MIN6 pancreatic beta cell line.

Activation of mitochondrial KATP channels mediates neuroprotection induced by chronic morphine preconditioning in hippocampal CA-1 neurons following cerebral ischemia

PURPOSE

Pharmacologic preconditioning, through activating several mechanisms and mediators, can increase the tolerance of different tissues against ischemia/reperfusion (I/R) injury. Recent studies have shown that morphine preconditioning has protective effects in different organs, especially in the heart. Nevertheless, its mechanisms are not well elucidated in the brain. The present study aimed to clarify whether the activation of mitochondrial KATP (mKATP) channels in chronic morphine (CM) preconditioning could decrease hippocampus damage following I/R injury.

MATERIALS AND METHODS

CM preconditioning was performed by the administration of additive doses of morphine for 5days before I/R injury induction. I/R injury was induced by the occlusion of bilateral common carotid arteries. The possible role of mKATP channels was evaluated by the injection of 5-hydroxydecanoate (5-HD) before I/R injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) was performed to detect apoptosis in hippocampal neurons. The expressions of B-cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein (BAX) and levels of malondialdehyde (MDA) and catalase (CAT) enzymes were assessed.

RESULTS

CM attenuated apoptosis in the hippocampal CA1 neurons (P<0.001 vs I/R), and mKATP channel blocking with 5-HD significantly increased apoptosis (P<0.001 vs CM+I/R). CM increased CAT activity (P<0.05 vs I/R) and Bcl-2 protein expression (P<0.01 vs I/R), while it decreased MDA level (P<0.05 vs I/R) and BAX protein expression (P<0.05 vs I/R). Pretreatment with 5-HD abolished all the above-mentioned effects of CM.

CONCLUSIONS

These findings describe novel evidence whereby CM preconditioning in hippocampal CA1 neurons can improve oxidative stress and apoptosis through the activation of mKATP channels and eventually protect the hippocampal tissue against I/R injury.

Mechanisms involved in adenosine pharmacological preconditioning-induced cardioprotection

Adenosine is a naturally occurring breakdown product of adenosine triphosphate and plays an important role in different physiological and pathological conditions. Adenosine also serves as an important trigger in ischemic and remote preconditioning and its release may impart cardioprotection. Exogenous administration of adenosine in the form of adenosine preconditioning may also protect heart from ischemia-reperfusion injury. Endogenous release of adenosine during ischemic/remote preconditioning or exogenous adenosine during pharmacological preconditioning activates adenosine receptors to activate plethora of mechanisms, which either independently or in association with one another may confer cardioprotection during ischemia-reperfusion injury. These mechanisms include activation of K_ATP channels, an increase in the levels of antioxidant enzymes, functional interaction with opioid receptors; increase in nitric oxide production; decrease in inflammation; activation of transient receptor potential vanilloid (TRPV) channels; activation of kinases such as protein kinase B (Akt), protein kinase C, tyrosine kinase, mitogen activated protein (MAP) kinases such as ERK 1/2, p38 MAP kinases and MAP kinase kinase (MEK 1) MMP. The present review discusses the role and mechanisms involved in adenosine preconditioning-induced cardioprotection.

Lipid signaling to membrane proteins: From second messengers to membrane domains and adapter-free endocytosis

Hilgemann et al. explain how lipid signaling to membrane proteins involves a hierarchy of mechanisms from lipid binding to membrane domain coalescence.

Lipids influence powerfully the function of ion channels and transporters in two well-documented ways. A few lipids act as bona fide second messengers by binding to specific sites that control channel and transporter gating. Other lipids act nonspecifically by modifying the physical environment of channels and transporters, in particular the protein–membrane interface. In this short review, we first consider lipid signaling from this traditional viewpoint, highlighting innumerable Journal of General Physiology publications that have contributed to our present understanding. We then switch to our own emerging view that much important lipid signaling occurs via the formation of membrane domains that influence the function of channels and transporters within them, promote selected protein–protein interactions, and control the turnover of surface membrane.

The trafficking protein, EHD2, positively regulates cardiac sarcolemmal KATP channel surface expression: role in cardioprotection

ATP-sensitive K⁺ (K_ATP) channels uniquely link cellular energy metabolism to membrane excitability and are expressed in diverse cell types that range from the endocrine pancreas to neurons and smooth, skeletal, and cardiac muscle. A decrease in the surface expression of K_ATP channels has been linked to various disorders, including dysregulated insulin secretion, abnormal blood pressure, and impaired resistance to cardiac injury. In contrast, up-regulation of K_ATP channel surface expression may be protective, for example, by mediating the beneficial effect of ischemic preconditioning. Molecular mechanisms that regulate K_ATP channel trafficking are poorly understood. Here, we used cellular assays with immunofluorescence, surface biotinylation, and patch clamping to demonstrate that Eps15 homology domain-containing protein 2 (EHD2) is a novel positive regulator of K_ATP channel trafficking to increase surface K_ATP channel density. EHD2 had no effect on cardiac Na⁺ channels (Nav1.5). The effect is specific to EHD2 as other members of the EHD family-EHD1, EHD3, and EHD4-had no effect on K_ATP channel surface expression. EHD2 did not directly affect K_ATP channel properties as unitary conductance and ATP sensitivity were unchanged. Instead, we observed that the mechanism by which EHD2 increases surface expression is by stabilizing K_ATP channel-containing caveolar structures, which results in a reduced rate of endocytosis. EHD2 also regulated K_ATP channel trafficking in isolated cardiomyocytes, which validated the physiologic relevance of these observations. Pathophysiologically, EHD2 may be cardioprotective as a dominant-negative EHD2 mutant sensitized cardiomyocytes to ischemic damage. Our findings highlight EHD2 as a potential pharmacologic target in the treatment of diseases with K_ATP channel trafficking defects.-Yang, H. Q., Jana, K., Rindler, M. J., Coetzee, W. A. The trafficking protein, EHD2, positively regulates cardiac sarcolemmal K_ATP channel surface expression: role in cardioprotection.

Ubiquitination mediates Kv1.3 endocytosis as a mechanism for protein kinase C-dependent modulation

The voltage-dependent potassium channel Kv1.3 plays essential physiological functions in the immune system. Kv1.3, regulating the membrane potential, facilitates downstream Ca²⁺ -dependent pathways and becomes concentrated in specific membrane microdomains that serve as signaling platforms. Increased and/or delocalized expression of the channel is observed at the onset of several autoimmune diseases. In this work, we show that adenosine (ADO), which is a potent endogenous modulator, stimulates PKC, thereby causing immunosuppression. PKC activation triggers down-regulation of Kv1.3 by inducing a clathrin-mediated endocytic event that targets the channel to lysosomal-degradative compartments. Therefore, the abundance of Kv1.3 at the cell surface decreases, which is clearly compatible with an effective anti-inflammatory response. This mechanism requires ubiquitination of Kv1.3, catalyzed by the E3 ubiquitin-ligase Nedd4-2. Postsynaptic density protein 95 (PSD-95), a member of the MAGUK family, recruits Kv1.3 into lipid-raft microdomains and protects the channel against ubiquitination and endocytosis. Therefore, the Kv1.3/PSD-95 association fine-tunes the anti-inflammatory response in leukocytes. Because Kv1.3 is a promising multi-therapeutic target against human pathologies, our results have physiological relevance. In addition, this work elucidates the ADO-dependent PKC-mediated molecular mechanism that triggers immunomodulation by targeting Kv1.3 in leukocytes.

Cardiovascular KATP channels and advanced aging

With advanced aging, there is a decline in innate cardiovascular function. This decline is not general in nature. Instead, specific changes occur that impact the basic cardiovascular function, which include alterations in biochemical pathways and ion channel function. This review focuses on a particular ion channel that couple the latter two processes, namely the K_ATP channel, which opening is promoted by alterations in intracellular energy metabolism. We show that the intrinsic properties of the K_ATP channel changes with advanced aging and argue that the channel can be further modulated by biochemical changes. The importance is widespread, given the ubiquitous nature of the K_ATP channel in the cardiovascular system where it can regulate processes as diverse as cardiac function, blood flow and protection mechanisms against superimposed stress, such as cardiac ischemia. We highlight questions that remain to be answered before the K_ATP channel can be considered as a viable target for therapeutic intervention.