Phosphatidylinositol 4,5-biphosphate (PIP2) modulates syntaxin-1A binding to sulfonylurea receptor 2A to regulate cardiac ATP-sensitive potassium (KATP) channels

The Syntaxin-1A gene single nucleotide polymorphism rs4717806 associates with the risk of ischemic heart disease

Ischemic heart disease (IHD) has a genetic predisposition and a number of cardiovascular risk factors are known to be affected by genetic factors. Development of metabolic syndrome and insulin resistance, strongly influenced by lifestyle and environmental factors, frequently occur in subjects with a genetic susceptibility. The definition of genetic factors influencing disease susceptibility would allow to identify individuals at higher risk and thus needing to be closely monitored.To this end, we focused on a complex of soluble-N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs), playing an important role in metabolic syndrome and insulin resistance, involved in endothelial dysfunction and heart disease. We assessed if genetic variants of the SNARE genes are associated with IHD.SNAP25 rs363050, Stx-1A rs4717806, rs2293489, and VAMP2 26bp ins/del genetic polymorphisms were analyzed in a cohort of 100 participants who underwent heart surgery; 56 of them were affected by IHD, while 44 were not. A statistical association of plasma glycemia and insulin resistance, calculated as Triglyceride glucose (TyG) index, was observed in IHD (P < .001 and P = .03, respectively) after binomial logistic stepwise regression analysis, adjusted by age, gender, diabetes positivity, waist circumference, and cholesterol plasma level. Among genetic polymorphisms, rs4717806(A) and rs2293489(T), as well as the rs4717806 - rs2293489 (A-T) haplotype were associated with higher risk for IHD (Pc = .02; Pc = .02; P = .04, respectively). Finally, a statistical association of rs4717806(AA) genotype with higher TyG index in IHD patients (P = .03) was highlighted by multiple regression analysis considering log-transformed biochemical parameters as dependent variable and presence of coronary artery disease, age, gender, waist circumference, presence of diabetes as predictors. These results point to a role of the Stx-1A rs4717806 SNP in IHD, possibly due to its influence on Stx-1A expression and, as a consequence, on insulin secretion and glucose metabolism.

G protein βγ subunits play a critical role in the actions of amphetamine

Abnormal levels of dopamine (DA) are thought to contribute to several neurological and psychiatric disorders including drug addiction. Extracellular DA levels are regulated primarily via reuptake by the DA transporter (DAT). Amphetamine, a potent psychostimulant, increases extracellular DA by inducing efflux through DAT. Recently, we discovered that G protein βγ subunits (Gβγ) interact with DAT, and that in vitro activation of Gβγ promotes DAT-mediated efflux. Here, we investigated the role of Gβγ in the actions of amphetamine in DA neurons in culture, ex vivo nucleus accumbens (NAc), and freely moving rats. Activation of Gβγ with the peptide myr-Ser-Ile-Arg-Lys-Ala-Leu-Asn-Ile-Leu-Gly-Tyr-Pro-Asp-Tyr-Asp (mSIRK) in the NAc potentiated amphetamine-induced hyperlocomotion, but not cocaine-induced hyperlocomotion, and systemic or intra-accumbal administration of the Gβγ inhibitor gallein attenuated amphetamine-induced, but not cocaine-induced hyperlocomotion. Infusion into the NAc of a TAT-fused peptide that targets the Gβγ-binding site on DAT (TAT-DATct1) also attenuated amphetamine-induced but not cocaine-induced hyperlocomotion. In DA neurons in culture, inhibition of Gβγ with gallein or blockade of the Gβγ-DAT interaction with the TAT-DATct1 peptide decreased amphetamine-induced DA efflux. Furthermore, activation of Gβγ with mSIRK potentiated and inhibition of Gβγ with gallein reduced amphetamine-induced increases of extracellular DA in the NAc in vitro and in freely moving rats. Finally, systemic or intra-accumbal inhibition of Gβγ with gallein blocked the development of amphetamine-induced, but not cocaine-induced place preference. Collectively, these results suggest that interaction between Gβγ and DAT plays a critical role in the actions of amphetamine and presents a novel target for modulating the actions of amphetamine in vivo.

Functional protection against cardiac diseases depends on ATP-sensitive potassium channels

ATP-sensitive potassium channels (KATP) channels are widely distributed in various tissues, including pancreatic beta cells, muscle tissue and brain tissue. KATP channels play an important role in cardioprotection in physiological/pathological situations. KATP channels are inhibited by an increase in the intracellular ATP concentration and are stimulated by an increase in the intracellular MgADP concentration. Activation of KATP channels decreases ischaemia/reperfusion injury, protects cardiomyocytes from heart failure, and reduces the occurrence of arrhythmias. KATP channels are involved in various signalling pathways, and their participation in protective processes is regulated by endogenous signalling molecules, such as nitric oxide and hydrogen sulphide. KATP channels may act as a new drug target to fight against cardiovascular disease in the development of related drugs in the future. This review highlights the potential mechanisms correlated with the protective role of KATP channels and their therapeutic value in cardiovascular diseases.

KATP Channels in the Cardiovascular System

KATP channels are integral to the functions of many cells and tissues. The use of electrophysiological methods has allowed for a detailed characterization of KATP channels in terms of their biophysical properties, nucleotide sensitivities, and modification by pharmacological compounds. However, even though they were first described almost 25 years ago (Noma 1983, Trube and Hescheler 1984), the physiological and pathophysiological roles of these channels, and their regulation by complex biological systems, are only now emerging for many tissues. Even in tissues where their roles have been best defined, there are still many unanswered questions. This review aims to summarize the properties, molecular composition, and pharmacology of KATP channels in various cardiovascular components (atria, specialized conduction system, ventricles, smooth muscle, endothelium, and mitochondria). We will summarize the lessons learned from available genetic mouse models and address the known roles of KATP channels in cardiovascular pathologies and how genetic variation in KATP channel genes contribute to human disease.