Study The Effects Of Ethanol On KCNQ1 Channels And Regulation Of Kv4.3 Channels By Protein Kinase

Proteins encoded by KCNQ gene are an important branch of voltage gated potassium channels and highly express in human heart.KCNE1(mink) gene encodes a protein family which usually interacts with KCNQ channels,acting as a modulator.KCNQ1/KCNE1 current is the slow component ofâ…¢stage repolarization delayed rectifier(I_ks) in cardiac action potential.LQTS is an inherited heart disease associated with prolonged QT interval. It is associated with syncope(fainting),tachycardia and sudden death due to ventricular arrhythmias.KCNQ1 gene disfigurement or mutant will cause LQT1.We know that ethanol has negative effect on brain,heart and liver,but we are not clear about the mechanism.KCNQ1 channels are highly expressed in heart and have close relationship with inherited heart disease.To study the interaction between KCNQ1 channel and alcohol or some other anaesthetic will give us effectively clue to clinic, pharmacology,pathology and development of new drugs.The main research achievements about interaction between ethanol and KCNQ1/KCNE1 channel in this study are as follows:(1) The blocking of n-alkanols to KCNQ1 depends on voltage and length of alkyl chain.(2) Close-state blocking exits in the inhibition of ethanol to KCNQ1.(3) No use-dependent exit in the inhibition of ethanol to KCNQ1.(4) The I257 in KCNQ1 works as a key residue for the sensitivity to n-alkanols.Kv4.3 is an essential component of I stage repolarization current I_to in cardiac action potential.Calmodulin(CAM) is a ubiquitous Ca²⁺-binding protein that plays an important role in the Ca²⁺-signaling pathways.The calcium/calmodulin-dependent kinases(CaMKs) are involved in a large number of cellular responses induced by hormones, neurotransmitters and other signalling.Elevation of calcium functions as a major second messenger,where the intracellular concentration of calcium can be maintained at extremely low levels and susequently increased following specific calcium-mobilizing stimuli.The activity of Ca²⁺/CaMKII increases in the different types of heart disease, including ventricular arrhythmias.W-7,a commonly used inhibitor of Ca²⁺-CaM,has been reported to suppress ventricular arrhythmias in animalmodels.To gain an understanding of the mechanisms underlying the effects of W-7,we examined the effects of W-7 and KN-93(an inhibitor of CaMKII) on the Kv4.3 voltage-gated K⁺ channel.Our data demonstrate voltage- dependent pore block by W-7,but not KN-93.In addition,we have shown that the effects of W-7 did not solely result from inhibition of Ca²⁺/CaMKII activity.Protein kinase C(PKC) has been proven to participate many process of cellular signaling and conduction,such as multiplication,polarization,secretion and apoptosis since it was identified in 1977.A PKC activator,PMA or PKC from rat brain had opposite effects on the relative magnitude of CSI in the two isoforms of Kv4.3(Kv4.3-S and Kv4.3-L).Data from Kv4.3-L mutant T504A indicates the phosphorylation site(T504) in the 19 aa insert in WT Kv4.3-L plays an important role in modulating closed-state inactivation and accounts in part for the different responses to PMA in Kv4.3-S and Kv4.3-L.The effects of PMA on the gating properties of Kv4.3 are mediated via increased PKC activity.Phosphorylation sites within C-terminus play an important role in modulation of Kv4.3 closed-state,as well as open-state inactivation.