Big On Bk Current Insights Into The Function Of Large Conductance Voltage And Ca2 Activated K Channels At The Molecular Cellular And Systemic Levels

DOWNLOAD

Download Big On Bk Current Insights Into The Function Of Large Conductance Voltage And Ca2 Activated K Channels At The Molecular Cellular And Systemic Levels PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Big On Bk Current Insights Into The Function Of Large Conductance Voltage And Ca2 Activated K Channels At The Molecular Cellular And Systemic Levels book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page

Big On Bk

DOWNLOAD
Author :
language : en
Publisher: Academic Press
Release Date : 2016-05-26

Big On Bk written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-05-26 with Science categories.

Big on Bk: Current Insights into the Function of Large Conductance Voltage- and Ca2+- Activated K+ Channels at the Molecular, Cellular and Systemic Levels, a volume in the International Review of Neurobiology series, is a comprehensive overview of the state-of-the-art research into this area. It reviews current knowledge and understanding, and also provides a starting point for researchers and practitioners entering the field. The latest volume in the International Review of Neurobiology series Provides a broad coverage of subject matter at the molecular, cellular and systemic levels Presents an ideal resource for researchers and practitioners, and those just entering the field

Bk Channels Integrators Of Cellular Signals In Health And Disease

DOWNLOAD
Author : Thomas M. Weiger
language : en
Publisher: Frontiers Media SA
Release Date : 2017-11-10

Bk Channels Integrators Of Cellular Signals In Health And Disease written by Thomas M. Weiger and has been published by Frontiers Media SA this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-11-10 with Electronic book categories.

Maxi calcium-activated potassium channels (BK) are an amazing category of ion channels which are found in cellular plasma membranes as well as in membranes of intracellular organelles. The function of these channels is to repolarize any excited membrane by passing a potassium outward current, in response to depolarization and/or increase in local calcium levels. Thus, voltage and calcium ions are involved in gating the channel under physiological conditions. This dual activation makes them perfect sensors for many cellular events that require integration between intracellular calcium levels and electrical signals. A plethora of physiological and pathophysiological functions, such as membrane hyperpolarization, modulation of synaptic transmission, hormone secretion or mental deficiencies, vaso-regulation, epilepsies, heart diseases, myotonic dystrophies, hypertension etc, in almost all cells and tissues were reported for these channels. BK channels are main targets for important ligands like alcohol and gaseous neurotransmitters, such as NO, CO or H2S, to name a few. In the last years, the molecular entities and mechanisms involved in modulation of BK channels have gained tremendous attention, as the key role of these channels in cellular processes became increasingly recognized. Indeed, accessory proteins such as slob, beta and gamma subunits, all serve to modulate the channel gating characteristics. Moreover, channel subunit expression and function is further tuned by phosphorylation/ dephosphorylation processes, redox mechanisms and the lipid microenvironment of the BK channel protein complex. This e-book contains structural and functional aspects of BK channels, channel modulation by a variety of agents and cellular components, as well as the channel’s relevance in health and disease.

Novel Structural And Physiological Functions Of High Conductance K Channels Of The Slo Family

DOWNLOAD
Author : Gonzalo Budelli
language : en
Publisher:
Release Date : 2013

Novel Structural And Physiological Functions Of High Conductance K Channels Of The Slo Family written by Gonzalo Budelli and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Electronic dissertations categories.

The SLO family channels are high conductance K+ channels that are gated both by voltage and intracellular ions. Structurally they resemble voltage gated channels but have additional large conserved intracellular domains appended on the C-terminal that allow them to be gated by different intracellular ions. Two members of this unique family of K+ channels are Slo1 (BK) which is activated by Ca2+, and Slo2.2 (Slack) which is activated by sodium. Both channels are widely expressed in the brain and other tissues in many species from C. elegans to humans. The large conductance Ca2+- activated K+ channel (Slo1 or BK for Big conductance K+ channel) is widely distributed and controls many different physiological processes including cellular excitability, neurotransmitter release, muscle contraction, hair cell function, insulin release, and blood pressure. Defects in Slo1 channels have been associated with hypertension, autism and mental retardation, obesity, asthma, epilepsy, and cerebellar ataxia. Slo1 channels are activated by Ca2+, voltage, and Mg2+ through different allosteric pathways providing a model system to study allosteric coupling and pathways in channel gating and protein function. The structure of Slo1 has two functional domains, a "Core" consisting of seven transmembrane elements (S0-S6) which assemble to form a voltage sensing domain which allosterically confers voltage sensitivity to the pore gate domain, and a "Tail" that forms a large intracellular gating ring thought to confer Ca2+ and Mg2+ sensitivity through different transduction pathways from gating ring to Core. The large modular Slo1 channel is known to undergo many complex allosteric interactions during channel gating, some within subdomains of the Core itself, some within the massive Tail, and some between Tail and Core. Because of its great size and complexity it has not been possible to understand all these allosteric structural changes nor dissect the contributions of the different transduction pathways to channel gating. A new and valuable tool for answering these questions would be the ability to express the voltage-sensitive Core alone, free of the influence of the large and complex Tail. This would allow the determination of the baseline gating properties of the isolated Core, which would permit experiments such as adding the transduction pathways back one at a time and in combination, to reveal the functions of each. Unfortunately, it has not previously been possible to express the Core without the gating ring. However, we have been able to develop novel constructs of the Core without the gating ring that I have been able to express and analyze using the Xenopus oocyte heterologous expression system. I will show that currents from these constructs are from heterologously expressed gating ring-less channels and not from possible endogenously expressed channels. This allows determination for the first time, of the baseline properties of the Slo1 Core without passive or active allosteric input from the gating ring. The studies I performed show that the baseline properties of the isolated Core differ considerably from the properties of the intact Slo1 channel in the isolation of Ca2+. This shows that the gating ring imparts passive properties and interactions with the core, even in the absence of Ca2+. Thus, removing the gating ring reduces single-channel conductance ~30%, removes all Ca2+- and Mg2+-sensitivity, greatly reduces single channel mean open channel duration and burst duration; and right-shifts the G/V relation. Knowing these baseline properties of the Core then provides us with a novel tool and a guide for understanding the allosteric basis for gating in Slo1 channels. Such knowledge may facilitate the development of agents to restore normal function in genetic syndromes where Slo1 channels are involved. Also, this more complete understanding of how these complicated channels function could be important for understanding other channels that are activated by more than one factor (as TRP channels) or for other proteins which undergo complicated allosteric structural changes. The goal of the second project was to reveal the physiological relevance of Slo2 (Slack and Slick) Na+-dependent K+ channels. The discovery of high conductance Na+-dependent K+ channels in heart and brain presented a conundrum, the sodium concentrations needed to activate these channels in inside-out patches far exceeded the intracellular concentration of Na+ under normal physiological conditions. Thus, it was proposed that Na+-dependent K+ channels were an emergency conductance only activated under very special conditions such as during hypoxia or ischemia where the Na+ levels increase inside the cell. However, other reports indicated that these channels could be active under normal physiological conditions. Also, there is evidence of these channels being widely expressed all over the mammalian brain. I present data here showing that one of the largest components of the delayed outward current that is active under physiological conditions in many mammalian neurons, such as medium spiny neurons of the striatum and tufted-mitral cells of the olfactory bulb, is expressed by Na+-activated K+ channels and has previously gone unnoticed. Previous studies of K+ currents in mammalian neurons may have overlooked this large outward component because the sodium channel blocker tetrodotoxin (TTX) is typically used in studies of K+ channels. However, we found that TTX also eliminated this Na+-dependent delayed outward component in rat neurons as a secondary consequence. Unexpectedly, we found that the activity of persistent inward sodium current is highly effective at activating this large Na+-dependent (TTX sensitive) delayed outward current. Using siRNA techniques, I identified the Slo2.2 channel as a carrier of this delayed outward current. These findings have far reaching implications for many aspects of cellular and systems neuroscience, as well as clinical neurology and pharmacology. The final part of this dissertation involves the study of the effect of divalent cations on Slo2.2 channels. The activating effect of virtually all divalent cations on Slo1 is well documented, but the effect of divalent cations on Slo2.2 channels is largely unstudied. In exploring this question, I was surprised to observe that all of the divalent ions that activate Slo1 channels have the opposite effect on Slo2.2 channels; they reduce channel activity. After making this observation I turned my attention towards understanding the mechanism of blocking. I considered two hypotheses: 1) Divalent ions blocked the pore of Slo2.2 channels, and 2) Divalent ions functioned at a site away from the pore and either competed with sodium ion binding or produced allosteric changes leading to channel inhibition. My results indicate that the effect of divalent ions on Slo2.2 is not by blocking the pore. I also showed that the blocking effect of divalent cations on Slo2.2 channels is conserved in the orthologous channel from Drosophila which has been cloned in our lab. In addition, I show that the Drosophila Slo2 channel is sodium dependent, unlike the Slo2 channel in another invertebrate, C. elegans, which lacks sodium sensitivity and is instead, activated by Ca2+. Finally, by site-directed mutagenesis, we have tentatively located the site of interaction of divalent cations with the Slo2.2 channel. In the conclusion to this section, I discuss the possible physiological relevance of my findings to a proposed mechanism of action of Slo2 channels.

Molecular Mechanism Of The Allosteric Coupling For Ca2 Activation Of The Voltage And Ca2 Activated K Bk Channels

DOWNLOAD
Author : Junqiu Yang
language : en
Publisher:
Release Date : 2011

Molecular Mechanism Of The Allosteric Coupling For Ca2 Activation Of The Voltage And Ca2 Activated K Bk Channels written by Junqiu Yang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Electronic dissertations categories.

The large conductance voltage- and Ca2+-activated K+ (BK) channel is important for many physiological functions. The BK channel is activated by both membrane depolarization and intracellular Ca2+ so that it integrates these two important cellular signals. Ca2+ sensing of the BK channel is mediated by two binding sites, both located on the cytosolic domain. The structure of the cytosolic domain indicates that both binding sites are away from the pore-gate domain, suggesting that a coupling mechanism between the binding sites and the gate is required for Ca2+-dependent activation. The work in this dissertation focuses on the coupling mechanism, which can be divided into two steps. The first step of the coupling mechanism is within the cytosolic domain and mediated by the AC region, which is on top of the cytosolic domain and adjacent to the membrane. The coupling mechanism of the AC region is regulated by its dynamics, which can be altered by either the disease-associated mutation D369G or changes in solution viscosity. The second step of the coupling mechanism transmits Ca2+ binding energy across the interface between the cytosolic and membrane-spanning domains, which is found in the form of relative movements between these two domains. Using an electrostatic interaction between the two domains, we further show that the relative movements may be the coupling mechanism for both voltage- and Ca2+-dependent activation pathways. Therefore, we have revealed novel properties of the coupling mechanism for Ca2+-dependent activation in BK channels. Our findings are particularly important for understanding the structure-function relationship of the BK channel.

An Integrated Approach To Understanding The Structure And Function Of The Large Conductance Voltage And Calcium Activated Potassium Channel

DOWNLOAD
Author : Jacob E. McMillan
language : en
Publisher:
Release Date : 2014

An Integrated Approach To Understanding The Structure And Function Of The Large Conductance Voltage And Calcium Activated Potassium Channel written by Jacob E. McMillan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014 with categories.

The large-conductance, voltage- and calcium-activated potassium channel (BKCa channel) is an important transmembrane ion channel involved in many physiological and pathophysiological processes. However, little is known about its atomic-level three-dimensional structure. The functional channel requires four alpha subunits assembled as a potassium pore and is typically associated with four beta subunits that regulate function in various ways depending on the isoform of the beta subunit is interacting with the channel. Currently, the only major high-resolution atomic structure available is of the cytosolic tail domain of the alpha subunit. In the absence of structural information, electrophysiology has allowed for extensive characterization of the channel’s role in physiological processes and advanced understanding of BKCa channel pharmacology including inhibition of BKCa by physiologically relevant concentrations of cholesterol and stimulation of BKCa by the related sterol, lithocholic acid. However, many questions still remain including how does cholesterol exert effects on the alpha subunit, what are the structures of the different beta subunits, and can therapeutic lead compounds be developed to selectively target BKCa beta subunits in a tissue specific manner. The difficulty of obtaining transmembrane protein structures has made characterization a major challenge.Herein, work is described where 1) the BKCa beta 1 subunit was successfully expressed and purified from E. coli for the first time with a yield of approximately 32mg/L of bacterial growth and several assays were attempted to demonstrate protein functionality. However, functional assessment of purified protein has remained elusive due to the hydrophobic nature of known ligands. Additional effort is needed to establish ligand recognition using solution nuclear magnetic resonance spectroscopy. 2) Multiple generations of pharmacophore models have been developed to aid in virtual screening efforts to find therapeutic lead compounds targeting BKCa through the beta 1 subunit. Sixteen compounds have been selected from virtual screening of the PubChem database that can be tested in vitro for model validation. 3) Molecular dynamics simulations were utilized to study the underlying mechanism of the interaction between cholesterol and the BKCa alpha subunit cytosolic tail domain showing differential behavior of cholesterol in mutant and wild type simulations that agree with experimental data.

A Large Entrance To The Inner Cavity Of Bk Channels Is Required For Their Large Conductance

DOWNLOAD
Author :
language : en
Publisher:
Release Date : 2009

A Large Entrance To The Inner Cavity Of Bk Channels Is Required For Their Large Conductance written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.

Large conductance voltage and Ca2+ activated K+ (BK) channels control electrical excitability in many cell types. BK channels have the largest conductance (~250 pS) of all K+ selective channels. To explore whether a large entrance to the inner cavity of BK channels is required for their large conductance, I examined if changing the size of the entrance alters the single-channel current amplitude. Previous studies suggest that residues E321/E324 in BK channels are located at the entrance to the inner cavity. To test if positions 321/324 are accessible to intracellular ions, I compared single-channel outward current before and after attaching thiol reagents at E321C/E324C. Attachment of MBB and MTSET altered single-channel currents, indicating that positions 321/324 are accessible to the conduction pathway. Decreasing the size of the entrance to the inner cavity by substituting residues with larger side chains, such as tyrosine and tryptophan, at positions 321/324 decreased the conductance, whereas increasing the size of the entrance had little effect on conductance. Increasing [K+]i from 0.15 to 2.5 M negated differences in single-channel outward current associated with side chain volume. Substitutions had less effect on inward currents. Plots of conductance vs. substituted side chain volume could be approximated with a simple model for the conduction pathway described by two resistors in series, R1 and R2. R2 is a variable resistor, with the resistance proportional to the inverse of the volume of the entrance to the inner cavity not occupied by the side chains. R1 is a fixed resistor arising from the other parts of the conduction pathway including the selectivity filter. Fitting the experimental observations indicated that R1+R2 ~5.4 G &!for glycine substitution, with an R1/R2 ratio of ~17, and an effective radius and length of the entrance to the inner cavity of ~9.0 and 5.4 ¿, respectively. The volume of K+ and water were not taken into account. Taken together, the above observations suggest that a large entrance to the inner cavity is needed for the large conductance of BK channels, as my study shows that the entrance is large and that decreasing the entrance size decreases the currents.

Voltage Gated Calcium Channels

DOWNLOAD
Author : Gerald Werner Zamponi
language : en
Publisher: Springer Nature
Release Date : 2022-11-07

Voltage Gated Calcium Channels written by Gerald Werner Zamponi and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-11-07 with Science categories.

This book covers the tremendous progress in the current understanding of the molecular physiology of voltage-gated calcium channels. This book includes unparalleled insights into structural features of calcium channels due to X-ray crystallography and cryo-EM, which in turn yielded critical information into how these channels function under normal and pathophysiological conditions, and how they interact with calcium channel therapeutics. The chapters investigate how, with the advent of high throughput genome sequencing, numerous mutations in various calcium channel genes have been identified in patients with neurological, cardiovascular, neuropsychiatric and other disorders. This is further complemented through a much larger in vivo toolkit such as knock-out and knock-in mice. The chapters further discuss the increased complexity of calcium channel physiology that arises from mRNA editing and splicing. Finally, the book also provides an overview of the updated research on calcium channel inhibitors that can be used both in vivo and in vitro, and which may serve as a spring board for new calcium channel therapeutics for human disease. Voltage-Gated Calcium Channels is useful for academic researchers at all levels in neuroscience, biophysics, cell biology and drug discovery.

An Investigation Of The Properties Of Large Conductance Ca2 Activated K Channels Of Rat Arterial Smooth Muscle And Their Modulation By Vasoconstrictors

DOWNLOAD
Author : Anna Sowerby
language : en
Publisher:
Release Date : 2009

An Investigation Of The Properties Of Large Conductance Ca2 Activated K Channels Of Rat Arterial Smooth Muscle And Their Modulation By Vasoconstrictors written by Anna Sowerby and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.

Large-conductance Ca2-activated K (BKCa) channels play an important role in the regulation of vascular tone. They are activated by membrane depolarization and increases in local Ca2+ concentration ([Ca2+]). Their location in the plasma membrane allows them to be activated by transient releases of Ca2+ from ryanodine receptors (RyR) in the sarcoplasmic reticulum, termed Ca2+ sparks, leading to the efflux of K+ known as a spontaneous transient outward current (STOC). Activation of BKCa channels in this manner provides a negative feedback mechanism to regulate vasoconstriction by hyperpolarizing the cell membrane and so reducing Ca2+ influx through L-type voltage dependent Ca2+ channels. In this thesis I have investigated the relationship between [Ca2+]i and membrane potential using inside-out patches excised from smooth muscle cells isolated from rat mesenteric artery. Whole-cell BKCa currents in these cells were also investigated both in the form of STOCs and by using voltage pulses to activate BKCa channels. The effects of the vasoconstrictors endothelin-1 (ET- 1) and angiotensin II (Ang II) on both pulse-induced BKCa currents and STOC amplitude and frequency were investigated. Single BKCa channels with a slope conductance of 189 pA were recorded and their activation was shown to be dependent on [Ca2+]i and membrane potential. Membrane depolarization also increased BKCa whole-cell current and the frequency and amplitude of STOCs. ET-1 and Ang II were found to inhibit pulse-induced BKCa currents and this effect of ET-1 could be inhibited using a peptide PKC inhibitor. ET-1 and Ang II also caused a decrease in both STOC amplitude and frequency, although the decrease in frequency may be the result of the reduction in amplitude. Finally, 1, 2-dioctanoyl-sn-glycerol (DOG), an analogue of the endogenous PKC activator diacylglycerol (DAG), was seen to inhibit both BKCa whole-cell and single channel currents, possibly due to direct inhibition of BKCa channels.

Molecular Determinants Of Bk Channel Gating And Pharmacology

DOWNLOAD
Author : Alexandre Vouga
language : en
Publisher:
Release Date : 2021

Molecular Determinants Of Bk Channel Gating And Pharmacology written by Alexandre Vouga and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.

Large conductance Ca2+-activated K+ channels (BK channels) are expressed ubiquitously in both excitable and non-excitable cells and are important for a range of physiological functions. BK channels gate K+ efflux in response to concurrent depolarized membrane voltage and increased intracellular Ca2+ to modulate action potential shape and duration in neurons, regulate contractility in smooth muscle, and control fluid secretion by epithelial cells in the airway and gut. In addition, mutations in the human BK channel gene (KCNMA1) are linked to neurological disease, such as epilepsy and paroxysmal dyskinesia. Thus, BK channel modulators may provide treatment avenues for BK channelopathies. It will be important to expand our arsenal of BK channel-selective activators and inhibitors and to grow our understanding of their molecular mechanisms of action. Discovery of new channel modulators will further lead to a greater understanding of BK channel structure and function. To better understand the basic structure-function relationship of BK channel gating in response to increased intracellular Ca2+ concentration, in this work I initially investigate structural determinants of BK channel activation in response to conformational changes following Ca2+ binding. I analyze crystal structures of the BK channel cytosolic Ca2+-sensing domain (CSD), also known as the "gating ring", formed by the C-terminal domains of each of the four identical pore-forming subunits. In the Ca2+-bound state, N449 from the adjacent subunit contacts the bound Ca2+ ion, forming a "Ca2+ bridge." Mutating N449 to alanine eliminates this coordinate interaction, and using electrophysiology, I found that BK channels with the N449A mutation exhibit a shift in the voltage required for half maximal activation (V1/2) towards more positive voltages. Using size-exclusion chromatography, I observed that the purified BK channel CSD with the N449A mutation shows reduced gating ring oligomerization in response to Ca2+ compared to the wild-type CSD. To further probe molecular determinants of BK channel gating and increase our arsenal of BK channel gating modulators, I optimized a fluorescence-based high throughput screening approach to discover compounds with BK channel inhibitor activity with 99.73% confidence. Through this approach I discovered that the -opioid receptor agonist, loperamide, is a potent BK channel inhibitor. Loperamide (LOP) reduced the open probability of channels at depolarized voltages, but not at very negative voltages when the voltage-sensor is at rest. I observed a weak voltage dependence of loperamide inhibition, consistent with loperamide binding shallow within the inner cavity to block the channel pore. I quantified the inhibitory effect of LOP using an allosteric model in which LOP blocks conduction through open channels and binds with 45-fold higher affinity to the open state over the closed state. These data suggest that loperamide may represent a new class of "use-dependent," open channel blockers. Together this work describes an approach to understanding BK channel structure and function with the goal of identifying and developing novel therapeutics for the treatment of BK-related diseases.

Insights Into Assembly And Trafficking Of The Cardiac Small Conductance Calcium Activated Potassium Channel Sk2

DOWNLOAD
Author : Sassan Rafizadeh
language : en
Publisher:
Release Date : 2011

Insights Into Assembly And Trafficking Of The Cardiac Small Conductance Calcium Activated Potassium Channel Sk2 written by Sassan Rafizadeh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.

Proper mechanical activity of the heart is delicately interrelated with its timely electrical activation. It is the underlying ionic currents in each cell that lead to electrical activity, manifested as the cardiac action potential. In order to have a normal cardiac action potential, a specific number of functional ion channels need to be present on the plasma membrane. Defects in channel assembly or trafficking may lead to abnormalities in the corresponding ionic currents and shape of the action potential, which may lead to cardiac arrhythmias. The most prominent type of arrhythmia is atrial fibrillation (AF), which is associated with a significant increase in the risk of stroke. The incidence of AF is projected to increase three-fold by 2050 and therapeutic options for AF remain suboptimal. Current pharmacological therapies are associated with extracardiac toxicity while catheter ablation is invasive and can be associated with serious adverse events.Our group, as well as others, have previously documented the expression of several isoforms of small-conductance Ca2+ -activated K+ (SK) channels in human and mouse atrial myocytes. SK channels mediate the repolarization phase of the atrial action potential, with little effect on ventricular excitation. Indeed, we have previously documented that SK2 channel knock-out mice are prone to the development of AF. On the other hand, a recent study by Diness JG, et al. suggests that inhibition of Ca2+ activated K+ current may prevent AF. Taken together, these studies underpin the importance of these channels in atria and their potential to serve as a future therapeutic target for AF. Three isoforms of SK channel subunits (SK1, SK2 and SK3) are found to be expressed with SK2 as the most predominant isotype. In the first portion (CHAPTER 2) of this dissertation, I investigate the heteromultimeric formation and the domain necessary for the assembly of three SK channel subunits (SK1-SK3). My biochemical and functional data provides evidence for the formation of heteromultimeric complexes among different SK channel subunits in atrial myocytes. Using an innovative patch-clamp technique, applied here for the first time in cardiac myocytes, I show reduction of I[K,Ca] via inhibition of heteromultimerization. Since SK channels are predominantly expressed in atrial myocytes, specific ligands of the different isoforms of SK channel subunits may offer a unique therapeutic opportunity to directly modify atrial cells without interfering with ventricular myocytes. In addition to having proper subunit assembly and channel formation, there need to be a precise number of channels at specific locations on the plasma membrane. This means that there must be highly regulated sorting and trafficking pathways for ion channels. The importance of these processes is underscored by a number of disease conditions that involve mishandled trafficking of membrane proteins. It is important to note that the complete intracellular trafficking pathways are not known for any single channel. In the subsequent chapters, I identify [alpha]-actinin2 and Filamin A molecules, as important regulators of SK2 channel trafficking. Using various functional methods, including total internal reflection fluorescence microscopy (TIRF-M), I show SK2 channel interacts with FLNA to increase number of channels on the sarcolemma through increasing rate of recycling via recycling endosomes. I also show increased forward trafficking of SK2 as a result of interaction with [alpha]-actinin2 via an early endosomal-mediated trafficking pathway. Insight into the trafficking of SK2 channels may serve as a novel approach to modify SK2 current and atrial excitability without interfering with ventricular activity. The work done advances a new frontier towards understanding membrane localization of ion channels in cardiac muscle and other excitable cells. The demonstration of the mechanisms for targeting, anchoring and cell surface expression of the channel would help further understanding the ion channel function.