Areas of Interest
- Cell biology of membranes
- Ion Channels and Receptors
- Sodium Channel Blockers
- Activation gating in Human Heart Na+ channels
1. Therapeutic Na+ channel blockers: Receptor & Drug Design: The goals of this, proposal are (1) to map the topology of the local anesthetic (LA) receptor in voltage-regulated Na+ channels, (2) to design better Na+ channel blockers toward this LA receptor, and (3) to utilize these blockers in vivo as long-acting LAs. The putative receptor for LAs and their quaternary ammonium (QA) derivatives has been assigned within the a-subunit of the voltage-regulated Na+ channel. We plan to mutate various amino acid residues on this putative LA receptor by the site-directed mutagenesis method. Mutants and wildtype muscle Na+ charmers of rat µI clones will be expressed in transiently transfected mammalian cells, and their binding to conventional LAs and newly synthesized QA drugs will be assessed in patch membranes and/or in planar lipid bilayers at the single channel level with batrachotoxin present. The binding contacts to the tertiary amine, the intermediate chain, the phenyl ring, and the putative second hydrophobic group of LA/QA drugs will be charted within the LA receptor. In conjunction, we will continue to design a series of QA derivatives from various LAs; among LAs used are tonicaine, procaine, tetracaine, and etidocaine. These high-affinity Na+ channel blockers, in turn, will be employed to resolve further the topology of the LA receptor. Newly synthesized drugs will be tested first in vitro for their binding affinities in native Na+ channels and subsequently in vivo for their efficacy in rat sciatic nerve block and in rat spinal block. N-butyl tetracaine and its related QA derivatives that block sciatic sensory and motor functions for more than one week will be examined for their local anesthetic and neurolytic characteristics. Neurolytic compounds that destroy nerve fibers but retain the tissue inteety for later nerve regeneration will then be explored as potential ultralong acting local anesthetics. Together, these experiments should give us a clearer view of the LA receptor at the molecular level and likely provide us better Na+ channel blockers with longer duration of block. These high affinity Na+ channel blockers may be beneficial for patients with chronic as well as intractable cancer pain.
2. Molecular Basis of Ligand-Na+ Channel Interactions: The broad objectives of this project are (1) to understand better the molecular basis of state dependent interactions between voltage-gated Na+ channels and local anesthetics (LAs) and (2) to explore the interplay between LAs and the Na+ permeation pathway. This pathway, in part, consists of a selectivity filter, permeant ion binding sites and an inactivation gate. Among LAs included are putative inactivation enhancers, such as benzocaine and tricaine, putative open-channel blockers, such as cocaine, bupivacaine, and quaternary ammonium (QA) compounds, and putative dual blockers such as tetracaine and procaine. In this proposal we plan to examine the structural basis that distinguishes these three distinct LA types. Two separate hypotheses will be tested: first, only one single receptor is present within the Na+ permeation pathway for all three types of Las and second, the common amino gropu on the phenyl ring of inactivation enhancers and dual blockers preferentially stabilizes the inactivated state of the Na+ channel. Both whole cell and single channel currents will be measured in order to obtain detailed kinetic information on the dynamic interactions between Na+ channels and LAs. Because ion-ion repulsion within the pore is a common trait for ion permeation, demonstration and further characterization of a knockout phenomenon of LA/QA ions by the inflowing cations through the Na+ selectivity filter will be obtained to provide crucial evidence that the LA binding site is indeed located within the Na+ permeation pathway. Concurrently, we will delineate LA channel interactions at the molecular level. At first, the LA binding toward cloned 41 muscle Na+ channels will be studied with and without subunit -present. Subsequently, the roles of two separate regions of µI Na+ channels, including the intemal QA binding site (probably within the pore and S6 regions) and the inactivation-related loop (between domain III and IV), on LA binding affinities will be examined by the macropatch technique in Xenopus oocytes injected with wildtype and µI mutant mRNAs. Together, these studies should provide a clearer understanding of LA Na+ channel interactions as well as the whereabouts of the LA/QA binding site within the Na+ permeation pathway.
3. Activation Gating in Human Heart Na+ Channels: The long-term objective of this project is to understand better how the activation gate of voltage gated Na+ channels works during state transitions. As a first step, we plan to delimit the whereabouts of this activation gate. We hypothesize that the Na+ channel activation gate is adjacent to the batrachotoxin (BTX) binding site and is situated at the S6 segment-crossing region. Our rationale is based on the fact that BTX affects the activation gate of Na+ channels drastically and that its receptor encompasses multiple S6 segments. Our specific aims are (1) to create, express, and characterize a series of cysteine-substituted mutants at positions 15-28 of S6 segments (~28 residues/S6) in all four homologous domains (DI-D4), (2) to determine the reactivity rate of selected S6 mutants with cysteine-modifying reagents or Cd2+, ions, and (3) to create, express, and characterize additional mutants with residues of different size, hydrophobicity, and polarity at the putative activation gate. Mutants of the human heart a-subunit Na+ channel (hHl) clone will be created and subsequently expressed in human embryonic kidney cells by transient transfection. Mutant Na+ channels and their gating properties will be characterized under whole-cell voltage-clamp conditions. The effects of BTX binding on activation gating will be also measured in these mutants. Selected mutants will be further assayed in inside-out patches before and after application of cysteine-modifying reagents or Cd2+ ions. Repetitive pulses will then be applied to obtain the cysteine reactivity rate during open state transitions. If needed, BTX will be used to measure the cysteine reactivity rate of the open state. These gating and BTX binding profiles along with the cysteine reactivity rate will allow us to infer the location of the activation gate. Subsequent characterizations of this specific region with additional mutations may unravel how the Na+ channel opens upon depolarization at the molecular level. This activation gate also governs the access of various clinical drugs such as local anesthetics, antiarrhythmics, and anticonvulsants to their overlapping receptor site within the Na+ channel inner vestibule. Detailed mapping of the Na+ channel activation gate may provide insights for the design of new therapeutic drugs that target this important region.
- Wang, S.Y. and Wang, G.K., “Single rat muscle Na+ channel mutation confers batrachotoxin autoresistance found in poison-dart frog Phyllobates terribilis Proc. Natl. Acad. Sci. USA, (2017), DOI: 10.1073/pnas.1707873114
- Wang, J., Russell G., Wang SY, Strichartz GR. and Wang GK. "R-duloxetine and N-methyl duloxetine as novel analgesics against experimental post-incisional pain" Anaesthesia & Analgesia (2016), 122:719-729.
- Wang GK, Wang SY. Block of human cardiac sodium channels by lacosamide: evidence for slow drug binding along the activation pathway. Mol Pharmacol. (2014) May; 85(5):692-702. doi: 10.1124/mol.113.091173. Epub 2014 Feb 21.
- Wang GK, Russell G, Wang SY. Persistent human cardiac Na+ currents in stably transfected mammalian cells: Robust expression and distinct open-channel selectivity among Class 1 antiarrhythmics. Channels (Austin). (2013) Jul-Aug; 7(4):263-74.
- Wang, S.Y., J.Calderon, and G.K.Wang. Block of neuronal Na+ channels by antidepressant duloxetine in a state-dependent manner. Anesthesiology (2010) 113: 655-665
- Wang, G.K., Calderon J, Jaw S.J., Wang, S.Y. State-Dependent Block of Na+ Channels by Articaine via the Local Anaesthetic Receptor. J. Membrane Biol. 229 (1):1-9 (2009)
- Wang, C.F., Gerner, P., Schmidt, B., Xu, Z.Z., Nau, C., Wang, S-Y, Ji, R-R, and Wang, G.K. Use of bulleyaconitine A as an adjuvant for prolonged cutaneous analgesia in the rat. Anesthetics & Analgesia (2008)
- Wang, G.K., Mitchell, J., and Wang, S.Y. Block of persistent late Na+ currents by antidepressant sertraline and paroxetine. J. Membr. Biol. 222:79-90 (2008)
- Wang, C.F., Gerner, P., Schmidt, B., Wang, S.Y., and Wang, G. K. Prolonged Cutaneous Analgesia in Rats Induced by 3-Acetylaconitine as an Additive. Drug Development Research 69:1-6 (2008)
- Wang, S.Y., J. Mitchell, and G. K. Wang. .Preferential block of inactivation-deficient Na+ currents by capsaicin reveals a non-TRPV1 receptor within the Na+ channel. Pain 127:73-83. (2007)
- Wang, S.Y., D. B. Tikhonov, B. S. Zhorov, J. Mitchell, and G. K. Wang.. Serine-401 as a batrachotoxin- and local anesthetic-sensing residue in the human cardiac Na (+) channel. Pflugers Arch.454 (2): 277-87 (2007)
- Wang , C-F, P. Gerner, S.Y. Wang, G. K. Wang. An alkaloid isolated from Aconitum bulleyanum roots, bulleyaconitine A, displays long-acting local anesthetic properties in vitro and in vivo Anesthesiology 107:82-90 (2007)
- Wang, S.Y., Tikhonov, D.B., Mitchell, J., Zhorov, B.S., and Wang, G.K. Irreversible block of cardiac mutant Na+ channels by batrachotoxin Channels 1:179-188 (2007)
- Wang, G.K., Calderon J., and Wang, S.Y. State- and use-dependent block of muscle Nav1.4 and neuronal Nav1.7 voltage-gated Na+ channel isoforms by ranolazine. Mol Pharmacol 73 (3):940-8 (2007)
- Wang, S.Y., Jane Mitchell, Denis B. Tikhonov, Boris S. Zhorov, and Ging Kuo Wang. How batrachotoxin modifies the sodium channel permeation pathway: computer modeling and site-directed mutagenesis. Mol. Pharmacol. 69:788-795 (2006)
- Wang GK, T Edrich, and Wang, S.Y. Time-dependent block and resurgent tail currents induced by mouse β4154-167 peptide in cardiac Na+ channels. J Gen Physiol 127:277-89. (2006)
- Sheets, P. L., P. Gerner, C. F. Wang, S.Y. Wang, G. K. Wang, and T. R. Cummins. Inhibition of Nav1.7 and Nav1.4 sodium channels by trifluoperazine involves the local anesthetic receptor. J Neurophysiol. 96:1848-1859 (2006).
- Wang, S.Y. and G.K.Wang.. Block of inactivation-deficient cardiac Na(+) channels by acetyl- KIFMK-amide. Biochem Biophys Res Commun. 329:780-788. (2005)
- Wang,S.Y., C.Russell, and G.K.Wang. Tryptophan substitution of a putative D4S6 gating hinge alters slow inactivation in cardiac sodium channels. Biophys J. 88(6):3991-9. (2005).
- Xiao YF, Ma F, Wang, S.Y., Josephson ME, Wang GK, Morgan JP, and Leaf A. Potent block of inactivation-deficient Na channels by N-3 polyunsaturated fatty acids. Am. J. Physiol. Cell Physiol. (2005)
- Edrich T, Wang, S.Y. and Wang G K State-Dependent Block of Human Cardiac hNav1.5 Sodium Channels by Propafenone. J Membr Biol 207:35-43. (2005)
- Wang, G.K., Russell, C., and Wang, S-Y., Mexiletine block of wild-type and inactivation-deficient human skeletal muscle hNav1.4 Na+ channels. J. Physiol. 554:621-633. (2004)
- Wang,G.K., C.Russell, and S.Y.Wang. State-dependent block of voltage-gated Na+ channels by amitriptyline via the local anesthetic receptor and its implication for neuropathic pain. Pain 110:166-17(2004)
- Xiao,Y.F., Q.Ke, S.Y.Wang, Y.Yang, Y.Chen, G.K.Wang, J.P.Morgan, B.Cox, and A.Leaf. Electrophysiologic properties of lidocaine, cocaine, and n-3 fatty-acids block of cardiac Na+ channels. Eur J Pharmacol 485:31-41. (2004)
- Wang, S.Y., J.Mitchell, E.Moczydlowski, and G.K.Wang. Block of inactivation-deficient Na+ channels by local anesthetics in stably transfected mammalian cells: evidence for drug binding along the activation pathway. J Gen Physiol 124:691-701. (2004)
- Wang, S-Y. and Wang, G.K. Voltage-Gated Sodium Channels as Primary Targets of Diverse Lipid-Soluble Neurotoxins. Cellular Signalling 15, 151-159 March (2003).
- Nau C., S-Y. Wang, G.K. Wang. Point mutations at L1280 in Nav1.4 channel D3-S6 modulate binding affinity and stereoselectivity of bupivacaine enantiomers. Mol Pharmaco 63:1398-1406 (2003).
- O'Reilly J.P., S-Y. Wang, G.K. Wang. Methanethiosulfonate-modification in rNav1.4 wild-type and cysteine-substituted mutants S1276C and L1280C alters local anesthetic affinity. J Memb Biol .193:47-55 May (2003).
- Wang G.K., S-Y. Wang. 2003. Veratridine block of voltage-gated rNav1.4 sodium channels in the inner vestibule. J Physiol 548: 667-675 (2003).
- Wang S-Y., K. Bonner, C. Russell, G.K. Wang. Tryptophan scanning of D1S6 and D4S6 C-termini in voltage-gated sodium channels. Biophys. J. 85:911-920 August (2003).
- Mohapatra, D.P., Wang, S.-Y., Wang, GK., and Nau, C. A tyrosine residue in TM6 of the vanilloid receptor TRPV1 involved in desensitization and calcium permeability of capsaicin-activated currents. Molecular and Cellular Neuroscience 23, 314-324 (2003).
- Wang, G.K., Russell, C., and Wang, S-Y. State-dependent block of rNav1.4 wild-type and inactivation-deficient mutant sodium channels by flecainide. J. General Physiol. 122: 1-11 (2003).
- Rathee, P.K., Distler, C., Obreja, O., Neuhuber, W., Wang, GK, Wang, S-Y., Nau, C., and Kress, M. PKA/AKAP/VR-1 module: a common link of Gs-mediated signaling to thermal hyperalgesia. J. Neuroscience 22, 4740-4745 (2002).
- Mujtaba, M.G., Wang, S-Y, and Wang , G.K. Prenylamine block of Nav 1.5 channel is mediated via a receptor distinct form that of local anesthetics. Molecular Pharmacology 62, 415-422 August ( 2002).
- Wang, G.K. and Wang, S-Y. Modification of Human Cardiac Sodium Channel Gating by UVA light: Via an oxidative pathway. J. Membrane Biology 189, 153-165 September (2002).
- Wang, S-Y., Barile M, and Wang GK, A phenylalanine residue at segment D3-S6 in Nav1 voltage-gated Na channels is critical for Pyrethroid action. Mol Pharmacology 60: 620-628, September (2001).
- O'Reilly J, Wang GK, and Wang S-Y. Residue-specific effects at V787 in D2-S6 on slow activation in Na v 1.4 sodium channels. Biophysical J. 81:2100-2111 (2001).
- Wang, S-Y., Barile, M., and Wang, G. K., Disparate role of Na+ channel D2-S6 residues in batrachotoxin and local anesthetic binding. Mole. Pharmacol. 59;1-8 (2001).
- Xiao, Y. F., Ke. O., Wang, S-Y, Auktor, K. Yang, Y., Wang, G. K., Morgan, J. P. and Leaf, A. Single point mutations affect fatty acid block of human myocardial sodium channel alpha subunit Na+ channels. Proc. Natl. Acad. Sci. USA, 98:(6);3606-3611 (2001)
- O'Reilly, J.P., Wang, S-Y. and G. K. Wang. A point mutation in domain 4-segment 6 of the skeletal muscle sodium channel produces an atypical inactivation state. Biophys J. 78:773-784 (2000).
- Nau, C., M. Seaver, Wang, S-Y., and G. K. Wang. Block of human heart hH1 sodium channels by amitriptyline. J. Pharmacology & Experimental Therapeutics 292:1015-1023 (2000)
- Wang, G. K., Quan, C., Seaver, M. and Wang, S-Y Modificaiton of wild-type and batrachotoxin resistant muscle µ1 Na+ channels by veratridine. Pflügers Archiv 439:705-713 (2000)
- Wang, S-Y, C. Nau, G. K. Wang. Residues in Na+ channel D3-S6 segment modulate both batrachotoxin and local anesthetic affinities. Biophys J. 79:1379-1387 (2000).
- Wright, S.,. Wang, S-Y, & G. K. Wang, State Dependant Cocaine Block of Na Channel Isoforms, Chimeras and Channels Coexpressed with the Betal Subunit, Biophysical J. 76:233-245 (1999)
- Wang, S-Y, G. K. Wang, Batrachotoxin-resistant Na+ Channels Derived From Point Mutations in Transmembrane Segment D4-S6. Biophys J. 76:3141-3149 (1999).
- Nau,C. Wang S.-Y., G. R. Strichartz, G. K. Wang. Point Mutations at N434 in D1-S6 of µl Na+ Channels Modulate Binding Affinity and Stereoselectivity of Local Anesthetic Enantiomers. Mol. Pharmacol. 56:404-413 (1999)
- Wang, S.-Y. And Wang, G. K. Point Mutations in Segment I-s6 Render Voltage-gated Na+ Channels Resistant to Batrachotoxin. Proc. Natl. Acad. Si. USA 95:2653-2658 (1998).
- Wang, G. K., c. Quan and Wang S.-Y., Local Anesthetic Block of Batrachotoxin-resistant Muscle Na Channels. Molecular Pharmacology, 54:389-396 (1998).
- Wang, S.-Y. And Wang, G. K. A mutation in segment I-S6 alters the C-type inactivation of sodium channels. Biophysical J. 2:11633-11640 (1997).
- Wang, S-Y A retinoid acid inducible GATA binding protein binds to the regulatory region of J6 serpin gene, J. Biological Chemistry. 269:607-613 (1994)
- Wang, G.K. & Wang, S-Y. Binding of Banzocaine in Batrachotoxin Modified Na+ channels: State Dependent Interaction. J. Gen. Physiol. 103:501-518 (1994)
- Henle, K. J., Wang, S-Y., Nagle, W. A., and Lumpkin, C. K. Heat shock glycoprotein GP50: Product of the Retinoic Acid-Inducible J6 Gene. Exptl. Cell Res. (1994). 210:185-191.
- Wang, G.K. and Wang, S-Y. Inactivation of batrachotoxin-modified Na+ channels in GH3 cells: characterization and pharmacological modification. J. Gen. Physiol. 99:1-20 (1992).
- Wang, S-Y Structure of the gene and its retinoic acid regulatory region for murine J6 serpin - a F9 teratocarcinoma cell retinoic acid inducible protein. J. Biol. Chem. 267:15362-15366 (1992).
- Wang, G.K., and Wang, S-Y. Altered stereoselectivity of cocaine and bupivacaine isomers in normal and batrachotoxin-modified Na+ channels. J. Gen. Physiol. 100:1003-1020 (1992).
- Wang, S-Y and Gudas, L.J. A retinoic acid inducible mRNA from F9 teratocarcinoma cells encodes a novel protease inhibitor homologue. J. Biol. Chem. 265:15818-15822 (1990).
- Wang, S-Y., Roguska, M.A. and Gudas, L.J. Defective post-translational modification of collagen IV in a mutant F9 teratocarcinoma cell line is associated with delayed differentiation and growth arrest in response to retinoic acid. J. Biol. Chem. 264:15556-15564 (1989).