Voltage-dependent Na-channels are a class of membrane proteins responsible for the rapidly activating and inactivating, inward Na- current that underlies the fast action potential of excitable cells. The long-term objective of this project is to advance understanding of the structure and mechanism of this class of ion channels.
The specific aims of this phase of the project focus on three areas of research: (1) Biochemical analysis and investigation of the functional significance of an unusual water- soluble receptor for saxitoxin that is present in bullfrog skeletal muscle. (2) Analysis of the molecular basis for binding of guanidinium toxins such as saxitoxin and tetrodotoxin to a specific receptor site on various Na-channel subtypes. (3) Analysis of the mechanisms of block of Na-channels by diverse inorganic and organic cations, with particular emphasis on high-affinity block of tetrodotoxin-insensitive Na-channels by Zn2+ and on the possibility of multiple sites of action of local anesthetics. Specific binding of (3H) saxitoxin will be used as an assay in the purification of a novel toxin receptor in frog skeletal muscle that may be a water-soluble form of a tetrodotoxin-insensitive Na- channel. Biochemical studies on the purified receptor will be used to establish its structural relationship to known Na-channel proteins. Reconstitution into planar lipid bilayers will be attempted as an approach to the possible Na-channel function of this receptor. Batrachotoxin-activated Na-channels of various subtypes incorporated into planar lipid bilayers will be used as an in vitro model system to study blocking mechanisms at the single channel level. Statistical analysis of toxin blocking events will provide detailed kinetic information on ligand-receptor interactions at the tetrodotoxin binding site. A similar approach will be used to investigate the mechanism of block of Na-channels from canine heart and rat skeletal muscle by Zn2+, local anesthetics, antiarrhythmic and anticonvulsant drugs. An evaluation of the physiological significance of high-affinity Zn2+ block will also be attempted by patch-clamp experiments on cultured cells that express toxin-insensitive Na-channels. The results of this project should further basic understanding of Na-channel biochemistry and pharmacology and may find ultimate applications in musculoskeletal, cardiovascular and neurological diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM051172-10
Application #
2189503
Study Section
Physiology Study Section (PHY)
Project Start
1986-09-01
Project End
1997-08-31
Budget Start
1995-09-01
Budget End
1996-08-31
Support Year
10
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Yale University
Department
Pharmacology
Type
Schools of Medicine
DUNS #
082359691
City
New Haven
State
CT
Country
United States
Zip Code
06520
Huang, Chien-Jung; Schild, Laurent; Moczydlowski, Edward G (2012) Use-dependent block of the voltage-gated Na(+) channel by tetrodotoxin and saxitoxin: effect of pore mutations that change ionic selectivity. J Gen Physiol 140:435-54
Bian, S; Favre, I; Moczydlowski, E (2001) Ca2+-binding activity of a COOH-terminal fragment of the Drosophila BK channel involved in Ca2+-dependent activation. Proc Natl Acad Sci U S A 98:4776-81
Krishnan, G; Morabito, M A; Moczydlowski, E (2001) Expression and characterization of Flag-epitope- and hexahistidine-tagged derivatives of saxiphilin for use in detection and assay of saxitoxin. Toxicon 39:291-301
Huang, C J; Moczydlowski, E (2001) Cytoplasmic polyamines as permeant blockers and modulators of the voltage-gated sodium channel. Biophys J 80:1262-79
Lenarcic, B; Krishnan, G; Borukhovich, R et al. (2000) Saxiphilin, a saxitoxin-binding protein with two thyroglobulin type 1 domains, is an inhibitor of papain-like cysteine proteinases. J Biol Chem 275:15572-7
Favre, I; Moss, G W; Goldenberg, D P et al. (2000) Structure-activity relationships for the interaction of bovine pancreatic trypsin inhibitor with an intracellular site on a large conductance Ca(2+)-activated K(+) channel. Biochemistry 39:2001-12
Huang, C J; Favre, I; Moczydlowski, E (2000) Permeation of large tetra-alkylammonium cations through mutant and wild-type voltage-gated sodium channels as revealed by relief of block at high voltage. J Gen Physiol 115:435-54
Favre, I; Moczydlowski, E (1999) Simultaneous binding of basic peptides at intracellular sites on a large conductance Ca2+-activated K+ channel. Equilibrium and kinetic basis of negatively coupled ligand interactions. J Gen Physiol 113:295-320
Favre, I; Sun, Y M; Moczydlowski, E (1999) Reconstitution of native and cloned channels into planar bilayers. Methods Enzymol 294:287-304
Moczydlowski, E (1998) Chemical basis for alkali cation selectivity in potassium-channel proteins. Chem Biol 5:R291-301

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