MOLECULAR MECHANISMS OF GATING IN IONIC CHANNELS

  • Nonner, Wolfgang F., (PI)

Project: Research project

Description

Biophysical studies are proposed concerning (l) the mechanisms by which
excitatory and inhibitory ligand-gated ion channels select between cations
and anions, (2) the gate mechanism of a large-conductance K channel at
subzero temperatures. The experiments use embryonic rat central neurons
(hippocampus, spinal cord) and myotubes maintained in primary tissue
culture. The patch clamp technique will be used to study currents from
individual channels in excised membrane patches. The excitatory or inhibitory effects of the structurally homologous ion
channels operated by the neurotransmitters ACh, GABA, or glycine are
determined by the channels' ability to select permeant ions by charge
polarity. In the AChR channel, several treatments (high ionic strength,
pH, and a carboxyl reagent) will be used to neutralize groups with
negative net charges, to assess their importance in the cation/anion
selection. In GABA-R and Gly-R channels, the roles of intracellular and
extracellular divalent cations in establishing a high selectivity for
anions will be studied (a substantial cation leakage through channels
exposed to divalent-free salines and partial restoration of anion
selectivity by external Ca have observed). The divalent in requirements
will be determined and tests will be applied to distinguish between
structural and direct electrostatic effects of divalent cations. A new level of kinetic phenomena underlying the gating of large-
conductance Ca-activated K channels will be studied at temperatures down
to -30 degrees C using techniques developed in our laboratory. These
experiments will investigate the operation of the molecular gate by which
the ionic current of the channel pore is controlled. At room temperature
this gate acts like an instant switch, but at very low temperature channel
transitions are slowed to an extent that a cadence of ion current changes
can be measured from which the behavior of the actual gate can be
inferred. These studies address fundamental questions concerning ionic channels of
neurons and muscle, and thus should provide basic information important
for understanding normal and impaired function in these tissues.
StatusFinished
Effective start/end date8/1/816/30/99

Funding

  • National Institutes of Health: $100,000.00
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health: $198,171.00
  • National Institutes of Health
  • National Institutes of Health: $184,308.00
  • National Institutes of Health

Fingerprint

Ion Channels
Membranes
Patch-Clamp Techniques
Anions
Cations
Temperature
Ions
Divalent Cations
Neurons
Carisoprodol
Glycine
gamma-Aminobutyric Acid
Permeability
Hippocampus
Thiamine
Spinal Ganglia
Ligand-Gated Ion Channels
cations
Membrane Potentials
Tissue culture

ASJC

  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)