Extracellular Chloride Influences Both Desensitization Of GlyRs And GABA_ARs And Their Action Sites

Phospholipid bilayer cell surface membrane insert various proteins which are used to pass through ions, these proteins are the ion channels. Ions channels can be classify to different sorts according to their properties, for example, ligand-gated ion channels,these channles can transport sodium ions, potassium ions and chloride ions,and so on.In the brain, certral nervous system, there are two inhibitory neurotransmitter ion channel receptors, glycine receptors (GlyRs) and y-aminobutyric acid receptors (GABAR), both are dependent chloride ion ligand-gated ion channels, mainly in the neuronal synapses, and modulate inhibitory neuronal transduction, to maintain the balance between excitation and inhibition which glutamate receptors as a representative of excitatory receptors in the brain.These two receptors have many endogenous and exogenous modulators, and different modulators have different binding sites. Recent studies reported that intracellular chloride ion can regulate these two types of receptors’dynamics function, and with the associated crystal X-ray diffraction techniques found that they have chloride ion binding sites in the receptors’extracellular and intracellular domains. However whether extracellular chloride ion have effects on these two receptors’structure and functions are unknown. So we decreased the extracellular chloride ion concentration, use the whole-cell patch clamp recording technique to record currents produced by these two receptors. We found that, in the low chloride ion concentrantion environment, GlyRs and GABA A type receptors are overexpressed on human embryo kidney cell 293 (HEK293), respectively, these receptors have similar changes on channel kinetics-desensitization, the tau value is significantly decreased, and current is also increased. Meanwhile after incubate brain stem and striatum brain slices with artificial cerebrospinal fluid (ACSF) of low chloride ion concentration, Glycinergic and GABAergic spontaneous inhititory postsynapses current (sIPSC) decay time are also decreased.Because above results, GlyRs and GABAaR are both more sensitive to chloride when they are in the low chloride solutions, and there are some literatures indicted that chloride binding sites are located in (35 domain. In GlyRs and GABAARs β5 fragment, there are some basic amino acid which are conservative. So we find out chloride ion binding domain is loctated on β5 segment of GlyRs and GABAARs subunits extracellular domain. After these sequences alignment, with amino acids electrical reversal mutations, we get two possible chloride ion binding sites and some other sites can influence channels kinetics. These all provide a solid foundation to deeperly understand function of ion channels.