The Effects Of Vitamin C On The Function Of Different Subtypes Of Glycine Receptors

Glycine receptors(GlyRs)belong to the large Cys-Loop superfamily,which is structurally similar to many ligand-gated ion channels.During activation,the GlyR can selectively allow chloride ions to pass through its central channel,leading to hyperpolarization of neurons and therefore mediating the inhibitory neurotransmission.GlyRs are widely distributed in the central nervous system,especially in the brain stem and the spinal cord.The function of GlyRs can be regulated by many drugs and endogenous molecules in organisms,such as cannabinoids,alcohol,zinc ions,steroids,etc.Vitamin C,also known as L-ascorbic acid,has been extensively studied in a large number of literatures.Vitamin C is abundant in brain tissues and nerve cells.However,no studies on the relationship between vitamin C and GlyR have been reported.Here,in the HEK-293T cells transfected with GlyRs,we examined whether vitamin C could affect the function of GlyRs by the patch-clamp recording.Firstly,we co-transfected the HEK-293T cells with plasmids expressing different subtypes of GlyRs and plasmids expressing green fluorescent protein(GFP).Cells were then incubated with different concentrations of vitamin C,and the whole-cell patch clamp technique was used to record the current induced by puffing glycine.We found that vitamin C could dose-dependently increase the currents mediated by the al and ?3 subunits of GlyRs,with ?3 subunits being the most sensitive to vitamin C.Vitamin C had no significant effect on the current mediated by the ?2 subunit of GlyRs.Intracellular application of the high concentration of vitamin C also enhanced the GlyR-mediated currents.Cell incubation with the blockers of vitamin C transporters did not affect the vitamin C-induced potentiation of GlyR function.The amino acid mutation at position 307(S307A)on the third transmembrane domain of the ?3 GlyR significantly inhibited the potentiating effect of vitamin C,suggesting that the interacting site of vitamin C may be located in the transmembrane domain of GlyR.