Zhang_2014_Neuropharmacol_89C_391

Glycine receptor (GlyR) chloride channels mediate fast inhibitory neurotransmission in the spinal cord and brainstem. Four GlyR subunits (alpha1-3, beta) have been identified in humans, and their differential anatomical distributions underlie a diversity of synaptic isoforms with unique physiological and pharmacological properties. To improve our understanding of these properties, we induced the formation of recombinant synapses between cultured spinal neurons and HEK293 cells expressing GlyR subunits of interest plus the synapse-promoting molecule, neuroligin-2A. In the heterosynapses thus formed, recombinant alpha1beta and alpha3beta GlyRs mediated fast decaying inhibitory postsynaptic currents (IPSCs) whereas alpha2beta GlyRs mediated slow decaying IPSCs. These results are consistent with the fragmentary information available from native synapses and single channel kinetic studies. As beta subunit incorporation is considered essential for localizing GlyRs at the synapse, we were surprised that alpha1-3 homomers supported robust IPSCs with beta subunit incorporation accelerating IPSC rise and decay times in alpha2beta and alpha3beta heteromers only. Finally, heterosynapses incorporating alpha1D80Abeta and alpha1A52Sbeta GlyRs exhibited accelerated IPSC decay rates closely resembling those recorded in native synapses from mutant mice homozygous for these mutations, providing an additional validation of our technique. Glycinergic heterosynapses should prove useful for evaluating the effects of drugs, hereditary disease mutations or other interventions on defined GlyR subunit combinations under realistic synaptic activation conditions.