Identification of a Novel Protein Complex Containing ASIC1a and GABAA Receptors and Their Interregulation

Abstract

Acid-sensing ion channels (ASICs) belong to the family of the epithelial sodium channel/degenerin (ENaC/DEG) and are activated by extracellular protons. They are widely distributed within both the central and peripheral nervous systems. ASICs were modified by the activation of γ-aminobutyric acid receptors (GABAA), a ligand-gated chloride channels, in hippocampal neurons. In contrast, the activity of GABAA receptors were also modulated by extracellular pH. However so far, the mechanisms underlying this intermodulation remain obscure. We hypothesized that these two receptors-GABAA receptors and ASICs channels might form a novel protein complex and functionally interact with each other. In the study reported here, we found that ASICs were modified by the activation of GABAA receptors either in HEK293 cells following transient co-transfection of GABAA and ASIC1a or in primary cultured dorsal root ganglia (DRG) neurons. Conversely, activation of ASIC1a also modifies the GABAA receptor-channel kinetics. Immunoassays showed that both GABAA and ASIC1a proteins were co-immunoprecipitated mutually either in HEK293 cells co-transfected with GABAA and ASIC1a or in primary cultured DRG neurons. Our results indicate that putative GABAA and ASIC1a channels functionally interact with each other, possibly via an inter-molecular association by forming a novel protein complex.

A modulatory role of ASICs on GABAergic synapses in rat hippocampal cell cultures

“…Protons are considered to be neurotransmitters regulating synaptic plasticity in the lateral amygdala [ 5 ]. In spite of growing evidence indicating that the density of ASICs is substantially higher in GABAergic interneurons than in glutamatergic cells [ 17 ] and recent demonstration of functional crosstalk between ASICs and GABA A -receptors [ 10 , 11 ], the possible involvement of ASICs in the regulation of GABAergic transmission remained unclear. In our work we present evidence for the first time that ASICs play a functional role at hippocampal GABAergic synapses.…”

“…Functional interaction between ASICs and GABA A -receptors in isolated neurons has been recently demonstrated [ 10 , 11 ]. Activation of GABA A -receptors strongly changed ASIC-currents amplitude and pharmacological sensitivity [ 10 ], and the effect was blocked by antagonists of GABA A receptors [ 10 ].…”

“…However, the synaptic cleft acidification occurs also at inhibitory GABAergic synapses [ 1 ], and selective deletion of ASIC1a in GABAergic cells, has important functional consequences [ 9 ]. Finally, functional crosstalk between ASICs and GABA A -receptors has been recently reported [ 10 , 11 ]. This notwithstanding, possible involvement of ASICs in the regulation of GABAergic transmission is still poorly investigated.…”

ASICs may affect GABAergic synapses

“…Still, functional crosstalk between ASICs and GABA A receptors has been previously reported in isolated neurons [8]. …”

Suppression of GABAergic Synaptic Transmission by Azidin: Probable Mechanism of a Seizure-Inducing Side Effect

“…Such an assumption is indirectly confirmed by the fact that amyloride, another blocker of protonactivated channels, influences considerably the effects induced by application of exogenous GABA [6,7] and GABA-mediated PSCs [8]. Recently, it was found that functional interaction between GABA A receptors and ASIC1a channels is quite possible; a protein complex including both abovementioned receptors has been identified [9].…”