Expression of GABA Receptor ρ Subunits in Rat Brain

Abstract

The GABA receptor ρ1, ρ2, and ρ3 subunits are expressed in the retina where they form bicuculline‐insensitive GABAC receptors. We used northern blot, in situ hybridization, and RT‐PCR analysis to study the expression of ρ subunits in rat brains. In situ hybridization allowed us to detect ρ‐subunit expression in the superficial gray layer of the superior colliculus and in the cerebellar Purkinje cells. RT‐PCR experiments indicated that (a) in retina and in domains that may contain functional GABAC receptors, ρ2 and ρ1 subunits are expressed at similar levels; and (b) in domains and in tissues that are unlikely to contain GABAC receptors, ρ2 mRNA is enriched relative to ρ1 mRNA. These results suggest that both ρ1 and ρ2 subunits are necessary to form a functional GABAC receptor. The use of RT‐PCR also showed that, except in the superior colliculus, ρ3 is expressed along with ρ1 and ρ2 subunits. We also raised an antibody against a peptide sequence unique to the ρ1 subunit. The use of this antibody on cerebellum revealed the rat ρ1 subunit in the soma and dendrites of Purkinje neurons. The allocation of GABAC receptor subunits to identified neurons paves the way for future electrophysiological studies.

Suppression of Neuronal Hyperexcitability and Associated Delayed Neuronal Death by Adenoviral Expression of GABACReceptors

“…Binding of the ligand GABA opens the integral chloride ion channel, driving the membrane potential toward the chloride equilibrium potential and thus reducing sensitivity to excitatory neurotransmitters. The rarer GABA C receptor, another member of the inotropic GABA receptor family, is a homomeric assembly of 1 subunits (Shimada et al, 1992;Amin and Weiss, 1996); a search for endogenous mRNA using reverse transcription-PCR found 1 only in bipolar cells of the retina (Boue-Grabot et al, 1998), although other types of subunits are found elsewhere in the CNS (Wang et al, 1994;Enz and Cutting, 1999). Recent evidence that 1 subunits do not coimmunoprecipitate in vitro with ␣ 1 , ␣ 5 , or ␤ 1 subunits of GABA A suggests that 1 subunits do not associate with GABA A subunits to form receptors (Hackam et al, 1998).…”

Cross-talk and Co-trafficking between ρ1/GABA Receptors and ATP-gated Channels

“…Recent data suggest that a 1 subunit could co-assemble with a GABA A subunit (5,6). Neuronal ATP and GABA C ionotropic receptors are involved in fast excitatory and inhibitory synaptic transmission, respectively, and display overlapping distribution in many regions of the nervous system, including DRG, dorsal horn of the spinal cord (7,8), retina (9 -13), hippocampus (14 -15), cerebellum (14,16), and anterior pituitary (17,18).…”

“…Because P2X and 1/GABA receptors are co-expressed in the central nervous system (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), we investigated potential molecular and functional interactions between these two types of transmitter-gated channels in heterologous expression systems. We report here an intracellular inhibitory cross-talk between P2X 2 and GABA C 1 receptors.…”

Tax1-binding protein 1 is expressed in the retina and interacts with the GABAC receptor ρ1 subunit

“…Besides being expressed in the retina, GABA C receptor ρ subunits were also found in other brain regions such as the hippocampus, cerebellum and the superior colliculus, as well as in the spinal cord [33][34][35][36]. Furthermore, ρ subunits were detected in secretory cells of the pituitary, in neurons of the gastrointestinal tract and in a neuroendocrine tumour cell line of the gut [37][38][39][40].…”