GABAA receptor needs two homologous domains of the &amp; beta;-subunit for activation by GABA but not by pentobarbital

Amin, Jahanshah; Weiss, David S.

doi:10.1038/366565a0

Cited by 396 publications

(390 citation statements)

References 29 publications

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“…Mutagenesis studies have identified amino acids within the N-terminal domains of both GABA A receptor ␣ and ␤ subunits that are involved in the formation of GABA-binding sites, leading to the hypothesis that the GABA-binding site is located at the interface between the ␣ and ␤ subunits (Amin and Weiss 1993;Smith and Olsen, 1995). Interestingly, residues between 57 and 69 within ␣1 have previously been implicated in the binding of receptor agonists (Smith and Olsen, 1995).…”

Section: Discussionmentioning

confidence: 99%

Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

et al. 2000

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GABA A receptors can be constructed from a range of differing subunit isoforms: ␣, ␤, ␥, ␦, and ⑀. Expression studies have revealed that production of GABA-gated channels is achieved after coexpression of ␣ and ␤ subunits. The expression of a ␥ subunit isoform is essential to confer benzodiazepine sensitivity on the expressed receptor. However, how the specificity of subunit interactions is controlled during receptor assembly remains unknown. Here we demonstrate that residues 58-67 within ␣ subunit isoforms are important in the assembly of receptors comprised of ␣␤ and ␣␤␥ subunits. Deletion of these residues from the ␣1 or ␣6 subunits results in retention of either ␣ subunit isoform in the endoplasmic reticulum on coexpression with the ␤3, or ␤3 and ␥2 subunits. Immunoprecipitation revealed that residues 58-67 mediated oligomerization of the ␣1 and ␤3 subunits, but were without affect on the production of ␣/␥ complexes. Within this domain, glutamine 67 was of central importance in mediating the production of functional ␣1␤3 receptors. Mutation of this residue resulted in a drastic decrease in the cell surface expression of ␣1␤3 receptors and the resulting expression of ␤3 homomers. Sucrose density gradient centrifugation revealed that this residue was important for the production of a 9S ␣1␤3 complex representing functional GABA A receptors.Therefore, our studies detail residues that specify GABA A receptor ␣␤ subunit interactions. This domain, which is conserved in all ␣ subunit isoforms, will therefore play a critical role in the assembly of GABA A receptors composed of ␣␤ and ␣␤␥ subunits. Key words: GABA A -receptor; assembly; cell surface expression; N-terminal; oligomerization; ␣ subunitGABA A receptors are critical mediators of fast synaptic inhibition in the brain and are also important drug targets for a range of compounds, including the benzodiazepines and barbiturates (MacDonald and Olsen, 1994;Rabow et al., 1995). GABA A receptors are members of the ligand-gated ion channel superfamily that includes glycine, nicotinic acetylcholine (AChR), and 5-HT 3 receptors (Unwin, 1993). Molecular cloning has revealed a range of GABA A receptor subunits that can be divided by homology into subunit classes with multiple members: ␣(1-6), ␤ (1-3), ␥(1-3), ␦, ⑀, and (MacDonald and Olsen, 1994;Rabow et al., 1995;Davies et al., 1997;Hedblom and Kirkness, 1997). There is considerable spatial and temporal variation in subunit expression, with many neuron types expressing multiple numbers of receptor subunits (Laurie et al., 1992;MacDonald and Olsen, 1994;Rabow et al., 1995). Clearly, to delineate the true diversity of GABA A receptor structure in the brain, it is important to gain some insights into how these receptor subunits are assembled.Studies using heterologous expression focusing on the receptor ␣1, ␤1-2, and ␥2 subunits, have revealed that access to the cell surface is limited to the combinations ␣␤ and ␣␤␥2 (Angelotti and MacDonald 1993;MacDonald and Olsen, 1994;Rabow et al., 1995;Connolly et al., 1996). Most s...

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Section: Discussionmentioning

confidence: 99%

Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

et al. 2000

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“…Similar to benzodiazepines, barbiturates also stimulate inhibitory GABA A receptors in the brain. However, barbiturates appear to augment benzodiazepines' efficacy at the GABA A receptor (35). In addition, barbiturates can also inhibit stimulatory glutamate receptors, which are upregulated in alcohol withdrawal (36 -38).…”

Section: Discussionmentioning

confidence: 99%

A strategy of escalating doses of benzodiazepines and phenobarbital administration reduces the need for mechanical ventilation in delirium tremens*

Gold

Rimal

Nolan

et al. 2007

Critical Care Medicine

154

164

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Objective-Patients with severe alcohol withdrawal and delirium tremens are frequently resistant to standard doses of benzodiazepines. Case reports suggest that these patients have a high incidence of requiring intensive care and many require mechanical ventilation. However, few data exist on treatment strategies and outcomes for these subjects in the medical intensive care unit (ICU). Our goal was a) to describe the outcomes of patients admitted to the medical ICU solely for treatment of severe alcohol withdrawal and b) to determine whether a strategy of escalating doses of benzodiazepines in combination with phenobarbital would improve outcomes. Design-Retrospective cohort study.Setting-Inner-city municipal hospital.Patients-Subjects admitted to the medical ICU solely for the treatment of severe alcohol withdrawal. Interventions-Institution of guidelines emphasizing escalating doses of diazepam in combination with phenobarbital.Measurements and Main Results-Preguideline (n = 54) all subjects were treated with intermittent boluses of diazepam with an average total and maximal individual dose of 248 mg and 32 mg, respectively; 17% were treated with phenobarbital. Forty-seven percent required intubation due to inability to achieve adequate sedation and need for constant infusion of sedative-hypnotics. Intubated subjects had longer length of stay (5.6 vs. 3.4 days; p = .09) and higher incidence of nosocomial pneumonia (42 vs. 21% p = .08). Postguideline (n = 41) there were increases in maximum individual dose of diazepam (32 vs. 86 mg; p = .001), total amount of diazepam (248 vs. 562 mg; p = .001), and phenobarbital use (17 vs. 58%; p = .01). This was associated with a reduction in the need for mechanical ventilation (47 vs. 22%; p = .008), with trends toward reductions in ICU length of stay and nosocomial pneumonia.Conclusions-Patients admitted to a medical ICU solely for treatment of severe alcohol withdrawal have a high incidence of requiring mechanical ventilation. Guidelines emphasizing escalating bolus doses of diazepam, and barbiturates if necessary, significantly reduced the need for mechanical ventilation and showed trends toward reductions in ICU length of stay and nosocomial infections.

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“…5); thus, it is not surprising that changing it to serine or alanine in the 5-HT 3 native aromatic, phenylalanine, resulted in changed functional receptor characteristics (an ϳ10-fold increase in EC 50 ) but not in binding affinity (K d not significantly different from WT), thus supporting a role for the hydroxyl group in receptor gating. Extensive site-directed mutagenesis of the residue at this location has shown that it is important in the nACh receptor (39), the ␥-aminobutyric acid A receptor (40), and the glycine receptor (41), although there is some debate as to whether it affects the binding affinity (42) or the gating constant (43). The binding of dTC and its analogues to the nACh receptor has been particularly well studied, and there was evidence that these compounds might interact via cation-interactions with Tyr 198 (35).…”

Section: Discussionmentioning

confidence: 99%

The Role of Tyrosine Residues in the Extracellular Domain of the 5-Hydroxytryptamine3 Receptor

Price

Lummis

2004

Journal of Biological Chemistry

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GABAA receptor needs two homologous domains of the & beta;-subunit for activation by GABA but not by pentobarbital

Cited by 396 publications

References 29 publications

Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

A strategy of escalating doses of benzodiazepines and phenobarbital administration reduces the need for mechanical ventilation in delirium tremens*

The Role of Tyrosine Residues in the Extracellular Domain of the 5-Hydroxytryptamine3 Receptor

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GABAA receptor needs two homologous domains of the & beta;-subunit for activation by GABA but not by pentobarbital

Cited by 396 publications

References 29 publications

Identification of Residues within GABAAReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

Identification of Residues within GABAAReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

A strategy of escalating doses of benzodiazepines and phenobarbital administration reduces the need for mechanical ventilation in delirium tremens*

The Role of Tyrosine Residues in the Extracellular Domain of the 5-Hydroxytryptamine3 Receptor

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Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits

Identification of Residues within GABA_AReceptor α Subunits That Mediate Specific Assembly with Receptor β Subunits