GABA acts as a ligand chaperone in the early secretory pathway to promote cell surface expression of GABAA receptors

Eshaq, Randa S.; Stahl, Letha D.; Stone, Randolph; Smith, Sheryl S.; Robinson, Lucy C.; Leidenheimer, Nancy J.

doi:10.1016/j.brainres.2010.05.030

Cited by 40 publications

(62 citation statements)

References 82 publications

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“…This result correlates with the increase at 15 h of GABA exposure of protein expression of a1 and b3 subunit and with the higher percentage of cells responding to the agonist in whole-cell recordings. In agreement with our results, it was reported that GABA acts promoting cell surface expression of GABA A R in transiently transfected cells [13]. In Jurkat cells, we detected macroscopic currents elicited by GABA, revealing that ionotropic GABA receptors are functional.…”

Section: Discussionsupporting

confidence: 93%

“…Since under certain conditions, such as antigen/mitogen-activation, lymphocytes are capable of synthesizing, and, probably, releasing the neurotransmitter [9], the GABA levels achieved at the proximity of lymphocyte GABA A R are probably higher than those detected in blood. Therefore, the GABA concentration chosen to study this phenomenon was higher than the blood concentration in healthy individuals (0.1 mM, [21]) but was similar or lower to that used by others to explore plasticity [5,13]. The changes detected at mRNA level after GABA incubation revealed a differential modulation of subunit expression.…”

Section: Discussionmentioning

confidence: 91%

“…Moreover, cell surface expression of GABA A R can be promoted by GABA exposure [13]. Therefore, we evaluated whether changes in GABA A R subunits occur in Jurkat cells upon exposure to 100 mM GABA.…”

Section: Gaba Exposure Modifies Mrna Levels Of Gaba a R Subunits In Jmentioning

confidence: 99%

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GABAA receptor plasticity in Jurkat T cells

et al. 2013

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Section: Discussionsupporting

confidence: 93%

Section: Discussionmentioning

confidence: 91%

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GABAA receptor plasticity in Jurkat T cells

et al. 2013

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“…Indeed, two lines of evidence support the assertion that bupropion and ibogaine increase K590A DAT protein and function by acting as pharmacological chaperones: 1) pharmacological blockade of ER to Golgi transport with BFA eliminates the effect of bupropion and ibogaine, and 2) the effect of ibogaine is dependent on SEC24D. BFA blocks transport from the ER to the Golgi and has traditionally been used to demonstrate action of drugs in the ER (34,35). Because BFA blocks the effect of bupropion and ibogaine, it suggests that ER to Golgi transport is necessary for the rescue of K590A.…”

Section: Discussionmentioning

confidence: 83%

Pharmacological Chaperones of the Dopamine Transporter Rescue Dopamine Transporter Deficiency Syndrome Mutations in Heterologous Cells

Beerepoot¹,

Lam²,

Salahpour

2016

Journal of Biological Chemistry

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A number of pathological conditions have been linked to mutations in the dopamine transporter gene, including hereditary dopamine transporter deficiency syndrome (DTDS). DTDS is a rare condition that is caused by autosomal recessive loss-offunction mutations in the dopamine transporter (DAT), which often affects transporter trafficking and folding. We examined the possibility of using pharmacological chaperones of DAT to rescue DTDS mutations. After screening a set of known DAT ligands for their ability to increase DAT surface expression, we found that bupropion and ibogaine increased DAT surface expression, whereas others, including cocaine and methylphenidate, had no effect. Bupropion and ibogaine increased wild type DAT protein levels and also promoted maturation of the endoplasmic reticulum (ER)-retained DAT mutant K590A. Rescue of K590A could be blocked by inhibiting ER to Golgi transport using brefeldin A. Furthermore, knockdown of coat protein complex II (COPII) component SEC24D, which is important in the ER export of wild type DAT, also blocked the rescue effects of bupropion and ibogaine. These data suggest that bupropion and ibogaine promote maturation of DAT by acting as pharmacological chaperones in the ER. Importantly, both drugs rescue DAT maturation and functional activity of the DTDS-associated mutations A314V and R445C. Together, these results are the first demonstration of pharmacological chaperoning of DAT and suggest this may be a viable approach to increase DAT levels in DTDS and other conditions associated with reduced DAT function. The dopamine transporter (DAT)4 is responsible for controlling levels of extracellular dopamine and maintaining dopamine stores by transporting dopamine back into neurons after release (1, 2). DAT is part of the Na ϩ /Cl Ϫ -dependent neurotransmitter symporter solute carrier 6 (SLC6) family, which also includes the serotonin, norepinephrine, taurine, and GABA transporters (GAT) (3). A variety of pathological conditions have been associated with mutations in both coding and non-coding regions of the DAT gene (SLC6A3), most of which result in reduced DAT function (4 -7). A recently discovered condition, hereditary DAT deficiency syndrome (DTDS) is caused by autosomal recessive loss-of-function mutations in DAT (6,8,9). The disorder is characterized by parkinsonismdystonia and elevated dopamine metabolites in the cerebrospinal fluid. To date, very few diagnosed DTDS patients have survived to adulthood; the majority of patients die in infancy or adolescence (8, 9). When expressed in heterologous cells, DTDS mutations prevent DAT protein maturation past the endoplasmic reticulum (ER) and result in reduction or elimination of dopamine uptake activity (9). ER retention is a common consequence of mutations in membrane proteins and does not necessarily reflect complete misfolding (10). However, the quality control in the ER is so stringent that mutated proteins that are otherwise partially or completely functional can be retained and degraded (11). Indeed, folding of eve...

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“…It was reported that GABA A receptor ligands could promote receptor trafficking as ligand chaperones (Eshaq et al, 2010). However, we did not find significant chaperone effects of either GABA or diazepam on wildtype or mutant receptors (data not shown).…”

Section: Discussionmentioning

confidence: 99%

Three epilepsy-associated GABRG2 missense mutations at the γ+/β− interface disrupt GABAA receptor assembly and trafficking by similar mechanisms but to different extents

Huang

Hernández

et al. 2014

Neurobiology of Disease

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We compared the effects of three missense mutations in the GABAA receptor γ2 subunit on GABAA receptor assembly, trafficking and function in HEK293T cells cotransfected with α1, β2, and wildtype or mutant γ2 subunits. The mutations R82Q and P83S were identified in families with genetic epilepsy with febrile seizures plus (GEFS+), and N79S was found in a single patient with generalized tonic-clonic seizures (GTCS). Although all three mutations were located in an N terminal loop that contributes to the γ+/β− subunit-subunit interface, we found that each mutation impaired GABAA receptor assembly to a different extent. The γ2(R82Q) and γ2(P83S) subunits had reduced α1β2γ2 receptor surface expression due to impaired assembly into pentamers, endoplasmic reticulum (ER) retention and degradation. In contrast, γ2(N79S) subunits were efficiently assembled into GABAA receptors with only minimally altered receptor trafficking, suggesting that N79S was a rare or susceptibility variant rather than an epilepsy mutation. Increased structural variability at assembly motifs was predicted by R82Q and P83S, but not N79S, substitution, suggesting that R82Q and P83S substitutions were less tolerated. Membrane proteins with missense mutations that impair folding and assembly often can be “rescued” by decreased temperatures. We coexpressed wildtype or mutant γ2 subunits with α1 and β2 subunits and found increased surface and total levels of both wildtype and mutant γ2 subunits after decreasing the incubation temperature to 30 °C for 24 hours, suggesting that lower temperatures increased GABAA receptor stability. Thus epilepsy-associated mutations N79S, R82Q and P83S disrupted GABAA receptor assembly to different extents, an effect that could be potentially rescued by facilitating protein folding and assembly.

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GABA acts as a ligand chaperone in the early secretory pathway to promote cell surface expression of GABAA receptors

Cited by 40 publications

References 82 publications

GABAA receptor plasticity in Jurkat T cells

GABAA receptor plasticity in Jurkat T cells

Pharmacological Chaperones of the Dopamine Transporter Rescue Dopamine Transporter Deficiency Syndrome Mutations in Heterologous Cells

Three epilepsy-associated GABRG2 missense mutations at the γ+/β− interface disrupt GABAA receptor assembly and trafficking by similar mechanisms but to different extents

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