Journal
JOURNAL OF NEUROSCIENCE
Volume 24, Issue 40, Pages 8672-8677Publisher
SOC NEUROSCIENCE
DOI: 10.1523/JNEUROSCI.2717-04.2004
Keywords
GABA(A) receptor; R43Q mutation; endoplasmic reticulum; receptor trafficking; childhood absence epilepsy; febrile seizures
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Funding
- NINDS NIH HHS [R01 NS33300, R01 NS033300] Funding Source: Medline
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The GBA(A) receptor gamma2 subunit mutation R43Q is an autosomal dominant mutation associated with childhood absence epilepsy and febrile seizures. Previously, we demonstrated that homozygous alpha1beta3gamma2L(R43Q) receptor whole-cell currents had reduced amplitude with unaltered time course, suggesting reduced cell surface expression of functional receptors. In human embryonic kidney 293-T cells, we demonstrate that both heterozygous and homozygous alpha1beta2gamma2S(R43Q) GABA(A) receptor current amplitudes were reduced when receptors were assembled from coexpressed alpha1, beta2, and gamma2S subunits and from beta2-alpha1 tandem subunits coexpressed with the gamma2L subunit. Using fluorescence confocal microscopy, we demonstrated that mutant receptors containing enhanced yellow fluorescent protein-tagged gamma2S subunits had reduced surface expression and were retained in the endoplasmic reticulum. In addition, using biotinylation of surface receptors and immunoblotting, we confirmed that alpha1beta2gamma2S(R43Q) receptors had reduced surface expression. These results provide evidence that the gamma2S(R43Q) mutation impaired GABA(A) receptor function by compromising receptor trafficking and reducing surface expression.
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