The Journal of Neuroscience, October 6, 2004, 24(40):8672-8677; doi:10.1523/JNEUROSCI.2717-04.2004
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BRIEF COMMUNICATION
The GABAA Receptor 
2 Subunit R43Q Mutation Linked to Childhood Absence Epilepsy and Febrile Seizures Causes Retention of 
1
22S Receptors in the Endoplasmic Reticulum
Jingqiong Kang1 and
Robert L. Macdonald1,2,3
Departments of 1Neurology, 2Molecular Physiology and Biophysics, and 3Pharmacology, Vanderbilt University, Nashville, Tennessee 37212
The GABAA receptor 
2 subunit mutation R43Q is an autosomal dominant mutation associated with childhood absence epilepsy and febrile seizures. Previously, we demonstrated that homozygous 
1
32L(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 122S(R43Q) GABAA receptor current amplitudes were reduced when receptors were assembled from coexpressed 1, 2, and 2S subunits and from 2-1 tandem subunits coexpressed with the 2L subunit. Using fluorescence confocal microscopy, we demonstrated that mutant receptors containing enhanced yellow fluorescent protein-tagged 2S subunits had reduced surface expression and were retained in the endoplasmic reticulum. In addition, using biotinylation of surface receptors and immunoblotting, we confirmed that 122S(R43Q) receptors had reduced surface expression. These results provide evidence that the 2S(R43Q) mutation impaired GABAA receptor function by compromising receptor trafficking and reducing surface expression.
Key words: GABAA receptor; R43Q mutation; endoplasmic reticulum; receptor trafficking; childhood absence epilepsy; febrile seizures
Received March 13, 2004;
revised August 23, 2004;
accepted August 23, 2004.
