The Journal of Neuroscience, October 6, 2004, 24(40):8672-8677; doi:10.1523/JNEUROSCI.2717-04.2004
Previous Article | Next Article 
BRIEF COMMUNICATION
The GABAA Receptor
2 Subunit R43Q Mutation Linked to Childhood Absence Epilepsy and Febrile Seizures Causes Retention of
1
2
2S 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
3
2L(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
1
2
2S(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
1
2
2S(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.