Approximately 3% of people develop epilepsy at some point during their life and one third of these patients will not have their seizures controlled with antiepileptic medication. Our long term goal is to elucidate mechanisms of genetic epilepsy in an effort to help develop more effective antiepileptic therapies. Juvenile myoclonic epilepsy is one of the most common epilepsy syndromes and it accounts for approximately 5% of all cases of epilepsy. The non-conserved, missense mutation A322D in the GABA-A receptor alpha 1 subunit gene (GABRA1) is associated with an autosomal dominant form of juvenile myoclonic epilepsy (ADJME). Recently, we demonstrated that in a mammalian, non-neuronal expression system, the ADJME mutation reduces alpha 1 subunit expression after protein translation, but before subunit oligomerization, data which suggested that the mutation causes enhanced endoplasmic reticulum associated degradation (ERAD) of the alpha 1 subunit. ERAD is a complex process that utilizes numerous chaperone proteins and thus it is likely that ERAD in neurons would differ from that in fibroblast cell lines. Although neuronal ERAD deficiencies have been studied in relation to some neurodegenerative diseases, its role as a normal response to misfolded mutated proteins is unknown. We propose to elucidate the role of normal ERAD of native alpha 1, recombinant wild type, and mutant alpha 1(A322D) subunits in both a neuronal cell line (HT-22) and in cultured cortical neurons. We propose three Specific Aims. 1) We will determine the effect of the ADJME alpha 1 subunit mutation on alpha 1 subunit biosynthesis and degradation and its association with the ubiquitin proteasome system in both fibroblasts and neurons. 2) We will characterize the effect of this mutation on the GABA-A receptor physiology in neurons. 3) We will characterize neurons'compensatory response to degradation of the alpha 1 subunit resulting from the ADJME mutation;specifically, we will study neurons'alteration of expression of other alpha subunits and the resulting changes in postsynaptic GABA physiology.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Scientist Development Award - Research (K02)
Project #
5K02NS055979-03
Application #
7624218
Study Section
NST-2 Subcommittee (NST)
Program Officer
Stewart, Randall R
Project Start
2007-06-01
Project End
2012-05-31
Budget Start
2009-06-01
Budget End
2010-05-31
Support Year
3
Fiscal Year
2009
Total Cost
$178,248
Indirect Cost
Name
Vanderbilt University Medical Center
Department
Neurology
Type
Schools of Medicine
DUNS #
004413456
City
Nashville
State
TN
Country
United States
Zip Code
37212
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Arain, Fazal M; Boyd, Kelli L; Gallagher, Martin J (2012) Decreased viability and absence-like epilepsy in mice lacking or deficient in the GABAA receptor ?1 subunit. Epilepsia 53:e161-5
Ding, Li; Feng, Hua-Jun; Macdonald, Robert L et al. (2010) GABA(A) receptor alpha1 subunit mutation A322D associated with autosomal dominant juvenile myoclonic epilepsy reduces the expression and alters the composition of wild type GABA(A) receptors. J Biol Chem 285:26390-405
Macdonald, Robert L; Kang, Jing-Qiong; Gallagher, Martin J (2010) Mutations in GABAA receptor subunits associated with genetic epilepsies. J Physiol 588:1861-9
Kang, Jing-Qiong; Shen, Wangzhen; Lee, Melissa et al. (2010) Slow degradation and aggregation in vitro of mutant GABAA receptor gamma2(Q351X) subunits associated with epilepsy. J Neurosci 30:13895-905
Feng, Hua-Jun; Kao, Chris; Gallagher, Martin J et al. (2010) Alteration of GABAergic neurotransmission by pulsed infrared laser stimulation. J Neurosci Methods 192:110-4