The Journal of Neuroscience, February 14, 2007, 27(7):1692-1701; doi:10.1523/JNEUROSCI.3155-06.2007
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Cellular/Molecular
Phosholipase C-Related Inactive Protein Is Involved in Trafficking of
2 Subunit-Containing GABAA Receptors to the Cell Surface
Akiko Mizokami,1
Takashi Kanematsu,1
Hitoshi Ishibashi,2
Taku Yamaguchi,4
Isei Tanida,5
Kei Takenaka,6
Keiichi I. Nakayama,3
Kiyoko Fukami,7
Tadaomi Takenawa,6
Eiki Kominami,5
Stephen J. Moss,8
Tsuneyuki Yamamoto,9
Junichi Nabekura,10 and
Masato Hirata1
1Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, and Station for Collaborative Research, 2Department of Cellular and System Physiology, Faculty of Medical Science, and 3Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan, 4Department of Neuropharmacology, Graduate School of Medicine, Hokkaido University, Sapporo 060-8638, Japan, 5Department of Biochemistry, Juntendo University School of Medicine, Tokyo 113-8421, Japan, 6Department of Biochemistry, Institute of Medical Science, The University of Tokyo, Tokyo 108-8639, Japan, 7Laboratory of Genome and Biosignal, Tokyo University of Pharmacy and Life Science, Tokyo 192-0392, Japan, 8Department of Neuroscience, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, 9Department of Pharmacology, Faculty of Pharmaceutical Science, Nagasaki International University, Nagasaki 859-3298, Japan, and 10Department of Developmental Physiology, National Institute for Physiological Sciences, Okazaki 444-8585, Japan
Correspondence should be addressed to Dr. Masato Hirata, Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, and Station for Collaborative Research, Kyushu University, Fukuoka 812-8582, Japan. Email: hirata1{at}dent.kyushu-u.ac.jp
The subunit composition of GABAA receptors is known to be associated with distinct physiological and pharmacological properties. Previous studies that used phospholipase C-related inactive protein type 1 knock-out (PRIP-1 KO) mice revealed that PRIP-1 is involved in the assembly and/or the trafficking of
2 subunit-containing GABAA receptors. There are two PRIP genes in mammals; thus the roles of PRIP-1 might be compensated partly by those of PRIP-2 in PRIP-1 KO mice. Here we used PRIP-1 and PRIP-2 double knock-out (PRIP-DKO) mice and examined the roles for PRIP in regulating the trafficking of GABAA receptors. Consistent with previous results, sensitivity to diazepam was reduced in electrophysiological and behavioral analyses of PRIP-DKO mice, suggesting an alteration of
2 subunit-containing GABAA receptors. The surface numbers of diazepam binding sites (
/
2 subunits) assessed by [3H]flumazenil binding were reduced in the PRIP-DKO mice as compared with those of wild-type mice, whereas the cell surface GABA binding sites (
/ß subunits, assessed by [3H]muscimol binding) were increased in PRIP-DKO mice. The association between GABAA receptors and GABAA receptor-associated protein (GABARAP) was reduced significantly in PRIP-DKO neurons. Disruption of the direct interaction between PRIP and GABAA receptor ß subunits via the use of a peptide corresponding to the PRIP-1 binding site reduced the cell surface expression of
2 subunit-containing GABAA receptors in cultured cell lines and neurons. These results suggest that PRIP is implicated in the trafficking of
2 subunit-containing GABAA receptors to the cell surface, probably by acting as a bridging molecule between GABARAP and the receptors.
Key words: benzodiazepine; GABAA receptor; GABARAP; knock-out mice; PRIP; trafficking
Received July 24, 2006;
revised Dec. 15, 2006;
accepted Jan. 8, 2007.
Correspondence should be addressed to Dr. Masato Hirata, Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, and Station for Collaborative Research, Kyushu University, Fukuoka 812-8582, Japan. Email: hirata1{at}dent.kyushu-u.ac.jp
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