Allosteric modulation of AMPA-type glutamate receptors increases activity of the promoter for the neural cell adhesion molecule, N-CAM.
To study regulation in vivo of the promoter for the neural cell adhesion molecule, N-CAM, we have used homologous recombination to insert the bacterial lacZ gene between the transcription and translation initiation sites of the N-CAM gene. This insertion disrupts the gene and places the expression of beta-galactosidase under the control of the N-CAM promoter. Animals homozygous for the disrupted allele did not express N-CAM mRNA or protein, but the pattern of beta-galactosidase expression in heterozygous and homozygous embryos was similar to that of N-CAM mRNA in wild-type animals. The homozygotes exhibited many of the morphological abnormalities observed in previously reported N-CAM knockout mice, with the exception that hippocampal long-term potentiation in the Schaffer collaterals was identical in homozygous, heterozygous, and wild-type animals. Heterozygous mice were used to examine the regulation of the N-CAM promoter in response to enhanced synaptic transmission. Treatment of the mice with an ampakine, an allosteric modulator of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors that enhances normal glutamate-mediated synaptic transmission, increased the expression of beta-galactosidase in vivo as well as in tissue slices in vitro. Similar treatments also increased the expression of N-CAM mRNA in the heterozygotes. The effects of ampakine in slices were strongly reduced in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an AMPA receptor antagonist. Taken together, these results indicate that facilitation of AMPA receptor-mediated transmission leads to activation of the N-CAM promoter and provide support for the hypothesis that N-CAM synthesis is regulated in part by synaptic activity.
Holst
B D
BD
Department of Neurobiology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA.
Vanderklish
P W
PW
Krushel
L A
LA
Zhou
W
W
Langdon
R B
RB
McWhirter
J R
JR
Edelman
G M
GM
Crossin
K L
KL
D000494:Allosteric Regulation; D000818:Animals; D004622:Embryo, Mammalian; D019706:Excitatory Postsynaptic Potentials; D005786:Gene Expression Regulation; D006579:Heterozygote; D006624:Hippocampus / Q000502:physiology*; D006720:Homozygote; D017774:Long-Term Potentiation; D051379:Mice; D018345:Mice, Knockout; D019006:Neural Cell Adhesion Molecules / Q000096:biosynthesis* / Q000235:genetics*; D009924:Organ Culture Techniques; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D018091:Receptors, AMPA / Q000737:chemistry / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis
D019006:Neural Cell Adhesion Molecules; D012333:RNA, Messenger; D018091:Receptors, AMPA; D011993:Recombinant Fusion Proteins; D001616:beta-Galactosidase