Functional Expression of a Recombinant Unitary Glutamate Receptor from Xenopus, Which Contains N-Methyl-D-aspartate (NMDA) and Non-NMDA Receptor Subunits

doi:10.1074/jbc.271.51.32572

Functional Expression of a Recombinant Unitary Glutamate Receptor from Xenopus, Which Contains N-Methyl-D-aspartate (NMDA) and Non-NMDA Receptor Subunits*

From the ^‡ Molecular Neurobiology Unit, Royal Free Hospital School of Medicine, London NW3 2PF, United Kingdom, the
^§ Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Moscow 117871, Russia, the
^¶ Department of Life Science, University of Nottingham, Nottingham NG7 2RD, United Kingdom,
^∥ Allelix Biopharmaceuticals Inc., Mississauga, Ontario L4V 1V7, Canada, and the
** Asahi Chemical Industry Co., Fuji-shi, Shizuoka-ken, Japan

^§§Supported by the Wellcome Trust. To whom correspondence should be addressed. Tel.: 44-171-830-2415; Fax: 44-171-431-1973; E-mail: barnard{at}rfhsm.ac.uk

Abstract

A cDNA encoding a 100-kDa subunit (XenNR1) of the N-methyl-D-aspartate (NMDA) glutamate receptor type has been cloned from Xenopus central nervous system. When XenNR1 is coexpressed in a mammalian cell line with a recently cloned 51-kDa non-NMDA receptor subunit (XenU1), also from Xenopus, it forms a functional unitary receptor exhibiting the pharmacological properties characteristic of both NMDA and non-NMDA receptors. Firstly, XenU1 can replace NR2 subunits, in complementing XenNR1 to introduce the ligand binding properties of a complete NMDA receptor. Second, responses to both NMDA and non-NMDA receptor agonists and antagonists were obtained in patch-clamp recordings from the cotransfected cells, but no significant responses were recorded when the cells were singly transfected. Third, from solubilized cell membranes from the cotransfected cells, an antibody to the NR1 subunit coprecipitated the binding sites of the non-NMDA receptor subunit. The unitary glutamate receptor has a unique set of properties that denote intersubunit interaction, including a glycine requirement for the responses to non-NMDA as well as to NMDA receptor agonists and voltage-dependent block by Mg²⁺ of the non-NMDA agonist responses.

Footnotes

↵^‡‡ Supported by the United States Army European Office.
↵* The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) X94156[GenBank].
↵¹ The abbreviations used are:

NMDA

N-methyl-D-aspartate

AMPA

α-amino-3-hydroxy-5-methylisoxazole-4-propionic-acid

MK-801

dizocilpine

DCKA

5,7-dichlorokynurenic acid

SSC

standard saline citrate

PCR

polymerase chain reaction

V_H

holding potential.
↵²M. J. Brierley, Z. Y. Shao, I. R. Mellor, H. Sudan, J. Harris, and P. N. R. Usherwood, unpublished data.
- Received June 11, 1996.
- Revision received October 14, 1996.