Properties of glutamate receptors of Alzheimer's disease brain transplanted to frog oocytes

doi:10.1073/pnas.0611513104

Properties of glutamate receptors of Alzheimer's disease brain transplanted to frog oocytes

*Department of Neurobiology and Behavior, University of California, Irvine, CA 92697-4550;
^†Department of Physiology and Pathology and Centre for Neuroscience B.R.A.I.N., University of Trieste, via Fleming 22, I-34127 Trieste, Italy; and
^§Instituto de Neurobiología, Universidad Nacional Autónoma de México, Campus Juriquilla, AP 1-1141, Querétaro, México

Contributed by Ricardo Miledi, December 27, 2006 (received for review December 17, 2006)

Abstract

It is known that Alzheimer's disease (AD) is a synaptic disease that involves various neurotransmitter systems, particularly those where synaptic transmission is mediated by acetylcholine or glutamate (Glu). Nevertheless, very little is known about the properties of neurotransmitter receptors of the AD human brain. We have shown previously that cell membranes, carrying neurotransmitter receptors from the human postmortem brain, can be transplanted to frog oocytes, and their receptors will still be functional. Taking advantage of this fact, we have now studied the properties of Glu receptors (GluRs) from the cerebral cortices of AD and non-AD brains and found that oocytes injected with AD membranes acquired GluRs that have essentially the same functional properties as those of oocytes injected with membranes from non-AD brains. However, the amplitudes of the currents elicited by Glu were always smaller in the oocytes injected with membranes from AD brains. Western blot analyses of the same membrane preparations used for the electrophysiological studies showed that AD membranes contained significantly fewer GluR2/3 subunit proteins. Furthermore, the corresponding mRNAs were also diminished in the AD brain. Therefore, the smaller amplitude of membrane currents elicited by Glu in oocytes injected with membranes from an AD brain is a consequence of a reduced number of GluRs in cell membranes transplanted from the AD brain. Thus, using the comparatively simple method of microtransplantation of receptors, it is now possible to determine the properties of neurotransmitter receptors of normal and diseased human brains. That knowledge may help to decipher the etiology of the diseases and also to develop new treatments.

Footnotes

^¶To whom correspondence should be addressed. E-mail: rmiledi{at}uci.edu
Author contributions: A.B., Z.D., J.M.R.-R., and R.M. designed research; A.B., Z.D., J.M.R.-R., and R.M. performed research; F.R. contributed new reagents/analytic tools; A.B., Z.D., J.M.R.-R., F.R., and R.M. analyzed data; and A.B., J.M.R.-R., F.R., and R.M. wrote the paper.
↵ ^‡Present address: Universidad Nacional de Colombia, Ciudad Universitaria, Transversal 38 No. 40-01, Facultad de Medicina, Bogotá, Colombia.
The authors declare no conflict of interest.
This article contains supporting information online at www.pnas.org/cgi/content/full/0611513104/DC1.
Abbreviations:

AD,

Alzheimer's disease;

AD oocytes,

oocytes injected with membranes from an AD brain;

Glu,

glutamate;

GluR,

Glu receptor;

Glu current,

membrane current elicited by Glu;

Kai,

kainate;

CTZ,

cyclothiazide;

WB,

Western blot;

qRT-PCR,

quantitative real-time PCR;

CNQX,

6-cyano-7-nitroquinoxaline-2,3-dione;

I–V,

current–voltage.