Calpain-mediated regulation of NMDA receptor structure and function.
Calpains have been previously shown to regulate AMPA receptor properties by producing partial truncation of the C-terminal domains of several receptor subunits. We now report that NMDA receptor subunits, in particular NR2 subunits, are also subjected to calpain-mediated truncation. Treatment of synaptic membranes with calpain I resulted in truncation of both NR1 and NR2 subunits, with the appearance of NR2 species with lower mol.wt. than native subunits, but still recognized by antibodies directed at the C-terminal domain. This treatment did not modify the binding of several ligands of the NMDA receptors, such as glutamate, glycine or TCP. Incubation of thin frozen-thawed brain sections with calcium resulted in calpain-mediated selective degradation of NR2 subunits, as truncation into smaller fragments was totally blocked by calpain inhibitors. Under the same conditions, TCP binding to sections was decreased by about 50%, an effect also blocked by calpain inhibitors. Treatment of hippocampal slices in culture with the excitotoxin, kainic acid, also produced calpain-mediated truncation of the C-terminal domain of NR2 but not NR1 subunits of the NMDA receptors. The results indicate that calpain activation produces several modifications of NMDA receptors, including the truncation of the C-terminal domain of NR2 subunits, and changes in channel binding properties. They suggest that calpain-mediated regulation of NMDA receptors might represent a feed-back regulation of the receptors which could be used to limit receptor activation.
Bi
X
X
Neuroscience Program, University of Southern California, Los Angeles, CA 90089-2520, USA.
Rong
Y
Y
Chen
J
J
Dang
S
S
Wang
Z
Z
Baudry
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005615:Freezing; D018698:Glutamic Acid / Q000494:pharmacology; D006624:Hippocampus / Q000737:chemistry / Q000201:enzymology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007608:Kainic Acid / Q000494:pharmacology; D009473:Neuronal Plasticity / Q000502:physiology; D009924:Organ Culture Techniques; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists / Q000737:chemistry* / Q000502:physiology*; D013570:Synaptic Membranes / Q000737:chemistry / Q000201:enzymology
D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D018690:Excitatory Amino Acid Agonists; D016194:Receptors, N-Methyl-D-Aspartate; C071482:calpeptin; D018698:Glutamic Acid; D002154:Calpain; D007608:Kainic Acid; D002118:Calcium