title: Src-mediated tyrosine phosphorylation of NR2 subunits of N-methyl-D-aspartate receptors protects from calpain-mediated truncation of their C-terminal domains.
abstract: Src-mediated tyrosine phosphorylation of N-methyl-d-aspartate receptor subunits has been shown to modify the functional properties of N-methyl-d-aspartate receptors. Moreover, calpain-mediated truncation of N-methyl-d-aspartate receptor subunits has been found to alter the structure of the receptors. In the present study, we first used immunoprecipitation with a variety of antibodies against N-methyl-d-aspartate receptor subunits and anti-phosphotyrosine antibodies to show that tyrosine-phosphorylated subunits of N-methyl-d-aspartate receptor are protected against calpain-mediated truncation of their C-terminal domains. A GST fusion protein containing the C-terminal domain of NR2A was used to identify the calpain cutting sites in the C-terminal domain. One site was identified at residues 1278-1279, corresponding to one of the preferred calpain truncation sites. This site is adjacent to a consensus sequence for Src-mediated tyrosine phosphorylation, and Src-mediated tyrosine phosphorylation of the GST-NR2A C-terminal fusion protein also inhibited calpain-mediated truncation of the fusion protein. We propose that phosphorylation of NR2 subunits and the resulting inhibition of calpain-mediated truncation of their C-terminal domains provide for the stabilization of the N-methyl-d-aspartate receptors in postsynaptic structures.
authors.affiliation: Neuroscience Program, University of Southern California, Los Angeles, California 90089-2520, USA.
authors.forename: R
authors.initials: R
authors.lastname: Bi
authors.forename: Y
authors.initials: Y
authors.lastname: Rong
authors.forename: A
authors.initials: A
authors.lastname: Bernard
authors.forename: M
authors.initials: M
authors.lastname: Khrestchatisky
authors.forename: M
authors.initials: M
authors.lastname: Baudry
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002154:Calpain / Q000378:metabolism*; D015723:Gene Library; D008969:Molecular Sequence Data; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism*; D018909:src Homology Domains
chemical_list: C120997:NR2A NMDA receptor; C121001:NR2B NMDA receptor; D016194:Receptors, N-Methyl-D-Aspartate; D014443:Tyrosine; D002154:Calpain