Premium
Characterization of Calpain‐Mediated Proteolysis of GluR1 Subunits of α‐Amino‐3‐Hydroxy‐5‐Methylisoxazole‐4‐Propionate Receptors in Rat Brain
Author(s) -
Bi Xiaoning,
Chen Jing,
Dang Sandeeb,
Wenthold Robert J.,
Tocco Georges,
Baudry Michel
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.68041484.x
Subject(s) - ampa receptor , calpain , cnqx , proteolysis , receptor , propionate , biochemistry , glutamate receptor , chemistry , calcium , western blot , biology , enzyme , organic chemistry , gene
Previous results have indicated that GluR1 subunits of α‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionate (AMPA) receptors are targets of calpain. In the present study, we determined the effects of calpain treatment of synaptic membranes on GluR1 subunits using western blots with antibodies directed against the C‐terminal (C‐Ab) and the N‐terminal (N‐Ab) domains of the proteins, and compared them with the effects of calcium treatment of frozen‐thawed brain sections. Calpain treatment of synaptic membranes resulted in a large decrease in the GluR1 band (105 kDa) labeled with C‐Ab and in the formation of a doublet band labeled with N‐Ab due to the appearance of a new species of GluR1 (98 kDa). These effects were blocked almost completely by calpain inhibitors. Calpain‐induced changes in GluR1 immunological properties were not associated with modifications of [ 3 H]AMPA or 6‐cyano‐7‐[ 3 H]nitroquinoxaline‐2,3‐dione ([ 3 H]CNQX) binding. Treatment of frozen‐thawed brain sections with concentrations of calcium as low as 0.2 m M resulted in a large decrease in the 105‐kDa GluR1 band and in the concurrent appearance of the 98‐kDa band. This treatment was associated with increased [ 3 H]AMPA and [ 3 H]CNQX binding. These results suggest that there exist several types/states of GluR1 subunits exhibiting different sensitivities to calpain. Our data also indicate the existence of additional calcium‐dependent processes regulating the characteristics of receptors in intact tissues.