Evidence of [Ca(2+)]i elevation by anti-calreticulin immunoreactive protein in neurons.
Calreticulin is a multifunctional Ca(2+)-binding protein. The effect of anti-calreticulin antibody on intracellular free calcium concentration [Ca(2+)]i was studied in cultured neurons using fura-2 based microfluorometry. Anti-calreticulin increased [Ca(2+)]i in a dose dependent manner. The anti-calreticulin antibody produced a rapid transient [Ca(2+)]i peak followed by a long slowly decaying plateau. Anti-calreticulin induced extracellular Ca(2+) influx in cultured neuron cells was blocked partially by N-methyl-D-aspartate receptor (NMDAR) antagonist 2-amino-5-phosphonovaleric acid (AP5) and spider polyamine toxin JSTX-3, which is recognized as a blocker of glutamatergic nervous system. Furthermore, anti-calreticulin induced intracellular Ca(2+) desensitized NMDAR. Dual immunofluorescent staining studies revealed that NMDAR co-localized with calreticulin in the cultured neurons. Thus, the signal transduction system of NMDA might be closely concerned with the extracellular calreticulin like protein.
Hossain
M A
MA
Suntory Institute for Bioorganic Research, 1-1-1 Wakayamadai, Shimamotocho, Mishimagun, Osaka, Japan. hossain@sunbor.or.jp
Murayama
N
N
Oka
T
T
Nakajima
T
T
D000663:Amphibians; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000032:analysis*; D037282:Calreticulin; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D006801:Humans; D007150:Immunohistochemistry; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012261:Ribonucleoproteins / Q000032:analysis*
D002135:Calcium-Binding Proteins; D037282:Calreticulin; D012261:Ribonucleoproteins; D002118:Calcium