Abstracts

RATIONALE: B/K protein is a member of the double C2-like domain protein family. It is abundantly expressed in the brain, especially in the hypothalamus, pituitary gland, cerebral cortex and hippocampus. Although its physiologic function is not evident, we found that its expression was increased in vulnerable regions under several pathologic conditions such as cerebral, renal and retinal ischemia.
METHODS: Seizure was induced in adult male Sprague-Dawley rats by intraperitoneal injection of kainic acid. Time- and dose-dependent changes of the immunoreactivity to B/K protein and BiP were examined by immunohistochemistry. Subcellular localization of the B/K protein and colocalization with BiP were also studied by electron and confocal microscopic studies, respectively.
RESULTS: In this report, we demonstrated that, in the kainic acid-induced seizure model, the immunoreactivity of the B/K protein increased dose- and time-dependently in the CA3 and CA1 regions of the hippocampus. Expression of the B/K protein reached the maximum at 6 - 12 h after kainic acid injection, and was partially blocked by MK-801 pre-treatment. Microscopically, the immunoreactivity was not homogenous but punctated in the cytoplasm, especially in the perinuclear region, and it was localized primarily in the endoplasmic reticulum (ER) in the electron microscopic study. Interestingly, the immunoreactivity of BiP, a marker of ER stress response showed the similar time-dependent expression pattern to the B/K protein in the CA3 and CA1 regions. Moreover, the fluorescent signal of B/K protein was co-localized with BiP in some neuronal cells.
CONCLUSIONS: These data suggest the possibility that the expression of B/K protein in the kainic acid seizure model may be related to ER stress response.
[Supported by: The Fund for the Promotion of Basic Medical Science 2001 supported by the Korean Medical Association]