Calbindin-D28kin the Brain Influences the Expression of Cellular Prion Protein

Abstract

The phenotypes ofcalbindin-D9k- (CaBP-9k-) knockout (KO),calbindin-D28k- (CaBP-28k-) KO, andCaBP-9k/28k-KO mice are similar to those of wild-type (WT) mice due to the compensatory action of other calcium transport proteins. In this study, we investigated the expression of cellular prion protein (PrPC) in the brains ofCaBP-9k-,CaBP-28k-, andCaBP-9k/28k-KO mice. PrPCexpression was significantly upregulated in the brain of all three strains. Levels of phospho-Akt (Ser473) and phospho-Bad (Ser136) were significantly elevated, but those of phospho-ERK and phospho-Bad (Ser155 and 112) were significantly reduced in the brains ofCaBP-9k-,CaBP-28k-, andCaBP-9k/28k-KO mice. The expressions of the Bcl-2, p53, Bax, Cu/Zn-SOD, and Mn-SOD proteins were decreased in the brains of all KO mice. Expression of the endoplasmic reticulum marker protein BiP/GRP78 was decreased, and that of the CHOP protein was increased in the brains of those KO mice. To identify the roles ofCaBP-28k, we transfected PC12 cells with siRNA forCaBP-28kand found increased expression of the PrPCprotein compared to the levels in control cells. These results suggest thatCaBP-28kexpression may regulate PrPCprotein expression and these mice may be vulnerable to the influence of prion disease.