Chronic overexpression of the calcineurin inhibitory gene DSCR1 (Adapt78) is associated with Alzheimer's disease

Abstract

The DSCR1 (Adapt78) gene was independently discovered as a resident of the "Down syndrome candidate region"and as an "adaptive response"shock or stress gene that is transiently induced during oxidative stress. Recently the DSCR1 (Adapt78) gene product was discovered to be an inhibitor of the serine/threonine phosphatase, calcineurin, and its signaling pathways. We hypothesized that DSCR1 (Adapt78) might also be involved in the development of Alzheimer's disease. To address this question we first studied DSCR1 (Adapt78) in multiple human tissues and found significant expression in brain, spinal cord, kidney, liver, mammary gland, skeletal muscle, and heart. Within the brain DSCR1 (Adapt78) is predominantly expressed in neurons within the cerebral cortex, hippocampus, substantia nigra, thalamus, and medulla oblongata. When we compared DSCR1 (Adapt78) mRNA expression in post-mortem brain samples from Alzheimer's disease patients and individuals who had died with no Alzheimer's diagnosis, we found that DSCR1 (Adapt78) mRNA levels were about twice as high in age-matched Alzheimer's patients as in controls. DSCR1 (Adapt78) mRNA levels were actually three times higher in patients with extensive neurofibrillary tangles (a hallmark of Alzheimer's disease) than in controls. In comparison, post-mortem brain samples from Down syndrome patients (who suffer Alzheimer's symptoms) also exhibited DSCR1 (Adapt78) mRNA levels two to three times higher than controls. Using a cell culture model we discovered that the amyloid beta(1-42) peptide, which is a major component of senile plaques in Alzheimer's, can directly induce increased expression of DSCR1 (Adapt78). Our findings associate DSCR1 (Adapt78) with such major hallmarks of Alzheimer's disease as amyloid protein, senile plaques, and neurofibrillary tangles.