Caspr interaction with Amyloid Precursor Protein reduces amyloid-β generation in vitro.

Contactin associated protein (Caspr), an adhesion molecule, plays roles in formation of paranodal junctions in myelinated axons, neurite outgrowth, synaptic plasticity in nervous system. Here we have shown a novel function of Caspr in pathogenesis of Alzheimer's disease (AD). Caspr distributes around amyloid plaques in APP/PS1 mice. Levels of Caspr increase in the cerebral cortex of 7-month-old APP/PS1 mice comparing to wild-type littermates. Caspr decreased protein levels of APP in both HEK-293 cells stably transfected with Indiana mutant APP (V717F; HEK-APP) and CHO cells which express endogenous APP, while it did not alter mRNA levels of APP. Furthermore, Caspr co-localizes and interacts with APP. Amyloid-β (Aβ) 40 and Aβ42 generation were also reduced in HEK-APP cells by Caspr overexpression.