Presenilin mutations associated with Alzheimer disease cause defective intracellular trafficking of beta-catenin, a component of the presenilin protein complex

The presenilin proteins are components of high-molecular-weight protein com plexes in the endoplasmic reticulum and Golgi apparatus that also contain b eta-catenin. We report here that presenilin mutations associated with famil ial Alzheimer disease (but not the non-pathogenic Glu318Gly polymorphism) a lter the intracellular trafficking of beta-catenin after activation of the Wnt/beta-catenin signal transduction pathway. As with their effect on beta APP processing, the effect of PS1 mutations on trafficking of beta-catenin arises from a dominant 'gain of aberrant function' activity. These results indicate that mistrafficking of selected presenilin ligands is a candidate mechanism for the genesis of Alzheimer disease associated with presenilin m utations, and that dysfunction in the presenilin-beta-catenin protein compl exes is central to this process.