The invention relates to isolated nucleic acid molecules coding for SES-3 proteins or muted SES-3 proteins, and vectors and transgenic organisms containing such nucleic acid molecules. The invention also relates to uses of such nucleic acid molecules or others which are functionally similar, for producing pharmaceuticals and for producing model organisms. The invention further relates to the corresponding SES-3 proteins and muted SES-3 proteins, and the antibodies induced thereby. Finally, the invention relates to the use of substances which increase the expression of human presenilin, for the treatment of Alzheimer's disease, in addition to said substances themselves and pharmaceutical compositions containing the same.