Effect of protein kinase A inhibitors on the production of Abeta40 and Abeta42 by human cells expressing normal and Alzheimer's disease-linked mutated betaAPP and presenilin 1.

1. We previously established that the formation of both alpha- and beta/gamma-secretase-derived products generated by human embryonic kidney 293 cells (HEK293) expressing either wild type or mutant betaAPP could be stimulated by agonists of the cyclic AMP/protein kinase A pathways. This cyclic AMP-dependent effect modulates post-translational events since it is not prevented by actinomycin D or cycloheximide. 2. We show here that two protein kinase A inhibitors, H89 and PKI, both trigger dose-dependent inhibition of the basal constitutive production of Abeta40 and Abeta42 by HEK293 cells expressing wild type betaAPP751. 3. H89 also potently inhibits the total Abeta produced by the neocortical neuronal cell line TSM1. 4. These two inhibitors also drastically reduce the recovery of Abeta40 and Abeta42 produced by HEK293 cells expressing the Swedish (Sw) betaAPP and M146V-presenilin 1 (PS1) mutations responsible for cases of the early-onset forms of Familial Alzheimer's disease (FAD). 5. By contrast, H89 and PKI do not significantly affect the recovery of the physiological alpha-secretase-derived fragment APPalpha. 6. Our study indicates that protein kinase A inhibitors selectively lower the formation of Abeta40 and Abeta42 in human cells expressing normal and mutant betaAPP and PS1 without affecting the physiological alpha-secretase pathway in these cells. Selective inhibitors of protein kinase A may be of therapeutic value in both sporadic and Familial Alzheimer's disease, since they may decrease the production of Abeta that is thought to be responsible for the neurodegenerative process.