RESUMO
Presenilins are involved in the proteolytic production of Alzheimer's amyloid peptides, but are also known to regulate Ca(2+) homeostasis in various cells types. In the present study, we examined intracellular Ca(2+) stores coupled to muscarinic receptors and capacitative Ca(2+) entry (CCE) in the human neuroblastoma SH-SY5Y cell line, and how these were modulated by over-expression of either wild-type presenilin 1 (PS1wt) or a mutant form of presenilin 1 (PS1 deltaE9) which predisposes to early-onset Alzheimer's disease. Ca(2+) stores discharged by application of 100 microM muscarine (in Ca(2+)-free perfusate) in PS1wt and PS1 DeltaE9 cells were significantly larger than those in control cells, as determined using Fura-2 microfluorimetry. Subsequent CCE, observed in the absence of muscarine when Ca(2+) was re-admitted to the perfusate, was unaffected in PS1wt cells, but significantly suppressed in PS1 deltaE9 cells. However, when Ca(2+) stores were fully depleted with thapsigargin, CCE was similar in all three cell groups. Western blots confirmed increased levels of PS1 in the transfected cells, but also demonstrated that the proportion of intact PS1 in the PS1 deltaE9 cells was far greater than in the other two cell groups. This study represents the first report of modulation of both Ca(2+) stores and CCE in a human, neurone-derived cell line, and indicates a distinct effect of the PS1 mutation deltaE9 over wild-type PS1.
