Calcium Signalling and Alzheimer's Disease

New insights into how Ca2+ regulates learning and memory have begun to provide clues as to how the amyloid-dependent remodelling of neuronal Ca2+ signalling pathways can disrupt the mechanisms of learning and memory in Alzheimer's disease (AD). The calcium hypothesis of AD proposes that activation of the amyloidogenic pathway remodels the neuronal Ca2+ signalling pathways responsible for cognition by enhancing the entry of Ca2+ and/or the release of internal Ca2+ by ryanodine receptors or InsP(3) receptors. The specific proposal is that Ca2+ signalling remodelling results in a persistent elevation in the level of Ca2+ that constantly erases newly acquired memories by enhancing the mechanism of long-term depression (LTD). Neurons can still form memories through the process of LTP, but this stored information is rapidly removed by the persistent activation of LTD. Further dysregulation in Ca2+ signalling will then go on to induce the neurodegeneration that characterizes the later stages of dementia.