RESUMO
Neurodegeneration in Alzheimer's disease (AD) is associated with the appearance of dystrophic neuronal growth profiles that most likely reflect an impairment of neuronal reorganization. This process of morphodysregulation, which eventually goes awry and becomes a disease itself, might be triggered either by a variety of life events that place an additional burden on the plastic capability of the brain or by genetic pertubations that shift the threshold for decompensation. This paper summarizes recent evidence that impairment of the p21ras intracellular signal transduction, which is is mediated by a hierarchy of phosphorylation signals and eventually results in loss of differentiation control and an attempt of neurons to re-enter the cell-cycle, is critically involved in this process. Neurodegeneration might thus be viewed as an alternative effector pathway of those events that in the dividing cell would lead to cellular transformation. This hypothesis might be of heuristic value for the development of a therapeutic strategy.