Protein quality control in time and space - links to cellular aging.

The evolutionary theory of aging regards aging as an evolved characteristic of the soma, and proponents of the theory state that selection does not allow the evolution of aging in unicellular species lacking a soma-germ demarcation. However, the life history of some microorganisms, reproducing vegetatively by either budding or binary fission, has been demonstrated to encompass an ordered, polar-dependent, segregation of damage leading to an aging cell lineage within the clonal population. In the yeast Saccharomyces cerevisiae and the bacterium Escherichia coli, such segregation is under genetic control and includes an asymmetrical inheritance of protein aggregates and inclusions. Herein, the ultimate and proximate causation for such an asymmetrical inheritance, with special emphasis on damaged/aggregated proteins in budding yeast, is reviewed.