Aging at the cellular and molecular levels and future perspectives

The damage induced to cellular components by reactive oxygen species is believed to be a main contributor to the aging process. Cellular aging is characterized by a build up of oxidized proteins that can be due to increased protein damage, decreased oxidized protein elimination (i.e.. degradation or repair), or the combination of both mechanisms. The proteasome is the major intracellular proteolytic system involved in both degradation of oxidatively modified proteins and general turnover of cytosolic proteins. Evidence has been provided that proteasome function is declining with age. Other protein maintenance systems, such as the repair enzyme peptide methionine sulfoxide reductases or the Lon mitochondrial protease, seem to be also affected with age, and may therefore contribute to the age-associated impairment of protein quality control.