Aging is loosely defined as the accumulation of changes in an organism
over time. At the cellular level such changes are distinct and
multidimensional: DNA replication ceases, cells stop dividing, they
become senescent and eventually die. DNA metabolism and chromosomal
maintenance, together with protein metabolism are critical in the aging
process. The focus of this book is on the role of protein metabolism and
homeostasis in aging. An overview is provided of the current knowledge
in the area, including protein synthesis, accuracy and repair,
post-translational modifications, degradation and turnover, and how they
define and influence aging. The chapters mainly focus on
well-characterised factors and pathways, but new areas are also
presented, where associations with aging are just being elucidated by
current experimental data. Protein turnover, the balance between protein
synthesis and protein degradation are carefully maintained in healthy
cells. Chapters 1 and 2 illustrate that aging cells are characterised by
alterations in the rate, level and accuracy of protein synthesis
compared to young ones, and that mRNA translation, essential for cell
growth and survival, is controlled at multiple levels. The theory that
growth and somatic maintenance are believed to be antagonistic processes
is described in Chapter 3: inhibition of protein synthesis results in
decreased rates of growth and development, but also confers an extension
of lifespan, as shown for example by the effects of dietary restriction
in various models organisms.