Model of Chaperones in Aging

J. Krall and J.O. Nehlin

The molecular chaperones or heat shock proteins (Hsp) are constitutive and stress-induced proteins participating in "housekeeping" functions such as proofreading and folding of other polymers (proteins, RNA, DNA), preventing the aggregation of polymers, disgregation of misfolded molecules, facilitation of the transport of polymers across biological membranes, and participation in the degradation of ubiquitinated molecules. The decrease in the constitutive expression and inductivity of the chaperones with age—possibly caused by progressive silencing of the chaperone genes—probably contributes decisively to the phenotype of aging, as illustrated also from the progeric syndromes caused by mutational defects of the RecQ protein/DNA chaperones. Conversely, high levels of chaperone expression is a common denominator in conditions or procedures leading to an increase in cellular and species longevity as well as in the process of cellular immortalization, the inherent immortality of the embryonic stem cells, and the inhibition of cellular apoptosis.

The inherent immortality of the embryonic stem cells implies that replicative senescence as possibly the aging of species are epigenetic phenomena. The involvement of RNA chaperones in the process of cellular immortalization and mutational DNA chaperones in the progeric syndromes suggests that RNA/DNA-chaperones are of major importance for the definition of cellular and species longevity. Accordingly, evidence has been presented to suggest that the evolution of longevity depends on alterations in the expression of relatively few regulatory genes. Possibly the molecular chaperones are evolution facilitators, contributing to the definition of the life span of differentiated cells as well as the longevity of species.

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