Evolution of Senescence: Longevity and the Expression of Heat Shock Proteins

Abstract

Senescence is the progressive deterioration of organismal function leading to accelerating rates of mortality. Cumulative extrinsic and intrinsic stresses are thought to contribute to senescence. Molecular chaperones, such as heat shock proteins, are hypothesized to modulate senescence through their ability to mitigate protein damage. Recent discoveries made with the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster lend strong support to this theory. Longevity extending mutants of the nematode also increase intrinsic and inducible thermotolerance, and they overexpress heat shock proteins upon thermal shock. Intriguingly, these genes regulate dauer (diapause) formation, and are associated with an insulin-like dependent signal transduction pathway. Direct evidence for a casual role of hsp70 in aging is provided by analysis of transgenic fruit flies. When hsp70 is induced by mild heat shock, flies that overexpress the protein have greatly reduced mortality rates during subsequent weeks of aging at normal temperatures. Current work with fruit flies focuses on the relationship between insulin-like receptors, ovarian diapause, heat shock and aging.