Extended longevity of Caenorhabditis elegans by knocking in extra copies of hsp70F, a homolog of mot-2 (mortalin)/mthsp70/Grp75

Regulation of aging and age-related disease by DAF-16 and heat-shock factor

The Caenorhabditis elegans transcription factor HSF-1, which regulates the heat-shock response, also influences aging. Reducing hsf-1 activity accelerates tissue aging and shortens life-span, and we show that hsf-1 overexpression extends lifespan. We find that HSF-1, like the transcription factor DAF-16, is required for daf-2-insulin/IGF-1 receptor mutations to extend life-span. Our findings suggest this is because HSF-1 and DAF-16 together activate expression of specific genes, including genes encoding small heat-shock proteins, which in turn promote longevity. The small heat-shock proteins also delay the onset of polyglutamine-expansion protein aggregation, suggesting that these proteins couple the normal aging process to this type of age-related disease.

Lifespan extension in C. elegans by a molecular chaperone dependent upon insulin-like signals

Insulin-like signalling is a key determinate of lifespan in diverse species including mammals but the mechanism by which this pathway influences the rate of aging is unknown. In the roundworm Caenorhabditis elegans, mutations in the insulin-like signalling pathway extend adult lifespan and are associated with up-regulation of stress response genes including those for heat shock proteins (HSPs). We tested the hypothesis that the C. elegans insulin-like signalling pathway determines longevity through modulating HSP levels. We introduced extra copies of the gene encoding HSP-16 and this conferred stress resistance and longevity both in a wildtype and a long-lived mutant strain. The DAF-16 transcription factor is essential for maximal hsp-16 expression and for lifespan extension conferred by hsp-16. This demonstrates that lifespan is determined in part by insulin-like regulation of molecular chaperones.

Unearthing Loci that influence life span

It is known that certain hormones are involved in determining longevity (for example, insulin and insulin-like growth factor). Results presented in a paper published in this week's issue of Science allow us to add steroid hormones to this list. Anne Simon and colleagues show for the first time that a sterol hormone--ecdysone of the fly Drosophila melanogaster--regulates life span. In this Perspective, I discuss the implications of this result in the context of gene regulation and mechanisms of aging.

The endocrine regulation of aging by insulin-like signals

Reduced signaling of insulin-like peptides increases the life-span of nematodes, flies, and rodents. In the nematode and the fly, secondary hormones downstream of insulin-like signaling appear to regulate aging. In mammals, the order in which the hormones act is unresolved because insulin, insulin-like growth factor-1, growth hormone, and thyroid hormones are interdependent. In all species examined to date, endocrine manipulations can slow aging without concurrent costs in reproduction, but with inevitable increases in stress resistance. Despite the similarities among mammals and invertebrates in insulin-like peptides and their signal cascade, more research is needed to determine whether these signals control aging in the same way in all the species by the same mechanism.

Longevity and heat stress regulation in Caenorhabditis elegans

Aging is the most complex phenotype for a multicellular organism. This process is now being under severe investigation. Here I will review the different processes known to affect longevity in the nematode Caenorhabditis elegans and their relationship with thermotolerance. All the longevity mutants that have been tested so far show an increase in stress resistance. In particular, long-lived mutants affected in the IGF/insulin pathway and those affected in the germ-line formation are both thermotolerant and long-lived. The mechanisms that activate the stress resistance are now been understood including the DAF-16 fork head transcription factor transport to the nucleus and the activation of genes involved in the defense to stress. The high correlation between stress resistance and longevity suggests that the same molecular activities that defend the cell from stress can defend the cell from the damage caused by aging.

Mortalin: present and prospective

Mortalin, also known as mthsp70/PBP74/GRP75, resides in multiple subcellular sites including mitochondria, ER, plasma membrane, cytoplasmic vesicles and cytosol. It is differentially distributed in normal and cancerous cells; the latter, when reverted back to normal phenotype, also show change in mortalin staining pattern similar to normal cells. Depending on its different subcellular niche and binding partner therein, mortalin is expected to perform multiple functions relevant to cell survival, control of proliferation and stress response.

An Hsp70 family chaperone, mortalin/mthsp70/PBP74/Grp75: what, when, and where?

Mortalin/mthsp70/PBP74/Grp75 (called mortalin hereafter), a member of the Hsp70 family of chaperones, was shown to have different subcellular localizations in normal and immortal cells. It has been assigned to multiple subcellular sites and implicated in multiple functions ranging from stress response, intracellular trafficking, antigen processing, control of cell proliferation, differentiation, and tumorigenesis. The present article compiles and reviews information on the multiple sites and functions of mortalin in different organisms. The relevance of its differential distributions and functions in normal and immortal cell phenotypes is discussed.