Sangsoon Park

The role of insulin/IGF-1 signaling in the longevity of model invertebrates, C. elegans and D. melanogaster.

Insulin/insulin-like growth factor (IGF)-1 signaling (IIS) pathway regulates aging in many organisms, ranging from simple invertebrates to mammals, including humans. Many seminal discoveries regarding the roles of IIS in aging and longevity have been made by using the roundworm Caenorhabditis elegans and the fruit fly Drosophila melanogaster. In this review, we describe the mechanisms by which various IIS components regulate aging in C. elegans and D. melanogaster. We also cover systemic and tissue-specific effects of the IIS components on the regulation of lifespan. We further discuss IIS-mediated physiological processes other than aging and their effects on human disease models focusing on C. elegans studies. As both C. elegans and D. melanogaster have been essential for key findings regarding the effects of IIS on organismal aging in general, these invertebrate models will continue to serve as workhorses to help our understanding of mammalian aging. [BMB Reports 2016; 49(2): 81-92]

Longevity Regulation by Insulin/IGF-1 Signalling

For the past three decades, many ageing-regulatory pathways have been identified using C. elegans as a model organism. The insulin/insulin-like growth factor (IGF)-1 signalling (IIS) pathway is one of the most evolutionarily well-conserved ageing-regulatory pathways ranging from worms to mammals. Here, we review the molecular mechanism and the functional significance of IIS in C. elegans ageing. Specifically, we describe the roles of key components of IIS in ageing, systemic ageing regulation by IIS, and other known physiological functions of IIS that contribute to longevity. We also discuss possible implications of IIS in mammalian health and ageing.

Genes and Pathways That Influence Longevity in Caenorhabditis elegans

The roundworm Caenorhabditis elegans is one of the most popular model organisms for research on aging because of its short lifespan and genetic tractability. Studies using C. elegans have identified many genes and pathways that regulate aging, several of which are conserved in other species, including mammals. In this chapter, we describe longevity-regulatory pathways including insulin/IGF-1 (insulin-like growth factor 1) signaling, TOR (target of rapamycin) signaling, autophagy, mitochondrial respiration, and HIF-1 (hypoxia-inducible factor 1) pathways. We also review the effects of dietary restriction, a key environmental factor that influences aging, on longevity-regulatory genetic factors. In addition, we illustrate the roles of two important C. elegans tissues, those of the sensory neural and reproductive systems, in regulating longevity at the molecular level. For each of the subtopics, we explain how changes in the expression of genes involved in each pathway and system alter longevity. We also speculate on the evolutionary significance of the genes and pathways that affect longevity. Given the conserved nature of longevity regulation, the dissection of the roles of these genetic factors in determining the C. elegans lifespan will provide important clues for understanding the secrets of human aging.

RNA helicase SACY-1 is required for longevity caused by various genetic perturbations in Caenorhabditis elegans

ABSTRACT RNA helicases, which unwind RNAs, are essential for RNA metabolism and homeostasis. However, the roles of RNA helicases in specific physiological processes remain poorly understood. We recently reported that an RNA helicase, HEL-1, promotes long lifespan conferred by reduced insulin/insulin-like growth factor-1 (IGF-1) signaling (IIS) in Caenorhabditis elegans. We also showed that HEL-1 induces the expression of longevity genes by physically interacting with Forkhead box O (FOXO) transcription factor. Thus, the HEL-1 RNA helicase appears to regulate lifespan by specifically activating FOXO in IIS. In the current study, we report another longevity-promoting RNA helicase, Suppressor of ACY-4 sterility 1 (SACY-1). SACY-1 contributed to the longevity of daf-2/insulin/IGF-1 receptor mutants. Unlike HEL-1, SACY-1 was also required for the longevity due to mutations in genes involved in non-IIS pathways. Thus, SACY-1 appears to function as a general longevity factor for various signaling pathways, which is different from the specific function of HEL-1.

Inverse correlation between longevity and developmental rate among wild C. elegans strains

Genetic studies using model organisms have shown that many long-lived mutants display impaired fitness, such as reduced fecundity and delayed development. However, in several wild animals, the association between longevity and fitness does not seem to be inevitable. Thus, the relationship between longevity and fitness in wild organisms remains inconclusive. Here, we determined the correlation between lifespan and fitness, developmental rate and brood size, by using 16 wild-derived C. elegans strains originated from various geographic areas. We found a negative correlation between lifespan and developmental rate. In contrast, we did not find such negative correlation between longevity and developmental rate among the individuals of C. elegans strains. These data imply that polymorphic genetic variants among wild isolates determine resource allocation to longevity and developmental rate.

RNAi targeting Caenorhabditis elegans α-arrestins has small or no effects on lifespan

Background: α-arrestins are a family of proteins that are implicated in multiple biological processes, including metabolism and receptor desensitization. Methods: Here, we sought to examine the roles of α-arrestins in the longevity of Caenorhabditis elegans through an RNA interference screen. Results: We found that knocking down each of 24 out of total 29 C. elegans α-arrestins had small or no effects on lifespan. Thus, individual C. elegans α-arrestins may have minor effects on longevity. Conclusions: This study will provide useful information for future research on the functional role of α-arrestins in aging and longevity.

RNAi targeting Caenorhabditis elegans α-arrestins marginally affects lifespan

Background: α-arrestins are a family of proteins that are implicated in multiple biological processes, including metabolism and receptor desensitization. Methods: Here, we sought to examine the roles of α-arrestins in the longevity of Caenorhabditis elegans through an RNA interference screen. Results: We found that knocking down each of 24 out of total 29 C. elegans α-arrestins had small or no effects on lifespan. Thus, individual C. elegans α-arrestins may have minor effects on longevity. Conclusions: This study will provide useful information for future research on the functional role of α-arrestins in aging and longevity.

RNAi targeting Caenorhabditis elegans α-arrestins has little effect on lifespan

Background: α-arrestins are a family of proteins that are implicated in multiple biological processes, including metabolism and receptor desensitization. Methods: Here, we sought to examine the roles of α-arrestins in the longevity of Caenorhabditis elegans through an RNA interference screen. Results: We found that feeding worms with bacteria expressing double-stranded RNA against each of 24 out of total 29 C. elegans α-arrestins had little effect on lifespan. Thus, individual C. elegans α-arrestins may have minor effects on longevity. Conclusions: This study will provide useful information for future research on the functional role of α-arrestins in aging and longevity.