No abstract

Reducing insulin/IGF-1 signaling (IIS) extends lifespan, promotes protein homeostasis (proteostasis), and elevates stress resistance of worms, flies, and mammals. How these functions are orchestrated across the organism is only partially understood. Here, we report that in the nematode the IIS positively regulates the expression of (), a gene which is primarily expressed in neurons of the adult worm and underlies the formation of caveolae, a subtype of lipid microdomains that serve as platforms for signaling complexes. Accordingly, IIS reduction lowers expression and lessens the quantity of neuronal caveolae. Reduced expression extends lifespan and mitigates toxic protein aggregation by modulating the expression of aging-regulating and signaling-promoting genes. Our findings define caveolae as aging-governing signaling centers and underscore the potential for as a novel therapeutic target for the promotion of healthy aging.

Although aging-regulating pathways were discovered a few decades ago, it is not entirely clear how their activities are orchestrated, to govern lifespan and proteostasis at the organismal level. Here, we utilized the nematode Caenorhabditis elegans to examine whether the alteration of aging, by reducing the activity of the Insulin/IGF signaling (IIS) cascade, affects protein SUMOylation. We found that IIS activity promotes the SUMOylation of the germline protein, CAR-1, thereby shortening lifespan and impairing proteostasis. In contrast, the expression of mutated CAR-1, that cannot be SUMOylated at residue 185, extends lifespan and enhances proteostasis. A mechanistic analysis indicated that CAR-1 mediates its aging-altering functions, at least partially, through the notch-like receptor glp-1. Our findings unveil a novel regulatory axis in which SUMOylation is utilized to integrate the aging-controlling functions of the IIS and of the germline and provide new insights into the roles of SUMOylation in the regulation of organismal aging.

The protein homeostasis (proteostasis) network (PN) encompasses mechanisms that maintain proteome integrity by controlling various biological functions. Loss of proteostasis leads to toxic protein aggregation (proteotoxicity), which underlies the manifestation of neurodegeneration. How the PN responds to dissimilar proteotoxic challenges and how these responses are regulated at the organismal level are largely unknown. Here, we report that, while torsin chaperones protect from the toxicity of neurodegeneration-causing polyglutamine stretches, they exacerbate the toxicity of the Alzheimer's disease-causing Ab peptide in neurons and muscles. These opposing effects are accompanied by differential modulations of gene expression, including that of three neuropeptides that are involved in tailoring the organismal response to dissimilar proteotoxic insults. This mechanism is regulated by insulin/IGF signaling and the transcription factor SKN-1/ NRF. Our work delineates a mechanism by which the PN orchestrates differential responses to dissimilar proteotoxic challenges and points at potential targets for therapeutic interventions.

Loss of protein homeostasis is a hazardous situation that jeopardizes cellular functionality and viability. Cells have developed mechanisms that supervise protein integrity and direct misfolded molecules for degradation. Nevertheless, subsets of aggregation-prone proteins escape degradation and form aggregates that can underlie the development of neurodegenerative disorders. In some cases, cells deposit hazardous protein aggregates in designated sites, like aggresomes, or secrete them with vesicles. The prion protein (PrP) is an aggregation-prone, membrane-anchored glycoprotein, whose aggregation causes familial and sporadic, fatal, neurodegenerative diseases. The proper maturation of PrP is assisted by cyclophilin B, an endoplasmic reticulum-resident foldase. Accordingly, the inhibition of cyclophilins by the drug cyclosporin A (CsA) leads to the accumulation of aggregated PrP and to its deposition in aggresomes. In this study, we asked whether secretion is an alternative strategy that cells adopt to get rid of misfolded PrP molecules and found that, upon treatment with CsA, cells secrete PrP by exosomes, a subtype of secretion vesicles, and by additional types of vesicles. CsA-induced, PrP-containing exosomes originate from the endoplasmic reticulum in a Golgi-independent manner. These findings divulge a new cellular response that is activated upon CsA treatment to secrete misfolded PrP species from the cell and may underlie the spreading of toxic prions among cells and across tissues.-Pan, I., Roitenberg, N., Cohen, E. Vesicle-mediated secretion of misfolded prion protein molecules from cyclosporin A-treated cells.