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Susana M Garcia et al. (2003) International Worm Meeting "Molecular Modulators of Protein Homeostasis in C. Elegans"

Alejandro Chavez, Margarida Amaral, Richard Morimoto, Jason Merchant, Susana M Garcia

[

International Worm Meeting,

2003]

The folded state of proteins can be affected by many factors; these include alterations in the cellular environment and protein folding machinery. Also, the presence of misfolded proteins has been linked to several human pathologies. One class of these diseases comprises eight human neurodegenerative disorders; these are characterized by the misfolding and aggregation of different proteins having in common expanded polyglutamine (polyQ) tracts. The expression of polyQ repeats as YFP (yellow fluorescent protein) fusion proteins in body wall muscle cells in C. elegans results in the appearance of cytoplasmic protein aggregates that occur in a polyQ length dependent manner. Our lab has previously demonstrated a role for molecular chaperones, specifically Hsp104, in reducing polyglutamine aggregation in C. elegans (Satyal et al. 2000 PNAS 97, 5750-5755). We have also observed that expression of other well characterized chaperones including the yeast ssa1 (hsp70) and ydj1 (hsp40) proteins in body wall muscle cells lead to the appearance of diffuse polyQ YFP 'patches' in an otherwise aggregated phenotype. Likewise, we have seen that aging or the reduction of cellular hsf-1 levels using RNAi lead to the appearance of aggregates in worm lines expressing near the threshold Q lengths (Morley et al. 2002 PNAS 99, 10417-10422). Taken together, these observations indicate that a change in the aggregation phenotype is possible by altering the levels of the components involved in the protein folding process. In our studies, C. elegans has been used as a genetic model system to identify novel components regulating protein homeostasis. Using a forward genetic approach we mutagenized C. elegans expressing q24-yfp and scored for mutants with a visible change in the Q24-YFP soluble phenotype. We have screened 20,000 haploid genomes and have so far isolated one mutant, phi-1(rm7) for Protein Homeostasis Interference. The phi-1 mutant exhibits a visible change in the Q24-YFP solubility with the appearance of aggregate-like structures in a time dependent manner. Genetic data indicates that the Phi phenotype is caused by two recessive mutations linked to chromosomes IV and X. We are currently characterizing the mutant and performing positional cloning.

Rodrigues, Pedro Reis et al. (2009) International Worm Meeting "A variety of age-dependant aggregating proteins determine lifespan."

Peters, Theodore, Gibson, Brad, Lithgow, Gordon, Hughes, Robert, Alavez, Silvestre, Rodrigues, Pedro Reis, Czerwieniec, Gregg

[

International Worm Meeting,

2009]

Protein aggregation has for long been hypothesised as a determinant of lifespan. Briefly, normal cellular activity may give rise to damaged proteins causing them to become insoluble, missfold and aggregate. To test this hypothesis we adapted a protocol in order to extract insoluble proteins from synchronously aging populations of C. elegans. Proteins were separated based on their aqueous and detergent solubility and the insoluble fraction was resolubilized in 70%; formic acid. Insoluble proteins were chemically labelled, identified and quantified by liquid chromatography coupled with mass spectrometry (LC- ESI-MS/MS). We identified a range of proteins with roles in various cellular processes and possibly from a range of cellular compartments. 27%; of the proteins identified as forming aggregates have previously been shown to be important in keeping low levels of polyglutamine aggregation1. This suggests that reduced soluble levels of these proteins caused by age-related aggregation may cause increased risk of polyglutamine aggregation. We then considered whether proteins that appear to form aggregates during normal aging influenced lifespan. To test this notion we, reduced their expression in adult animals (from 4 days old) by RNA interference (RNAi). 34%; of the RNAi treatments were found to significantly extend mean lifespan in C. elegans suggesting that a variety of age-dependant aggregating proteins determine lifespan. Among the insoluble proteins, DAF-21, an ortholog of the mammalian HSP-90, showed age-dependant aggregation and is being used as a marker to study the role of several molecular pathways in protein aggregation. Taken together our results suggest that protein aggregation may play a common and key role in aging and age-related disease. 1 - Nollen, E., Garcia, S., Haaften, G., Kim, S., Chavez, A., Morimoto, R., Plasterk, R., Genome-wide RNA interference screen identified previously undescribed regulators of polyglutamine aggregation. Proc Natl. Acad. Sci., 101, 6403-6408, 2004.

Ellen Nollen et al. (2006) European Worm Meeting "C. elegans Models of Protein Misfolding Diseases"

Ellen Nollen, Tjakko van Ham, Ronald H. A. Plasterk.

[

European Worm Meeting,

2006]

Ellen Nollen, Tjakko van Ham & Ronald H. A. Plasterk. Aggregation of misfolded proteins occurs in various age-related neurodegenerative disorders, including Parkinsons, Alzheimers, and Huntingtons disease. To understand how cells protect themselves against misfolded proteins, we search for genes that enhance or prevent protein aggregation. C. elegans strains expressing polyglutamine stretches fused to YFP with visible, age-dependend protein aggregation are used as a genetic model. Using a genome-wide RNAi screen, we have previously identified 186 genes that, when knocked down, cause premature protein aggregation. These genes include genes involved in protein synthesis, folding, degradation and RNA synthesis and processing. 1. Conversely, we performed a forward mutagenesis screen to identify genes that, when mutated, suppress age-dependent polyglutamine aggregation. For one suppressor mutant, in which aggregation is suppressed by more than 75%, we have now identified the responsible mutation. This mutation is a missense mutation in a gene encoding a protein of unknown function that is highly conserved between C. elegans and humans. Knock-down by RNAi of the same gene in wild-type worms yielded a similar reduction in aggregation, suggesting a loss-of-function mutation. We are currently further characterizing this mutant and the remaining suppressor mutants. In addition, to establish whether the genes we have identified are specific for polyglutamine aggregation or whether they comprise of a general protein homeostatic buffer, we have developed a worm model for aggregation of alpha synuclein, which occurs in Parkinson''s disease. Altogether our results will provide insight into cellular protection against misfolded proteins and yield targets for therapy against protein misfolding diseases.. 1Nollen E.A.A., Garcia S.M., van Haaften G., Kim S., Chavez A., Morimoto R.I., Plasterk R.H. (2004) Genome-wide RNA interference screen identifies previously undescribed regulators of polyglutamine aggregation. Proc. Natl. Acad. Sci. U.S.A. 101(17):6403-8.

T.J. van Ham et al. (2007) International Worm Meeting "A C. elegans model links novel modifiers of a-synuclein inclusion formation to aging."

K.L. Thijssen, E.A.A. Nollen, T.J. van Ham, R.H.A. Plasterk

[

International Worm Meeting,

2007]

Accumulation and aggregation of a-synuclein in the brain is characteristic of, and considered to be causatively related to, several age-related neurodegenerative diseases such as Parkinsons disease (PD). To study early stages of aS accumulation and to identify modifier genes, we created transgenic C. elegans expressing the human aS gene fused to YFP in the body wall muscle. These transgenic animals show localization of aS-YFP to discrete foci during aging, which is not seen for YFP alone, indicating specificity to aS. These foci are present as early as day two after hatching, and become more abundant during aging. By fluorescence recovery after photobleaching (FRAP) we determined that the foci contain mobile material until day 11. However, at old age also immobilized aggregated protein is present. The amount of aS-foci increases to day 11 and decreases thereafter. Interestingly, this decrease in foci formation is associated with a relative increase in the amount of immobilized aggregates. We performed a genome-wide RNAi screen for modifiers of foci formation, and found 108 genes that repeatedly showed increased foci formation when silenced. Remarkably, none of these genes overlaps with genes found in a screen for polyglutamine aggregation we performed in C. elegans1. This might indicate that different mechanisms are involved in these diseases. To further characterize genes found in the screen, deletion strains of a selection of the genes representing different functional classes were crossed into the aS-YFP strain. Deletion of a gene - involved in aging and encoding one of the most potent suppressors of foci-formation - resulted in a twofold increase in the amount of foci on day thirteen. We are currently further characterizing the deletion strains. In conclusion, we developed a new animal model that captures features of age-related PD. We used the model to dentify novel modifiers of aS-YFP foci formation, of which we are further characterizing the effect of deletion of these genes on aS-YFP foci formation. These results can provide insight into the early cellular mechanisms involved in aS accumulation, and could thereby yield molecular targets for therapy. 1 Nollen E.A.A., Garcia S.M., van Haaften G., Kim S., Chavez A., Morimoto R.I., Plasterk R.H.A. (2004) Genome-wide RNA interference screen identifies previously undescribed regulators of polyglutamine aggregation. Proc. Natl. Acad. Sci. U.S.A. 101(17):6403-8.