Soukas AA, Carr CE, Ruvkun G. Genetic regulation of Caenorhabditis elegans lysosome related organelle function.
PLoS Genet 2013;
9:e1003908. [PMID:
24204312 PMCID:
PMC3812091 DOI:
10.1371/journal.pgen.1003908]
[Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 09/11/2013] [Indexed: 12/28/2022] Open
Abstract
Lysosomes are membrane-bound organelles that contain acid hydrolases that degrade cellular proteins, lipids, nucleic acids, and oligosaccharides, and are important for cellular maintenance and protection against age-related decline. Lysosome related organelles (LROs) are specialized lysosomes found in organisms from humans to worms, and share many of the features of classic lysosomes. Defective LROs are associated with human immune disorders and neurological disease. Caenorhabditis elegans LROs are the site of concentration of vital dyes such as Nile red as well as age-associated autofluorescence. Even though certain short-lived mutants have high LRO Nile red and high autofluorescence, and other long-lived mutants have low LRO Nile red and low autofluorescence, these two biologies are distinct. We identified a genetic pathway that modulates aging-related LRO phenotypes via serotonin signaling and the gene kat-1, which encodes a mitochondrial ketothiolase. Regulation of LRO phenotypes by serotonin and kat-1 in turn depend on the proton-coupled, transmembrane transporter SKAT-1. skat-1 loss of function mutations strongly suppress the high LRO Nile red accumulation phenotype of kat-1 mutation. Using a systems approach, we further analyzed the role of 571 genes in LRO biology. These results highlight a gene network that modulates LRO biology in a manner dependent upon the conserved protein kinase TOR complex 2. The results implicate new genetic pathways involved in LRO biology, aging related physiology, and potentially human diseases of the LRO.
Lysosome related organelles (LROs) are specialized, membrane-bound organelles that share many common features of canonical lysosomes. Mutations in critical components of LRO biogenesis lead to human diseases of immunity, blood clotting, and pigmentation. In Caenorhabditis elegans, LROs are the site of accumulation of aging-related autofluorescence and the vital dye Nile red when fed to living C. elegans. Through classical genetics we show that the LRO is regulated by a conserved genetic pathway involving serotonin, a mitochondrial ketothiolase, and a proton-coupled solute transporter. Though previously thought to be linked in an obligatory manner, through systems level analysis we show that accumulation of C. elegans LRO Nile red and autofluorescence are mechanistically distinct processes. Contrary to the prior notion that LRO Nile red indicates lipid stores, we show that LRO Nile red is not correlated with, and may be anticorrelated with, C. elegans lipid stores. Using hundreds of candidate gene inactivations that disrupt Nile red accumulation, we determined which LRO regulatory genes specifically interact with 6 genetic mutants known to have altered LRO biology, identifying changes specifically dependent upon target of rapamycin complex 2 signaling. These data reveal relationships between LRO biology and aging and metabolism in C. elegans.
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