using-caenorhabditis-elegans-as-model-system-to-study-protein

Using <em>Caenorhabditis elegans</em> as a Model System to Study Protein Homeostasis in a Multicellular Organism

The folding and assembly of proteins is essential for protein function, the long-term health of the cell, and longevity of the organism. Historically, the ...

using-caenorhabditis-elegans-to-screen-for-tissue-specific-chaperone

Using <em>Caenorhabditis elegans</em> to Screen for Tissue-Specific Chaperone Interactions

Correct folding and assembly of proteins and protein complexes are essential for cellular function. Cells employ quality control pathways that correct, ...

Ben-Gurion University of the Negev

Proteome stability is central to cellular function and the lifespan of an organism. This is apparent in muscle cells, where incorrect folding and assembly of the sarcomere contributes to disease and aging. Apart from the myosin-assembly factor UNC-45, the complete network of chaperones involved in assembly and maintenance of muscle tissue is currently unknown. To identify additional factors required for sarcomere quality control, we performed genetic screens based on suppressed or synthetic motility defects in Caenorhabditis elegans. In addition to ethyl methyl sulfonate-based mutagenesis, we employed RNAi-mediated knockdown of candidate chaperones in unc-45 temperature-sensitive mutants and screened for impaired movement at permissive conditions. This approach confirmed the cooperation between UNC-45 and Hsp90. Moreover, the screens identified three novel co-chaperones, CeHop (STI-1), CeAha1 (C01G10.8) and Cep23 (ZC395.10), required for muscle integrity. The specific identification of Hsp90 and Hsp90 co-chaperones highlights the physiological role of Hsp90 in myosin folding. Our work thus provides a clear example of how a combination of mild perturbations to the proteostasis network can uncover specific quality control modules. 

Challenging muscle homeostasis uncovers novel chaperone interactions in Caenorhabditis elegans.

Safeguarding the proteome is central to the health of the cell. In multi-cellular organisms, the composition of the proteome, and by extension, protein-folding requirements, varies between cells. In agreement, chaperone network composition differs between tissues. Here, we ask how chaperone expression is regulated in a cell type-specific manner and whether cellular differentiation affects chaperone expression. Our bioinformatics analyses show that the myogenic transcription factor HLH-1 (MyoD) can bind to the promoters of chaperone genes expressed or required for the folding of muscle proteins. To test this experimentally, we employed HLH-1 myogenic potential to genetically modulate cellular differentiation of Caenorhabditis elegans embryonic cells by ectopically expressing HLH-1 in all cells of the embryo and monitoring chaperone expression. We found that HLH-1-dependent myogenic conversion specifically induced the expression of putative HLH-1-regulated chaperones in differentiating muscle cells. Moreover, disrupting the putative HLH-1-binding sites on ubiquitously expressed daf-21(Hsp90) and muscle-enriched hsp-12.2(sHsp) promoters abolished their myogenic-dependent expression. Disrupting HLH-1 function in muscle cells reduced the expression of putative HLH-1-regulated chaperones and compromised muscle proteostasis during and after embryogenesis. In turn, we found that modulating the expression of muscle chaperones disrupted the folding and assembly of muscle proteins and thus, myogenesis. Moreover, muscle-specific over-expression of the DNAJB6 homolog DNJ-24, a limb-girdle muscular dystrophy-associated chaperone, disrupted the muscle chaperone network and exposed synthetic motility defects. We propose that cellular differentiation could establish a proteostasis network dedicated to the folding and maintenance of the muscle proteome. Such cell-specific proteostasis networks can explain the selective vulnerability that many diseases of protein misfolding exhibit even when the misfolded protein is ubiquitously expressed.

Shiran Dror

Department of Life Sciences,
National Institute for Biotechnology in the Negev,
Department of Life Sciences, National Institute for Biotechnology in the Negev

Ben-Gurion University of the Negev

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

Using Caenorhabditis elegans to Screen for Tissue-Specific Chaperone Interactions

Shiran Dror

Department of Life Sciences,National Institute for Biotechnology in the Negev,Department of Life Sciences, National Institute for Biotechnology in the Negev

Ben-Gurion University of the Negev

Using Caenorhabditis elegans as a Model System to Study Protein Homeostasis in a Multicellular Organism

Using Caenorhabditis elegans to Screen for Tissue-Specific Chaperone Interactions

Department of Life Sciences,
National Institute for Biotechnology in the Negev,
Department of Life Sciences, National Institute for Biotechnology in the Negev