1. Reduction of Derlin activity suppresses Notch-dependent tumours in the C. elegans germ line
- Author
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Dave Hansen, Ramya Singh, Chris Wang, Hilary Racher, Xin Wang, and Ryan B. Smit
- Subjects
Cancer Research ,Protein Folding ,Mutant ,Cancer Treatment ,Immunostaining ,QH426-470 ,Biochemistry ,Germline ,0302 clinical medicine ,RNA interference ,Cell Signaling ,Neoplasms ,Medicine and Health Sciences ,Macromolecular Structure Analysis ,Receptor ,Genetics (clinical) ,Caenorhabditis elegans ,Notch Signaling ,Staining ,0303 health sciences ,biology ,Receptors, Notch ,Helminth Proteins ,Specimen preparation and treatment ,Cell biology ,Nucleic acids ,Oncology ,Genetic interference ,Epigenetics ,Stem cell ,Anatomy ,Genital Anatomy ,Research Article ,Signal Transduction ,Protein Structure ,Notch signaling pathway ,Endoplasmic-reticulum-associated protein degradation ,03 medical and health sciences ,Genetics ,Animals ,Gonads ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology ,Reproductive System ,DAPI staining ,Biology and Life Sciences ,Cancers and Neoplasms ,Proteins ,Cell Biology ,biology.organism_classification ,Research and analysis methods ,Germ Cells ,Nuclear staining ,Mutation ,Unfolded protein response ,RNA ,Gene expression ,030217 neurology & neurosurgery - Abstract
Regulating the balance between self-renewal (proliferation) and differentiation is key to the long-term functioning of all stem cell pools. In the Caenorhabditis elegans germline, the primary signal controlling this balance is the conserved Notch signaling pathway. Gain-of-function mutations in the GLP-1/Notch receptor cause increased stem cell self-renewal, resulting in a tumour of proliferating germline stem cells. Notch gain-of-function mutations activate the receptor, even in the presence of little or no ligand, and have been associated with many human diseases, including cancers. We demonstrate that reduction in CUP-2 and DER-2 function, which are Derlin family proteins that function in endoplasmic reticulum-associated degradation (ERAD), suppresses the C. elegans germline over-proliferation phenotype associated with glp-1(gain-of-function) mutations. We further demonstrate that their reduction does not suppress other mutations that cause over-proliferation, suggesting that over-proliferation suppression due to loss of Derlin activity is specific to glp-1/Notch (gain-of-function) mutations. Reduction of CUP-2 Derlin activity reduces the expression of a read-out of GLP-1/Notch signaling, suggesting that the suppression of over-proliferation in Derlin loss-of-function mutants is due to a reduction in the activity of the mutated GLP-1/Notch(GF) receptor. Over-proliferation suppression in cup-2 mutants is only seen when the Unfolded Protein Response (UPR) is functioning properly, suggesting that the suppression, and reduction in GLP-1/Notch signaling levels, observed in Derlin mutants may be the result of activation of the UPR. Chemically inducing ER stress also suppress glp-1(gf) over-proliferation but not other mutations that cause over-proliferation. Therefore, ER stress and activation of the UPR may help correct for increased GLP-1/Notch signaling levels, and associated over-proliferation, in the C. elegans germline., Author summary Notch signaling is a highly conserved signaling pathway that is utilized in many cell fate decisions in many organisms. In the C. elegans germline, Notch signaling is the primary signal that regulates the balance between stem cell proliferation and differentiation. Notch gain-of-function mutations cause the receptor to be active, even when a signal that is normally needed to activate the receptor is absent. In the germline of C. elegans, gain-of-function mutations in GLP-1, a Notch receptor, results in over-proliferation of the stem cells and tumour formation. Here we demonstrate that a reduction or loss of Derlin activity, which is a conserved family of proteins involved in endoplasmic reticulum-associated degradation (ERAD), suppresses over-proliferation due to GLP-1/Notch gain-of-function mutations. Furthermore, we demonstrate that a surveillance mechanism utilized in cells to monitor and react to proteins that are not folded properly (Unfolded Protein Response-UPR) must be functioning well in order for the loss of Derlin activity to supress over-proliferation caused by glp-1/Notch gain-of-function mutations. This suggests that activation of the UPR may be the mechanism at work for suppressing this type of over-proliferation, when Derlin activity is reduced. Therefore, decreasing Derlin activity may be a means of reducing the impact of phenotypes and diseases due to certain Notch gain-of-function mutations.
- Published
- 2021