Dataset Information

SIL1-depleted HEK293 cells - Cellular Signature of SIL1 Depletion: Disease Pathogenesis due to Alterations in Protein Composition Beyond the ER Machinery

ABSTRACT: Marinesco-Sjögren syndrome (MSS) is a neurodegenerative disorder caused by autosomal recessive SIL1 mutations. SIL1 acts as a nucleotide exchange factor for the endoplasmic reticulum (ER) resident chaperone BiP. As BiP controls many ER-related processes, it is likely to contribute to MSS pathology. Owing to the absence of appropriate in vitro models, the precise pathophysiological mechanisms leading to neurodegeneration in MSS are still elusive. Here, we demonstrate for the first time that SIL1-depleted HEK293 cells can be used to reveal these mechanisms using ultra-structural, cell biological, and biochemical approaches.

INSTRUMENT(S): LTQ Orbitrap Elite

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Kidney Cell

SUBMITTER: René Zahedi

LAB HEAD: René Peiman Zahedi

PROVIDER: PXD001197 | Pride | 2017-02-28

REPOSITORIES: pride

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Cellular Signature of SIL1 Depletion: Disease Pathogenesis due to Alterations in Protein Composition Beyond the ER Machinery.

Roos Andreas A Kollipara Laxmikanth L Buchkremer Stephan S Labisch Thomas T Brauers Eva E Gatz Christian C Lentz Chris C Gerardo-Nava José J Weis Joachim J Zahedi René P RP

Molecular neurobiology 20151014 8

SIL1 acts as nucleotide exchange factor for the endoplasmic reticulum chaperone BiP. Mutations of SIL1 cause Marinesco-Sjögren syndrome (MSS), a neurodegenerative disorder. Moreover, a particular function of SIL1 for etiopathology of amyotrophic lateral sclerosis (ALS) was highlighted, thus declaring the functional SIL1-BiP complex as a modifier for neurodegenerative disorders. Thereby, depletion of SIL1 was associated with an earlier manifestation and in strengthened disease progression in ALS. ...[more]

PMID: 26468156

Similar Datasets

Project description:SIL1 acts as a co-chaperone for the major ER-resident chaperone BiP and thus plays a role in many BiP-dependent cellular functions such as protein folding control and unfolded protein response. Whereas increase of BiP upon cellular stress conditions is a well-known phenomenon, elevation of SIL1 under stress conditions was thus far solely studied in yeast and different studies indicated an adverse effect of SIL1 increase. This is seemingly in contrast with the beneficial effect of SIL1 increase in surviving neurons in neurodegenerative disorders such as Amyotrophic Lateral Sclerosis and Alzheimer disease. In the present study, we systematically addressed these controversial findings. Using cell biological, morphological and biochemical methods, we could demonstrate that that SIL1 is increased in various mammalian cells and neuronal tissues upon induction of cellular stress. Investigation of heterozygous SIL1/Sil1 mutant cells and tissues supported this finding. Moreover, SIL1 protein was found to be stabilized during ER stress. Increased SIL1 initiates ER stress in a concentration-dependent manner which is in accordance with the described adverse effect of increased SIL1. However, our results also suggest that protective levels are achieved by the secretion of excessive SIL1 and GRP170 (no longer perturbing ER homeostasis) and that moderately increased SIL1 also ameliorates cellular fitness under stress conditions. Results of our immunoprecipitation studies indicate that under cellular stress conditions SIL1 might act in a BiP-independent manner. Unbiased proteomic studies revealed that elevated SIL1 levels alter the expression of several proteins including crucial players in neurodegeneration, especially in Alzheimer disease. This finding is in accordance with our observation of increased SIL1-immunoreactivity in surviving neurons of Alzheimer disease autopsy cases and supports the assumption that SIL1 plays a protective role in neurodegenerative disorders.

Project description:Marinesco-Sjogren syndrome (MSS) is a rare multisystem pediatric disorder, caused by loss of function of the endoplasmic reticulum cochaperone SIL1 in about 60% of the patients. SIL1 acts as a nucleotide exchange factor for BiP, which plays a central role in secretory protein folding. SIL1-deficient cells have reduced BiP-assisted protein folding, cannot fulfil their protein needs and experience chronic activation of the unfolded protein response (UPR). Maladaptive UPR may explain the cerebellar and skeletal muscle degeneration re-sponsible for the ataxia and muscle weakness typical of MSS. However, the cause of other, more variable, clinical manifestations, such as mild to severe mental retardation, hypogonadism, short stature and skeletal deformities, are less clear. To gain insights into the pathogenic mechanisms of MSS, we carried out cell bio-logical and proteomic investigations in skin fibroblasts derived from a young patient carrying the SIL1 ... mutation. Despite fibroblasts are not overtly affected in MSS we found morphological and biochemical changes consistent with UPR and metabolic alterations. All the cell machineries involved in RNA splicing and translation were strongly downregulated, while protein degradation via lysosome-based structures was boosted, consistent with an attempt of the cell to reduce the workload of the endoplasmic reticulum and dis-pose misfolded proteins. Cell metabolism was extensively affected as we observed a reduction in lipid syn-thesis, an increase in beta oxidation and an enhancement of the tricarboxylic acid cycle, with upregulation of eight of its enzymes. Finally, the catabolic pathways of various amino acids, including valine, leucine, isoleu-cine, tryptophane, lysine, aspartate and phenylalanine, were enhanced, while the biosynthetic pathways of arginine, serine, glycine and cysteine were reduced. These results indicate profound metabolic alterations in MSS cells in addition to UPR activation and increased protein degradation, which may contribute to make them resistant to SIL1 loss.

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