A multi-omic analysis of optineurin proteinopathy in a yeast model suggests the involvement of lipid metabolism in Amyotrophic Lateral Sclerosis

Abstract

27Amyotrophic Lateral Sclerosis (ALS) is an incurable fatal neurodegenerative disease for 28 which the precise mechanisms of toxicity remain unclear despite some significant 29 advances in our understanding of the underlying genetic basis. A holistic, integrated 30 view of cellular changes will be critical to understanding the processes of 31 neurodegeneration and the development of effective treatments. Mutant forms of 32 optineurin (a ubiquitin-binding protein involved in autophagy, membrane trafficking, 33 and NF-kB activation) are found associated with cytoplasmic inclusions containing 34 TDP43 or SOD1 in some ALS patients. We have taken a multi-omics approach to 35 understand the cellular response to OPTN overexpression in a yeast model of ALS. We 36 found that genetic interaction screens and metabolomics provided parallel, highly 37 complementary data on OPTN toxicity. Genetic enhancers of OPTN toxicity in yeast 38 relate directly to the native function of OPTN in vesicular trafficking and intracellular 39 transport, suggesting the human OPTN protein is functional when expressed in yeast 40 even though there is no yeast ortholog. Crucially, we find that the genetic modifiers and 41 the metabolic response are distinct for different ALS-linked genes expressed in yeast. 42This lends strong support to the use of yeast as a model system and omics platform to 43 study ALS. 44 45 46 47 48 Keywords 49 ALS; Systems Biology; Metabolomics 50 51 52 Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease for which 53 there is no effective treatment available. ALS has been divided into familial (FALS) and 54 sporadic (SALS) forms on the basis of family history, with FALS patients accounting 55 for 5% of all ALS cases overall, but this dichotomy is now questioned[1]. Despite our 56 incomplete picture of the genetic landscape of ALS, it is considered a genetic disease. 57 Associated genetic variants, particularly the hexanucleotide repeat expansion of 58 C9orf72[2,3] and mutations in SOD1[4], TDP43[5,6] and FUS[7,8], are the basis for 59 experimental models of ALS in most model systems. Genetic variants and model 60 organism studies implicate a wide range of cellular pathways in the neurodegenerative 61 processes occurring in ALS, including oxidative stress, RNA metabolism, protein 62 aggregation and degradation (autophagy, and the ubiquitin-proteasome system), and 63 intracellular trafficking[9]. The hallmark histopathological feature of ALS is the 64 presence of intracellular protein aggregates. In most cases, these aggregates contain the 65 TDP43 protein, even though mutations in the TDP43 gene are only a rare cause of ALS. 66 A notable exception is patients with SOD1 mutations, where intracellular aggregates 67 contain the SOD1 protein, but not TDP43. With such a complex pathology 68 underpinning ALS, it is vital to develop multi-omics approaches to understand how the 69 interaction of multiple pathways is driving disease progression. 70 71 The OPTN gene encodes Optineurin, a ubiquitin-binding protein ...