A genetic titration of membrane composition in Caenorhabditis elegans reveals its importance for multiple cellular and physiological traits.

Communicating editor: B. Grant The composition and biophysical properties of cellular membranes must be tightly regulated to maintain the proper functions of myriad processes within cells. To better understand the importance of membrane homeostasis, we assembled a panel of five Caenorhabditis elegans strains that show a wide span of membrane composition and properties, ranging from excessively rich in saturated fatty acids (SFAs) and rigid to excessively rich in polyunsaturated fatty acids (PUFAs) and fluid.

Early-life mitochondrial DNA damage results in lifelong deficits in energy production mediated by redox signaling in Caenorhabditis elegans.

The consequences of damage to the mitochondrial genome (mtDNA) are poorly understood, although mtDNA is more susceptible to damage resulting from some genotoxicants than nuclear DNA (nucDNA), and many environmental toxicants target the mitochondria. Reports from the toxicological literature suggest that exposure to early-life mitochondrial damage could lead to deleterious consequences later in life (the "Developmental Origins of Health and Disease" paradigm), but reports from other fields often report beneficial ("mitohormetic") responses to such damage. Here, we tested the effects of low (causing no change in lifespan) levels of ultraviolet C (UVC)-induced, irreparable mtDNA damage during early development in Caenorhabditis elegans.

Leveraging a gain-of-function allele of Caenorhabditis elegans paqr-1 to elucidate membrane homeostasis by PAQR proteins.

The C. elegans proteins PAQR-2 (a homolog of the human seven-transmembrane domain AdipoR1 and AdipoR2 proteins) and IGLR-2 (a homolog of the mammalian LRIG proteins characterized by a single transmembrane domain and the presence of immunoglobulin domains and leucine-rich repeats in their extracellular portion) form a complex that protects against plasma membrane rigidification by promoting the expression of fatty acid desaturases and the incorporation of polyunsaturated fatty acids into phospholipids, hence increasing membrane fluidity. In the present study, we leveraged a novel gain-of-function allele of PAQR-1, a PAQR-2 paralog, to carry out structure-function studies.

Evolutionarily conserved long-chain Acyl-CoA synthetases regulate membrane composition and fluidity.

The human AdipoR1 and AdipoR2 proteins, as well as their homolog PAQR-2, protect against cell membrane rigidification by exogenous saturated fatty acids by regulating phospholipid composition. Here, we show that mutations in the gene help to suppress the phenotypes of mutant worms, including their characteristic membrane fluidity defects. encodes a homolog of the human acyl-CoA synthetase ACSL1, and localizes to the mitochondrial membrane where it likely activates long chains fatty acids for import and degradation.

Membrane fluidity is regulated by the transmembrane protein FLD-1 and its human homologs TLCD1/2.

Unlabelled: Dietary fatty acids are the main building blocks for cell membranes in animals, and mechanisms must therefore exist that compensate for dietary variations. We isolated mutants that improved tolerance to dietary saturated fat in a sensitized genetic background, including eight alleles of the novel gene that encodes a homolog of the human TLCD1 and TLCD2 transmembrane proteins. FLD-1 is localized on plasma membranes and acts by limiting the levels of highly membrane-fluidizing long-chain polyunsaturated fatty acid-containing phospholipids.

Membrane Fluidity Is Regulated Cell Nonautonomously by PAQR-2 and Its Mammalian Homolog AdipoR2.

Maintenance of membrane properties is an essential aspect of cellular homeostasis of which the regulatory mechanisms remain mostly uncharacterized. In , the PAQR-2 and IGLR-2 proteins act together as a plasma membrane sensor that responds to decreased fluidity by promoting fatty acid desaturation, hence restoring membrane fluidity. Here, we used mosaic analysis for and , and tissue-specific expression, to show that membrane homeostasis is achieved cell nonautonomously.

A Fluorescence Resonance Energy Transfer Assay For Monitoring α- Synclein Aggregation in a Caenorhabditis Elegans Model For Parkinson's Disease.

The aggregation of α-synuclein (Syn or S) to form insoluble fibrils is important in the pathogenesis of Parkinson's disease, but key risk factors remain ill-defined. We have developed Fluorescence Resonance Energy Transfer (FRET)-based assays for α-synuclein aggregation, using Green Fluorescent Protein variants Cerulean (C) or Venus (V), fused to each other (CV, VC) or to human synuclein (SC, SV etc). Bacterially expressed proteins were purified to homogeneity, and C-terminal fusions SC and SV largely retained their ability to aggregate in vitro.

Exposure to mitochondrial genotoxins and dopaminergic neurodegeneration in Caenorhabditis elegans.

Neurodegeneration has been correlated with mitochondrial DNA (mtDNA) damage and exposure to environmental toxins, but causation is unclear. We investigated the ability of several known environmental genotoxins and neurotoxins to cause mtDNA damage, mtDNA depletion, and neurodegeneration in Caenorhabditis elegans. We found that paraquat, cadmium chloride and aflatoxin B1 caused more mitochondrial than nuclear DNA damage, and paraquat and aflatoxin B1 also caused dopaminergic neurodegeneration.

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces mitochondrial and nuclear DNA damage in Caenorhabditis elegans.

The metabolites of the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) form DNA adducts in animal models. While there are many reports of formation of nuclear DNA adducts, one report also detected NNK-induced damage to the mitochondrial genome in rats. Using a different DNA damage detection technology, we tested whether this finding could be repeated in the nematode Caenorhabditis elegans.

Effects of α-synuclein overexpression in transgenic Caenorhabditis elegans strains.

The neural protein α-synuclein aggregates both in vivo and in vitro to form insoluble fibrils that are involved in Parkinson's disease pathogenesis. We have generated α-synuclein/fluorescent-protein fusion constructs overexpressed in muscle cells of the nematode, Caenorhabdtis elegans. Green Fluorescent Protein (GFP) variants, Cerulean (C) or Venus (V), were fused to the C-terminus of human α-synuclein (S); the resultant fusion genes were designated SV and SC, plus a CV fusion as well as S, C and V singly.

Low-intensity microwave irradiation does not substantially alter gene expression in late larval and adult Caenorhabditis elegans.

Reports that low-intensity microwave radiation induces heat-shock reporter gene expression in the nematode, Caenorhabditis elegans, have recently been reinterpreted as a subtle thermal effect caused by slight heating. This study used a microwave exposure system (1.0 GHz, 0.