C. Elegans Fatty Acid Two-Hydroxylase Regulates Intestinal Homeostasis by Affecting Heptadecenoic Acid Production

Abstract

Background/Aims: The hydroxylation of fatty acids at the C-2 position is the first step of fatty acid α-oxidation and generates sphingolipids containing 2-hydroxy fatty acyl moieties. Fatty acid 2-hydroxylation is catalyzed by Fatty acid 2-hydroxylase (FA2H) enzyme. However, the precise roles of FA2H and fatty acid 2-hydroxylation in whole cell homeostasis still remain unclear. Methods: Here we utilize Caenorhabditis elegans as the model and systemically investigate the physiological functions of FATH-1/C25A1.5, the highly conserved worm homolog for mammalian FA2H enzyme. Immunostaining, dye-staining and translational fusion reporters were used to visualize FATH-1 protein and a variety of subcellular structures. The “click chemistry” method was employed to label 2-OH fatty acid in vivo. Global and tissue-specific RNAi knockdown experiments were performed to inactivate FATH-1 function. Lipid analysis of the fath-1 deficient mutants was achieved by mass spectrometry. Results: C. elegans FATH-1 is expressed at most developmental stages and in most tissues. Loss of fath-1 expression results in severe growth retardation and shortened lifespan. FATH-1 function is crucially required in the intestine but not the epidermis with stereospecificity. The “click chemistry” labeling technique showed that the FATH-1 metabolites are mainly enriched in membrane structures preferable to the apical side of the intestinal cells. At the subcellular level, we found that loss of fath-1 expression inhibits lipid droplets formation, as well as selectively disrupts peroxisomes and apical endosomes. Lipid analysis of the fath-1 deficient animals revealed a significant reduction in the content of heptadecenoic acid, while other major FAs remain unaffected. Feeding of exogenous heptadecenoic acid (C17: 1), but not oleic acid (C18: 1), rescues the global and subcellular defects of fath-1 knockdown worms. Conclusion: Our study revealed that FATH-1 and its catalytic products are highly specific in the context of chirality, C-chain length, spatial distribution, as well as the types of cellular organelles they affect. Such an unexpected degree of specificity for the synthesis and functions of hydroxylated FAs helps to regulate protein transport and fat metabolism, therefore maintaining the cellular homeostasis of the intestinal cells. These findings may help our understanding of FA2H functions across species, and offer potential therapeutical targets for treating FA2H-related diseases.

A lipid-mTORC1 nutrient sensing pathway regulates animal development by peroxisome-derived hormones

“…Strikingly, we found that in cgt-1/2/3(−) animals, most intestinal peroxisomes, marked by a peroxisomal matrix protein DAF-22∷GFP(Joo et al, 2009), accumulated in the apical region (Figure 4A-B). The notion that GlcCer deficiency causes apical peroxisomal accumulation is also consistent with a reported observation that apical peroxisomal accumulation was observed with RNAi knockdown of fath-1 (fatty acid 2-hydroxylase)(Li et al, 2018). FATH-1 is involved in biosynthesis of 2-hydroxyl very long chain fatty acid that is present in major GlcCers in C. elegans (Chitwood et al, 1995; Zhang et al, 2011; Zhu et al, 2013)(Figure 1A).…”

Hydroxylated sphingolipid biosynthesis regulates photoreceptor apical domain morphogenesis

“…We next sought to quantify the extent of Rh1 being delivered to the rhabdomeres. Hydroxylated fatty acid metabolism in worms has been shown to influence membrane trafficking mediated by the small GTPases, Rab11 and Rab7 ( Li et al, 2018 ). In Drosophila PRCs, Rab11 colocalizes extensively to newly synthesized Rh1 following its exit from the Golgi and before being deposited in the rhabdomere.…”

Genome analysis of sphingolipid metabolism‐related genes in Tetrahymena thermophila and identification of a fatty acid 2‐hydroxylase involved in the sexual stage of conjugation

“…The enzyme has been also studied in the yeast Saccharomyces cerevisiae where it was shown to be nonessential for growth (Haak et al, 1997), in the plant Arabidopsis thaliana where it was shown to be involved in the resistance to oxidative stress (Nagano et al, 2012) and in the invertebrate Caenorhabditis elegans in which it was shown to affect intestinal homeostasis, by interfering with heptadecenoic acid production (Li et al, 2018). Alternatively, our experiments demonstrated that growth and morphological parameters were not significantly different between KO and WT strains, suggesting that the gene is nonessential during T. thermophila vegetative growth.…”

“…2‐hydroxy ceramides also regulate the differentiation of various cell types (epidermal keratinocytes, schwan‐noma cells, adipocytes, and megakaryocytic cells) and have been showed to mediate proapoptotic signaling distinct from non‐hydroxy ceramide, as well as the involvement in the regulation of gastric tumor growth (Hama, 2010; Yao et al ., 2019). The enzyme has been also studied in the yeast Saccharomyces cerevisiae where it was shown to be nonessential for growth (Haak et al ., 1997), in the plant Arabidopsis thaliana where it was shown to be involved in the resistance to oxidative stress (Nagano et al ., 2012) and in the invertebrate Caenorhabditis elegans in which it was shown to affect intestinal homeostasis, by interfering with heptadecenoic acid production (Li et al ., 2018). Alternatively, our experiments demonstrated that growth and morphological parameters were not significantly different between KO and WT strains, suggesting that the gene is nonessential during T. thermophila vegetative growth.…”