Glutathione transferases kappa 1 and kappa 2 localize in peroxisomes and mitochondria, respectively, and are involved in lipid metabolism and respiration in Caenorhabditis elegans

Abstract

To elucidate the function of kappa class glutathione transferases (GSTs) in multicellular organisms, their expression and silencing were investigated in Caenorhabditis elegans. In contrast with most vertebrates, which possess only one GST kappa gene, two distinct genes encoding GSTK-1 and GSTK-2 are present in the C. elegans genome. The amino acid sequences of GSTK-1 and GSTK-2 share around 30% similarity with the human hGSTK1 sequence and, like the human transferase, GSTK-1 contains a C-terminal peroxisomal targeting sequence. gstk-1 and gstk-2 genes show distinct developmental and tissue expression patterns. We show that GSTK-2 is localized in the mitochondria and expressed mainly in the pharynx, muscles and epidermis, whereas GSTK-1 is restricted to peroxisomes and expressed in the intestine, body wall muscles and epidermis. In order to determine the potential role(s) of GST kappa genes in C. elegans, specific silencing of the gstk-1 and gstk-2 genes was performed by an RNA interference approach. Knockdown of gstk-1 or gstk-2 had no apparent effect on C. elegans reproduction, development, locomotion or lifespan. By contrast, when biological functions (oxygen consumption and lipid metabolism) related to peroxisomes and ⁄ or mitochondria were investigated, we observed a significant decrease in respiration rate and a lower concentration of the monounsaturated fatty acid cis-vaccenic acid (18:1x7) when worms were fed on bacteria expressing RNA interference targeting both gstk-1 and gstk-2. These results demonstrate that GST kappa, although not essential for the worm's life, may be involved in energetic and lipid metabolism, two functions related to mitochondria and peroxisomes.Abbreviations Dsba, protein disulfide isomerase A; FAME, fatty acid methyl ester; GFP, green fluorescent protein; GST, glutathione transferase; PTS1, peroxisomal targeting signal 1; RNAi, RNA interference.

Mitochondrial Thiols in Antioxidant Protection and Redox Signaling: Distinct Roles for Glutathionylation and Other Thiol Modifications

“…Mitochondrial GSTs can, in principle, protect against many of these electrophiles by conjugating them to GSH. This protective role is consistent with the finding that silencing the ortholog of GST-K in Caenorhabditis elegans disrupts mitochondrial function (161); however, the importance of GST-K in protecting mitochondria against oxidative damage is uncertain.…”

Mitochondria are targets for peroxisome-derived oxidative stress in cultured mammalian cells

“…Note that, as (i) C11-Bodipy 581/591 accumulates in virtually all cellular membranes [64], (ii) this reporter molecule can be the primary target of lipid peroxidation or oxidized by lipid radicals as part of (downstream) propagation reactions [64], and (iii) the activated lipid species may also be exchanged between membranes [65], our experimental setup did not allow us to determine unambiguously in which subcellular compartment the primary lipid radicals are formed and located. However, to gain more insight into this complex issue, we first investigated whether overexpression of GSTK1-roGFP2-PTS1 (po-GSTK1), a green fluorescent protein having the potential to detoxify lipid peroxides [66], could block po-KR-and/or mt-KRinduced lipid peroxidation. From these experiments, it is evident that po-GSTK1 functions only as a lipid peroxidation quencher for po-KR (compare Figs.…”

The autophagosomal protein LGG-2 acts synergistically with LGG-1 in dauer formation and longevity in C. elegans

“…RNAi by feeding was performed as described. 41,53 Briefly, synchronized worms at L4 larval stage were placed onto IPTG-containing NGM plates seeded with bacteria (E. coli HT115[DE3] carrying the empty vector L4440 (pPD129.36) or the bacterial clones from the J. Ahringer library (lgg-1, WBRNAi00011484; lgg-2, WBRNAi00022071; rab-7, WBRNAi00009246). CeTOR clone was a gift from Malene Hansen.…”