Regulation of Drosophila Metamorphosis by Xenobiotic Response Regulators

Abstract

Mammalian Nrf2-Keap1 and the homologous Drosophila CncC-dKeap1 protein complexes regulate both transcriptional responses to xenobiotic compounds as well as native cellular and developmental processes. The relationships between the functions of these proteins in xenobiotic responses and in development were unknown. We investigated the genes regulated by CncC and dKeap1 during development and the signal transduction pathways that modulate their functions. CncC and dKeap1 were enriched within the nuclei in many tissues, in contrast to the reported cytoplasmic localization of Keap1 and Nrf2 in cultured mammalian cells. CncC and dKeap1 occupied ecdysone-regulated early puffs on polytene chromosomes. Depletion of either CncC or dKeap1 in salivary glands selectively reduced early puff gene transcription. CncC and dKeap1 depletion in the prothoracic gland as well as cncCK6/K6 and dKeap1EY5/EY5 loss of function mutations in embryos reduced ecdysone-biosynthetic gene transcription. In contrast, dKeap1 depletion and the dKeap1EY5/EY5 loss of function mutation enhanced xenobiotic response gene transcription in larvae and embryos, respectively. Depletion of CncC or dKeap1 in the prothoracic gland delayed pupation by decreasing larval ecdysteroid levels. CncC depletion suppressed the premature pupation and developmental arrest caused by constitutive Ras signaling in the prothoracic gland; conversely, constitutive Ras signaling altered the loci occupied by CncC on polytene chromosomes and activated transcription of genes at these loci. The effects of CncC and dKeap1 on both ecdysone-biosynthetic and ecdysone-regulated gene transcription, and the roles of CncC in Ras signaling in the prothoracic gland, establish the functions of these proteins in the neuroendocrine axis that coordinates insect metamorphosis.

Multiple roles of Nrf2-Keap1 signaling

“…Opposite effects of dKeap1 and CncC on transcription of xenobiotic response genes were revealed in our study and also previously reported. 11,12 This is consistent with the conserved function of Keap1/dKeap1 as suppressor of Nrf2/CncC. I hypothesize that Keap1 regulates xenobiotic response genes through inhibiting nuclear Nrf2 levels, while regulates some developmental genes through facilitating Nrf2 binding to chromatin ( Fig.…”

“…16,17 However, ubiquitinated Nrf2 is prominently nuclear in HepG2 cells. 16 We found that both dKeap1 and CncC predominantly localize to the nuclei of a number of Drosophila tissues, 11 suggesting that dKeap1 interacts with CncC mainly in the nuclei. Therefore, Keap1/dKeap1 may regulate Nrf2/CncC using multiple mechanisms that are not mutually exclusive.…”

“…11 CncC and dKeap1, the homologs of Nrf2 and Keap1, mediate oxidative and xenobiotic responses in Drosophila. 12,13 Immunostaining of polytene chromosomes revealed that both CncC and dKeap1 bind to ecdysone-regulated early puffs, indicating a relationship between the CncC-dKeap1 pathway and ecdysone signaling.…”

Increasing autophagy and blocking Nrf2 suppress laminopathy‐induced age‐dependent cardiac dysfunction and shortened lifespan

“…In a Drosophila model of noncardiac muscle laminopathies, Cap‐and‐collar C (CncC) [the orthologue of mammalian nuclear erythroid 2‐related factor 2 (Nrf2)] redox transcriptional regulator (Deng & Kerppola, 2013, 2014) accumulated in myonuclei and activated cellular detoxification genes (Dialynas et al., 2015). To determine whether CncC accumulated in this cardiac model of laminopathies, hearts expressing wild‐type and mutant LamC were stained with antibody to CncC (Deng & Kerppola, 2013, 2014). Hearts expressing wild‐type LamC showed CncC localization within the cytoplasm (Fig.…”

“…Nuclear CncC (Nrf2) is a characteristic of redox imbalance (Deng & Kerppola, 2013, 2014). To determine the redox status of the hearts, reduced (GSH) and oxidized (GSSH) glutathione were measured (Anderson, 1985; Dialynas et al., 2015).…”