Interfacing mitochondrial biogenesis and elimination to enhance host pathogen defense and longevity

C. elegans as a model to study mitochondrial biology and disease

Mitochondria perform a myriad of essential functions that ensure organismal homeostasis, including maintaining bioenergetic capacity, sensing and signalling the presence of pathogenic threats, and determining cell fate. Their function is highly dependent on mitochondrial quality control and the appropriate regulation of mitochondrial size, shape, and distribution during an entire lifetime, as well as their inheritance across generations. The roundworm Caenorhabditis elegans has emerged as an ideal model organism through which to study mitochondria. The remarkable conservation of mitochondrial biology has allowed C. elegans researchers to investigate complex processes that are challenging to study in higher organisms. In this review, we explore the key recent contributions of C. elegans to mitochondrial biology through the lens of mitochondrial dynamics, organellar removal, and mitochondrial inheritance, as well as their involvement in immune responses, various types of stress, and transgenerational signalling.

Associations of BNIP3 and DAPK1 gene polymorphisms with disease susceptibility, clinicopathologic features, anxiety, and depression in gastric cancer patients

The purpose of this study is to explore the associations of BNIP3 and DAPK1 polymorphisms with disease susceptibility, clinicopathologic characteristics, depression, and anxiety in gastric cancer (GC) patients. In this study, 150 GC patients and 100 healthy controls were recruited. 1000 Genomes database and Haploview 4.0 software were used to select tag SNPs. Improved multiplex ligase detection reaction was used for genotyping. Data were analyzed using Chi-square test (χ² test) and univariate and multivariate logistic regression. The results demonstrated that the rs10781582 of BNIP3 in the dominant model was associated with a reduced risk of GC in the younger group (P _BH = 0.015), and the minor allele G of rs1329600 at DAPK1 was associated with reduced risk of GC (P _BH = 0.018). In the stratified analysis, the rs3793742 and rs10781582 of BNIP3 in the dominant model were associated with gender and age of GC patients, respectively (rs3793742: P _BH = 0.033; rs10781582: P _BH = 0.030). The rs10781582 of BNIP3 in the dominant model was correlated with depression in GC patients (P _BH = 0.003). However, no association was found between BNIP3 and DAPK1 polymorphisms and differentiation degree, TNM stage, lymph node metastases, visceral metastasis, and anxiety. In summary, polymorphisms of BNIP3 and DAPK1 were associated with a protective effect against GC. So far, this is the first study to explore the association between BNIP3 and DAPK1 gene polymorphism and GC risk, which may provide new insight about biologic mechanisms of GC pathogenesis.

Metabolic regulation of lifespan from a C. elegans perspective

Decline of cellular functions especially cognitive is a major deficit that arises with age in humans. Harnessing the strengths of small and genetic tractable model systems has revealed key conserved regulatory biochemical and signaling pathways that control aging. Here, we review some of the key signaling and biochemical pathways that coordinate aging processes with special emphasis on Caenorhabditis elegans as a model system and discuss how nutrients and metabolites can regulate lifespan by coordinating signaling and epigenetic programs. We focus on central nutrient-sensing pathways such as mTOR and insulin/insulin-like growth factor signaling and key transcription factors including the conserved basic helix-loop-helix transcription factor HLH-30/TFEB.

Controlling quality and amount of mitochondria by mitophagy: insights into the role of ubiquitination and deubiquitination

Mitophagy is a selective autophagy pathway conserved in eukaryotes and plays an essential role in mitochondrial quality and quantity control. Mitochondrial fission and fusion cycles maintain a certain amount of healthy mitochondria and allow the isolation of damaged mitochondria for their elimination by mitophagy. Mitophagy can be classified into receptor-dependent and ubiquitin-dependent pathways. The mitochondrial outer membrane protein Atg32 is identified as the only known receptor for mitophagy in baker's yeast, whereas mitochondrial proteins FUNDC1, NIX/BNIP3L, BNIP3 and Bcl2L13 are recognized as mitophagy receptors in mammalian cells. Earlier studies showed that ubiquitination and deubiquitination occurs in yeast, yet there is no direct evidence for an ubiquitin-dependent mitophagy pathway in this organism. In contrast, a ubiquitin-/PINK1-/Parkin-dependent mitophagy pathway was unraveled and was extensively characterized in mammals in recent years. Recently, a quantitative method termed synthetic quantitative array (SQA) technology was developed to identify modulators of mitophagy in baker's yeast on a genome-wide level. The Ubp3-Bre5 deubiquitination complex was found as a negative regulator of mitophagy while promoting other autophagic pathways. Here we discuss how ubiquitination and deubiquitination regulates mitophagy and other selective forms of autophagy and what argues for using baker's yeast as a model to study the ubiquitin-dependent mitophagy pathway.

A Genetic Analysis of the Caenorhabditis elegans Detoxification Response

Oxidative damage contributes to human diseases of aging including diabetes, cancer, and cardiovascular disorders. Reactive oxygen species resulting from xenobiotic and endogenous metabolites are sensed by a poorly understood process, triggering a cascade of regulatory factors and leading to the activation of the transcription factor Nrf2 (Nuclear factor-erythroid-related factor 2, SKN-1 in Caenorhabditis elegans). Nrf2/SKN-1 activation promotes the induction of the phase II detoxification system that serves to limit oxidative stress. We have extended a previous C. elegans genetic approach to explore the mechanisms by which a phase II enzyme is induced by endogenous and exogenous oxidants. The xrep (xenobiotics response pathway) mutants were isolated as defective in their ability to properly regulate the induction of a glutathione S-transferase (GST) reporter. The xrep-1 gene was previously identified as wdr-23, which encodes a C. elegans homolog of the mammalian β-propeller repeat-containing protein WDR-23 Here, we identify and confirm the mutations in xrep-2, xrep-3, and xrep-4 The xrep-2 gene is alh-6, an ortholog of a human gene mutated in familial hyperprolinemia. The xrep-3 mutation is a gain-of-function allele of skn-1 The xrep-4 gene is F46F11.6, which encodes a F-box-containing protein. We demonstrate that xrep-4 alters the stability of WDR-23 (xrep-1), a key regulator of SKN-1 (xrep-3). Epistatic relationships among the xrep mutants and their interacting partners allow us to propose an ordered genetic pathway by which endogenous and exogenous stressors induce the phase II detoxification response.