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Optogenetic rejuvenation of mitochondrial membrane potential extends C. elegans lifespan
Abstract
Despite longstanding scientific interest in the centrality of mitochondria to biological aging, directly controlling mitochondrial function to test causality has eluded researchers. We show that specifically boosting mitochondrial membrane potential through a light-activated proton pump reversed age-associated phenotypes and extended C. elegans lifespan. We show that harnessing the energy of light to experimentally increase mitochondrial membrane potential during adulthood alone is sufficient to slow the rate of aging.
... 1101/2022 and overall mitochondrial health, and thereby enabled lifespan extension. This connection is supported by a recent study that demonstrated that boosting MMP by photo-activation of an ectopically expressed proton pump is sufficient to prolong lifespan in C. elegans (Berry et al., 2022). ...
Mitochondrial membrane potential directly powers many critical functions of mitochondria, including ATP production, mitochondrial protein import, and metabolite transport. Its loss is a cardinal feature of aging and mitochondrial diseases, and cells closely monitor membrane potential as an indicator of mitochondrial health. Given its central importance, it is logical that cells would modulate mitochondrial membrane potential in response to demand and environmental cues, but there has been little exploration of this question. We report that loss of the Sit4 protein phosphatase in yeast increases mitochondrial membrane potential, both through inducing the electron transport chain and the phosphate starvation response. Indeed, a similarly elevated mitochondrial membrane potential is also elicited simply by phosphate starvation or by abrogation of the Pho85-dependent phosphate sensing pathway. This enhanced membrane potential is primarily driven by an unexpected activity of the ADP/ATP carrier. We also demonstrate that this connection between phosphate limitation and enhancement of the mitochondrial membrane potential is also observed in primary and immortalized mammalian cells as well as in Drosophila . These data suggest that mitochondrial membrane potential is subject to environmental stimuli and intracellular signaling regulation and raise the possibility for therapeutic enhancement of mitochondrial functions even with defective mitochondria.
The field of biogerontology has established itself through significant lines of research in recent decades. However, despite early breakthroughs, progress in understanding the aging process has been slow. To push the field forward, new methodologies and technologies are likely needed to unravel the complexity of aging. This meeting brought together leading scientists and innovators to explore some emerging approaches, presenting groundbreaking advancements in four key sessions, culminating in a panel discussion.
Mitochondrial membrane potential directly powers many critical functions of mitochondria, including ATP production, mitochondrial protein import, and metabolite transport. Its loss is a cardinal feature of aging and mitochondrial diseases, and cells closely monitor membrane potential as an indicator of mitochondrial health. Given its central importance, it is logical that cells would modulate mitochondrial membrane potential in response to demand and environmental cues, but there has been little exploration of this question. We report that loss of the Sit4 protein phosphatase in yeast increases mitochondrial membrane potential, both through inducing the electron transport chain and the phosphate starvation response. Indeed, a similarly elevated mitochondrial membrane potential is also elicited simply by phosphate starvation or by abrogation of the Pho85-dependent phosphate sensing pathway. This enhanced membrane potential is primarily driven by an unexpected activity of the ADP/ATP carrier. We also demonstrate that this connection between phosphate limitation and enhancement of mitochondrial membrane potential is observed in primary and immortalized mammalian cells as well as in Drosophila . These data suggest that mitochondrial membrane potential is subject to environmental stimuli and intracellular signaling regulation and raise the possibility for therapeutic enhancement of mitochondrial function even in defective mitochondria.
Diverse models have been long explored to impel the progress of food science, while Caenorhabditis elegans (C. elegans) models applied in food toxicology and food function evaluation received vigorous advances recently. With multifaceted advantages such as short lifespan, apparent phenotypes and well-recognized genetic background, C. elegans is becoming a driving model organism in food science. In this review, we comprehensively reviewed the research progress of C. elegans models based on the literature published in past two decades, and systematically categorized the methods of C. elegans models’ construction, summarized the applications of nematodes in food toxicology, mainly involved in microbial contamination, food additives, pesticide residues, heavy metals, food packaging, and physical pollution. C. elegans models’ exploitations for functional foods assessments were also exemplified, and biological properties included anti-oxidant, anti-aging, anti-obesity, anti-glucotoxicity, anti-neurodegenerative and immunoregulation. Research gaps between present shortcomings and future orientations have been further discussed. We believed that this review would inspire ideas and strategies for further nematodes model’s exploration and multi-models-cooperation in food science.
Organisms adapt to their environment through coordinated changes in mitochondrial function and metabolism. The mitochondrial protonmotive force (PMF) is an electrochemical gradient that powers ATP synthesis and adjusts metabolism to energetic demands via cellular signaling. It is unknown how or where transient PMF changes are sensed and signaled due to the lack of precise spatiotemporal control in vivo. We addressed this by expressing a light‐activated proton pump in mitochondria to spatiotemporally “turn off” mitochondrial function through PMF dissipation in tissues with light. We applied our construct—mitochondria‐OFF (mtOFF)—to understand how metabolic status impacts hypoxia resistance, a response that relies on mitochondrial function. Activation of mtOFF induced starvation‐like behavior mediated by AMP‐activated protein kinase (AMPK). We found prophylactic mtOFF activation increased survival following hypoxia, and that protection relied on neuronal AMPK. Our study links spatiotemporal control of mitochondrial PMF to cellular metabolic changes that mediate behavior and stress resistance.
Protein quantification without isotopic labels has been a long-standing interest in the proteomics field. However, accurate and robust proteome-wide quantification with label-free approaches remains a challenge. We developed a new intensity determination and normalization procedure called MaxLFQ that is fully compatible with any peptide or protein separation prior to LC-MS analysis. Protein abundance profiles are assembled using the maximum possible information from MS-signals given that the presence of quantifiable peptides varies from sample to sample. On a benchmark dataset with two proteomes mixed at known ratios, we accurately detect the mixing ratio over the entire protein expression range, with higher precision for abundant proteins. The significance of individual label-free quantifications is obtained by a t-test approach. On a second benchmark dataset, we accurately quantify fold changes over several orders of magnitudes, a task that is challenging with label-based methods. MaxLFQ is a generic label-free quantification technology that is readily applicable to tackle many biological questions and it is compatible with standard statistical analysis workflows, and it has been validated in many and diverse biological projects. Our algorithms can handle very large experiments of 500+ samples in manageable computing time. It is implemented in the freely-available MaxQuant computational proteomics platform and works completely seamlessly at the click of a button (www.maxquant.org).
Mitochondrial respiration generates an electrochemical proton gradient across the mitochondrial inner membrane called protonmotive force (PMF) to drive diverse functions and synthesize ATP. Current techniques to manipulate the PMF are limited to its dissipation; yet, there is no precise and reversible method to increase the PMF. To address this issue, we aimed to use an optogenetic approach and engineered a mitochondria-targeted light-activated proton pump that we name mitochondria-ON (mtON) to selectively increase the PMF in Caenorhabditis elegans. Here we show that mtON photoactivation increases the PMF in a dose-dependent manner, supports ATP synthesis, increases resistance to mitochondrial toxins, and modulates energy-sensing behavior. Moreover, transient mtON activation during hypoxic preconditioning prevents the well-characterized adaptive response of hypoxia resistance. Our results show that optogenetic manipulation of the PMF is a powerful tool to modulate metabolism and cell signaling.
Homology-directed repair (HDR) of breaks induced by the RNA-programmed nuclease Cas9 has become a popular method for genome editing in several organisms. Most HDR protocols rely on plasmid-based expression of Cas9 and the gene-specific guide RNAs. Here, we report that direct injection of in vitro-assembled Cas9/crRNA-tracrRNA ribonucleoprotein complexes into the gonad of Caenorhabditis elegans yields HDR edits at a high frequency. Building on our earlier finding that PCR fragments with 35-bases homology are efficient repair templates, we developed an entirely cloning-free protocol for the generation of seamless HDR edits without selection. Combined with the co-CRISPR method of Arribere et al., 2014, this protocol is sufficiently robust for use with low-efficiency guide RNAs and to generate complex edits, including ORF replacement and simultaneous tagging of two genes with fluorescent proteins.
Copyright © 2015, The Genetics Society of America.
Low energy states delay aging in multiple species, yet mechanisms coordinating energetics and longevity across tissues remain poorly defined. The conserved energy sensor AMP-activated protein kinase (AMPK) and its corresponding phosphatase calcineurin modulate longevity via the CREB regulated transcriptional coactivator (CRTC)-1 in C. elegans. We show that CRTC-1 specifically uncouples AMPK/calcineurin-mediated effects on lifespan from pleiotropic side effects by reprogramming mitochondrial and metabolic function. This pro-longevity metabolic state is regulated cell nonautonomously by CRTC-1 in the nervous system. Neuronal CRTC-1/CREB regulates peripheral metabolism antagonistically with the functional PPARα ortholog, NHR-49, drives mitochondrial fragmentation in distal tissues, and suppresses the effects of AMPK on systemic mitochondrial metabolism and longevity via a cell-nonautonomous catecholamine signal. These results demonstrate that while both local and distal mechanisms combine to modulate aging, distal regulation overrides local contribution. Targeting central perception of energetic state is therefore a potential strategy to promote healthy aging.
Copyright © 2015 Elsevier Inc. All rights reserved.
One approach to understanding behavior is to define the cellular components of neuronal circuits that control behavior. In the nematode Caenorhabditis elegans, neuronal circuits have been delineated based on patterns of synaptic connectivity derived from ultrastructural analysis. Individual cellular components of these anatomically defined circuits have previously been characterized on the sensory and motor neuron levels. In contrast, interneuron function has only been addressed to a limited extent. We describe here several classes of interneurons (AIY, AIZ, and RIB) that modulate locomotory behavior in C. elegans. Using mutant analysis as well as microsurgical mapping techniques, we found that the AIY neuron class serves to tonically modulate reversal frequency of animals in various sensory environments via the repression of the activity of a bistable switch composed of defined command interneurons. Furthermore, we show that the presentation of defined sensory modalities induces specific alterations in reversal behavior and that the AIY interneuron class mediates this alteration in locomotory behavior. We also found that the AIZ and RIB interneuron classes process odorsensory information in parallel to the AIY interneuron class. AIY, AIZ, and RIB are the first interneurons directly implicated in chemosensory signaling. Our neuronal mapping studies provide the framework for further genetic and functional dissections of neuronal circuits in C. elegans.