bims-mitpro 2024-08-11 papers

Issue of 2024‒08‒11
three papers selected by
Andreas Kohler, Umeå University

Nat Commun. 2024 Aug 03. 15(1): 6594

Neuro-intestinal acetylcholine signalling regulates the mitochondrial stress response in Caenorhabditis elegans.

Rebecca Cornell, Wei Cao, Bernie Harradine, Rasoul Godini, Ava Handley, Roger Pocock.

Neurons coordinate inter-tissue protein homeostasis to systemically manage cytotoxic stress. In response to neuronal mitochondrial stress, specific neuronal signals coordinate the systemic mitochondrial unfolded protein response (UPRmt) to promote organismal survival. Yet, whether chemical neurotransmitters are sufficient to control the UPRmt in physiological conditions is not well understood. Here, we show that gamma-aminobutyric acid (GABA) inhibits, and acetylcholine (ACh) promotes the UPRmt in the Caenorhabditis elegans intestine. GABA controls the UPRmt by regulating extra-synaptic ACh release through metabotropic GABAB receptors GBB-1/2. We find that elevated ACh levels in animals that are GABA-deficient or lack ACh-degradative enzymes induce the UPRmt through ACR-11, an intestinal nicotinic α7 receptor. This neuro-intestinal circuit is critical for non-autonomously regulating organismal survival of oxidative stress. These findings establish chemical neurotransmission as a crucial regulatory layer for nervous system control of systemic protein homeostasis and stress responses.

DOI: https://doi.org/10.1038/s41467-024-50973-y

Methods Mol Biol. 2024 ;2845 1-14

Fluorescence Microscopy and Immunoblotting for Mitophagy in Budding Yeast.

Yuki Nakayama, Koji Okamoto.

Selective removal of excess or damaged mitochondria is an evolutionarily conserved process that contributes to mitochondrial quality and quantity control. This catabolic event relies on autophagy, a membrane trafficking system that sequesters cytoplasmic constituents into double membrane-bound autophagosomes and delivers them to lysosomes (vacuoles in yeast) for hydrolytic degradation and is thus termed mitophagy. Dysregulation of mitophagy is associated with various diseases, highlighting its physiological relevance. In budding yeast, the pro-mitophagic single-pass membrane protein Atg32 is upregulated under prolonged respiration or nutrient starvation, anchored on the surface of mitochondria, and activated to recruit the autophagy machinery for the formation of autophagosomes surrounding mitochondria. In this chapter, we provide protocols to assess Atg32-mediated mitophagy using fluorescence microscopy and immunoblotting.

Keywords: Atg32; Budding yeast; Fluorescence microscopy; Immunoblotting; Mitochondria

DOI: https://doi.org/10.1007/978-1-0716-4067-8_1

Neurobiol Dis. 2024 Aug 06. pii: S0969-9961(24)00225-0. [Epub ahead of print] 106625

Disease-associated mutations in C-terminus of HSP70 interacting protein (CHIP) impair its ability to negatively regulate mitophagy.

Rebecca Earnshaw, Yu Tong Zhang, Gregory Heymann, Kazuko Fujisawa, Sarah Hui, Minesh Kapadia, Lorraine V Kalia, Suneil K Kalia.

C-terminus of HSP70 interacting protein (CHIP) is an E3 ubiquitin ligase and HSP70 cochaperone. Mutations in the CHIP encoding gene are the cause of two forms of neurodegenerative conditions: spinocerebellar ataxia autosomal dominant type 48 (SCA48) and autosomal recessive type 16 (SCAR16). The mechanisms underlying CHIP-associated diseases are currently unknown. Mitochondrial dysfunction, specifically dysfunction in mitochondrial autophagy (mitophagy), is increasingly being implicated in neurodegenerative diseases and loss of CHIP has been demonstrated to result in mitochondrial dysfunction in multiple animal models, although how CHIP is involved in mitophagy regulation has been previously unknown. Here, we demonstrate that CHIP acts as a negative regulator of the PTEN-induced kinase 1 (PINK1)/Parkin-mediated mitophagy pathway, promoting the degradation of PINK, impairing Parkin translocation to the mitochondria, and suppressing mitophagy in response to mitochondrial stress. We also show that loss of CHIP enhances neuronal mitophagy in a PINK1 and Parkin dependent manner in Caenorhabditis elegans. Furthermore, we find that multiple disease-associated mutations in CHIP dysregulate mitophagy both in vitro and in vivo in C. elegans neurons, a finding which could implicate mitophagy dysregulation in CHIP-associated diseases.

Keywords: Ataxia; Mitophagy; Neurodegeneration; SCA48; STUB1

DOI: https://doi.org/10.1016/j.nbd.2024.106625