bims-lypmec 2023-12-03 papers

Issue of 2023‒12‒03
five papers selected by
Satoru Kobayashi, New York Institute of Technology

Sci Signal. 2023 Nov 28. 16(813): eadn0652

Stress granules plug holes.

John F Foley.

Ruptures in lysosomal membranes stimulate the formation of stress granules that plug the holes to enable repair.

DOI: https://doi.org/10.1126/scisignal.adn0652

Eur J Clin Invest. 2023 Dec 01. e14138

Metabolic control of mitophagy.

Andreas Zimmermann, Frank Madeo, Abhinav Diwan, Junichi Sadoshima, Simon Sedej, Guido Kroemer, Mahmoud Abdellatif.

Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.

Keywords: AMPK; NAD; acetyl-CoA; ageing; ageing-related disease; metabolism; mitophagy; spermidine

DOI: https://doi.org/10.1111/eci.14138

J Biol Chem. 2023 Nov 25. pii: S0021-9258(23)02524-3. [Epub ahead of print] 105496

Intracellular sphingolipid sorting drives membrane phase separation in the yeast vacuole.

Hyesoo Kim, Itay Budin.

The yeast vacuole membrane can phase separate into ordered and disordered domains, a phenomenon that is required for micro-lipophagy under nutrient limitation. Despite its importance as a biophysical model and physiological significance, it is not yet resolved if specific lipidome changes drive vacuole phase separation. Here we report that the metabolism of sphingolipids (SLs) and their sorting into the vacuole membrane can control this process. We first developed a vacuole isolation method to identify lipidome changes during the onset of phase separation in early stationary stage cells. We found that early stationary stage vacuoles are defined by increased abundance of putative raft components, including 40% higher ergosterol content and a nearly 3-fold enrichment in complex SLs. These changes were not found in the corresponding whole cell lipidomes, indicating that lipid sorting is associated with domain formation. Several facets of SL composition - headgroup stoichiometry, chain lengths, and increased hydroxylations - were also markers of phase-separated vacuole lipidomes. To test SL function in vacuole phase separation, we carried out a systematic genetic dissection of their biosynthetic pathway. The abundance of CSLs controlled the extent of domain formation and associated micro-lipophagy processes, while their headgroup composition altered domain morphology. These results suggest that lipid trafficking can drive membrane phase separation in vivo and identify SLs as key mediators of this process in yeast.

Keywords: ergosterol; lipid rafts; lysosome; microautophagy; sphingolipids

DOI: https://doi.org/10.1016/j.jbc.2023.105496

J Mol Cell Cardiol. 2023 Nov 30. pii: S0022-2828(23)00166-9. [Epub ahead of print]186 111-124

Mechanistic target of rapamycin in regulating macrophage function in inflammatory cardiovascular diseases.

MariaSanta C Mangione, Jinhua Wen, Dian J Cao.

The mechanistic target of rapamycin (mTOR) is evolutionarily conserved from yeast to humans and is one of the most fundamental pathways of living organisms. Since its discovery three decades ago, mTOR has been recognized as the center of nutrient sensing and growth, homeostasis, metabolism, life span, and aging. The role of dysregulated mTOR in common diseases, especially cancer, has been extensively studied and reported. Emerging evidence supports that mTOR critically regulates innate immune responses that govern the pathogenesis of various cardiovascular diseases. This review discusses the regulatory role of mTOR in macrophage functions in acute inflammation triggered by ischemia and in atherosclerotic cardiovascular disease (ASCVD) and heart failure with preserved ejection fraction (HFpEF), in which chronic inflammation plays critical roles. Specifically, we discuss the role of mTOR in trained immunity, immune senescence, and clonal hematopoiesis. In addition, this review includes a discussion on the architecture of mTOR, the function of its regulatory complexes, and the dual-arm signals required for mTOR activation to reflect the current knowledge state. We emphasize future research directions necessary to understand better the powerful pathway to take advantage of the mTOR inhibitors for innovative applications in patients with cardiovascular diseases associated with aging and inflammation.

Keywords: Atherosclerosis; Inflammation; Ischemia; Macrophage; mTOR

DOI: https://doi.org/10.1016/j.yjmcc.2023.10.011

Autophagy. 2023 Nov 27.

TRIM22 facilitates autophagosome-lysosome fusion by mediating the association of GABARAPs and PLEKHM1.

Hansol Heo, Hyungsun Park, Myung Shin Lee, Jongyoon Kim, Juyeong Kim, Soon-Young Jung, Sun Kyeon Kim, Seongju Lee, Jaerak Chang.

Tripartite motif (TRIM) proteins are a large family of E3 ubiquitin ligases implicated in antiviral defense systems, tumorigenesis, and protein quality control. TRIM proteins contribute to protein quality control by regulating the ubiquitin-proteasome system, endoplasmic reticulum-associated degradation, and macroautophagy/autophagy. However, the detailed mechanisms through which various TRIM proteins regulate downstream events have not yet been fully elucidated. Herein, we identified a novel function of TRIM22 in the regulation of autophagy. TRIM22 promotes autophagosome-lysosome fusion by mediating the association of GABARAP family proteins with PLEKHM1, thereby inducing the autophagic clearance of protein aggregates, independent of its E3 ubiquitin ligase activity. Furthermore, a TRIM22 variant associated with early-onset familial Alzheimer disease interferes with autophagosome-lysosome fusion and autophagic clearance. These findings suggest TRIM22 as a critical autophagic regulator that orchestrates autophagosome-lysosome fusion by scaffolding autophagy-related proteins, thus representing a potential therapeutic target in neurodegenerative diseases.

Keywords: Alzheimer disease; PLEKHM1; TRIM22; autophagosome-lysosome fusion; autophagy

DOI: https://doi.org/10.1080/15548627.2023.2287925