bims-lypmec 2023-01-22 papers

bims-lypmec

Biomed News

on Lysosomal positioning and metabolism in cardiomyocytes

Issue of 2023–01–22
seven papers selected by
Satoru Kobayashi, New York Institute of Technology

The role of lysosomes in lipid homeostasis.
Functional restoration of lysosomes and mitochondria through modulation of AKT activity ameliorates senescence.
Targeting the Autophagy-Lysosome Pathway in a Pathophysiologically Relevant Murine Model of Reversible Heart Failure.
Nucleic acid uptake occurs independent of lysosomal acidification but dependent on ATP consumption during RNautophagy/DNautophagy.
TFEB-mediated lysosomal exocytosis alleviates high fat diet-induced lipotoxicity in the kidney.
A ratiometric fluorescent probe based on spiropyran in situ switching for tracking dynamic changes of lysosomal autophagy and anticounterfeiting.
Retromer oligomerization drives SNX-BAR coat assembly and membrane constriction.

Biol Chem. 2023 Jan 20.

The role of lysosomes in lipid homeostasis.

Florian Fröhlich, Ayelén González Montoro.

  Lipids function as the major building blocks of cellular membranes, as signaling molecules and as energy stores for metabolism. These important functions require a precise regulation of lipid biosynthesis, transport, turnover and storage. Lipids are exchanged among organelles through a sophisticated network of vesicular and non-vesicular transport routes. Lysosomes, as the main catabolic organelle, are at the center of this network and have recently evolved as one of the master-regulators of cellular lipid metabolism. Lipids from both endogenous and exogenous sources can be processed, sensed and sorted in and out of the lysosome. In this review, we focus on the role of the lysosome in lipid catabolism, transport and signaling. We highlight recent discoveries on the transport of lipids out of the lysosomal lumen and their exchange with other organelles via membrane contact sites. We also discuss the direct role of lysosomal lipids in the TORC1 signaling pathway, a regulator of cellular metabolism. Finally, we address lysosomal biogenesis, its role in the sorting of lipid metabolic enzymes and the dysregulation of these processes in disease.

Keywords:  TORC1; contact sites; lipids; lysosome; sphingolipids; vacuole

DOI:  https://doi.org/10.1515/hsz-2022-0287
Exp Gerontol. 2023 Jan 16. pii: S0531-5565(23)00012-8. [Epub ahead of print] 112091

Functional restoration of lysosomes and mitochondria through modulation of AKT activity ameliorates senescence.

Myeong Uk Kuk, Haneur Lee, Eun Seon Song, Yun Haeng Lee, Ji Yun Park, Subin Jeong, Hyung Wook Kwon, Youngjoo Byun, Sang Chul Park, Joon Tae Park.

  Senescence is a phenomenon defined by alterations in cellular organelles and is the primary cause of aging and aging-related diseases. Recent studies have shown that oncogene-induced senescence is driven by activation of serine/threonine protein kinases (AKT1, AKT2 and AKT3). In this study, we evaluated twelve AKT inhibitors and revealed GDC0068 as a potential agent to ameliorate senescence. Senescence-ameliorating effect was evident from the finding that GDC0068 yielded lysosomal functional recovery as observed by reduction in lysosomal mass and induction in autophagic flux. Furthermore, GDC0068-mediated restoration of lysosomal function activated the removal of dysfunctional mitochondria, resulting in restoration of mitochondrial function. Together, our findings revealed a unique mechanism by which senescence is recovered by functional restoration of lysosomes and mitochondria through modulation of AKT activity.

Keywords:  AKT; GDC0068; Lysosome; Mitochondria; Senescence amelioration

DOI:  https://doi.org/10.1016/j.exger.2023.112091
JACC Basic Transl Sci. 2022 Dec;7(12): 1214-1228

Targeting the Autophagy-Lysosome Pathway in a Pathophysiologically Relevant Murine Model of Reversible Heart Failure.

Sarah Evans, Xiucui Ma, Xiqiang Wang, Yana Chen, Chen Zhao, Carla J Weinheimer, Attila Kovacs, Brian Finck, Abhinav Diwan, Douglas L Mann.

  The key biological "drivers" that are responsible for reverse left ventricle (LV) remodeling are not well understood. To gain an understanding of the role of the autophagy-lysosome pathway in reverse LV remodeling, we used a pathophysiologically relevant murine model of reversible heart failure, wherein pressure overload by transaortic constriction superimposed on acute coronary artery (myocardial infarction) ligation leads to a heart failure phenotype that is reversible by hemodynamic unloading. Here we show transaortic constriction + myocardial infarction leads to decreased flux through the autophagy-lysosome pathway with the accumulation of damaged proteins and organelles in cardiac myocytes, whereas hemodynamic unloading is associated with restoration of autophagic flux to normal levels with incomplete removal of damaged proteins and organelles in myocytes and reverse LV remodeling, suggesting that restoration of flux is insufficient to completely restore myocardial proteostasis. Enhancing autophagic flux with adeno-associated virus 9-transcription factor EB resulted in more favorable reverse LV remodeling in mice that had undergone hemodynamic unloading, whereas overexpressing transcription factor EB in mice that have not undergone hemodynamic unloading leads to increased mortality, suggesting that the therapeutic outcomes of enhancing autophagic flux will depend on the conditions in which flux is being studied.

Keywords:  AAV9, adeno-associated virus 9; CMV, cytomegalovirus; CQ, chloroquine; GFP, green red fluorescent protein; HF, heart failure; HF-DB, TAC + MI mice that have undergone debanding; LFEF, left ventricular ejection fraction; LV, left ventricle; MI, myocardial infarction; RFP, red fluorescent protein; TAC, transaortic constriction; TEM, transmission electron microscopic; TFEB, transcription factor EB; autophagy; dsDNA, double stranded DNA; eGFP, enhanced green fluorescent protein; mTOR, mammalian target of rapamycin; reverse left ventricle remodeling

DOI:  https://doi.org/10.1016/j.jacbts.2022.06.003
Biochem Biophys Res Commun. 2023 Jan 02. pii: S0006-291X(22)01769-7. [Epub ahead of print]644 105-111

Nucleic acid uptake occurs independent of lysosomal acidification but dependent on ATP consumption during RNautophagy/DNautophagy.

Viorica Raluca Contu, Ryohei Sakai, Yuuki Fujiwara, Chihana Kabuta, Keiji Wada, Tomohiro Kabuta.

  RNautophagy/DNautophagy (RDA) is an autophagic process that refers to the direct uptake of nucleic acids by lysosomes for degradation. Autophagy relies on lysosomes and lysosomal acidification is crucial for the degradation of intracellular components. However, whether lysosomal acidification interferes with nucleic acid uptake during RDA is unclear. In this study, we focused on vacuolar H+-ATPase (V-ATPase), the major proton pump responsible for maintaining an acidic pH in lysosomes. Our results show that lysosomes take up nucleic acids independently of the intralysosomal acidic pH during RDA. Isolated lysosomes treated with bafilomycin A1, a potent V-ATPase inhibitor, did not degrade, but took up RNA at similar levels as the control lysosomes. Similarly, the knockdown of Atp6v1a, the gene that encodes V-ATPase catalytic subunit A, did not affect the RNA uptake ability of isolated lysosomes. In addition, we demonstrated that nucleic acid uptake by isolated lysosomes necessitates ATP consumption, although V-ATPase is not required for the uptake process. These results broaden our understanding of the mechanisms underlying nucleic acid degradation via autophagy.

Keywords:  Bafilomycin A1; DNautophagy; Lysosomal acidification; Nucleic acid uptake; RNautophagy; V-ATPase

DOI:  https://doi.org/10.1016/j.bbrc.2022.12.090
JCI Insight. 2023 Jan 17. pii: e162498. [Epub ahead of print]

TFEB-mediated lysosomal exocytosis alleviates high fat diet-induced lipotoxicity in the kidney.

Jun Nakamura, Takeshi Yamamoto, Yoshitsugu Takabatake, Tomoko Namba-Hamano, Satoshi Minami, Atsushi Takahashi, Jun Matsuda, Shinsuke Sakai, Hiroaki Yonishi, Shihomi Maeda, Sho Matsui, Isao Matsui, Takayuki Hamano, Masatomo Takahashi, Maiko Goto, Yoshihiro Izumi, Takeshi Bamba, Miwa Sasai, Masahiro Yamamoto, Taiji Matsusaka, Fumio Niimura, Motoko Yanagita, Shuhei Nakamura, Tamotsu Yoshimori, Andrea Ballabio, Yoshitaka Isaka.

  Obesity is a major risk factor for end-stage kidney disease. We previously found that lysosomal dysfunction and impaired autophagic flux contributed to lipotoxicity in obesity-related kidney disease, both in humans and experimental animal models. However, the regulatory factors involved in countering renal lipotoxicity are largely unknown. Here we found that palmitic acid (PA) strongly promoted dephosphorylation and nuclear translocation of transcription factor EB (TFEB) by inhibiting the mechanistic target of rapamycin kinase complex 1 (MTORC1) pathway in a Rag GTPase-dependent manner, although these effects gradually diminished after extended treatment. We then investigated the role of TFEB in the pathogenesis of obesity-related kidney disease. Proximal tubular epithelial cell (PTEC)-specific Tfeb-deficient mice fed a high-fat diet (HFD) exhibited greater phospholipid accumulation in enlarged lysosomes, which manifested as multilamellar bodies (MLBs). Activated TFEB mediated lysosomal exocytosis of phospholipids, which help reduce MLB accumulation in PTECs. Furthermore, HFD-fed PTEC-specific Tfeb-deficient mice showed autophagic stagnation and exacerbated injury upon renal ischemia-reperfusion. Finally, higher body mass index was associated with increased vacuolation and decreased nuclear TFEB in the proximal tubules of chronic kidney disease patients. These results indicate a critical role of TFEB-mediated lysosomal exocytosis in counteracting renal lipotoxicity.

Keywords:  Chronic kidney disease; Lysosomes; Metabolism; Nephrology; Obesity

DOI:  https://doi.org/10.1172/jci.insight.162498
Spectrochim Acta A Mol Biomol Spectrosc. 2023 Jan 13. pii: S1386-1425(23)00023-9. [Epub ahead of print]291 122338

A ratiometric fluorescent probe based on spiropyran in situ switching for tracking dynamic changes of lysosomal autophagy and anticounterfeiting.

Yujing Zuo, Yanfu Chai, Xiaofei Liu, Zhiming Gao, Xiaofeng Jin, Feng Wang, Yongjie Bai, Zhijun Zheng.

  Autophagy is the controlled breakdown of cellular components that dysfunctional or nonessential, and the decomposition products are further recycled and synthesized for the normal physiological activities of cells. Lysosomal autophagy has been implicated in cancer, neurological disorders, Parkinson's disease, etc. Therefore, it is necessary to develop a fluorescent probe that can clearly describe the process of lysosomal autophagy. However, there are currently limited fluorescent probes for ratiometric monitoring of the autophagic process in dual channels. To solve this problem, a fluorescent probe based on spiropyran with lysosomal targeting and pH response for ratiometric monitoring the autophagy process of lysosomes were designed. The sensitive response of the probe to pH in vitro was verified by UV and fluorescence spectrum tests. Meanwhile, the probe demonstrated the ability to monitor the intracellular pH fluctuations. In addition, the application of Lyso-SD in the field of anti-counterfeiting has been proposed based on the obvious photoluminescence ability of Lyso-SD under UV irradiation.

Keywords:  Autophagy; Bioimaging; Lysosomal targeting; Spiropyran; UV and pH responsive

DOI:  https://doi.org/10.1016/j.saa.2023.122338
EMBO J. 2023 Jan 16. 42(2): e112287

Retromer oligomerization drives SNX-BAR coat assembly and membrane constriction.

Navin Gopaldass, Maria Giovanna De Leo, Thibault Courtellemont, Vincent Mercier, Christin Bissig, Aurélien Roux, Andreas Mayer.

  Proteins exit from endosomes through tubular carriers coated by retromer, a complex that impacts cellular signaling, lysosomal biogenesis and numerous diseases. The coat must overcome membrane tension to form tubules. We explored the dynamics and driving force of this process by reconstituting coat formation with yeast retromer and the BAR-domain sorting nexins Vps5 and Vps17 on oriented synthetic lipid tubules. This coat oligomerizes bidirectionally, forming a static tubular structure that does not exchange subunits. High concentrations of sorting nexins alone constrict membrane tubes to an invariant radius of 19 nm. At lower concentrations, oligomers of retromer must bind and interconnect the sorting nexins to drive constriction. Constricting less curved membranes into tubes, which requires more energy, coincides with an increased surface density of retromer on the sorting nexin layer. Retromer-mediated crosslinking of sorting nexins at variable densities may thus tune the energy that the coat can generate to deform the membrane. In line with this, genetic ablation of retromer oligomerization impairs endosomal protein exit in yeast and human cells.

Keywords:  endosomes; lysosomes; membrane traffic; retromer; yeast

DOI:  https://doi.org/10.15252/embj.2022112287