bims-apauto 2021-07-11 papers

Issue of 2021–07–11
six papers selected by
Su Hyun Lee, Seoul National University

Autophagy. 2021 Jul 07. 1-18

RAB7 activity is required for the regulation of mitophagy in oocyte meiosis and oocyte quality control during ovarian aging.

Xin Jin, Kehan Wang, Lu Wang, Wenwen Liu, Chi Zhang, Yuexin Qiu, Wei Liu, Huiyu Zhang, Dong Zhang, Zhixia Yang, Tinghe Wu, Jing Li.

There is increasing evidence that mitophagy, a specialized form of autophagy to degrade and clear long-lived or damaged mitochondria, is impaired in aging and age-related disease. Previous study has demonstrated the obesity-exposed oocytes accumulate and transmit damaged mitochondria due to an inability to activate mitophagy. However, it remains unknown whether mitophagy functions in oocyte and what's the regulatory mechanism in oocyte aging. In the study, when fully grown oocytes were treated with CCCP, an uncoupling agent to induce mitophagy, we found the activation of the PRKN-mediated mitophagy pathway accompanied the blockage of meiosis at metaphase I stage. Our result then demonstrated its association with the decreased activity of RAB7 and all the observed defects in CCCP treated oocytes could be effectively rescued by microinjection of mRNA encoding active RAB7Q67L or treatment with the RAB7 activator ML098. Further study indicated PRKN protein level as a rate-limiting factor to facilitate degradation of RAB7 and its GEF (guanine nucleotide exchange factor) complex CCZ1-MON1 through the ubiquitin-proteasome system. In GV oocytes collected during ovarian aging, we found the age-related increase of PINK1 and PRKN proteins and a significant decrease of RAB7 which resulted in defects of mitophagosome formation and the accumulation of damaged mitochondria. The age-related retardation of female fertility was improved after in vivo treatment of ML098. Thus, RAB7 activity is required to maintain the balance between mitophagy and chromosome stability and RAB7 activator is a good candidate to ameliorate age-related deterioration of oocyte quality.Abbreviations: ATG9: autophagy related 9A; ATP: adenosine triphosphate; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; CCZ1: CCZ1 vacuolar protein trafficking and biogenesis associated; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GAPs: GTPase-activating proteins; GEF: guanine nucleotide exchange factor; GV: germinal vesicle; GVBD: germinal vesicle breakdown; LAMP1: lysosomal-associated membrane protein 1; MI: metaphase I stage of meiosis; MII: metaphase II stage of meiosis; Mito: MitoTracker; mtDNA: mitochondrial DNA; MON1: MON1 homolog, secretory trafficking associated; OPTN: optineurin; PINK1: PTEN induced putative kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; RAB7: RAB7, member RAS oncogene family; ROS: reactive oxygen species; TEM: transmission electron microscopy; TOMM20/TOM20: translocase of outer mitochondrial membrane 20; TUBB: tubulin, beta; UB: ubiquitin.

Keywords: Aging; PRKN; RAB7; meiosis; mitophagy; oocyte

DOI: https://doi.org/10.1080/15548627.2021.1946739

Sci Rep. 2021 Jul 05. 11(1): 13863

FIP200 controls the TBK1 activation threshold at SQSTM1/p62-positive condensates.

David Schlütermann, Niklas Berleth, Jana Deitersen, Nora Wallot-Hieke, Olena Friesen, Wenxian Wu, Fabian Stuhldreier, Yadong Sun, Lena Berning, Annabelle Friedrich, María José Mendiburo, Christoph Peter, Constanze Wiek, Helmut Hanenberg, Anja Stefanski, Kai Stühler, Björn Stork.

The protein kinase TBK1 is a central regulator of innate immune responses and autophagy, and ablation of either function has been linked to neuroinflammatory or degenerative diseases. Autophagy is an intracellular process that recycles old or damaged proteins and organelles. In recent years, the TBK1-dependent regulation of autophagy pathways has been characterized. However, the autophagy-dependent regulation of TBK1 activity awaits further clarification. Here, we observed that TBK1 is recruited to SQSTM1/p62-containing aggregates via the selective autophagy receptor TAX1BP1. In these aggregates, TBK1 phosphorylates SQSTM1/p62 at serine 403 and thus presumably regulates the efficient engulfment and clearance of these structures. We found that TBK1 activation is strongly increased if FIP200, a component of the autophagy-inducing ULK1 complex, is not present or cannot bind to TAX1BP1. Given our collective findings, we hypothesize that FIP200 ensures the inducible activation of TBK1 at SQSTM1/p62 condensates.

DOI: https://doi.org/10.1038/s41598-021-92408-4

Autophagy. 2021 Jul 07. 1-3

A new insight into the lens: cytosolic PLAAT phospholipases degrade organelles to make the lens transparent.

Hideaki Morishita, Tomoya Eguchi, Noboru Mizushima.

All membrane-bound organelles are degraded during the terminal differentiation of lens fiber cells. How these organelles are degraded has been a long-standing question in biology. We recently revealed that PLAAT (phospholipase A and acyltransferase)-family phospholipases degrade organelles in the lens independently of macroautophagy. Here, we discuss the mechanism and physiological relevance of this new mode of intracellular degradation.

Keywords: Autophagy; HRASLS; PLA2G16; PLAAT; lens; mice; organelle degradation; phospholipase; zebrafish

DOI: https://doi.org/10.1080/15548627.2021.1950372

Cell Death Dis. 2021 Jul 08. 12(7): 686

c-FLIP regulates autophagy by interacting with Beclin-1 and influencing its stability.

Luana Tomaipitinca, Simonetta Petrungaro, Pasquale D'Acunzo, Angelo Facchiano, Amit Dubey, Salvatore Rizza, Federico Giulitti, Eugenio Gaudio, Antonio Filippini, Elio Ziparo, Francesco Cecconi, Claudia Giampietri.

c-FLIP (cellular FLICE-like inhibitory protein) protein is mostly known as an apoptosis modulator. However, increasing data underline that c-FLIP plays multiple roles in cellular homoeostasis, influencing differently the same pathways depending on its expression level and isoform predominance. Few and controversial data are available regarding c-FLIP function in autophagy. Here we show that autophagic flux is less effective in c-FLIP-/- than in WT MEFs (mouse embryonic fibroblasts). Indeed, we show that the absence of c-FLIP compromises the expression levels of pivotal factors in the generation of autophagosomes. In line with the role of c-FLIP as a scaffold protein, we found that c-FLIPL interacts with Beclin-1 (BECN1: coiled-coil, moesin-like BCL2-interacting protein), which is required for autophagosome nucleation. By a combination of bioinformatics tools and biochemistry assays, we demonstrate that c-FLIPL interaction with Beclin-1 is important to prevent Beclin-1 ubiquitination and degradation through the proteasomal pathway. Taken together, our data describe a novel molecular mechanism through which c-FLIPL positively regulates autophagy, by enhancing Beclin-1 protein stability.

DOI: https://doi.org/10.1038/s41419-021-03957-5

Nat Struct Mol Biol. 2021 Jul 08.

Membrane perturbation by lipidated Atg8 underlies autophagosome biogenesis.

Tatsuro Maruyama, Jahangir Md Alam, Tomoyuki Fukuda, Shun Kageyama, Hiromi Kirisako, Yuki Ishii, Ichio Shimada, Yoshinori Ohsumi, Masaaki Komatsu, Tomotake Kanki, Hitoshi Nakatogawa, Nobuo N Noda.

Autophagosome biogenesis is an essential feature of autophagy. Lipidation of Atg8 plays a critical role in this process. Previous in vitro studies identified membrane tethering and hemi-fusion/fusion activities of Atg8, yet definitive roles in autophagosome biogenesis remained controversial. Here, we studied the effect of Atg8 lipidation on membrane structure. Lipidation of Saccharomyces cerevisiae Atg8 on nonspherical giant vesicles induced dramatic vesicle deformation into a sphere with an out-bud. Solution NMR spectroscopy of Atg8 lipidated on nanodiscs identified two aromatic membrane-facing residues that mediate membrane-area expansion and fragmentation of giant vesicles in vitro. These residues also contribute to the in vivo maintenance of fragmented vacuolar morphology under stress in fission yeast, a moonlighting function of Atg8. Furthermore, these aromatic residues are crucial for the formation of a sufficient number of autophagosomes and regulate autophagosome size. Together, these data demonstrate that Atg8 can cause membrane perturbations that underlie efficient autophagosome biogenesis.

DOI: https://doi.org/10.1038/s41594-021-00614-5

JCI Insight. 2021 Jul 06. pii: 138183. [Epub ahead of print]

Aldehyde dehydrogenase 2 protects against acute kidney injury by regulating autophagy via Beclin-1 pathway.

Tonghui Xu, Jialin Guo, Maozeng Wei, Jiali Wang, Kehui Yang, Chang Pan, Jiaojiao Pang, Li Xue, Qiu-Huan Yuan, Mengyang Xue, Jian Zhang, Wentao Sang, Tangxing Jiang, Yuguo Chen, Feng Xu.

The mitochondrial enzyme acetaldehyde dehydrogenase 2 (ALDH2) catalyzes the detoxification of acetaldehyde and endogenous lipid aldehydes. Approximately 40% of East Asians, accounting for 8% of the human population, carry the E504K mutation in ALDH2 that leads to accumulation of toxic reactive aldehydes and increases the risk for cardiovascular disease (CVD), cancer and Alzheimer's, among other diseases. However, the role of ALDH2 in acute kidney injury (AKI) remains poorly defined and is therefore the subject of the present study using various cellular and organismal sources. In murine models in which AKI was induced by either the contrast agent Iohexol or renal ischemia/reperfusion, knockout and activation/overexpression of ALDH2 was associated with increased and decreased renal injury, respectively. In murine renal tubular epithelial cells (RTECs), ALDH2 upregulated Beclin-1 expression, promoted autophagy activation and eliminated reactive oxygen species (ROS). In vivo and in vitro, both 3-MA and Beclin-1 siRNAs inhibited autophagy and abolished ALDH2 mediated renoprotection. In mice with Iohexol induced AKI, ALDH2 knockdown in RTECs using AAV-shRNA impaired autophagy activation and aggravated renal injury. In human renal proximal tubular epithelial HK-2 cells exposed to Iohexol, ALDH2 activation potentiated autophagy and attenuated apoptosis. In mice with AKI induced by renal ischemia ischemia/reperfusion, ALDH2 overexpression or pretreatment regulated autophagy mitigating apoptosis of RTECs and renal injury. Our data collectively substantiate a critical role of ALDH2 in AKI via autophagy activation involving the Beclin-1 pathway.

Keywords: Autophagy; Hypoxia; Nephrology

DOI: https://doi.org/10.1172/jci.insight.138183