bims-nocaut 2022-10-16 papers

Issue of 2022–10–16
three papers selected by
Quentin Frenger, University of Strasbourg

Nat Commun. 2022 Oct 10. 13(1): 5986

Membrane-assisted assembly and selective secretory autophagy of enteroviruses.

Selma Dahmane, Adeline Kerviel, Dustin R Morado, Kasturika Shankar, Björn Ahlman, Michael Lazarou, Nihal Altan-Bonnet, Lars-Anders Carlson.

Enteroviruses are non-enveloped positive-sense RNA viruses that cause diverse diseases in humans. Their rapid multiplication depends on remodeling of cytoplasmic membranes for viral genome replication. It is unknown how virions assemble around these newly synthesized genomes and how they are then loaded into autophagic membranes for release through secretory autophagy. Here, we use cryo-electron tomography of infected cells to show that poliovirus assembles directly on replication membranes. Pharmacological untethering of capsids from membranes abrogates RNA encapsidation. Our data directly visualize a membrane-bound half-capsid as a prominent virion assembly intermediate. Assembly progression past this intermediate depends on the class III phosphatidylinositol 3-kinase VPS34, a key host-cell autophagy factor. On the other hand, the canonical autophagy initiator ULK1 is shown to restrict virion production since its inhibition leads to increased accumulation of virions in vast intracellular arrays, followed by an increased vesicular release at later time points. Finally, we identify multiple layers of selectivity in virus-induced autophagy, with a strong selection for RNA-loaded virions over empty capsids and the segregation of virions from other types of autophagosome contents. These findings provide an integrated structural framework for multiple stages of the poliovirus life cycle.

DOI: https://doi.org/10.1038/s41467-022-33483-7

J Immunol Res. 2022 ;2022 1481154

NLRP3 Inflammasome Simultaneously Involved in Autophagy and Phagocytosis of THP-1 Cells to Clear Aged Erythrocytes.

Qin Li, Fengyong Zhao, Jiamin Zhang, Ying Yang, Zhonghui Guo, Chen Wang, Qixiu Yang, Ying Sun, Ziyan Zhu.

Autophagy and phagocytosis are two important processes that capture and digest materials found in cellular interiors and exteriors, respectively. Aged red blood cells (RBCs) are cleared by phagocytes in vivo. We focused on determining whether autophagy occurs after phagocytes swallow sunset erythrocytes, and whether the degree of autophagy is related to scavenging ability of phagocytes to erythrocytes. In addition, the ability of NLR family pyrin domain containing protein 3 (NLRP3) inflammasome to regulate erythrocyte clearance by phagocytes and its association with autophagy-related protein 16-like protein 1 (ATG16L1) are confirmed. We constructed a stable and low-NLRP3 expression THP-1 cell line using CRISPR/Cas9 technology. The analysis of erythrocyte clearance and autophagy of THP-1 cells with low NLRP3 expression showed that autophagy changes together when THP-1 engulfs aged RBCs. The occurrence of autophagy was dominated by microtubule-associated protein 1A/1B-light chain 3- (LC3-) associated phagocytosis accompanied by canonical autophagy. A negative correlation exists between the clearance of RBCs by THP-1 cells and the degree of autophagy. Downregulating the expression of NLRP3 in THP-1 cells can simultaneously inhibit the scavenging ability of THP-1 to erythrocytes and the degree of autophagy. In addition, the autophagy inhibitor bafilomycin A1 (BafA1) can enhance the phagocytosis ability of THP-1 to erythrocytes and promote the NLRP3 activation in THP-1 cells, while the autophagy inducer rapamycin inhibits the phagocytosis ability of THP-1 to RBCs and downregulates the NLRP3 activation. Results showed that autophagy and phagocytosis may be dynamic balance processes that can provide sufficient nutrition and energy to cells. Choosing NLRP3 as a target may regulate the phagocytic ability and the degree of autophagy in the meantime. These findings may be a potential strategy for regulating the clearance rate of phagocytes to aged RBCs and the secretion of proinflammatory cytokines to ensure transfusion safety.

DOI: https://doi.org/10.1155/2022/1481154

Aging (Albany NY). 2022 Oct 13. 14(undefined):

AR12 increases BAG3 expression which is essential for Tau and APP degradation via LC3-associated phagocytosis and macroautophagy.

Paul Dent, Laurence Booth, Jane L Roberts, Andrew Poklepovic, Jennifer Martinez, Derek Cridebring, Eric M Reiman.

We defined the mechanisms by which the chaperone ATPase inhibitor AR12 and the multi-kinase inhibitor neratinib interacted to reduce expression of Tau and amyloid-precursor protein (APP) in microglia and neuronal cells. AR12 and neratinib interacted to increase the phosphorylation of eIF2A S51 and the expression of BAG3, Beclin1 and ATG5, and in parallel, enhanced autophagosome formation and autophagic flux. Knock down of BAG3, Beclin1 or ATG5 abolished autophagosome formation and significantly reduced degradation of p62, LAMP2, Tau, APP, and GRP78 (total and plasma membrane). Knock down of Rubicon, a key component of LC3-associated phagocytosis (LAP), significantly reduced autophagosome formation but not autophagic flux and prevented degradation of Tau, APP, and cell surface GRP78, but not ER-localized GRP78. Knock down of Beclin1, ATG5 or Rubicon or over-expression of GRP78 prevented the significant increase in eIF2A phosphorylation. Knock down of eIF2A prevented the increase in BAG3 expression and significantly reduced autophagosome formation, autophagic flux, and it prevented Tau and APP degradation. We conclude that AR12 has the potential to reduce Tau and APP levels in neurons and microglia via the actions of LAP, endoplasmic reticulum stress signaling and macroautophagy. We hypothesize that the initial inactivation of GRP78 catalytic function by AR12 facilitates an initial increase in eIF2A phosphorylation which in turn is essential for greater levels of eIF2A phosphorylation, greater levels of BAG3 and macroautophagy and eventually leading to significant amounts of APP/Tau degradation.

Keywords: AR12; Alzheimer’s disease; GRP78; LAP / LANDO; macroautophagy

DOI: https://doi.org/10.18632/aging.204337