TBK1 is part of a galectin 8 dependent membrane damage recognition complex and drives autophagy upon Adenovirus endosomal escape

Abstract

Intracellular pathogens cause membrane distortion and damage as they enter host cells. Cells perceive these membrane alterations as danger signals and respond by activating autophagy. This response has primarily been studied during bacterial invasion, and only rarely in viral infections. Here, we investigate the cellular response to membrane damage during adenoviral entry. Adenoviruses and their vector derivatives, that are an important vaccine platform against SARS-CoV-2, enter the host cell by endocytosis followed by lysis of the endosomal membrane. We previously showed that cells mount a locally confined autophagy response at the site of endosomal membrane lysis. Here we describe the mechanism of autophagy induction: endosomal membrane damage activates the kinase TBK1 that accumulates in its phosphorylated form at the penetration site. Activation and recruitment of TBK1 require detection of membrane damage by galectin 8 but occur independently of classical autophagy receptors or functional autophagy. Instead, TBK1 itself promotes subsequent autophagy that adenoviruses need to take control of. Depletion of TBK1 reduces LC3 lipidation during adenovirus infection and restores the infectivity of an adenovirus mutant that is restricted by autophagy. By comparing adenovirus-induced membrane damage to sterile lysosomal damage, we implicate TBK1 in the response to a broader range of types of membrane damage. Our study thus highlights an important role for TBK1 in the cellular response to adenoviral endosome penetration and places TBK1 early in the pathway leading to autophagy in response to membrane damage.

A mechanism that transduces lysosomal damage signals to stress granule formation for cell survival

“…Adenovirus enters cells through endocytosis and damages lysosomes by releasing its protease, enabling access to the cytosol for replication(A. Barlan et al, 2011; Greber et al, 1996; Pied et al, 2022; Wiethoff et al, 2015). We employed the wildtype human adenovirus species C2 (HAdV-C2 WT ) and its protease-deficient mutant TS1 (HAdV-C2 TS1 ), the latter lacking the ability to damage lysosomes(Gallardo et al, 2021; Greber et al, 1996; Martinez et al, 2015).…”

Lysosomal TBK1 Responds to Amino Acid Availability to Relieve Rab7-Dependent mTORC1 Inhibition

“…TBK1 is well characterized for phosphorylating multiple physiologically important substrates related to innate immunity and organelle quality control (Fitzgerald et al, 2003; Harding et al, 2021; Moore and Holzbaur, 2016; Pied et al, 2022; Weidberg and Elazar, 2011). However, two unbiased phospho-proteomics studies identified Rab7 as a major target for TBK1 (Heo et al, 2018; Ritter et al, 2020).…”

“…Cells must also monitor and manage lysosome integrity to ensure that lysosomes remain intact and lysosomal enzymes do not leak into the cytoplasm (Bohannon and Hanson, 2020; Yang and Tan, 2023). When lysosomes suffer severe damage that cannot be repaired, TANK-binding kinase 1 (TBK1) helps cells to clear severely damaged lysosomes via the process known as lysophagy where the damaged lysosomes are engulfed by autophagosomes and then delivered to intact lysosomes for degradation (Eapen et al, 2021; Hung et al, 2013; Maejima et al, 2013; Pied et al, 2022; Vargas et al, 2023). TBK1 also plays important roles in the autophagic clearance of damaged mitochondria and in signaling related to innate immunity (Fitzgerald et al, 2003; Harding et al, 2021; Heo et al, 2018; Moore and Holzbaur, 2016; Pomerantz and Baltimore, 1999).…”

Identification of TBK1 inhibitors against breast cancer using a computational approach supported by machine learning

“…This orchestrated response not only aids in combating viral infections but also assumes a central role in the broader antiviral defense mechanism of the host organism. Furthermore, TBK1’s influence extends beyond the realm of immune responses, encompassing essential cellular processes such as autophagy and mitochondrial quality control ( Pied et al, 2022 ). Its association with autophagy underscores its role in the degradation and recycling of impaired cellular constituents, thereby contributing to cellular homeostasis and survival ( Xiao et al, 2017 ).…”