Proteome-wide analysis of chaperone-mediated autophagy targeting motifs

Fischer

The Journal of Immunology

et al. 2020

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium that induces cell death of macrophages as a key virulence strategy. We have previously demonstrated that the induction of macrophage death is dependent on the host's type I IFN (IFN-I) response. IFN-I signaling has been shown to induce tripartite motif (TRIM) 21, an E3 ubiquitin ligase with critical functions in autoimmune disease and antiviral immunity. However, the importance and regulation of TRIM21 during bacterial infection remains poorly understood. In this study, we investigated the role of TRIM21 upon S. Typhimurium infection of murine bone marrow-derived macrophages. Although Trim21 expression was induced in an IFN-I-dependent manner, we found that TRIM21 levels were mainly regulated posttranscriptionally. Following TLR4 activation, TRIM21 was transiently degraded via the lysosomal pathway by chaperone-mediated autophagy (CMA). However, S. Typhimurium-induced mTORC2 signaling led to phosphorylation of Akt at S473, which subsequently impaired TRIM21 degradation by attenuating CMA. Elevated TRIM21 levels promoted macrophage death associated with reduced transcription of NF erythroid 2-related factor 2 (NRF2)-dependent antioxidative genes. Collectively, our results identify IFN-I-inducible TRIM21 as a negative regulator of innate immune responses to S. Typhimurium and a previously unrecognized substrate of CMA. To our knowledge, this is the first study reporting that a member of the TRIM family is degraded by the lysosomal pathway.

Section: Discussionmentioning

confidence: 99%

Section: Trim21 Is Degraded By Cmamentioning

confidence: 99%

TRIM21 Is Targeted for Chaperone-Mediated Autophagy during Salmonella Typhimurium Infection

Fischer

The Journal of Immunology

et al. 2020

Oxidative Medicine and Cellular Longevity

“…CMA [98] is a selective and direct elimination system, without building of a vesicle and highly selective for a particular group of soluble cytosolic proteins containing the pentapeptide KFERQ as recognition sequence. In brief, the motif consists of a glutamine (Q) flanked on either side by one or two of the positively charged residues K and R; one or two of the hydrophobic residues I, L, V, and F; and one of the negatively charged residues D and E [99]. Therefore, several different combinations of amino acids can result in a KFERQlike motif within the sequence of a protein.…”

Section: Endoplasmic Reticulum-associated Protein Degradation (Erad)mentioning

confidence: 99%

Proteostasis Failure in Neurodegenerative Diseases: Focus on Oxidative Stress

Höhn

Tramutola

Cascella

2020

106

Protein homeostasis or proteostasis is an essential balance of cellular protein levels mediated through an extensive network of biochemical pathways that regulate different steps of the protein quality control, from the synthesis to the degradation. All proteins in a cell continuously turn over, contributing to development, differentiation, and aging. Due to the multiple interactions and connections of proteostasis pathways, exposure to stress conditions may cause various types of protein damage, altering cellular homeostasis and disrupting the entire network with additional cellular stress. Furthermore, protein misfolding and/or alterations during protein synthesis results in inactive or toxic proteins, which may overload the degradation mechanisms. The maintenance of a balanced proteome, preventing the formation of impaired proteins, is accomplished by two major catabolic routes: the ubiquitin proteasomal system (UPS) and the autophagy-lysosomal system. The proteostasis network is particularly important in nondividing, long-lived cells, such as neurons, as its failure is implicated with the development of neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis. These neurological disorders share common risk factors such as aging, oxidative stress, environmental stress, and protein dysfunction, all of which alter cellular proteostasis, suggesting that general mechanisms controlling proteostasis may underlay the etiology of these diseases. In this review, we describe the major pathways of cellular proteostasis and discuss how their disruption contributes to the onset and progression of neurodegenerative diseases, focusing on the role of oxidative stress.

“…CMA is a selective form of autophagy and starts with the binding of Hsc70 onto a sequence of five peptides (KFERQ) in the substrates [17,21]. Approximately 40% of the mammalian proteins contain this motif and can become targets of CMA if the motif is exposed [21,22]. After substrate recognition, Hsc70 binds to Lamp2a on lysosomes, which then multimerizes and initiates translocation of the unfolded protein into the lysosomal lumen.…”

Section: Execution Of Autophagymentioning

confidence: 99%

The Role of Autophagy in Pancreatic Cancer: From Bench to the Dark Bedside

Görgülü

Diakopoulos

Kaya-Aksoy

et al. 2020

Cells

Pancreatic cancer is one of the deadliest cancer types urgently requiring effective therapeutic strategies. Autophagy occurs in several compartments of pancreatic cancer tissue including cancer cells, cancer associated fibroblasts, and immune cells where it can be subjected to a multitude of stimulatory and inhibitory signals fine-tuning its activity. Therefore, the effects of autophagy on pancreatic carcinogenesis and progression differ in a stage and context dependent manner. In the initiation stage autophagy hinders development of preneoplastic lesions; in the progression stage however, autophagy promotes tumor growth. This double-edged action of autophagy makes it a hard therapeutic target. Indeed, autophagy inhibitors have not yet shown survival improvements in clinical trials, indicating a need for better evaluation of existing results and smarter targeting techniques. Clearly, the role of autophagy in pancreatic cancer is complex and many aspects have to be considered when moving from the bench to the bedside.