Project description:Cargo receptors are well established elements of the selective autophagy in all eukaryotes. The NBR1-like family of such receptors is evolutionarily conserved, however plants have only one member of the family, which is a functional and structural hybrid of its two animal counterparts, p62 (SQSTM1) and NBR1. Examination of plants overexpressing NBR1 indicates that they are oversensitive to TOR inhibitors and have more autophagosomes than the parental lines. The observed changes in shoots suggested induction of ABA signalling pathway, what was further corroborated by the germination tests and the assay of ABA level. The transcriptome changes in roots, such as lower level of snoRNA and some tRNAs, suggested inhibition of ribosome biogenesis, what is supported by identification of RPS6, an important component of TOR-dependent translational control, as a novel partner of NBR1. Grant number: 2014/15/B/NZ3/04854 Grant funding source: National Science Centre (Poland) Grantee Name: Agnieszka Sirko Grant title: Upstream regulators and cellular targets of the selective autophagy cargo receptor AtNBR1 in different phases of sulfur deficiency in plants.
Project description:We used the CRISPR/Cas9 technique to construct nbr1-KO lines (KO1 and KO3) in order to test the effects of AtNBR1 depletion. Reduced expression of several ABA-up regulated genes were observed in shoots of the two KO lines. Grant number: 2014/15/B/NZ3/04854 Grant funding source: National Science Centre (Poland) Grantee Name: Agnieszka Sirko Grant title: Upstream regulators and cellular targets of the selective autophagy cargo receptor AtNBR1 in different phases of sulfur deficiency in plants.
Project description:Autophagy eliminates cytoplasmic content selected by autophagy receptors, which link cargoes to the membrane bound autophagosomal ubiquitin-like protein Atg8/LC3. Here, we discover a selective autophagy pathway for protein condensates formed by endocytic proteins. In this pathway, the endocytic yeast protein Ede1 functions as a selective autophagy receptor. Distinct domains within Ede1 bind Atg8 and mediate phase separation into condensates. Both properties are necessary for an Ede1-dependent autophagy pathway for endocytic proteins, which differs from regular endocytosis, does not involve other known selective autophagy receptors, but requires the core autophagy machinery. Cryo-electron tomography of Ede1-containing condensates – at the plasma membrane and in autophagic bodies – shows a phase-separated compartment at the beginning and end of the Ede1-mediated selective autophagy pathway. Our results imply an important role of autophagy in surveillance of membraneless compartments
Project description:Autophagy involvement in plant response to nitrogen, carbon and sulfur starvation was already reported, however the mechanisms responsible for its regulation and selectivity in such conditions were not yet investigated. We observed increased amounts of NBR1 transcript in plants exposed to sulfur deficit as compared to the control plants grown in nutrient sufficient conditions. This observation prompted us to investigate the role of this selective autophagy cargo receptor in plant response to sulfur deficit. Transcriptome analysis of the wild type and NBR overexpressing plants revealed differences in gene expression changes in response to sulfur deficit. Moreover, NBR1 overexpressors have significantly shorter roots than WT, when grown in nutrient deficient conditions in the presence of TOR kinase inhibitors, namely in the conditions leading to autophagy induction. Besides, NBR1 overexpression promoted stomata closure while NBR1 depletion stomata opening. Surprisingly, all lines had more closed stomata when grown in sulfur deficient than sulfur optimal conditions, what indicates that this effect is independent from NBR1. Similarly, ABA-dependent stomatal closure was independent from NBR1 and growth conditions. Cysteine also promoted stomatal closure in NBR1-independent way in plants grown in the optimal medium but in contrast, reduced the number of open stomata in plants from sulfur deficient medium. Interaction network analysis of the proteins co-purifying with NBR1 revealed links with proteins involved in degradation systems, and endosomal trafficking and a surprizing connection with nuclear transport. In addition, several proteins co-purifying with NBR1 were found only in sulfur deficient conditions. One of them, ribosomal protein S6 (RPS6) was further confirmed as a direct NBR1 interactor. Localization of the RPS6 interaction sites in NBR1 indicated that ubiquitin binding domain of NBR1 is not required for this interaction what means that it is rather not the classical “ubiquitinated target - autophagy receptor” interaction.
Project description:We used the CRISPR/Cas9 technique to construct nbr1-KO lines (KO1 and KO3) in order to test the effects of AtNBR1 depletion. Reduced expression of several ABA-up regulated genes were observed in shoots of the two KO lines. Grant number: 2014/15/B/NZ3/04854 Grant funding source: National Science Centre (Poland) Grantee Name: Agnieszka Sirko Grant title: Upstream regulators and cellular targets of the selective autophagy cargo receptor AtNBR1 in different phases of sulfur deficiency in plants.
Project description:DNA repair and autophagy are distinct biological processes vital for cell survival. Although autophagy helps maintain genome stability, there is no evidence of its direct role in the repair of DNA lesions. We discovered that in human cells, lysosomes process Topoisomerase 1-cleavage complexes (TOP1cc) DNA lesion. Selective degradation of TOP1cc by autophagy directs DNA damage repair and cell survival at clinically relevant doses of Topoisomerase 1 inhibitors. TOP1cc are exported from the nucleus to lysosomes through transient alteration of the nuclear envelope, and independent of the proteasome. Mechanistically, the autophagy receptor TEX264 acts as a TOP1cc sensor at DNA replication forks, triggering TOP1cc processing by the p97 ATPase and mediating TOP1cc delivery to lysosomes dependent on MRE11 nuclease and ATR kinase. We found an evolutionary conserved role for selective autophagy in DNA damage repair that enables cell survival, protects genome stability, and is clinically relevant for colorectal cancer patients.
Project description:Glucocorticoids are widely used to treat inflammatory disorders. Prolonged use results in side effects including osteoporosis, diabetes and obesity. The selective glucocorticoid receptor (GR) modulator Compound A (CpdA) exhibits an inflammation-suppressive effect, largely in absence of detrimental side effects. To understand the mechanistic differences between the classic glucocorticoid dexamethasone (DEX) and CpdA, we looked for proteins oppositely regulated using an unbiased proteomics approach. We found that the autophagy receptor p62 but not GR mediates the anti-inflammatory action of CpdA in macrophages. CpdA drives the upregulation of p62 by recruiting the NRF2 transcription factor to its promoter. Contrarily, the classic GR ligand dexamethasone recruits GR to p62 and other NRF2 controlled gene promoters, resulting in gene downregulation. Both DEX and CpdA are able to induce autophagy, albeit in a cell-type and time-dependent manner. Suppression of LPS-induced IL-6 and MCP1 genes in bone marrow-derived macrophages by CpdA is hampered upon p62 silencing, confirming that p62 is essential for the anti-inflammatory capacity of CpdA. Together, these results demonstrate how off-target mechanisms of selective GR ligands may establish a more efficient anti-inflammatory therapy
Project description:Autophagy is a conserved metabolic pathway that is central to many diseases. Recently, there has been a lot of interest in targeting autophagy with small molecule inhibitors as a possible therapeutic strategy. However, many of the compounds used for autophagy are non-selective. Here, we explored the inhibition of autophagy in pancreatic cancer cells using established selective small molecule inhibitors and discovered an unexpected link between the autophagy pathway and progression through the cell cycle. RNA-Seq analysis revealed that treatments with inhibitors that have different autophagy pathway targets block cell replication and activate other metabolic pathways to compensate for the blockade in autophagy. An unbiased screen looking for known drugs that might synergize with autophagy inhibition revealed new combination treatments that might provide a blueprint for therapeutic approaches to pancreatic cancer. The drugs quizartinib and THZ1 showed a strong synergistic effect in pancreatic cells with autophagy inhibition.
Project description:The protein p62/Sequestosome 1 (p62) has been described as a selective autophagy receptor and independently as a platform for pro-inflammatory and other intracellular signaling. How these seemingly disparate functional roles of p62 are coordinated has not been resolved. Here we show that TAK1, a kinase involved in immune signaling, negatively regulates p62 action in autophagy.