Autophagy最新文献

The recruitment of ATG12-ATG5-ATG16L1 complex to phagophore mediated by the specific interaction between ATG16L1 and WIPI2, is pivotal to the formation of autophagosomes during macroautophagy. Recently, we reported that ATG16L1 contains two distinct WIPI2-binding sites, the previously reported WIPI2-binding site (WBS1), and the newly identified site (WBS2). By determining the crystal structures of WIPI2 with ATG16L1 WBS1 and WBS2 respectively, we uncovered that, unlike ATG16L1 WBS1, ATG16L1 WBS2 and its binding mechanism to WIPI2 are conserved from yeast to mammals. Using cell-based functional assays, we further demonstrated that the integrity of two WIPI2-binding sites of ATG16L1 is essential for normal autophagic flux. In summary, our study provided mechanistic insights into the interaction of two key autophagic proteins, ATG16L1 and WIPI2, and revealed a dual-binding-site mode adopted by ATG16L1 to associate with WIPI2.Abbreviations: ATG: autophagy-related protein; CCD: coiled-coil domain; ITC: isothermal titration calorimetry; PI3KC3-C1: class III phosphatidylinositol 3-kinase complex I; PtdIns3P: phosphatidylinositol-3-phosphate; ULK: Unc-51-like kinase; WBS: WIPI2-binding site; WIPI: WD repeat domain phosphoinositide-interacting protein.

Abbreviations: Mtb, Mycobacterium tuberculosis; TB, tuberculosis; NCOA4, nuclear receptor coactivator 4; p38, p38 protein kinase; AKT1, AKT serine/threonine kinase 1; TRIM21, tripartite motif containing 21; FTH1, ferritin heavy chain 1; FTL, ferritin light chain; HERC2, HECT and RLD domain containing E3 ubiquitin protein ligase 2.

Autophagy plays an important role in the normal growth and morphogenesis of a variety of tissues. Its role in uterine maturation, however, is not fully characterized. Recently, we reported that BECN1 (Beclin1)-dependent autophagy, but not apoptosis, is crucial for stem cell-mediated endometrial programming and the establishment of pregnancy in mice. Upon genetic and pharmacological inhibition of BECN1-mediated autophagy, female mice displayed severe endometrial structural and functional defects leading to infertility. Specifically, conditional loss of Becn1 in the uterus induces apoptosis and results in the gradual loss of endometrial progenitor stem cells. Importantly, the restoration of BECN1-driven autophagy, but not apoptosis in Becn1 conditionally ablated mice promoted normal uterine adenogenesis and morphogenesis. Overall, our findings emphasize the critical role of intrinsic autophagy in endometrial homeostasis and on the molecular underpinnings of uterine differentiation.

Myelodysplastic syndrome (MDS) is a clonal malignancy that develops from hematopoietic stem cells (HSCs), but the underlying mechanisms of MDS initiation are not well understood. The phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway is often dysregulated in MDS. To investigate how PI3K inactivation affects HSC function, we generated a mouse model in which three Class IA PI3K genes were deleted in hematopoietic cells. Surprisingly, PI3K deficiency caused cytopenias, reduced survival, and multilineage dysplasia with chromosomal abnormalities, consistent with MDS initiation. PI3K-deficient HSCs had impaired autophagy, and pharmacologic treatment with autophagy-inducing reagents improved HSC differentiation. Furthermore, a similar autophagic degradation defect was observed in MDS patient HSCs. Therefore, our study uncovered a crucial protective role for Class IA PI3K in maintaining autophagic flux in HSCs to preserve the balance between self-renewal and differentiation.

Lysosomal membrane permeabilization (LMP) has emerged as a significant component of cellular signaling pathway by which autophagy or cell death is regulated under many pathological situations including alcohol-associated liver disease (ALD). However, the mechanisms involved in the regulation of LMP in ALD remain obscure. Recently, we demonstrated that lipotoxicity serves as a causal factor to trigger LMP in hepatocytes. We identified that the apoptotic protein BAX (BCL2 associated X, apoptosis regulator) could recruit MLKL (mixed lineage kinase domain-like pseudokinase), a necroptotic executive protein, to lysosomes and induce LMP in various ALD models. Importantly, the pharmacological or genetic inhibition of BAX or MLKL protects hepatocytes from lipotoxicity-induced LMP. Thus, our study reveals a novel molecular mechanism that activation of BAX/MLKL signaling contributes to the pathogenesis of ALD through mediating lipotoxicity-induced LMP.Abbreviations: ALD: alcohol-associated liver disease; BAX: BCL2 associated X; LAMP2: lysosomal associated membrane protein 2; LMP: lysosomal membrane permeabilization; MLKL: mixed lineage kinase domain-like pseudokinase; PA: palmitic acid.

We have employed artificial intelligence to streamline the small molecule drug screening pipeline and identified the cholesterol-reducing compound probucol in the process. Probucol augmented mitophagy and prevented loss of dopaminergic neurons in flies and zebrafish challenged with mitochondrial toxins. Further dissection of the mechanism of action led to the identification of ABCA1, the target of probucol, as a mitophagy modulator. Probucol treatment regulates lipid droplet dynamics during mitophagy and ABCA1 is required for these effects. Here we will summarize the combination of in silico and cell-based screening that led us to identify and characterize probucol as a compound that enhances mitophagy and include thoughts about future directions for the topics explored in our study.Abbreviations: ABCA1: ATP binding cassette transporter protein 1; ATP: Adenosine tri-phosphate; CCCP: carbonyl cyanide m-chlorophenylhydrazone; DsRed: Discosoma red; FDA: Food and drug administration; GFP: Green fluorescent protein; LAMP: lysosome-associated membrane glycoproteins; LD: Lipid droplet; PD: Parkinson's disease; PINK: PTEN-induced kinase.

Lymphatic malformation (LM) is a vascular anomaly from lymphatic endothelial cells (ECs), and a fraction of the patients could progress to the deadly malignant lymphangiosarcoma (LAS). Using genetic tools to delete an essential autophagy gene Rb1cc1/FIP200 or its mutation specifically blocking its autophagy function, we demonstrated that autophagy inhibition abrogated LM progression to LAS although not affecting LM formation in our recently developed mouse model of LAS. Analysis of the mouse models in vivo and vascular tumor cells in vitro showed that autophagy inhibition reduced vascular tumor cell proliferation in vitro and tumorigenicity in vivo without affecting mTORC1 signaling as an oncogenic driver directly. Transcriptional profiling of autophagy-deficient tumor cells and further mechanistic studies revealed a role for osteopontin (OPN) and its downstream Jak/Stat3 signaling in mediating regulation of vascular tumor cells by autophagy. Together, these results support potential new prophylactic strategies to targeting autophagy and/or its downstream OPN expression to prevent progression of the benign LM to the malignant and deadly LAS.Abbreviations: LM: lymphatic malformation; EC: endothelial cell; LAS: lymphangiosarcoma; OPN: osteopontin; RB1CC1: RB1 Inducible Coiled-Coil 1; FIP200: FAK family-interacting protein of 200 kDa.

Understanding how viruses evade innate defenses to efficiently spread in their hosts is crucial in the fight against infections. In our study, we provided new insights on the first step initiating an LC3C (microtubule associated protein 1 light chain 3 gamma)-associated degradative pathway exploited by HIV-1 (human immunodeficiency virus type 1) to overcome the antiviral action of the restriction factor BST2 (bone marrow stromal cell antigen 2)/tetherin. We have uncovered an unsuspected and unconventional function of the autophagy-related protein ATG5 in the recognition and engagement of BST2 molecules trapping viruses at the plasma membrane, and directing them toward this LC3C-associated pathway for degradation. Additionally, we highlighted that HIV-1 uses this LC3C-associated process to attenuate the inflammatory responses triggered by BST2-mediated sensing of viruses.

Autophagy, an important cellular stress response mechanism, is often exploited by a variety of cancer cells to sustain rapid growth under stresses such as nutrient deprivation and hypoxia. Autophagy also plays a key role in tumor resistance to chemotherapy, radiotherapy or targeted therapy. Inhibition of autophagy is therefore a promising tumor treatment strategy. However, there is still a lack of effective autophagy inhibitors suitable for clinical use. Most drug development has focused on enzymes like the VPS34 and ULK1 kinases, or the cysteine protease ATG4B, which plays different roles in autophagy. We discovered a drug molecule Eltrombopag that inhibits the expression of autophagic lysosomal genes at the stage of transcriptional level, where the synthesis of these proteins has not really begun, by directly inhibiting the TFEB (transcription factor EB). This drug can improve the therapeutic effect of Temozolomide on glioblastoma treatment, further confirming the value of inhibiting autophagy in the treatment of cancer.Abbreviation: VPS34: vacuolar protein sorting 34; ULK1: unc-51 like autophagy activating kinase 1; TFEB: transcription factor EB; MITF: microphthalmia-associated transcription factor; TFE3: transcription factor E3; EO: Eltrombopag; ITC: isothermal titration calorimetry; bHLH-LZ: basic helix-loop-helix leucine zipper; LAMP1: lysosomal-associated membrane protein 1; CTSF: cathepsin F; HEXA: hexosaminidase subunit alpha.

Induction of autophagy is a primordial function of the cGAS-STING pathway. However, the molecular mechanisms regulating autophagosome formation during STING-induced autophagy remain largely unknown. Recently, we reported that STING directly interacts with WIPI2 to recruit WIPI2 onto STING-positive vesicles for LC3 lipidation and autophagosome formation. We found that STING and PtdIns3P competitively bind to the FRRG motif of WIPI2, resulting in a mutual inhibition between STING-induced and PtdIns3P-dependent autophagy. We also showed that STING-WIPI2 interaction is necessary for cells to clear cytoplasmic DNA and attenuate activated cGAS-STING signaling. In summary, by identifying the interaction between STING and WIPI2, our study revealed a mechanism that allows STING to bypass the canonical upstream machinery to induce autophagosome formation.Abbreviations: ATG: autophagy-related; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; cGAMP: cyclic GMP-AMP; cGAS: cyclic GMP-AMP synthase; ER: endoplasmic reticulum; ERGIC: ER-Golgi intermediate compartment; IRF3: interferon regulatory factor 3; PtdIns3P: phosphatidylinositol-3-phosphate; SQSTM1: sequestosome 1; STING: stimulator of interferon genes; TBK1: TANK-binding kinase 1; ULK1: unc-51 like autophagy activating kinase 1; WIPI2: WD repeat domain, phosphoinositide interacting 2.