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Nature Sep 2022Lysosomal dysfunction has been increasingly linked to disease and normal ageing. Lysosomal membrane permeabilization (LMP), a hallmark of lysosome-related diseases, can...
Lysosomal dysfunction has been increasingly linked to disease and normal ageing. Lysosomal membrane permeabilization (LMP), a hallmark of lysosome-related diseases, can be triggered by diverse cellular stressors. Given the damaging contents of lysosomes, LMP must be rapidly resolved, although the underlying mechanisms are poorly understood. Here, using an unbiased proteomic approach, we show that LMP stimulates a phosphoinositide-initiated membrane tethering and lipid transport (PITT) pathway for rapid lysosomal repair. Upon LMP, phosphatidylinositol-4 kinase type 2α (PI4K2A) accumulates rapidly on damaged lysosomes, generating high levels of the lipid messenger phosphatidylinositol-4-phosphate. Lysosomal phosphatidylinositol-4-phosphate in turn recruits multiple oxysterol-binding protein (OSBP)-related protein (ORP) family members, including ORP9, ORP10, ORP11 and OSBP, to orchestrate extensive new membrane contact sites between damaged lysosomes and the endoplasmic reticulum. The ORPs subsequently catalyse robust endoplasmic reticulum-to-lysosome transfer of phosphatidylserine and cholesterol to support rapid lysosomal repair. Finally, the lipid transfer protein ATG2 is also recruited to damaged lysosomes where its activity is potently stimulated by phosphatidylserine. Independent of macroautophagy, ATG2 mediates rapid membrane repair through direct lysosomal lipid transfer. Together, our findings identify that the PITT pathway maintains lysosomal membrane integrity, with important implications for numerous age-related diseases characterized by impaired lysosomal function.
Topics: Autophagy-Related Proteins; Biological Transport; Cholesterol; Endoplasmic Reticulum; Intracellular Space; Lysosomes; Oxysterols; Phosphatidylinositol Phosphates; Phosphatidylinositols; Phosphatidylserines; Phosphotransferases (Alcohol Group Acceptor); Proteomics; Receptors, Steroid; Signal Transduction
PubMed: 36071159
DOI: 10.1038/s41586-022-05164-4 -
Nature Reviews. Molecular Cell Biology Dec 2022Phosphoinositides are signalling lipids derived from phosphatidylinositol, a ubiquitous phospholipid in the cytoplasmic leaflet of eukaryotic membranes. Initially... (Review)
Review
Phosphoinositides are signalling lipids derived from phosphatidylinositol, a ubiquitous phospholipid in the cytoplasmic leaflet of eukaryotic membranes. Initially discovered for their roles in cell signalling, phosphoinositides are now widely recognized as key integrators of membrane dynamics that broadly impact on all aspects of cell physiology and on disease. The past decade has witnessed a vast expansion of our knowledge of phosphoinositide biology. On the endocytic and exocytic routes, phosphoinositides direct the inward and outward flow of membrane as vesicular traffic is coupled to the conversion of phosphoinositides. Moreover, recent findings on the roles of phosphoinositides in autophagy and the endolysosomal system challenge our view of lysosome biology. The non-vesicular exchange of lipids, ions and metabolites at membrane contact sites in between organelles has also been found to depend on phosphoinositides. Here we review our current understanding of how phosphoinositides shape and direct membrane dynamics to impact on cell physiology, and provide an overview of emerging concepts in phosphoinositide regulation.
Topics: Phosphatidylinositols; Cell Membrane; Endosomes; Signal Transduction; Lysosomes
PubMed: 35589852
DOI: 10.1038/s41580-022-00490-x -
Nature Jun 2023The discovery and application of genome editing introduced a new era of plant breeding by giving researchers efficient tools for the precise engineering of crop genomes....
The discovery and application of genome editing introduced a new era of plant breeding by giving researchers efficient tools for the precise engineering of crop genomes. Here we demonstrate the power of genome editing for engineering broad-spectrum disease resistance in rice (Oryza sativa). We first isolated a lesion mimic mutant (LMM) from a mutagenized rice population. We then demonstrated that a 29-base-pair deletion in a gene we named RESISTANCE TO BLAST1 (RBL1) caused broad-spectrum disease resistance and showed that this mutation caused an approximately 20-fold reduction in yield. RBL1 encodes a cytidine diphosphate diacylglycerol synthase that is required for phospholipid biosynthesis. Mutation of RBL1 results in reduced levels of phosphatidylinositol and its derivative phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P). In rice, PtdIns(4,5)P is enriched in cellular structures that are specifically associated with effector secretion and fungal infection, suggesting that it has a role as a disease-susceptibility factor. By using targeted genome editing, we obtained an allele of RBL1, named RBL1, which confers broad-spectrum disease resistance but does not decrease yield in a model rice variety, as assessed in small-scale field trials. Our study has demonstrated the benefits of editing an LMM gene, a strategy relevant to diverse LMM genes and crops.
Topics: Disease Resistance; Gene Editing; Genome, Plant; Oryza; Phosphatidylinositols; Plant Breeding; Plant Diseases; Alleles; Phosphatidylinositol 4,5-Diphosphate; Diacylglycerol Cholinephosphotransferase
PubMed: 37316672
DOI: 10.1038/s41586-023-06205-2 -
Nature Chemical Biology Oct 2022The Hippo pathway plays a key role in development, organ size control and tissue homeostasis, and its dysregulation contributes to cancer. The LATS tumor suppressor...
The Hippo pathway plays a key role in development, organ size control and tissue homeostasis, and its dysregulation contributes to cancer. The LATS tumor suppressor kinases phosphorylate and inhibit the YAP/TAZ transcriptional co-activators to suppress gene expression and cell growth. Through a screen of marine natural products, we identified microcolin B (MCB) as a Hippo activator that preferentially kills YAP-dependent cancer cells. Structure-activity optimization yielded more potent MCB analogs, which led to the identification of phosphatidylinositol transfer proteins α and β (PITPα/β) as the direct molecular targets. We established a critical role of PITPα/β in regulating LATS and YAP. Moreover, we showed that PITPα/β influence the Hippo pathway via plasma membrane phosphatidylinositol-4-phosphate. This study uncovers a previously unrecognized role of PITPα/β in Hippo pathway regulation and as potential cancer therapeutic targets.
Topics: Humans; Biological Products; Hippo Signaling Pathway; Neoplasms; Phosphatidylinositols; Phospholipid Transfer Proteins; Phosphoproteins; Protein Serine-Threonine Kinases; Signal Transduction; Transcription Factors
PubMed: 35788180
DOI: 10.1038/s41589-022-01061-z -
Nature Communications Oct 2023Exosomes are secreted to the extracellular milieu when multivesicular endosomes (MVEs) dock and fuse with the plasma membrane. However, MVEs are also known to fuse with...
Exosomes are secreted to the extracellular milieu when multivesicular endosomes (MVEs) dock and fuse with the plasma membrane. However, MVEs are also known to fuse with lysosomes for degradation. How MVEs are directed to the plasma membrane for exosome secretion rather than to lysosomes is unclear. Here we report that a conversion of phosphatidylinositol-3-phosphate (PI(3)P) to phosphatidylinositol-4-phosphate (PI(4)P) catalyzed sequentially by Myotubularin 1 (MTM1) and phosphatidylinositol 4-kinase type IIα (PI4KIIα) on the surface of MVEs mediates the recruitment of the exocyst complex. The exocyst then targets the MVEs to the plasma membrane for exosome secretion. We further demonstrate that disrupting PI(4)P generation or exocyst function blocked exosomal secretion of Programmed death-ligand 1 (PD-L1), a key immune checkpoint protein in tumor cells, and led to its accumulation in lysosomes. Together, our study suggests that the PI(3)P to PI(4)P conversion on MVEs and the recruitment of the exocyst direct the exocytic trafficking of MVEs for exosome secretion.
Topics: Exosomes; Endosomes; Phosphatidylinositols; Multivesicular Bodies
PubMed: 37898620
DOI: 10.1038/s41467-023-42661-0 -
Science (New York, N.Y.) Dec 2022Cells respond to fluctuating nutrient supply by adaptive changes in organelle dynamics and in metabolism. How such changes are orchestrated on a cell-wide scale is...
Cells respond to fluctuating nutrient supply by adaptive changes in organelle dynamics and in metabolism. How such changes are orchestrated on a cell-wide scale is unknown. We show that endosomal signaling lipid turnover by MTM1, a phosphatidylinositol 3-phosphate [PI(3)P] 3-phosphatase mutated in X-linked centronuclear myopathy in humans, controls mitochondrial morphology and function by reshaping the endoplasmic reticulum (ER). Starvation-induced endosomal recruitment of MTM1 impairs PI(3)P-dependent contact formation between tubular ER membranes and early endosomes, resulting in the conversion of ER tubules into sheets, the inhibition of mitochondrial fission, and sustained oxidative metabolism. Our results unravel an important role for early endosomal lipid signaling in controlling ER shape and, thereby, mitochondrial form and function to enable cells to adapt to fluctuating nutrient environments.
Topics: Humans; Endoplasmic Reticulum; Endosomes; Mitochondria; Phosphatidylinositol Phosphates; Phosphatidylinositols; Signal Transduction; Protein Tyrosine Phosphatases, Non-Receptor; Mitochondrial Dynamics
PubMed: 36520888
DOI: 10.1126/science.abq5209 -
Cold Spring Harbor Perspectives in... Sep 2023Phosphoinositides (PIs) are phospholipids derived from phosphatidylinositol. PIs are regulated via reversible phosphorylation, which is directed by the opposing actions... (Review)
Review
Phosphoinositides (PIs) are phospholipids derived from phosphatidylinositol. PIs are regulated via reversible phosphorylation, which is directed by the opposing actions of PI kinases and phosphatases. PIs constitute a minor fraction of the total cellular lipid pool but play pleiotropic roles in multiple aspects of cell biology. Genetic mutations of PI regulatory enzymes have been identified in rare congenital developmental syndromes, including ciliopathies, and in numerous human diseases, such as cancer and metabolic and neurological disorders. Accordingly, PI regulatory enzymes have been targeted in the design of potential therapeutic interventions for human diseases. Recent advances place PIs as central regulators of membrane dynamics within functionally distinct subcellular compartments. This brief review focuses on the emerging role PIs play in regulating cell signaling within the primary cilium and in directing transfer of molecules at interorganelle membrane contact sites and identifies new roles for PIs in subcellular spaces.
Topics: Humans; Phosphatidylinositols; Signal Transduction; Phosphoric Monoester Hydrolases
PubMed: 37463718
DOI: 10.1101/cshperspect.a041406 -
The Journal of Cell Biology Sep 2023Phosphoinositide signaling lipids (PIPs) are key regulators of membrane identity and trafficking. Of these, PI(3,5)P2 is one of the least well-understood, despite key...
Phosphoinositide signaling lipids (PIPs) are key regulators of membrane identity and trafficking. Of these, PI(3,5)P2 is one of the least well-understood, despite key roles in many endocytic pathways including phagocytosis and macropinocytosis. PI(3,5)P2 is generated by the phosphoinositide 5-kinase PIKfyve, which is critical for phagosomal digestion and antimicrobial activity. However PI(3,5)P2 dynamics and regulation remain unclear due to lack of reliable reporters. Using the amoeba Dictyostelium discoideum, we identify SnxA as a highly selective PI(3,5)P2-binding protein and characterize its use as a reporter for PI(3,5)P2 in both Dictyostelium and mammalian cells. Using GFP-SnxA, we demonstrate that Dictyostelium phagosomes and macropinosomes accumulate PI(3,5)P2 3 min after engulfment but are then retained differently, indicating pathway-specific regulation. We further find that PIKfyve recruitment and activity are separable and that PIKfyve activation stimulates its own dissociation. SnxA is therefore a new tool for reporting PI(3,5)P2 in live cells that reveals key mechanistic details of the role and regulation of PIKfyve/PI(3,5)P2.
Topics: Animals; Dictyostelium; Endosomes; Mammals; Phagosomes; Phosphatidylinositols; Phosphatidylinositol 3-Kinases
PubMed: 37382666
DOI: 10.1083/jcb.202209077 -
Cell Research Aug 2023Migrasomes are recently discovered organelles, which are formed on the ends or branch points of retraction fibers at the trailing edge of migrating cells. Previously, we...
Migrasomes are recently discovered organelles, which are formed on the ends or branch points of retraction fibers at the trailing edge of migrating cells. Previously, we showed that recruitment of integrins to the site of migrasome formation is essential for migrasome biogenesis. In this study, we found that prior to migrasome formation, PIP5K1A, a PI4P kinase which converts PI4P into PI(4,5)P, is recruited to migrasome formation sites. The recruitment of PIP5K1A results in generation of PI(4,5)P at the migrasome formation site. Once accumulated, PI(4,5)P recruits Rab35 to the migrasome formation site by interacting with the C-terminal polybasic cluster of Rab35. We further demonstrated that active Rab35 promotes migrasome formation by recruiting and concentrating integrin α5 at migrasome formation sites, which is likely mediated by the interaction between integrin α5 and Rab35. Our study identifies the upstream signaling events orchestrating migrasome biogenesis.
Topics: Phosphatidylinositols; Integrin alpha5; Organelles; Signal Transduction; rab GTP-Binding Proteins; Phosphatidylinositol 4,5-Diphosphate
PubMed: 37142675
DOI: 10.1038/s41422-023-00811-5 -
Nature Immunology Mar 2023How lipidome changes support CD8 effector T (T) cell differentiation is not well understood. Here we show that, although naive T cells are rich in polyunsaturated...
How lipidome changes support CD8 effector T (T) cell differentiation is not well understood. Here we show that, although naive T cells are rich in polyunsaturated phosphoinositides (PIP with 3-4 double bonds), T cells have unique PIP marked by saturated fatty acyl chains (0-2 double bonds). PIP are precursors for second messengers. Polyunsaturated phosphatidylinositol bisphosphate (PIP) exclusively supported signaling immediately upon T cell antigen receptor activation. In late T cells, activity of phospholipase C-γ1, the enzyme that cleaves PIP into downstream mediators, waned, and saturated PIP became essential for sustained signaling. Saturated PIP was more rapidly converted to PIP with subsequent recruitment of phospholipase C-γ1, and loss of saturated PIP impaired T cell fitness and function, even in cells with abundant polyunsaturated PIP. Glucose was the substrate for de novo PIP synthesis, and was rapidly utilized for saturated PIP generation. Thus, separate PIP pools with distinct acyl chain compositions and metabolic dependencies drive important signaling events to initiate and then sustain effector function during CD8+ T cell differentiation.
Topics: Phosphatidylinositols; Phosphatidylinositol Phosphates; Signal Transduction; Type C Phospholipases; CD8-Positive T-Lymphocytes
PubMed: 36732424
DOI: 10.1038/s41590-023-01419-y