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Medicina (Kaunas, Lithuania) Sep 2023Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal hematopoietic disorder characterized by the lack of glycosylphosphatidylinositol-anchored proteins... (Review)
Review
Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal hematopoietic disorder characterized by the lack of glycosylphosphatidylinositol-anchored proteins (GPI-APs) as a consequence of somatic mutations in the phosphatidylinositol glycan anchor biosynthesis class A () gene. Clinical manifestations of PNH are intravascular hemolysis, thrombophilia, and bone marrow failure. Treatment of PNH mainly relies on the use of complement-targeted therapy (C5 inhibitors), with the newest agents being explored against other factors involved in the complement cascade to alleviate unresolved intravascular hemolysis and extravascular hemolysis. This review summarizes the biology and current treatment strategies for PNH with the aim of reaching a general audience with an interest in hematologic disorders.
Topics: Humans; Hemoglobinuria, Paroxysmal; Hemolysis; Complement System Proteins; Thrombophilia; Glycosylphosphatidylinositols; Biology
PubMed: 37763731
DOI: 10.3390/medicina59091612 -
Science (New York, N.Y.) Oct 2023Neurons relay information via specialized presynaptic compartments for neurotransmission. Unlike conventional organelles, the specialized apparatus characterizing the...
Neurons relay information via specialized presynaptic compartments for neurotransmission. Unlike conventional organelles, the specialized apparatus characterizing the neuronal presynapse must form de novo. How the components for presynaptic neurotransmission are transported and assembled is poorly understood. Our results show that the rare late endosomal signaling lipid phosphatidylinositol 3,5-bisphosphate [PI(3,5)P] directs the axonal cotransport of synaptic vesicle and active zone proteins in precursor vesicles in human neurons. Precursor vesicles are distinct from conventional secretory organelles, endosomes, and degradative lysosomes and are transported by coincident detection of PI(3,5)P and active ARL8 via kinesin KIF1A to the presynaptic compartment. Our findings identify a crucial mechanism that mediates the delivery of synaptic vesicle and active zone proteins to developing synapses.
Topics: Humans; Axonal Transport; Kinesins; Neurons; Synaptic Vesicles; Phosphatidylinositol Phosphates
PubMed: 37824668
DOI: 10.1126/science.adg1075 -
Nature Reviews. Molecular Cell Biology Aug 2023Cellular membranes function as permeability barriers that separate cells from the external environment or partition cells into distinct compartments. These membranes are... (Review)
Review
Cellular membranes function as permeability barriers that separate cells from the external environment or partition cells into distinct compartments. These membranes are lipid bilayers composed of glycerophospholipids, sphingolipids and cholesterol, in which proteins are embedded. Glycerophospholipids and sphingolipids freely move laterally, whereas transverse movement between lipid bilayers is limited. Phospholipids are asymmetrically distributed between membrane leaflets but change their location in biological processes, serving as signalling molecules or enzyme activators. Designated proteins - flippases and scramblases - mediate this lipid movement between the bilayers. Flippases mediate the confined localization of specific phospholipids (phosphatidylserine (PtdSer) and phosphatidylethanolamine) to the cytoplasmic leaflet. Scramblases randomly scramble phospholipids between leaflets and facilitate the exposure of PtdSer on the cell surface, which serves as an important signalling molecule and as an 'eat me' signal for phagocytes. Defects in flippases and scramblases cause various human diseases. We herein review the recent research on the structure of flippases and scramblases and their physiological roles. Although still poorly understood, we address the mechanisms by which they translocate phospholipids between lipid bilayers and how defects cause human diseases.
Topics: Humans; Lipid Bilayers; Phospholipids; Cell Membrane; Glycerophospholipids; Phosphatidylserines
PubMed: 37106071
DOI: 10.1038/s41580-023-00604-z -
Circulation Research Jan 2024Single-nucleotide polymorphisms linked with the rs1474868 T allele ( [mitofusin-2] T/T) in the human mitochondrial fusion protein gene are associated with reduced...
BACKGROUND
Single-nucleotide polymorphisms linked with the rs1474868 T allele ( [mitofusin-2] T/T) in the human mitochondrial fusion protein gene are associated with reduced platelet RNA expression and platelet counts. This study investigates the impact of MFN2 on megakaryocyte and platelet biology.
METHODS
Mice with megakaryocyte/platelet deletion of ( [ conditional knockout]) were generated using Pf4-Cre crossed with floxed mice. Human megakaryocytes were generated from cord blood and platelets isolated from healthy subjects genotyped for rs1474868. Ex vivo approaches assessed mitochondrial morphology, function, and platelet activation responses. In vivo measurements included endogenous/transfused platelet life span, tail bleed time, transient middle cerebral artery occlusion, and pulmonary vascular permeability/hemorrhage following lipopolysaccharide-induced acute lung injury.
RESULTS
Mitochondria was more fragmented in megakaryocytes derived from mice and from human cord blood with T/T genotype compared with control megakaryocytes. Human resting platelets of T/T genotype had reduced MFN2 protein, diminished mitochondrial membrane potential, and an increased rate of phosphatidylserine exposure during ex vivo culture. Platelet counts and platelet life span were reduced in mice accompanied by an increased rate of phosphatidylserine exposure in resting platelets, especially aged platelets, during ex vivo culture. also decreased platelet mitochondrial membrane potential (basal) and activated mitochondrial oxygen consumption rate, reactive oxygen species generation, calcium flux, platelet-neutrophil aggregate formation, and phosphatidylserine exposure following dual agonist activation. Ultimately, mice showed prolonged tail bleed times, decreased ischemic stroke infarct size after cerebral ischemia-reperfusion, and exacerbated pulmonary inflammatory hemorrhage following lipopolysaccharide-induced acute lung injury. Analysis of SNPs in the iSPAAR study (Identification of SNPs Predisposing to Altered ALI Risk) identified a significant association between and 28-day mortality in patients with acute respiratory distress syndrome.
CONCLUSIONS
Mfn2 preserves mitochondrial phenotypes in megakaryocytes and platelets and influences platelet life span, function, and outcomes of stroke and lung injury.
Topics: Aged; Animals; Humans; Mice; Acute Lung Injury; Blood Platelets; Hemorrhage; Lipopolysaccharides; Mitochondria; Phosphatidylserines
PubMed: 38156445
DOI: 10.1161/CIRCRESAHA.123.322914 -
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 -
Nature Aug 2023Distinct morphologies of the mitochondrial network support divergent metabolic and regulatory processes that determine cell function and fate. The mechanochemical...
Distinct morphologies of the mitochondrial network support divergent metabolic and regulatory processes that determine cell function and fate. The mechanochemical GTPase optic atrophy 1 (OPA1) influences the architecture of cristae and catalyses the fusion of the mitochondrial inner membrane. Despite its fundamental importance, the molecular mechanisms by which OPA1 modulates mitochondrial morphology are unclear. Here, using a combination of cellular and structural analyses, we illuminate the molecular mechanisms that are key to OPA1-dependent membrane remodelling and fusion. Human OPA1 embeds itself into cardiolipin-containing membranes through a lipid-binding paddle domain. A conserved loop within the paddle domain inserts deeply into the bilayer, further stabilizing the interactions with cardiolipin-enriched membranes. OPA1 dimerization through the paddle domain promotes the helical assembly of a flexible OPA1 lattice on the membrane, which drives mitochondrial fusion in cells. Moreover, the membrane-bending OPA1 oligomer undergoes conformational changes that pull the membrane-inserting loop out of the outer leaflet and contribute to the mechanics of membrane remodelling. Our findings provide a structural framework for understanding how human OPA1 shapes mitochondrial morphology and show us how human disease mutations compromise OPA1 functions.
Topics: Humans; Biocatalysis; Cardiolipins; GTP Phosphohydrolases; Membrane Fusion; Mitochondria; Mitochondrial Membranes; Mutation; Protein Domains; Protein Multimerization; Mitochondrial Dynamics
PubMed: 37612504
DOI: 10.1038/s41586-023-06441-6 -
Nutrients Jul 2023The intake of linoleic acid (LA) has increased dramatically in the standard American diet. LA is generally promoted as supporting human health, but there exists... (Review)
Review
The intake of linoleic acid (LA) has increased dramatically in the standard American diet. LA is generally promoted as supporting human health, but there exists controversy regarding whether the amount of LA currently consumed in the standard American diet supports human health. The goal of this narrative review is to explore the mechanisms that underlie the hypothesis that excessive LA intake may harm human health. While LA is considered to be an essential fatty acid and support health when consumed in modest amounts, an excessive intake of LA leads to the formation of oxidized linoleic acid metabolites (OXLAMs), impairments in mitochondrial function through suboptimal cardiolipin composition, and likely contributes to many chronic diseases that became an epidemic in the 20th century, and whose prevalence continues to increase. The standard American diet comprises 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids, with the majority of omega-6 intake coming from LA. As LA consumption increases, the potential for OXLAM formation also increases. OXLAMs have been associated with various illnesses, including cardiovascular disease, cancer, and Alzheimer's disease, among others. Lowering dietary LA intake can help reduce the production and accumulation of OXLAMs implicated in chronic diseases. While there are other problematic components in the standard American diet, the half-life of LA is approximately two years, which means the damage can be far more persistent than other dietary factors, and the impact of reducing excessive LA intake takes time. Therefore, additional research-evaluating approaches to reduce OXLAM formation and cardiolipin derangements following LA consumption are warranted.
Topics: Humans; Linoleic Acid; Cardiolipins; Chronic Disease; Diet
PubMed: 37513547
DOI: 10.3390/nu15143129 -
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 -
The Journal of Clinical Investigation Sep 2023The liver has a high demand for phosphatidylcholine (PC), particularly in overnutrition, where reduced phospholipid levels have been implicated in the development of...
The liver has a high demand for phosphatidylcholine (PC), particularly in overnutrition, where reduced phospholipid levels have been implicated in the development of nonalcoholic fatty liver disease (NAFLD). Whether other pathways exist in addition to de novo PC synthesis that contribute to hepatic PC pools remains unknown. Here, we identified the lysophosphatidylcholine (LPC) transporter major facilitator superfamily domain containing 2A (Mfsd2a) as critical for maintaining hepatic phospholipid pools. Hepatic Mfsd2a expression was induced in patients having NAFLD and in mice in response to dietary fat via glucocorticoid receptor action. Mfsd2a liver-specific deficiency in mice (L2aKO) led to a robust nonalcoholic steatohepatitis-like (NASH-like) phenotype within just 2 weeks of dietary fat challenge associated with reduced hepatic phospholipids containing linoleic acid. Reducing dietary choline intake in L2aKO mice exacerbated liver pathology and deficiency of liver phospholipids containing polyunsaturated fatty acids (PUFAs). Treating hepatocytes with LPCs containing oleate and linoleate, two abundant blood-derived LPCs, specifically induced lipid droplet biogenesis and contributed to phospholipid pools, while LPC containing the omega-3 fatty acid docosahexaenoic acid (DHA) promoted lipid droplet formation and suppressed lipogenesis. This study revealed that PUFA-containing LPCs drive hepatic lipid droplet formation, suppress lipogenesis, and sustain hepatic phospholipid pools - processes that are critical for protecting the liver from excess dietary fat.
Topics: Animals; Mice; Phospholipids; Non-alcoholic Fatty Liver Disease; Liver; Lysophospholipids; Phosphatidylcholines; Dietary Fats; Overnutrition
PubMed: 37463052
DOI: 10.1172/JCI171267 -
Journal of Biomedical Science Aug 2023Excess polymorphonuclear neutrophil (PMN) recruitment or excessive neutrophil extracellular trap (NET) formation can lead to the development of multiple organ...
BACKGROUND
Excess polymorphonuclear neutrophil (PMN) recruitment or excessive neutrophil extracellular trap (NET) formation can lead to the development of multiple organ dysfunction during sepsis. M2 macrophage-derived exosomes (M2-Exos) have exhibited anti-inflammatory activities in some inflammatory diseases to mediate organ functional protection, but their role in treating sepsis-related acute lung injury (ALI) remains unclear. In this study, we sought to investigate whether M2-Exos could prevent potentially deleterious inflammatory effects during sepsis-related ALI by modulating abnormal PMN behaviours.
METHODS
C57BL/6 wild-type mice were subjected to a caecal ligation and puncture (CLP) mouse model to mimic sepsis in vivo, and M2-Exos were administered intraperitoneally 1 h after CLP. H&E staining, immunofluorescence and immunohistochemistry were conducted to investigate lung tissue injury, PMN infiltration and NET formation in the lung. We further demonstrated the role of M2-Exos on PMN function and explored the potential mechanisms through an in vitro coculture experiment using PMNs isolated from both healthy volunteers and septic patients.
RESULTS
Here, we report that M2-Exos inhibited PMN migration and NET formation, alleviated lung injury and reduced mortality in a sepsis mouse model. In vitro, M2-Exos significantly decreased PMN migration and NET formation capacity, leading to lipid mediator class switching from proinflammatory leukotriene B4 (LTB4) to anti-inflammatory lipoxin A4 (LXA4) by upregulating 15-lipoxygenase (15-LO) expression in PMNs. Treatment with LXA4 receptor antagonist attenuated the effect of M2-Exos on PMNs and lung injury. Mechanistically, prostaglandin E2 (PGE2) enriched in M2-Exos was necessary to increase 15-LO expression in PMNs by functioning on the EP4 receptor, upregulate LXA4 production to downregulate chemokine (C-X-C motif) receptor 2 (CXCR2) and reactive oxygen species (ROS) expressions, and finally inhibit PMN function.
CONCLUSIONS
Our findings reveal a previously unknown role of M2-Exos in regulating PMN migration and NET formation through lipid mediator class switching, thus highlighting the potential application of M2-Exos in controlling PMN-mediated tissue injury in patients with sepsis.
Topics: Mice; Animals; Dinoprostone; Neutrophils; Neutrophil Infiltration; Extracellular Traps; Lung Injury; Immunoglobulin Class Switching; Mice, Inbred C57BL; Sepsis; Macrophages; Platelet Activating Factor
PubMed: 37533081
DOI: 10.1186/s12929-023-00957-9