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Hanada K. Metabolic channeling of lipids via the contact zones between different organelles. Bioessays 2024; 46:e2400045. [PMID: 38932642 DOI: 10.1002/bies.202400045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 05/28/2024] [Accepted: 05/29/2024] [Indexed: 06/28/2024]
Abstract
Various lipid transfer proteins (LTPs) mediate the inter-organelle transport of lipids. By working at membrane contact zones between donor and acceptor organelles, LTPs achieve rapid and accurate inter-organelle transfer of lipids. This article will describe the emerging paradigm that the action of LTPs at organelle contact zones generates metabolic channeling events in lipid metabolism, mainly referring to how ceramide synthesized in the endoplasmic reticulum is preferentially metabolized to sphingomyelin in the distal Golgi region, how cholesterol and phospholipids receive specific metabolic reactions in mitochondria, and how the hijacking of host LTPs by intracellular pathogens may generate new channeling-like events. In addition, the article will discuss how the function of LTPs is regulated, exemplified by a few representative LTP systems, and will briefly touch on experiments that will be necessary to establish the paradigm that LTP-mediated inter-organelle transport of lipids is one of the mechanisms of compartmentalization-based metabolic channeling events.
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Affiliation(s)
- Kentaro Hanada
- Center for Quality Management Systems, National Institute of Infectious Diseases, Tokyo, Japan
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2
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Varadharajan V, Ramachandiran I, Massey WJ, Jain R, Banerjee R, Horak AJ, McMullen MR, Huang E, Bellar A, Lorkowski SW, Gulshan K, Helsley RN, James I, Pathak V, Dasarathy J, Welch N, Dasarathy S, Streem D, Reizes O, Allende DS, Smith JD, Simcox J, Nagy LE, Brown JM. Membrane-bound O-acyltransferase 7 (MBOAT7) shapes lysosomal lipid homeostasis and function to control alcohol-associated liver injury. eLife 2024; 12:RP92243. [PMID: 38648183 PMCID: PMC11034944 DOI: 10.7554/elife.92243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2024] Open
Abstract
Recent genome-wide association studies (GWAS) have identified a link between single-nucleotide polymorphisms (SNPs) near the MBOAT7 gene and advanced liver diseases. Specifically, the common MBOAT7 variant (rs641738) associated with reduced MBOAT7 expression is implicated in non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis. However, the precise mechanism underlying MBOAT7-driven liver disease progression remains elusive. Previously, we identified MBOAT7-driven acylation of lysophosphatidylinositol lipids as key mechanism suppressing the progression of NAFLD (Gwag et al., 2019). Here, we show that MBOAT7 loss of function promotes ALD via reorganization of lysosomal lipid homeostasis. Circulating levels of MBOAT7 metabolic products are significantly reduced in heavy drinkers compared to healthy controls. Hepatocyte- (Mboat7-HSKO), but not myeloid-specific (Mboat7-MSKO), deletion of Mboat7 exacerbates ethanol-induced liver injury. Lipidomic profiling reveals a reorganization of the hepatic lipidome in Mboat7-HSKO mice, characterized by increased endosomal/lysosomal lipids. Ethanol-exposed Mboat7-HSKO mice exhibit dysregulated autophagic flux and lysosomal biogenesis, associated with impaired transcription factor EB-mediated lysosomal biogenesis and autophagosome accumulation. This study provides mechanistic insights into how MBOAT7 influences ALD progression through dysregulation of lysosomal biogenesis and autophagic flux, highlighting hepatocyte-specific MBOAT7 loss as a key driver of ethanol-induced liver injury.
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Affiliation(s)
- Venkateshwari Varadharajan
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Iyappan Ramachandiran
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - William J Massey
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Raghav Jain
- Department of Biochemistry, University of Wisconsin-MadisonMadisonUnited States
| | - Rakhee Banerjee
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Anthony J Horak
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Megan R McMullen
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Emily Huang
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Annette Bellar
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Shuhui W Lorkowski
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
| | - Kailash Gulshan
- Center for Gene Regulation in Health and Disease (GRHD), Cleveland State UniversityClevelandUnited States
| | - Robert N Helsley
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
- Department of Pharmacology & Nutritional Sciences, Saha Cardiovascular Research Center, University of Kentucky College of MedicineLexingtonUnited States
| | - Isabella James
- Department of Biochemistry, University of Wisconsin-MadisonMadisonUnited States
| | - Vai Pathak
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Jaividhya Dasarathy
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Family Medicine, Metro Health Medical Center, Case Western Reserve UniversityClevelandUnited States
| | - Nicole Welch
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Srinivasan Dasarathy
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - David Streem
- Lutheran Hospital, Cleveland ClinicClevelandUnited States
| | - Ofer Reizes
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - Daniela S Allende
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Anatomical Pathology, Cleveland ClinicClevelandUnited States
| | - Jonathan D Smith
- Department of Cancer Biology, Lerner Research Institute of the Cleveland ClinicClevelandUnited States
| | - Judith Simcox
- Department of Biochemistry, University of Wisconsin-MadisonMadisonUnited States
| | - Laura E Nagy
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland ClinicClevelandUnited States
| | - J Mark Brown
- Center for Microbiome and Human Health, Lerner Research Institute, Cleveland ClinicClevelandUnited States
- Northern Ohio Alcohol Center (NOAC), Lerner Research Institute, Cleveland ClinicClevelandUnited States
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Varadharajan V, Ramachandiran L, Massey WJ, Jain R, Banerjee R, Horak AJ, McMullen MR, Huang E, Bellar A, Lorkowski SW, Guilshan K, Helsley RN, James I, Pathak V, Dasarathy J, Welch N, Dasarathy S, Streem D, Reizes O, Allende DS, Smith JD, Simcox J, Nagy LE, Brown JM. Membrane Bound O-Acyltransferase 7 (MBOAT7) Shapes Lysosomal Lipid Homeostasis and Function to Control Alcohol-Associated Liver Injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.09.26.559533. [PMID: 37808828 PMCID: PMC10557709 DOI: 10.1101/2023.09.26.559533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Several recent genome-wide association studies (GWAS) have identified single nucleotide polymorphism (SNPs) near the gene encoding membrane-bound O -acyltransferase 7 ( MBOAT7 ) that is associated with advanced liver diseases. In fact, a common MBOAT7 variant (rs641738), which is associated with reduced MBOAT7 expression, confers increased susceptibility to non-alcoholic fatty liver disease (NAFLD), alcohol-associated liver disease (ALD), and liver fibrosis in those chronically infected with hepatitis viruses B and C. The MBOAT7 gene encodes a lysophosphatidylinositol (LPI) acyltransferase enzyme that produces the most abundant form of phosphatidylinositol 38:4 (PI 18:0/20:4). Although these recent genetic studies clearly implicate MBOAT7 function in liver disease progression, the mechanism(s) by which MBOAT7-driven LPI acylation regulates liver disease is currently unknown. Previously we showed that antisense oligonucleotide (ASO)-mediated knockdown of Mboat7 promoted non-alcoholic fatty liver disease (NAFLD) in mice (Helsley et al., 2019). Here, we provide mechanistic insights into how MBOAT7 loss of function promotes alcohol-associated liver disease (ALD). In agreement with GWAS studies, we find that circulating levels of metabolic product of MBOAT7 (PI 38:4) are significantly reduced in heavy drinkers compared to age-matched healthy controls. Hepatocyte specific genetic deletion ( Mboat7 HSKO ), but not myeloid-specific deletion ( Mboat7 MSKO ), of Mboat7 in mice results in enhanced ethanol-induced hepatic steatosis and high concentrations of plasma alanine aminotransferase (ALT). Given MBOAT7 is a lipid metabolic enzyme, we performed comprehensive lipidomic profiling of the liver and identified a striking reorganization of the hepatic lipidome upon ethanol feeding in Mboat7 HSKO mice. Specifically, we observed large increases in the levels of endosomal/lysosomal lipids including bis(monoacylglycero)phosphates (BMP) and phosphatidylglycerols (PGs) in ethanol-exposed Mboat7 HSKO mice. In parallel, ethanol-fed Mboat7 HSKO mice exhibited marked dysregulation of autophagic flux and lysosomal biogenesis when exposed to ethanol. This was associated with impaired transcription factor EB (TFEB)-mediated lysosomal biogenesis and accumulation of autophagosomes. Collectively, this works provides new molecular insights into how genetic variation in MBOAT7 impacts ALD progression in humans and mice. This work is the first to causally link MBOAT7 loss of function in hepatocytes, but not myeloid cells, to ethanol-induced liver injury via dysregulation of lysosomal biogenesis and autophagic flux.
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Tóth DJ, Tóth JT, Damouni A, Hunyady L, Várnai P. Effect of hormone-induced plasma membrane phosphatidylinositol 4,5-bisphosphate depletion on receptor endocytosis suggests the importance of local regulation in phosphoinositide signaling. Sci Rep 2024; 14:291. [PMID: 38168911 PMCID: PMC10761818 DOI: 10.1038/s41598-023-50732-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Accepted: 12/24/2023] [Indexed: 01/05/2024] Open
Abstract
Phosphatidylinositol 4,5-bisphosphate (PIP2) has been shown to be critical for the endocytosis of G protein-coupled receptors (GPCRs). We have previously demonstrated that depletion of PIP2 by chemically induced plasma membrane (PM) recruitment of a 5-phosphatase domain prevents the internalization of the β2 adrenergic receptor (β2AR) from the PM to early endosomes. In this study, we tested the effect of hormone-induced PM PIP2 depletion on β2AR internalization using type-1 angiotensin receptor (AT1R) or M3 muscarinic acetylcholine receptor (M3R). We followed the endocytic route of β2ARs in HEK 293T cells using bioluminescence resonance energy transfer between the receptor and endosome marker Rab5. To compare the effect of lipid depletion by different means, we created and tested an AT1R fusion protein that is capable of both recruitment-based and hormone-induced depletion methods. The rate of PM PIP2 depletion was measured using a biosensor based on the PH domain of phospholipase Cδ1. As expected, β2AR internalization was inhibited when PIP2 depletion was evoked by recruiting 5-phosphatase to PM-anchored AT1R. A similar inhibition occurred when wild-type AT1R was activated by adding angiotensin II. However, stimulation of the desensitization/internalization-impaired mutant AT1R (TSTS/4A) caused very little inhibition of β2AR internalization, despite the higher rate of measurable PIP2 depletion. Interestingly, inhibition of PIP2 resynthesis with the selective PI4KA inhibitor GSK-A1 had little effect on the change in PH-domain-measured PM PIP2 levels but did significantly decrease β2AR internalization upon either AT1R or M3R activation, indicating the importance of a locally synthetized phosphoinositide pool in the regulation of this process.
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Affiliation(s)
- Dániel J Tóth
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Tűzoltó utca 37-47, 1094, Hungary
- HUN-REN-SU Molecular Physiology Research Group, Hungarian Research Network and Semmelweis University, Budapest, Hungary
| | - József T Tóth
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Tűzoltó utca 37-47, 1094, Hungary
- Department of Anaesthesiology and Intensive Therapy, Faculty of Medicine, Semmelweis University, Budapest, Üllői út 78/B, 1082, Hungary
| | - Amir Damouni
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Tűzoltó utca 37-47, 1094, Hungary
| | - László Hunyady
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Tűzoltó utca 37-47, 1094, Hungary
- Institute of Enzymology, Centre of Excellence of the Hungarian Academy of Sciences, HUN-REN Research Centre for Natural Sciences, Budapest, Magyar tudósok körútja 2, 1117, Hungary
| | - Péter Várnai
- Department of Physiology, Faculty of Medicine, Semmelweis University, Budapest, Tűzoltó utca 37-47, 1094, Hungary.
- HUN-REN-SU Molecular Physiology Research Group, Hungarian Research Network and Semmelweis University, Budapest, Hungary.
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Bartho LA, Keenan E, Walker SP, MacDonald TM, Nijagal B, Tong S, Kaitu'u-Lino TJ. Plasma lipids are dysregulated preceding diagnosis of preeclampsia or delivery of a growth restricted infant. EBioMedicine 2023; 94:104704. [PMID: 37421807 PMCID: PMC10344703 DOI: 10.1016/j.ebiom.2023.104704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Revised: 06/21/2023] [Accepted: 06/27/2023] [Indexed: 07/10/2023] Open
Abstract
BACKGROUND Lipids serve as multifunctional metabolites that have important implications for the pregnant mother and developing fetus. Abnormalities in lipids have emerged as potential risk factors for pregnancy diseases, such as preeclampsia and fetal growth restriction. The aim of this study was to assess the potential of lipid metabolites for detection of late-onset preeclampsia and fetal growth restriction. METHODS We used a case-cohort of 144 maternal plasma samples at 36 weeks' gestation from patients before the diagnosis of late-onset preeclampsia (n = 22), delivery of a fetal growth restricted infant (n = 55, defined as <5th birthweight centile), gestation-matched controls (n = 72). We performed liquid chromatography-tandem mass spectrometry (LC-QQQ) -based targeted lipidomics to identify 421 lipids, and fitted logistic regression models for each lipid, correcting for maternal age, BMI, smoking, and gestational diabetes. FINDINGS Phosphatidylinositol 32:1 (AUC = 0.81) and cholesterol ester 17:1 (AUC = 0.71) best predicted the risk of developing preeclampsia or delivering a fetal growth restricted infant, respectively. Five times repeated five-fold cross validation demonstrated the lipids alone did not out-perform existing protein biomarkers, soluble tyrosine kinase-1 (sFlt-1) and placental growth factor (PlGF) for the prediction of preeclampsia or fetal growth restriction. However, lipids combined with sFlt-1 and PlGF measurements improved disease prediction. INTERPRETATION This study successfully identified 421 lipids in maternal plasma collected at 36 weeks' gestation from participants who later developed preeclampsia or delivered a fetal growth restricted infant. Our results suggest the predictive capacity of lipid measurements for gestational disorders holds the potential to improve non-invasive assessment of maternal and fetal health. FUNDING This study was funded by a grant from National Health and Medical Research Council.
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Affiliation(s)
- Lucy A Bartho
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia.
| | - Emerson Keenan
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia
| | - Susan P Walker
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia
| | - Teresa M MacDonald
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia
| | - Brunda Nijagal
- Metabolomics Australia, The Bio21 Institute of Molecular Science and Biotechnology, The University of Melbourne, Parkville, Victoria, Australia
| | - Stephen Tong
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia
| | - Tu'uhevaha J Kaitu'u-Lino
- Translational Obstetrics Group, The Department of Obstetrics and Gynaecology, Mercy Hospital for Women, University of Melbourne, 163 Studley Road, Heidelberg 3084, Victoria, Australia; Mercy Perinatal, Mercy Hospital for Women, Victoria, Australia
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Thallmair V, Schultz L, Evers S, Jolie T, Goecke C, Leitner MG, Thallmair S, Oliver D. Localization of the tubby domain, a PI(4,5)P2 biosensor, to E-Syt3-rich endoplasmic reticulum-plasma membrane junctions. J Cell Sci 2023; 136:jcs260848. [PMID: 37401342 PMCID: PMC10445746 DOI: 10.1242/jcs.260848] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 06/26/2023] [Indexed: 07/05/2023] Open
Abstract
The phospholipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] acts as a signaling lipid at the plasma membrane (PM) with pleiotropic regulatory actions on multiple cellular processes. Signaling specificity might result from spatiotemporal compartmentalization of the lipid and from combinatorial binding of PI(4,5)P2 effector proteins to additional membrane components. Here, we analyzed the spatial distribution of tubbyCT, a paradigmatic PI(4,5)P2-binding domain, in live mammalian cells by total internal reflection fluorescence (TIRF) microscopy and molecular dynamics simulations. We found that unlike other well-characterized PI(4,5)P2 recognition domains, tubbyCT segregates into distinct domains within the PM. TubbyCT enrichment occurred at contact sites between PM and endoplasmic reticulum (ER) (i.e. at ER-PM junctions) as shown by colocalization with ER-PM markers. Localization to these sites was mediated in a combinatorial manner by binding to PI(4,5)P2 and by interaction with a cytosolic domain of extended synaptotagmin 3 (E-Syt3), but not other E-Syt isoforms. Selective localization to these structures suggests that tubbyCT is a novel selective reporter for a ER-PM junctional pool of PI(4,5)P2. Finally, we found that association with ER-PM junctions is a conserved feature of tubby-like proteins (TULPs), suggesting an as-yet-unknown function of TULPs.
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Affiliation(s)
- Veronika Thallmair
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps UniversityMarburg, 35037 Marburg, Germany
| | - Lea Schultz
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
| | - Saskia Evers
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
| | - Theresa Jolie
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
| | - Christian Goecke
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
| | - Michael G. Leitner
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
- Institute of Physiology, Department of Physiology and Medical Physics, Medical University of Innsbruck, 6020 Innsbruck, Austria
- Drug Discovery Sciences, Boehringer Ingelheim Pharma GmbH&Co.KG, Birkendorfer Str. 65, 88400 Biberach an der Riß, Germany
| | - Sebastian Thallmair
- Frankfurt Institute for Advanced Studies, 60438 Frankfurt am Main, Germany
- Groningen Biomolecular Sciences and Biotechnology Institute and The Zernike Institute for Advanced Material, University of Groningen, 9747 AG Groningen, The Netherlands
| | - Dominik Oliver
- Department of Neurophysiology, Institute of Physiology and Pathophysiology, Philipps University Marburg, 35037 Marburg, Germany
- DFG Research Training Group, Membrane Plasticity in Tissue Development and Remodeling, GRK 2213, Philipps UniversityMarburg, 35037 Marburg, Germany
- Center for Mind, Brain and Behavior (CMBB), Universities of Marburg and Giessen, 35032 Marburg, Germany
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Bura A, Čabrijan S, Đurić I, Bruketa T, Jurak Begonja A. A Plethora of Functions Condensed into Tiny Phospholipids: The Story of PI4P and PI(4,5)P 2. Cells 2023; 12:1411. [PMID: 37408244 DOI: 10.3390/cells12101411] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Revised: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 07/07/2023] Open
Abstract
Phosphoinositides (PIs) are small, phosphorylated lipids that serve many functions in the cell. They regulate endo- and exocytosis, vesicular trafficking, actin reorganization, and cell mobility, and they act as signaling molecules. The most abundant PIs in the cell are phosphatidylinositol-4-monophosphate (PI4P) and phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2]. PI4P is mostly localized at the Golgi apparatus where it regulates the anterograde trafficking from the Golgi apparatus to the plasma membrane (PM), but it also localizes at the PM. On the other hand, the main localization site of PI(4,5)P2 is the PM where it regulates the formation of endocytic vesicles. The levels of PIs are regulated by many kinases and phosphatases. Four main kinases phosphorylate the precursor molecule phosphatidylinositol into PI4P, divided into two classes (PI4KIIα, PI4KIIβ, PI4KIIIα, and PI4KIIIβ), and three main kinases phosphorylate PI4P to form PI(4,5)P2 (PI4P5KIα, PI4P5KIβ, and PI4P5KIγ). In this review, we discuss the localization and function of the kinases that produce PI4P and PI(4,5)P2, as well as the localization and function of their product molecules with an overview of tools for the detection of these PIs.
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Affiliation(s)
- Ana Bura
- Laboratory of Hematopoiesis, Department of Biotechnology, University of Rijeka, R. Matejcic 2, 51000 Rijeka, Croatia
| | - Sara Čabrijan
- Laboratory of Hematopoiesis, Department of Biotechnology, University of Rijeka, R. Matejcic 2, 51000 Rijeka, Croatia
| | - Iris Đurić
- Laboratory of Hematopoiesis, Department of Biotechnology, University of Rijeka, R. Matejcic 2, 51000 Rijeka, Croatia
| | - Tea Bruketa
- Laboratory of Hematopoiesis, Department of Biotechnology, University of Rijeka, R. Matejcic 2, 51000 Rijeka, Croatia
| | - Antonija Jurak Begonja
- Laboratory of Hematopoiesis, Department of Biotechnology, University of Rijeka, R. Matejcic 2, 51000 Rijeka, Croatia
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Vormittag S, Hüsler D, Haneburger I, Kroniger T, Anand A, Prantl M, Barisch C, Maaß S, Becher D, Letourneur F, Hilbi H. Legionella- and host-driven lipid flux at LCV-ER membrane contact sites promotes vacuole remodeling. EMBO Rep 2023; 24:e56007. [PMID: 36588479 PMCID: PMC9986823 DOI: 10.15252/embr.202256007] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 12/12/2022] [Accepted: 12/14/2022] [Indexed: 01/03/2023] Open
Abstract
Legionella pneumophila replicates in macrophages and amoeba within a unique compartment, the Legionella-containing vacuole (LCV). Hallmarks of LCV formation are the phosphoinositide lipid conversion from PtdIns(3)P to PtdIns(4)P, fusion with ER-derived vesicles and a tight association with the ER. Proteomics of purified LCVs indicate the presence of membrane contact sites (MCS) proteins possibly implicated in lipid exchange. Using dually fluorescence-labeled Dictyostelium discoideum amoeba, we reveal that VAMP-associated protein (Vap) and the PtdIns(4)P 4-phosphatase Sac1 localize to the ER, and Vap also localizes to the LCV membrane. Furthermore, Vap as well as Sac1 promote intracellular replication of L. pneumophila and LCV remodeling. Oxysterol binding proteins (OSBPs) preferentially localize to the ER (OSBP8) or the LCV membrane (OSBP11), respectively, and restrict (OSBP8) or promote (OSBP11) bacterial replication and LCV expansion. The sterol probes GFP-D4H* and filipin indicate that sterols are rapidly depleted from LCVs, while PtdIns(4)P accumulates. In addition to Sac1, the PtdIns(4)P-subverting L. pneumophila effector proteins LepB and SidC also support LCV remodeling. Taken together, the Legionella- and host cell-driven PtdIns(4)P gradient at LCV-ER MCSs promotes Vap-, OSBP- and Sac1-dependent pathogen vacuole maturation.
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Affiliation(s)
- Simone Vormittag
- Institute of Medical MicrobiologyUniversity of ZürichZürichSwitzerland
| | - Dario Hüsler
- Institute of Medical MicrobiologyUniversity of ZürichZürichSwitzerland
| | - Ina Haneburger
- Institute of Medical MicrobiologyUniversity of ZürichZürichSwitzerland
| | - Tobias Kroniger
- Institute of MicrobiologyUniversity of GreifswaldGreifswaldGermany
| | - Aby Anand
- Division of Molecular Infection Biology and Center for Cellular NanoanalyticsUniversity of OsnabrückOsnabrückGermany
| | - Manuel Prantl
- Institute of Medical MicrobiologyUniversity of ZürichZürichSwitzerland
| | - Caroline Barisch
- Division of Molecular Infection Biology and Center for Cellular NanoanalyticsUniversity of OsnabrückOsnabrückGermany
| | - Sandra Maaß
- Institute of MicrobiologyUniversity of GreifswaldGreifswaldGermany
| | - Dörte Becher
- Institute of MicrobiologyUniversity of GreifswaldGreifswaldGermany
| | - François Letourneur
- Laboratory of Pathogen Host InteractionsUniversité de Montpellier, CNRS, INSERMMontpellierFrance
| | - Hubert Hilbi
- Institute of Medical MicrobiologyUniversity of ZürichZürichSwitzerland
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9
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Sun T, Liu X, Su Y, Wang Z, Cheng B, Dong N, Wang J, Shan A. The efficacy of anti-proteolytic peptide R7I in intestinal inflammation, function, microbiota, and metabolites by multi-omics analysis in murine bacterial enteritis. Bioeng Transl Med 2023; 8:e10446. [PMID: 36925697 PMCID: PMC10013768 DOI: 10.1002/btm2.10446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2022] [Revised: 10/21/2022] [Accepted: 10/30/2022] [Indexed: 11/11/2022] Open
Abstract
Increased antibiotic resistance poses a major limitation in tackling inflammatory bowel disease and presents a large challenge for global health care. Antimicrobial peptides (AMPs) are a potential class of antimicrobial agents. Here, we have designed the potential oral route for antimicrobial peptide R7I with anti-proteolytic properties to deal with bacterial enteritis in mice. The results revealed that R7I protected the liver and gut from damage caused by inflammation. RNA-Seq analysis indicated that R7I promoted digestion and absorption in the small intestine by upregulating transmembrane transporter activity, lipid and small molecule metabolic processes and other pathways, in addition to upregulating hepatic steroid biosynthesis and fatty acid degradation. For the gut microbiota, Clostridia were significantly reduced in the R7I-treated group, and Odoribacteraceae, an efficient isoalloLCA-synthesizing strain, was the main dominant strain, protecting the gut from potential pathogens. In addition, we further discovered that R7I reduced the accumulation of negative organic acid metabolites. Overall, R7I exerted better therapeutic and immunomodulatory potential in the bacterial enteritis model, greatly reduced the risk of disease onset, and provided a reference for the in vivo application of antimicrobial peptides.
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Affiliation(s)
- Taotao Sun
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Xuesheng Liu
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Yunzhe Su
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Zihang Wang
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Baojing Cheng
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Na Dong
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Jiajun Wang
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
| | - Anshan Shan
- Laboratory of Molecular Nutrition and Immunity, the Institute of Animal Nutrition Northeast Agricultural University Harbin China
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10
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STIM Proteins and Regulation of SOCE in ER-PM Junctions. Biomolecules 2022; 12:biom12081152. [PMID: 36009047 PMCID: PMC9405863 DOI: 10.3390/biom12081152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Revised: 08/12/2022] [Accepted: 08/15/2022] [Indexed: 11/30/2022] Open
Abstract
ER-PM junctions are membrane contact sites formed by the endoplasmic reticulum (ER) and plasma membrane (PM) in close apposition together. The formation and stability of these junctions are dependent on constitutive and dynamic enrichment of proteins, which either contribute to junctional stability or modulate the lipid levels of both ER and plasma membranes. The ER-PM junctions have come under much scrutiny recently as they serve as hubs for assembling the Ca2+ signaling complexes. This review summarizes: (1) key findings that underlie the abilities of STIM proteins to accumulate in ER-PM junctions; (2) the modulation of Orai/STIM complexes by other components found within the same junction; and (3) how Orai1 channel activation is coordinated and coupled with downstream signaling pathways.
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11
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Varadharajan V, Massey WJ, Brown JM. Membrane-bound O-acyltransferase 7 (MBOAT7)-driven phosphatidylinositol remodeling in advanced liver disease. J Lipid Res 2022; 63:100234. [PMID: 35636492 PMCID: PMC9240865 DOI: 10.1016/j.jlr.2022.100234] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 05/12/2022] [Accepted: 05/16/2022] [Indexed: 01/21/2023] Open
Abstract
Advanced liver diseases account for approximately 2 million deaths annually worldwide. Roughly, half of liver disease-associated deaths arise from complications of cirrhosis and the other half driven by viral hepatitis and hepatocellular carcinoma. Unfortunately, the development of therapeutic strategies to treat subjects with advanced liver disease has been hampered by a lack of mechanistic understanding of liver disease progression and a lack of human-relevant animal models. An important advance has been made within the past several years, as several genome-wide association studies have discovered that an SNP near the gene encoding membrane-bound O-acyltransferase 7 (MBOAT7) is associated with severe liver diseases. This common MBOAT7 variant (rs641738, C>T), which reduces MBOAT7 expression, confers increased susceptibility to nonalcoholic fatty liver disease, alcohol-associated liver disease, and liver fibrosis in patients chronically infected with viral hepatitis. Recent studies in mice also show that Mboat7 loss of function can promote hepatic steatosis, inflammation, and fibrosis, causally linking this phosphatidylinositol remodeling enzyme to liver health in both rodents and humans. Herein, we review recent insights into the mechanisms by which MBOAT7-driven phosphatidylinositol remodeling influences liver disease progression and discuss how rapid progress in this area could inform drug discovery moving forward.
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Affiliation(s)
- Venkateshwari Varadharajan
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA; Center for Microbiome and Human Health, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - William J Massey
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA; Center for Microbiome and Human Health, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
| | - J Mark Brown
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute Cleveland Clinic, Cleveland, OH, USA; Center for Microbiome and Human Health, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
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12
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Tu-Sekine B, Kim SF. The Inositol Phosphate System-A Coordinator of Metabolic Adaptability. Int J Mol Sci 2022; 23:ijms23126747. [PMID: 35743190 PMCID: PMC9223660 DOI: 10.3390/ijms23126747] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 06/10/2022] [Accepted: 06/13/2022] [Indexed: 11/16/2022] Open
Abstract
All cells rely on nutrients to supply energy and carbon building blocks to support cellular processes. Over time, eukaryotes have developed increasingly complex systems to integrate information about available nutrients with the internal state of energy stores to activate the necessary processes to meet the immediate and ongoing needs of the cell. One such system is the network of soluble and membrane-associated inositol phosphates that coordinate the cellular responses to nutrient uptake and utilization from growth factor signaling to energy homeostasis. In this review, we discuss the coordinated interactions of the inositol polyphosphates, inositol pyrophosphates, and phosphoinositides in major metabolic signaling pathways to illustrate the central importance of the inositol phosphate signaling network in nutrient responses.
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Affiliation(s)
- Becky Tu-Sekine
- Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University, Baltimore, MD 21224, USA;
| | - Sangwon F. Kim
- Department of Medicine and Neuroscience, Division of Endocrinology, Diabetes and Metabolism, Johns Hopkins University School of Medicine, Baltimore, MD 21224, USA
- Correspondence:
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13
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Pretransplant Systemic Lipidomic Profiles in Allogeneic Stem Cell Transplant Recipients. Cancers (Basel) 2022; 14:cancers14122910. [PMID: 35740576 PMCID: PMC9220974 DOI: 10.3390/cancers14122910] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/30/2022] [Accepted: 06/08/2022] [Indexed: 01/27/2023] Open
Abstract
Simple Summary Stem cell transplantation is used in the treatment of aggressive hematological malignancies and consists of initial high-dose and potentially lethal chemotherapy, followed by rescue with the transplantation of hematopoietic stem cells. Transplantation with stem cells from a healthy donor (i.e., allogeneic stem cells) has the strongest anti-cancer effect, but also the highest risk of severe toxicity. Furthermore, the clinical status at the time of transplantation (inflammation, fluid overload) is associated with posttransplant mortality, and immune-mediated acute graft-versus-host disease (GVHD) is a potential lethal complication. Finally, lipid metabolism regulates the proliferation and survival of both malignant hematological cells and immunocompetent cells that cause GVHD. Our study shows that the pretransplant lipid profiles differ between allotransplant recipients and can be used for the subclassification of patients and possibly to identify patients with an increased risk of death due to disease relapse or treatment toxicity. The therapeutic targeting of lipid metabolism should therefore be further explored in these transplant recipients. Abstract Allogeneic stem cell transplantation is used in the treatment of high-risk hematological malignancies. However, this treatment is associated with severe treatment-related morbidity and mortality. The metabolic status of the recipient may be associated with the risk of development of transplant-associated complications such as graft-versus-host disease (GVHD). To better understand the impact of the lipidomic profile of transplant recipients on posttransplant complications, we evaluated the lipid signatures of patients with hematological disease using non-targeted lipidomics. In the present study, we studied pretransplant serum samples derived from 92 consecutive patients with acute myeloid leukemia (AML) or high-risk myelodysplastic syndrome (MDS). A total of 960 lipid biochemicals were identified, and the pretransplant lipidomic profiles differed significantly when comparing patients with and without the risk factors: (i) pretransplant inflammation, (ii) early fluid overload, and (iii) patients with and without later steroid-requiring acute GVHD. All three factors, but especially patients with pretransplant inflammation, were associated with decreased levels of several lipid metabolites. Based on the overall concentrations of various lipid subclasses, we identified a patient subset characterized by low lipid levels, increased frequency of MDS patients, signs of inflammation, decreased body mass index, and an increased risk of early non-relapse mortality. Metabolic targeting has been proposed as a possible therapeutic strategy in allotransplant recipients, and our present results suggest that the clinical consequences of therapeutic intervention (e.g., nutritional support) will also differ between patients and depend on the metabolic context.
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14
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Arora A, Taskinen JH, Olkkonen VM. Coordination of inter-organelle communication and lipid fluxes by OSBP-related proteins. Prog Lipid Res 2022; 86:101146. [PMID: 34999137 DOI: 10.1016/j.plipres.2022.101146] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 12/10/2021] [Accepted: 01/03/2022] [Indexed: 12/31/2022]
Abstract
Oxysterol-binding protein (OSBP) and OSBP-related proteins (ORPs) constitute one of the largest families of lipid-binding/transfer proteins (LTPs) in eukaryotes. The current view is that many of them mediate inter-organelle lipid transfer over membrane contact sites (MCS). The transfer occurs in several cases in a 'counter-current' fashion: A lipid such as cholesterol or phosphatidylserine (PS) is transferred against its concentration gradient driven by transport of a phosphoinositide in the opposite direction. In this way ORPs are envisioned to maintain the distinct organelle lipid compositions, with impacts on multiple organelle functions. However, the functions of ORPs extend beyond lipid homeostasis to regulation of processes such as cell survival, proliferation and migration. Important expanding areas of mammalian ORP research include their roles in viral and bacterial infections, cancers, and neuronal function. The yeast OSBP homologue (Osh) proteins execute multifaceted functions in sterol and glycerophospholipid homeostasis, post-Golgi vesicle transport, phosphatidylinositol-4-phosphate, sphingolipid and target of rapamycin (TOR) signalling, and cell cycle control. These observations identify ORPs as lipid transporters and coordinators of signals with an unforeseen variety of cellular processes. Understanding their activities not only enlightens the biology of the living cell but also allows their employment as targets of new therapeutic approaches for disease.
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Affiliation(s)
- Amita Arora
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Juuso H Taskinen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland
| | - Vesa M Olkkonen
- Minerva Foundation Institute for Medical Research, and Department of Anatomy, Faculty of Medicine, University of Helsinki, Finland.
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15
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De Camilli P. How a first research experience had an impact on my scientific journey. Mol Biol Cell 2021; 32:ae1. [PMID: 34735266 PMCID: PMC8694089 DOI: 10.1091/mbc.e21-08-0397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
As I look back to my scientific trajectory on the occasion of being the recipient of the E. B. Wilson Medal of the American Society for Cell Biology, I realize how much an early scientific experience had an impact on my research many years later. The major influence that the first scientific encounters can have in defining a scientist’s path makes the choice of the training environment so important for a future career.
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Affiliation(s)
- Pietro De Camilli
- Departments of Neuroscience and Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Kavli Institute for Neuroscience, Yale School of Medicine, New Haven, CT 06510
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16
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Schechter M, Sharon R. An Emerging Role for Phosphoinositides in the Pathophysiology of Parkinson’s Disease. JOURNAL OF PARKINSON'S DISEASE 2021; 11:1725-1750. [PMID: 34151859 PMCID: PMC8609718 DOI: 10.3233/jpd-212684] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Recent data support an involvement of defects in homeostasis of phosphoinositides (PIPs) in the pathophysiology of Parkinson’s disease (PD). Genetic mutations have been identified in genes encoding for PIP-regulating and PIP-interacting proteins, that are associated with familial and sporadic PD. Many of these proteins are implicated in vesicular membrane trafficking, mechanisms that were recently highlighted for their close associations with PD. PIPs are phosphorylated forms of the membrane phospholipid, phosphatidylinositol. Their composition in the vesicle’s membrane of origin, as well as membrane of destination, controls vesicular membrane trafficking. We review the converging evidence that points to the involvement of PIPs in PD. The review describes PD- and PIP-associated proteins implicated in clathrin-mediated endocytosis and autophagy, and highlights the involvement of α-synuclein in these mechanisms.
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Affiliation(s)
- Meir Schechter
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Ein Kerem, Jerusalem, Israel
| | - Ronit Sharon
- Department of Biochemistry and Molecular Biology, IMRIC, The Hebrew University-Hadassah Medical School, Ein Kerem, Jerusalem, Israel
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17
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Steck TL, Tabei SMA, Lange Y. A basic model for cell cholesterol homeostasis. Traffic 2021; 22:471-481. [PMID: 34528339 DOI: 10.1111/tra.12816] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 08/26/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
Cells manage their cholesterol by negative feedback using a battery of sterol-responsive proteins. How these activities are coordinated so as to specify the abundance and distribution of the sterol is unclear. We present a simple mathematical model that addresses this question. It assumes that almost all of the cholesterol is associated with phospholipids in stoichiometric complexes. A small fraction of the sterol is uncomplexed and thermodynamically active. It equilibrates among the organelles, setting their sterol level according to the affinity of their phospholipids. The activity of the homeostatic proteins in the cytoplasmic membranes is then set by their fractional saturation with uncomplexed cholesterol in competition with the phospholipids. The high-affinity phospholipids in the plasma membrane (PM) are filled to near stoichiometric equivalence, giving it most of the cell sterol. Notably, the affinity of the phospholipids in the endomembranes (EMs) is lower by orders of magnitude than that of the phospholipids in the PM. Thus, the small amount of sterol in the EMs rests far below stoichiometric capacity. Simulations match a variety of experimental data. The model captures the essence of cell cholesterol homeostasis, makes coherent a diverse set of experimental findings, provides a surprising prediction and suggests new experiments.
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Affiliation(s)
- Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
| | - S M Ali Tabei
- Department of Physics, University of Northern Iowa, Cedar Falls, Iowa, USA
| | - Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
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18
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Reinisch KM, Prinz WA. Mechanisms of nonvesicular lipid transport. J Cell Biol 2021; 220:211813. [PMID: 33605998 PMCID: PMC7901144 DOI: 10.1083/jcb.202012058] [Citation(s) in RCA: 71] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 02/02/2021] [Accepted: 02/02/2021] [Indexed: 12/18/2022] Open
Abstract
We have long known that lipids traffic between cellular membranes via vesicles but have only recently appreciated the role of nonvesicular lipid transport. Nonvesicular transport can be high volume, supporting biogenesis of rapidly expanding membranes, or more targeted and precise, allowing cells to rapidly alter levels of specific lipids in membranes. Most such transport probably occurs at membrane contact sites, where organelles are closely apposed, and requires lipid transport proteins (LTPs), which solubilize lipids to shield them from the aqueous phase during their transport between membranes. Some LTPs are cup like and shuttle lipid monomers between membranes. Others form conduits allowing lipid flow between membranes. This review describes what we know about nonvesicular lipid transfer mechanisms while also identifying many remaining unknowns: How do LTPs facilitate lipid movement from and into membranes, do LTPs require accessory proteins for efficient transfer in vivo, and how is directionality of transport determined?
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Affiliation(s)
- Karin M Reinisch
- Department of Cell Biology, Yale School of Medicine, New Haven, CT
| | - William A Prinz
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD
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19
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Compartmentalization of phosphatidylinositol 4,5-bisphosphate metabolism into plasma membrane liquid-ordered/raft domains. Proc Natl Acad Sci U S A 2021; 118:2025343118. [PMID: 33619111 DOI: 10.1073/pnas.2025343118] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Possible segregation of plasma membrane (PM) phosphoinositide metabolism in membrane lipid domains is not fully understood. We exploited two differently lipidated peptide sequences, L10 and S15, to mark liquid-ordered, cholesterol-rich (Lo) and liquid-disordered, cholesterol-poor (Ld) domains of the PM, often called raft and nonraft domains, respectively. Imaging of the fluorescent labels verified that L10 segregated into cholesterol-rich Lo phases of cooled giant plasma-membrane vesicles (GPMVs), whereas S15 and the dye FAST DiI cosegregated into cholesterol-poor Ld phases. The fluorescent protein markers were used as Förster resonance energy transfer (FRET) pairs in intact cells. An increase of homologous FRET between L10 probes showed that depleting membrane cholesterol shrank Lo domains and enlarged Ld domains, whereas a decrease of L10 FRET showed that adding more cholesterol enlarged Lo and shrank Ld Heterologous FRET signals between the lipid domain probes and phosphoinositide marker proteins suggested that phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P 2] and phosphatidylinositol 4-phosphate (PtdIns4P) are present in both Lo and Ld domains. In kinetic analysis, muscarinic-receptor-activated phospholipase C (PLC) depleted PtdIns(4,5)P 2 and PtdIns4P more rapidly and produced diacylglycerol (DAG) more rapidly in Lo than in Ld Further, PtdIns(4,5)P 2 was restored more rapidly in Lo than in Ld Thus destruction and restoration of PtdIns(4,5)P 2 are faster in Lo than in Ld This suggests that Lo is enriched with both the receptor G protein/PLC pathway and the PtdIns/PI4-kinase/PtdIns4P pathway. The significant kinetic differences of lipid depletion and restoration also mean that exchange of lipids between these domains is much slower than free diffusion predicts.
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20
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Nakatsu F, Kawasaki A. Functions of Oxysterol-Binding Proteins at Membrane Contact Sites and Their Control by Phosphoinositide Metabolism. Front Cell Dev Biol 2021; 9:664788. [PMID: 34249917 PMCID: PMC8264513 DOI: 10.3389/fcell.2021.664788] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2021] [Accepted: 05/06/2021] [Indexed: 01/10/2023] Open
Abstract
Lipids must be correctly transported within the cell to the right place at the right time in order to be fully functional. Non-vesicular lipid transport is mediated by so-called lipid transfer proteins (LTPs), which contain a hydrophobic cavity that sequesters lipid molecules. Oxysterol-binding protein (OSBP)-related proteins (ORPs) are a family of LTPs known to harbor lipid ligands, such as cholesterol and phospholipids. ORPs act as a sensor or transporter of those lipid ligands at membrane contact sites (MCSs) where two different cellular membranes are closely apposed. In particular, a characteristic functional property of ORPs is their role as a lipid exchanger. ORPs mediate counter-directional transport of two different lipid ligands at MCSs. Several, but not all, ORPs transport their lipid ligand from the endoplasmic reticulum (ER) in exchange for phosphatidylinositol 4-phosphate (PI4P), the other ligand, on apposed membranes. This ORP-mediated lipid “countertransport” is driven by the concentration gradient of PI4P between membranes, which is generated by its kinases and phosphatases. In this review, we will discuss how ORP function is tightly coupled to metabolism of phosphoinositides such as PI4P. Recent progress on the role of ORP-mediated lipid transport/countertransport at multiple MCSs in cellular functions will be also discussed.
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Affiliation(s)
- Fubito Nakatsu
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
| | - Asami Kawasaki
- Department of Neurochemistry and Molecular Cell Biology, Niigata University School of Medicine and Graduate School of Medical/Dental Sciences, Niigata, Japan
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21
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Tong J, Tan L, Im YJ. Structure of human ORP3 ORD reveals conservation of a key function and ligand specificity in OSBP-related proteins. PLoS One 2021; 16:e0248781. [PMID: 33857182 PMCID: PMC8049286 DOI: 10.1371/journal.pone.0248781] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 03/04/2021] [Indexed: 11/19/2022] Open
Abstract
Human ORP3 belongs to the oxysterol-binding protein (OSBP) family of lipid transfer proteins and is involved in lipid trafficking and cell signaling. ORP3 localizes to the ER-PM interfaces and is implicated in lipid transport and focal adhesion dynamics. Here, we report the 2.6–2.7 Å structures of the ORD (OSBP-related domain) of human ORP3 in apo-form and in complex with phosphatidylinositol 4-phosphate. The ORP3 ORD displays a helix grip β-barrel fold with a deep hydrophobic pocket which is conserved in the OSBP gene family. ORP3 binds PI(4)P by the residues around tunnel entrance and in the hydrophobic pocket, whereas it lacks sterol binding due to the narrow hydrophobic tunnel. The heterologous expression of the ORDs of human ORP3 or OSBP1 rescued the lethality of seven ORP (yeast OSH1-OSH7) knockout in yeast. In contrast, the PI(4)P-binding site mutant of ORP3 did not complement the OSH knockout cells. The N-terminal PH domain and FFAT motif of ORP3 are involved in protein targeting but are not essential in yeast complementation. This observation suggests that the essential function conserved in the ORPs of yeast and human is mediated by PI(4)P-binding of the ORD domain. This study suggests that the non-vesicular PI(4)P transport is a conserved function of all ORPs in eukaryotes.
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Affiliation(s)
- Junsen Tong
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
| | - Lingchen Tan
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
| | - Young Jun Im
- College of Pharmacy, Chonnam National University, Gwangju, Republic of Korea
- * E-mail:
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22
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Lange Y, Steck TL. Active cholesterol 20 years on. Traffic 2020; 21:662-674. [PMID: 32930466 DOI: 10.1111/tra.12762] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 09/08/2020] [Accepted: 09/10/2020] [Indexed: 12/13/2022]
Abstract
This review considers the following hypotheses, some well-supported and some speculative. Almost all of the sterol molecules in plasma membranes are associated with bilayer phospholipids in complexes of varied strength and stoichiometry. These complexes underlie many of the material properties of the bilayer. The small fraction of cholesterol molecules exceeding the binding capacity of the phospholipids is thermodynamically active and serves diverse functions. It circulates briskly among the cell membranes, particularly through contact sites linking the organelles. Active cholesterol provides the upstream feedback signal to multiple mechanisms governing plasma membrane homeostasis, pegging the sterol level to a threshold set by its phospholipids. Active cholesterol could also be the cargo for various inter-organelle transporters and the form excreted from cells by reverse transport. Furthermore, it is integral to the function of caveolae; a mediator of Hedgehog regulation; and a ligand for the binding of cytolytic toxins to membranes. Active cholesterol modulates a variety of plasma membrane proteins-receptors, channels and transporters-at least in vitro.
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Affiliation(s)
- Yvonne Lange
- Department of Pathology, Rush University Medical Center, Chicago, Illinois, USA
| | - Theodore L Steck
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, USA
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23
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Conduit SE, Vanhaesebroeck B. Phosphoinositide lipids in primary cilia biology. Biochem J 2020; 477:3541-3565. [PMID: 32970140 PMCID: PMC7518857 DOI: 10.1042/bcj20200277] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/30/2020] [Accepted: 08/27/2020] [Indexed: 12/11/2022]
Abstract
Primary cilia are solitary signalling organelles projecting from the surface of most cell types. Although the ciliary membrane is continuous with the plasma membrane it exhibits a unique phospholipid composition, a feature essential for normal cilia formation and function. Recent studies have illustrated that distinct phosphoinositide lipid species localise to specific cilia subdomains, and have begun to build a 'phosphoinositide map' of the cilium. The abundance and localisation of phosphoinositides are tightly regulated by the opposing actions of lipid kinases and lipid phosphatases that have also been recently discovered at cilia. The critical role of phosphoinositides in cilia biology is highlighted by the devastating consequences of genetic defects in cilia-associated phosphoinositide regulatory enzymes leading to ciliopathy phenotypes in humans and experimental mouse and zebrafish models. Here we provide a general introduction to primary cilia and the roles phosphoinositides play in cilia biology. In addition to increasing our understanding of fundamental cilia biology, this rapidly expanding field may inform novel approaches to treat ciliopathy syndromes caused by deregulated phosphoinositide metabolism.
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Affiliation(s)
- Sarah E. Conduit
- UCL Cancer Institute, University College London, 72 Huntley Street, London WC1E 6BT, U.K
| | - Bart Vanhaesebroeck
- UCL Cancer Institute, University College London, 72 Huntley Street, London WC1E 6BT, U.K
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