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Arabiotorre A, Bankaitis VA, Grabon A. Regulation of phosphoinositide metabolism in Apicomplexan parasites. Front Cell Dev Biol 2023; 11:1163574. [PMID: 37791074 PMCID: PMC10543664 DOI: 10.3389/fcell.2023.1163574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Accepted: 07/11/2023] [Indexed: 10/05/2023] Open
Abstract
Phosphoinositides are a biologically essential class of phospholipids that contribute to organelle membrane identity, modulate membrane trafficking pathways, and are central components of major signal transduction pathways that operate on the cytosolic face of intracellular membranes in eukaryotes. Apicomplexans (such as Toxoplasma gondii and Plasmodium spp.) are obligate intracellular parasites that are important causative agents of disease in animals and humans. Recent advances in molecular and cell biology of Apicomplexan parasites reveal important roles for phosphoinositide signaling in key aspects of parasitosis. These include invasion of host cells, intracellular survival and replication, egress from host cells, and extracellular motility. As Apicomplexans have adapted to the organization of essential signaling pathways to accommodate their complex parasitic lifestyle, these organisms offer experimentally tractable systems for studying the evolution, conservation, and repurposing of phosphoinositide signaling. In this review, we describe the regulatory mechanisms that control the spatial and temporal regulation of phosphoinositides in the Apicomplexan parasites Plasmodium and T. gondii. We further discuss the similarities and differences presented by Apicomplexan phosphoinositide signaling relative to how these pathways are regulated in other eukaryotic organisms.
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Affiliation(s)
- Angela Arabiotorre
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
| | - Vytas A. Bankaitis
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
- Department of Biochemistry and Biophysics Texas A&M University College Station, College Station, TX, United States
- Department of Chemistry Texas A&M University College Station, College Station, TX, United States
| | - Aby Grabon
- Department of Cell Biology and Genetics, College of Medicine Texas A&M Health Sciences Center College Station, Bryan, TX, United States
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Arabiotorre A, Formanowicz M, Bankaitis VA, Grabon A. Phosphatidylinositol-4-phosphate signaling regulates dense granule biogenesis and exocytosis in Toxoplasma gondii. bioRxiv 2023:2023.01.09.523261. [PMID: 36712082 PMCID: PMC9882004 DOI: 10.1101/2023.01.09.523261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Phosphoinositide metabolism defines the foundation of a major signaling pathway that is conserved throughout the eukaryotic kingdom. The 4-OH phosphorylated phosphoinositides such as phosphatidylinositol-4-phosphate (PtdIns4P) and phosphatidylinositol-4,5-bisphosphate are particularly important molecules as these execute intrinsically essential activities required for the viability of all eukaryotic cells studied thus far. Using intracellular tachyzoites of the apicomplexan parasite Toxoplasma gondii as model for assessing primordial roles for PtdIns4P signaling, we demonstrate the presence of PtdIns4P pools in Golgi/trans-Golgi (TGN) system and in post-TGN compartments of the parasite. Moreover, we show that deficits in PtdIns4P signaling result in structural perturbation of compartments that house dense granule cargo with accompanying deficits in dense granule exocytosis. Taken together, the data report a direct role for PtdIns4P in dense granule biogenesis and exocytosis. The data further indicate that the biogenic pathway for secretion-competent dense granule formation in T. gondii is more complex than simple budding of fully matured dense granules from the TGN.
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Affiliation(s)
- Angela Arabiotorre
- Department of Cell Biology & Genetics, College of Medicine, Texas A&M Health Sciences Center, College Station, Texas 77843-1114, USA
| | - Megan Formanowicz
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843-2128
| | - Vytas A. Bankaitis
- Department of Cell Biology & Genetics, College of Medicine, Texas A&M Health Sciences Center, College Station, Texas 77843-1114, USA
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, Texas 77843-2128
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-2128
| | - Aby Grabon
- Department of Cell Biology & Genetics, College of Medicine, Texas A&M Health Sciences Center, College Station, Texas 77843-1114, USA
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Wang Y, Yuan P, Grabon A, Tripathi A, Lee D, Rodriguez M, Lönnfors M, Eisenberg-Bord M, Wang Z, Man Lam S, Schuldiner M, Bankaitis VA. Noncanonical regulation of phosphatidylserine metabolism by a Sec14-like protein and a lipid kinase. J Cell Biol 2021; 219:151686. [PMID: 32303746 PMCID: PMC7199851 DOI: 10.1083/jcb.201907128] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 12/20/2019] [Accepted: 02/10/2020] [Indexed: 01/20/2023] Open
Abstract
The yeast phosphatidylserine (PtdSer) decarboxylase Psd2 is proposed to engage in a membrane contact site (MCS) for PtdSer decarboxylation to phosphatidylethanolamine (PtdEtn). This proposed MCS harbors Psd2, the Sec14-like phosphatidylinositol transfer protein (PITP) Sfh4, the Stt4 phosphatidylinositol (PtdIns) 4-OH kinase, the Scs2 tether, and an uncharacterized protein. We report that, of these components, only Sfh4 and Stt4 regulate Psd2 activity in vivo. They do so via distinct mechanisms. Sfh4 operates via a mechanism for which its PtdIns-transfer activity is dispensable but requires an Sfh4-Psd2 physical interaction. The other requires Stt4-mediated production of PtdIns-4-phosphate (PtdIns4P), where Stt4 (along with the Sac1 PtdIns4P phosphatase and endoplasmic reticulum–plasma membrane tethers) indirectly modulate Psd2 activity via a PtdIns4P homeostatic mechanism that influences PtdSer accessibility to Psd2. These results identify an example in which the biological function of a Sec14-like PITP is cleanly uncoupled from its canonical in vitro PtdIns-transfer activity and challenge popular functional assumptions regarding lipid-transfer protein involvements in MCS function.
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Affiliation(s)
- Yaxi Wang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX.,Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - Peihua Yuan
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - Aby Grabon
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - Ashutosh Tripathi
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - Dongju Lee
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - Martin Rodriguez
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX
| | - Max Lönnfors
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | | | - Zehua Wang
- University of Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Sin Man Lam
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Vytas A Bankaitis
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX.,Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX.,Department of Chemistry, Texas A&M University, College Station, TX
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4
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McDermott MI, Diz R, Hur S, Lete MG, Applebee CJ, Grabon A, Tripathi A, Wakelam MJO, Larijani B, Bankaitis VA. A Reassessment of Phosphatidylinositol Transfer Protein Alpha's Growth Factor Signaling Role. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.lb326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Mark I. McDermott
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
| | - Ramiro Diz
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
| | - Seong Hur
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
| | - Marta G. Lete
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
- Ikerbasque Basque Foundation for ScienceResearch Center for Experimental Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU/CSIC) and University of the Basque CountryLeioaSpain
| | - Christopher J. Applebee
- Ikerbasque Basque Foundation for ScienceResearch Center for Experimental Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU/CSIC) and University of the Basque CountryLeioaSpain
| | - Aby Grabon
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
| | - Ashutosh Tripathi
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
| | | | - Banafshe Larijani
- Ikerbasque Basque Foundation for ScienceResearch Center for Experimental Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU/CSIC) and University of the Basque CountryLeioaSpain
| | - Vytas A. Bankaitis
- Molecular and Cellular MedicineE. L. Wehner‐Welch Laboratory, Texas A&M Health Science CenterCollege StationTX
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Grabon A, Bankaitis VA, McDermott MI. The interface between phosphatidylinositol transfer protein function and phosphoinositide signaling in higher eukaryotes. J Lipid Res 2018; 60:242-268. [PMID: 30504233 DOI: 10.1194/jlr.r089730] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Revised: 11/12/2018] [Indexed: 12/22/2022] Open
Abstract
Phosphoinositides are key regulators of a large number of diverse cellular processes that include membrane trafficking, plasma membrane receptor signaling, cell proliferation, and transcription. How a small number of chemically distinct phosphoinositide signals are functionally amplified to exert specific control over such a diverse set of biological outcomes remains incompletely understood. To this end, a novel mechanism is now taking shape, and it involves phosphatidylinositol (PtdIns) transfer proteins (PITPs). The concept that PITPs exert instructive regulation of PtdIns 4-OH kinase activities and thereby channel phosphoinositide production to specific biological outcomes, identifies PITPs as central factors in the diversification of phosphoinositide signaling. There are two evolutionarily distinct families of PITPs: the Sec14-like and the StAR-related lipid transfer domain (START)-like families. Of these two families, the START-like PITPs are the least understood. Herein, we review recent insights into the biochemical, cellular, and physiological function of both PITP families with greater emphasis on the START-like PITPs, and we discuss the underlying mechanisms through which these proteins regulate phosphoinositide signaling and how these actions translate to human health and disease.
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Affiliation(s)
- Aby Grabon
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
| | - Vytas A Bankaitis
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
| | - Mark I McDermott
- E. L. Wehner-Welch Laboratory, Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114
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Grabon A, Bankaitis VA. A Novel Multi‐domain Phosphatidylinositol Transfer Protein/Oxysterol Binding Protein Senses Specific Phosphoinositide Pools On
Toxoplasma
Dense Granules. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.540.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Aby Grabon
- Department of Molecular and Cellular MedicineTexas A&M UniversityCollege StationTX
| | - Vytas A. Bankaitis
- Department of Molecular and Cellular MedicineTexas A&M UniversityCollege StationTX
- Department of Biochemistry & BiophysicsTexas A&M UniversityCollege StationTX
- Department of ChemistryTexas A&M UniversityCollege StationTX
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7
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McDermott MI, Diz R, Hur S, Lete MG, Applebee CJ, Grabon A, Tripathi A, Wakelam MJO, Larijani B, Bankaitis VA. A Reevaluation of the Role of Phosphatidylinositol Transfer Protein a in Growth Factor Signaling. FASEB J 2018. [DOI: 10.1096/fasebj.2018.32.1_supplement.540.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Ramiro Diz
- Molecular and Cellular MedicineTexas A&MCollege StationTX
| | - Seong Hur
- Molecular and Cellular MedicineTexas A&MCollege StationTX
| | - Marta G. Lete
- Molecular and Cellular MedicineTexas A&MCollege StationTX
- Cell Biophysics LaboratoryIkerbasque Basque Foundation for ScienceResearch Center for Experimental Marine Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU, CSIC)University of the Basque CountryLeioaSpain
| | - Christopher J. Applebee
- Cell Biophysics LaboratoryIkerbasque Basque Foundation for ScienceResearch Center for Experimental Marine Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU, CSIC)University of the Basque CountryLeioaSpain
| | - Aby Grabon
- Molecular and Cellular MedicineTexas A&MCollege StationTX
| | | | | | - Banafshe Larijani
- Cell Biophysics LaboratoryIkerbasque Basque Foundation for ScienceResearch Center for Experimental Marine Biology and Biotechnology (PiE) and Biofisika Instituto (UPV/EHU, CSIC)University of the Basque CountryLeioaSpain
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Grabon A, Orłowski A, Tripathi A, Vuorio J, Javanainen M, Róg T, Lönnfors M, McDermott MI, Siebert G, Somerharju P, Vattulainen I, Bankaitis VA. Dynamics and energetics of the mammalian phosphatidylinositol transfer protein phospholipid exchange cycle. J Biol Chem 2017; 292:14438-14455. [PMID: 28718450 DOI: 10.1074/jbc.m117.791467] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 07/14/2017] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol-transfer proteins (PITPs) regulate phosphoinositide signaling in eukaryotic cells. The defining feature of PITPs is their ability to exchange phosphatidylinositol (PtdIns) molecules between membranes, and this property is central to PITP-mediated regulation of lipid signaling. However, the details of the PITP-mediated lipid exchange cycle remain entirely obscure. Here, all-atom molecular dynamics simulations of the mammalian StART-like PtdIns/phosphatidylcholine (PtdCho) transfer protein PITPα, both on membrane bilayers and in solvated systems, informed downstream biochemical analyses that tested key aspects of the hypotheses generated by the molecular dynamics simulations. These studies provided five key insights into the PITPα lipid exchange cycle: (i) interaction of PITPα with the membrane is spontaneous and mediated by four specific protein substructures; (ii) the ability of PITPα to initiate closure around the PtdCho ligand is accompanied by loss of flexibility of two helix/loop regions, as well as of the C-terminal helix; (iii) the energy barrier of phospholipid extraction from the membrane is lowered by a network of hydrogen bonds between the lipid molecule and PITPα; (iv) the trajectory of PtdIns or PtdCho into and through the lipid-binding pocket is chaperoned by sets of PITPα residues conserved throughout the StART-like PITP family; and (v) conformational transitions in the C-terminal helix have specific functional involvements in PtdIns transfer activity. Taken together, these findings provide the first mechanistic description of key aspects of the PITPα PtdIns/PtdCho exchange cycle and offer a rationale for the high conservation of particular sets of residues across evolutionarily distant members of the metazoan StART-like PITP family.
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Affiliation(s)
- Aby Grabon
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Adam Orłowski
- the Laboratory of Physics, Tampere University of Technology, FI-33720 Tampere, Finland.,the Department of Physics and Energy, University of Limerick, Limerick V94 T9PX, Ireland
| | - Ashutosh Tripathi
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Joni Vuorio
- the Laboratory of Physics, Tampere University of Technology, FI-33720 Tampere, Finland.,the Department of Physics, University of Helsinki, P. O. Box 64, FI-00014 Helsinki, Finland
| | - Matti Javanainen
- the Laboratory of Physics, Tampere University of Technology, FI-33720 Tampere, Finland
| | - Tomasz Róg
- the Laboratory of Physics, Tampere University of Technology, FI-33720 Tampere, Finland.,the Department of Physics, University of Helsinki, P. O. Box 64, FI-00014 Helsinki, Finland
| | - Max Lönnfors
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Mark I McDermott
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Garland Siebert
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843
| | - Pentti Somerharju
- the Department of Biochemistry and Developmental Biology, University of Helsinki, P. O. Box 63, FI-00014 Helsinki, Finland
| | - Ilpo Vattulainen
- the Laboratory of Physics, Tampere University of Technology, FI-33720 Tampere, Finland, .,the Department of Physics, University of Helsinki, P. O. Box 64, FI-00014 Helsinki, Finland.,the Department of Physics and Chemistry, MEMPHYS, Center for Biomembrane Physics, University of Southern Denmark, DK-5230 Odense, Denmark, and
| | - Vytas A Bankaitis
- From the Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas 77843, .,the Departments of Biochemistry and Biophysics and.,Chemistry, Texas A&M University, College Station, Texas 77843
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9
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Tribble EK, Ivanova PT, Grabon A, Alb JG, Faenza I, Cocco L, Brown HA, Bankaitis VA. Quantitative profiling of the endonuclear glycerophospholipidome of murine embryonic fibroblasts. J Lipid Res 2016; 57:1492-506. [PMID: 27256690 DOI: 10.1194/jlr.m068734] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Indexed: 01/18/2023] Open
Abstract
A reliable method for purifying envelope-stripped nuclei from immortalized murine embryonic fibroblasts (iMEFs) was established. Quantitative profiling of the glycerophospholipids (GPLs) in envelope-free iMEF nuclei yields several conclusions. First, we find the endonuclear glycerophospholipidome differs from that of bulk membranes, and phosphatidylcholine (PtdCho) and phosphatidylethanolamine species are the most abundant endonuclear GPLs by mass. By contrast, phosphatidylinositol (PtdIns) represents a minor species. We also find only a slight enrichment of saturated versus unsaturated GPL species in iMEF endonuclear fractions. Moreover, much lower values for GPL mass were measured in the iMEF nuclear matrix than those reported for envelope-stripped IMF-32 nuclei. The collective results indicate that the nuclear matrix in these cells is a GPL-poor environment where GPL occupies only approximately 0.1% of the total nuclear matrix volume. This value suggests GPL accommodation in this compartment can be satisfied by binding to resident proteins. Finally, we find no significant role for the PtdIns/PtdCho-transfer protein, PITPα, in shuttling PtdIns into the iMEF nuclear matrix.
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Affiliation(s)
- Emily K Tribble
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC
| | - Pavlina T Ivanova
- Departments of Pharmacology and Biochemistry, Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN
| | - Aby Grabon
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX
| | - James G Alb
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC
| | - Irene Faenza
- Cellular Signaling Laboratory, Department of Biomedical Sciences, University of Bologna, Bologna, Italy
| | - Lucio Cocco
- Cellular Signaling Laboratory, Department of Biomedical Sciences, University of Bologna, Bologna, Italy
| | - H Alex Brown
- Departments of Pharmacology and Biochemistry, Vanderbilt University School of Medicine, Vanderbilt Institute of Chemical Biology, Nashville, TN
| | - Vytas A Bankaitis
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX
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Grabon A, Khan D, Bankaitis VA. Phosphatidylinositol transfer proteins and instructive regulation of lipid kinase biology. Biochim Biophys Acta 2015; 1851:724-35. [PMID: 25592381 PMCID: PMC5221696 DOI: 10.1016/j.bbalip.2014.12.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 11/21/2014] [Accepted: 12/16/2014] [Indexed: 11/25/2022]
Abstract
Phosphatidylinositol is a metabolic precursor of phosphoinositides and soluble inositol phosphates. Both sets of molecules represent versatile intracellular chemical signals in eukaryotes. While much effort has been invested in understanding the enzymes that produce and consume these molecules, central aspects for how phosphoinositide production is controlled and functionally partitioned remain unresolved and largely unappreciated. It is in this regard that phosphatidylinositol (PtdIns) transfer proteins (PITPs) are emerging as central regulators of the functional channeling of phosphoinositide pools produced on demand for specific signaling purposes. The physiological significance of these proteins is amply demonstrated by the consequences that accompany deficits in individual PITPs. Although the biological problem is fascinating, and of direct relevance to disease, PITPs remain largely uncharacterized. Herein, we discuss our perspectives regarding what is known about how PITPs work as molecules, and highlight progress in our understanding of how PITPs are integrated into cellular physiology. This article is part of a Special Issue entitled Phosphoinositides.
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Affiliation(s)
- Aby Grabon
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA
| | - Danish Khan
- Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA
| | - Vytas A Bankaitis
- Department of Molecular & Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, USA; Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX 77843-2128, USA.
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Abstract
Kim et al. (2011) challenge the dogma that phosphatidylinositol synthesis is restricted to the endoplasmic reticulum (ER) by showing that a mobile membrane compartment transports phosphatidylinositol synthase from the ER to numerous cellular compartments, including the plasma membrane. These findings significantly impact our view of phosphoinositide signaling in the cell.
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Affiliation(s)
- Vytas A Bankaitis
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA.
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Abstract
Inositol and phosphoinositide signaling pathways represent major regulatory systems in eukaryotes. The physiological importance of these pathways is amply demonstrated by the variety of diseases that involve derangements in individual steps in inositide and phosphoinositide production and degradation. These diseases include numerous cancers, lipodystrophies and neurological syndromes. Phosphatidylinositol transfer proteins (PITPs) are emerging as fascinating regulators of phosphoinositide metabolism. Recent advances identify PITPs (and PITP-like proteins) to be coincidence detectors, which spatially and temporally coordinate the activities of diverse aspects of the cellular lipid metabolome with phosphoinositide signaling. These insights are providing new ideas regarding mechanisms of inherited mammalian diseases associated with derangements in the activities of PITPs and PITP-like proteins.
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Affiliation(s)
- Aaron H Nile
- Department of Cell & Developmental Biology, Lineberger Comprehensive Cancer Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-27090, USA
| | - Vytas A Bankaitis
- Department of Cell & Developmental Biology, Lineberger Comprehensive Cancer Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-27090, USA
| | - Aby Grabon
- Department of Cell & Developmental Biology, Lineberger Comprehensive Cancer Center School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-27090, USA
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