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Wang Y, Wakelam MJO, Bankaitis VA, McDermott MI. The wide world of non-mammalian phospholipase D enzymes. Adv Biol Regul 2024; 91:101000. [PMID: 38081756 DOI: 10.1016/j.jbior.2023.101000] [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: 11/10/2023] [Accepted: 11/15/2023] [Indexed: 02/25/2024]
Abstract
Phospholipase D (PLD) hydrolyses phosphatidylcholine (PtdCho) to produce free choline and the critically important lipid signaling molecule phosphatidic acid (PtdOH). Since the initial discovery of PLD activities in plants and bacteria, PLDs have been identified in a diverse range of organisms spanning the taxa. While widespread interest in these proteins grew following the discovery of mammalian isoforms, research into the PLDs of non-mammalian organisms has revealed a fascinating array of functions ranging from roles in microbial pathogenesis, to the stress responses of plants and the developmental patterning of flies. Furthermore, studies in non-mammalian model systems have aided our understanding of the entire PLD superfamily, with translational relevance to human biology and health. Increasingly, the promise for utilization of non-mammalian PLDs in biotechnology is also being recognized, with widespread potential applications ranging from roles in lipid synthesis, to their exploitation for agricultural and pharmaceutical applications.
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Affiliation(s)
- Y Wang
- Department of Cell Biology & Genetics, Texas A&M Health Science Center, College Station, TX, 77843, USA; Department of Microbiology, University of Washington, Seattle, WA98109, USA
| | - M J O Wakelam
- Babraham Institute, Babraham Research Campus, Cambridge, CB22 3AT, United Kingdom
| | - V A Bankaitis
- Department of Cell Biology & Genetics, Texas A&M Health Science Center, College Station, TX, 77843, USA; Department of Biochemistry & Biophysics, Texas A&M University, College Station, TX, 77843, USA; Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA
| | - M I McDermott
- Department of Cell Biology & Genetics, Texas A&M Health Science Center, College Station, TX, 77843, USA.
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2
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Bowling FZ, Frohman MA, Airola MV. Structure and regulation of human phospholipase D. Adv Biol Regul 2021; 79:100783. [PMID: 33495125 DOI: 10.1016/j.jbior.2020.100783] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 12/22/2020] [Accepted: 12/28/2020] [Indexed: 12/13/2022]
Abstract
Mammalian phospholipase D (PLD) generates phosphatidic acid, a dynamic lipid secondary messenger involved with a broad spectrum of cellular functions including but not limited to metabolism, migration, and exocytosis. As a promising pharmaceutical target, the biochemical properties of PLD have been well characterized. This has led to the recent crystal structures of human PLD1 and PLD2, the development of PLD specific pharmacological inhibitors, and the identification of cellular regulators of PLD. In this review, we discuss the PLD1 and PLD2 structures, PLD inhibition by small molecules, and the regulation of PLD activity by effector proteins and lipids.
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Affiliation(s)
- Forrest Z Bowling
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA
| | - Michael A Frohman
- Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY, USA
| | - Michael V Airola
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY, USA.
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3
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Zhou C, He M, Peng C, Yu J, Li Z, Zhou M, Li Y, Yang S, Ouyang H, Feng Y. Pharmacokinetic and Lipidomic Assessment of the In Vivo Effects of Parishin A-Isorhynchophylline in Rat Migraine Models. JOURNAL OF ANALYTICAL METHODS IN CHEMISTRY 2020; 2020:9101598. [PMID: 32695549 PMCID: PMC7362284 DOI: 10.1155/2020/9101598] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 03/27/2020] [Indexed: 06/11/2023]
Abstract
Migraine is a chronic brain disease that leads to periodic neurological attacks. Parishin A and isorhynchophylline (PI) is the active monomer component extracted from the traditional antimigraine Chinese medicinal combination of Gastrodia and Uncaria, respectively. In this study, using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) technology, we performed pharmacokinetic and lipidomic study on migraine model rats after administration of PI. For the detection of the compounds in plasma, AB Sciex Triple Quad™ 4500 was applied for quantitative analysis, and the COSMOSIL C18 column (2.1 × 100 mm, 2.6 μm) was used for separation. Isorhynchophylline (ISO: m/z 384.8-241.2) and its main metabolite rhynchophylline (RHY: m/z 384.8-160.2) were simultaneously detected under positive ion modes. Besides, parishin A (PA: m/z 995.1-726.9) and its main metabolite gastrodin (GAS: m/z 331.1-123.0) were simultaneously detected with negative ion modes. For the analysis of endogenous lipid components, Dionex Ultimate 3000 (UHPLC) Thermo Orbitrap Elite was applied for the detection, and the Waters UPLCRBEH C18 column (1.7 μm 100 ∗ 2.1 mm) was used for separation. Chloroform/methanol (2 : 1, v : v) was used for extraction. The results demonstrated that PI exists significant difference in metabolism between single- and coadministration and can regulate lipid levels associated with migraine.
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Affiliation(s)
- Chaoqun Zhou
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Mingzhen He
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- State Key Laboratory of Innovative Drug and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Chunyan Peng
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Jianjun Yu
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Zhifeng Li
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- State Key Laboratory of Innovative Drug and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Maofu Zhou
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Yan Li
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Shilin Yang
- State Key Laboratory of Innovative Drug and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Hui Ouyang
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
| | - Yulin Feng
- Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- State Key Laboratory of Innovative Drug and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
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4
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McDermott MI, Wang Y, Wakelam MJO, Bankaitis VA. Mammalian phospholipase D: Function, and therapeutics. Prog Lipid Res 2019; 78:101018. [PMID: 31830503 DOI: 10.1016/j.plipres.2019.101018] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Revised: 10/08/2019] [Accepted: 10/14/2019] [Indexed: 01/23/2023]
Abstract
Despite being discovered over 60 years ago, the precise role of phospholipase D (PLD) is still being elucidated. PLD enzymes catalyze the hydrolysis of the phosphodiester bond of glycerophospholipids producing phosphatidic acid and the free headgroup. PLD family members are found in organisms ranging from viruses, and bacteria to plants, and mammals. They display a range of substrate specificities, are regulated by a diverse range of molecules, and have been implicated in a broad range of cellular processes including receptor signaling, cytoskeletal regulation and membrane trafficking. Recent technological advances including: the development of PLD knockout mice, isoform-specific antibodies, and specific inhibitors are finally permitting a thorough analysis of the in vivo role of mammalian PLDs. These studies are facilitating increased recognition of PLD's role in disease states including cancers and Alzheimer's disease, offering potential as a target for therapeutic intervention.
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Affiliation(s)
- M I McDermott
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, United States of America.
| | - Y Wang
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, United States of America; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, United States of America
| | - M J O Wakelam
- Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, United Kingdom
| | - V A Bankaitis
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, TX 77843-1114, United States of America; Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128, United States of America; Department of Chemistry, Texas A&M University, College Station, Texas 77840, United States of America
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5
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Aktories K, Gierschik P, Heringdorf DMZ, Schmidt M, Schultz G, Wieland T. cAMP guided his way: a life for G protein-mediated signal transduction and molecular pharmacology-tribute to Karl H. Jakobs. Naunyn Schmiedebergs Arch Pharmacol 2019; 392:887-911. [PMID: 31101932 DOI: 10.1007/s00210-019-01650-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Accepted: 04/02/2019] [Indexed: 12/14/2022]
Abstract
Karl H. Jakobs, former editor-in-chief of Naunyn-Schmiedeberg's Archives of Pharmacology and renowned molecular pharmacologist, passed away in April 2018. In this article, his scientific achievements regarding G protein-mediated signal transduction and regulation of canonical pathways are summarized. Particularly, the discovery of inhibitory G proteins for adenylyl cyclase, methods for the analysis of receptor-G protein interactions, GTP supply by nucleoside diphosphate kinases, mechanisms in phospholipase C and phospholipase D activity regulation, as well as the development of the concept of sphingosine-1-phosphate as extra- and intracellular messenger will presented. His seminal scientific and methodological contributions are put in a general and timely perspective to display and honor his outstanding input to the current knowledge in molecular pharmacology.
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Affiliation(s)
- Klaus Aktories
- Institute for Experimental and Clinical Pharmacology and Toxicology, Faculty of Medicine, Albert Ludwigs University, 79104, Freiburg, Germany
| | - Peter Gierschik
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89070, Ulm, Germany
| | - Dagmar Meyer Zu Heringdorf
- Institute of General Pharmacology and Toxicology, University Hospital Frankfurt am Main, Goethe University, 60590, Frankfurt am Main, Germany
| | - Martina Schmidt
- Department of Molecular Pharmacology, University of Groningen, 9713AV, Groningen, The Netherlands
| | - Günter Schultz
- Department of Pharmacology, Charité University Medical Center Berlin, Campus Benjamin Franklin, 14195, Berlin, Germany
| | - Thomas Wieland
- Experimental Pharmacology Mannheim (EPM), European Center for Angioscience (ECAS), Medical Faculty Mannheim, Heidelberg University, Ludolf-Krehl-Str. 13 - 17, 68167, Mannheim, Germany.
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6
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Li X, Shi X, Kaliszewski MJ, Smith AW. Fluorescence cross-correlation spectroscopy of lipid-peptide interactions on supported lipid bilayers. ADVANCES IN BIOMEMBRANES AND LIPID SELF-ASSEMBLY 2019. [DOI: 10.1016/bs.abl.2019.01.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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7
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Breitbart H, Finkelstein M. Actin cytoskeleton and sperm function. Biochem Biophys Res Commun 2017; 506:372-377. [PMID: 29102633 DOI: 10.1016/j.bbrc.2017.11.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 11/01/2017] [Indexed: 11/17/2022]
Abstract
For the acquisition of the ability to fertilize the egg, mammalian spermatozoa should undergo a series of biochemical transformations in the female reproductive tract, collectively called capacitation. The capacitated sperm can undergo the acrosomal exocytosis process near or on the oocyte, which allows the spermatozoon to penetrate and fertilize it. One of the main processes in capacitation involves dynamic cytoskeletal remodeling particularly of actin. Actin polymerization occurs during sperm capacitation and the produced F-actin should be depolymerized prior to the acrosomal exocytosis. In the present review, we describe the mechanisms that regulate F-actin formation during sperm capacitation and the F-actin dispersion prior to the acrosomal exocytosis. During sperm capacitation, the actin severing proteins gelsolin and cofilin are inactive and they undergo activation prior to the acrosomal exocytosis.
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Affiliation(s)
- Haim Breitbart
- The Mina & Everard Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 5290002, Israel.
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8
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Wang X, Tao C, Yuan C, Ren J, Yang M, Ying H. AQP3 small interfering RNA and PLD2 small interfering RNA inhibit the proliferation and promote the apoptosis of squamous cell carcinoma. Mol Med Rep 2017; 16:1964-1972. [PMID: 28656282 PMCID: PMC5561784 DOI: 10.3892/mmr.2017.6847] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 04/19/2017] [Indexed: 01/15/2023] Open
Abstract
Aquaporin 3 (AQP3) and phospholipase D2 (PLD2) are abnormally expressed and/or localized in squamous cell carcinoma (SCC). AQP3 transports glycerol to PLD2 for the synthesis of lipid second messenger, which can mediate the effect of the AQP3/PLD2 signaling module in the regulation of keratinocyte proliferation and differentiation. However, the role of the AQP3/PLD2 signaling module in the pathogenesis of SCC remains to be fully elucidated. In the present study, the expression levels of AQP3 and PLD2 in tissue samples were examined using immunohistochemistry, it was found that the expression levels of AQP3 and PLD2 in tissue samples of actinic keratosis (AK), Bowen's disease (BD) and SCC were significantly increased. AQP3 small interfering RNA (siRNA) and PLD2 siRNA were constructed and used for transfection into the human A431 SCC cell line, and their anticancer effect on SCC was examined. The mRNA expression and protein expression levels of AQP3 and PLD2 were significantly downregulated following siRNA transfection. AQP3 siRNA and PLD2 siRNA inhibited the proliferation and promoted the apoptosis of A431 cells. Taken together, the findings of the present study suggested that increased levels of AQP3 and PLD2 were correlated with tumor progression and development in SCC. AQP3 siRNA and PLD2 siRNA significantly downregulated the mRNA and protein levels of AQP3 and PLD2 in the A431 cells; inhibiting proliferation and promoting apoptosis in vitro. The concomitant effects of AQP3/PLD2 signaling by inhibiting the expression of siRNA may be important for the treatment of SCC in the future.
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Affiliation(s)
- Xiaoyong Wang
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
| | - Chengjun Tao
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
| | - Chengda Yuan
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
| | - Jinping Ren
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
| | - Ming Yang
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
| | - Hangyu Ying
- Department of Dermatology, Hangzhou Hospital of Traditional Chinese Medicine, Hangzhou, Zhejiang 310007, P.R. China
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9
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Kim HJ, Jeong MH, Kim KR, Jung CY, Lee SY, Kim H, Koh J, Vuong TA, Jung S, Yang H, Park SK, Choi D, Kim SH, Kang K, Sohn JW, Park JM, Jeon D, Koo SH, Ho WK, Kang JS, Kim ST, Cho H. Protein arginine methylation facilitates KCNQ channel-PIP2 interaction leading to seizure suppression. eLife 2016; 5. [PMID: 27466704 PMCID: PMC4996652 DOI: 10.7554/elife.17159] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/27/2016] [Indexed: 12/14/2022] Open
Abstract
KCNQ channels are critical determinants of neuronal excitability, thus emerging as a novel target of anti-epileptic drugs. To date, the mechanisms of KCNQ channel modulation have been mostly characterized to be inhibitory via Gq-coupled receptors, Ca2+/CaM, and protein kinase C. Here we demonstrate that methylation of KCNQ by protein arginine methyltransferase 1 (Prmt1) positively regulates KCNQ channel activity, thereby preventing neuronal hyperexcitability. Prmt1+/- mice exhibit epileptic seizures. Methylation of KCNQ2 channels at 4 arginine residues by Prmt1 enhances PIP2 binding, and Prmt1 depletion lowers PIP2 affinity of KCNQ2 channels and thereby the channel activities. Consistently, exogenous PIP2 addition to Prmt1+/- neurons restores KCNQ currents and neuronal excitability to the WT level. Collectively, we propose that Prmt1-dependent facilitation of KCNQ-PIP2 interaction underlies the positive regulation of KCNQ activity by arginine methylation, which may serve as a key target for prevention of neuronal hyperexcitability and seizures. DOI:http://dx.doi.org/10.7554/eLife.17159.001 In the brain, cells called neurons transmit information along their length in the form of electrical signals. To generate electrical signals, ions move into and out of neurons through ion channel proteins – such as the KCNQ channel – in the surface of these cells, which open and close to control the electrical response of the neuron. Abnormally intense bursts of electrical activity from many neurons at once can cause seizures such as those experienced by people with epilepsy. A significant proportion of patients do not respond to current anti-seizure medications. Openers of KCNQ channels have emerged as a potential new class of anti-epileptic drugs. A better understanding of how KCNQ channels work, and how their opening by PIP2lipid signals is regulated, could help to develop more effective therapies for epilepsy. A process called methylation controls many biological tasks by changing the structure of key proteins inside cells. Although methylation occurs throughout the brain, its role in controlling how easily neurons are activated (a property known as “excitability”) remains unclear. Kim, Jeong, Kim, Jung et al. now show that a protein called Prmt1 methylates the KCNQ channels in mice, and that this methylation is essential for suppressing seizures. Mice born without the Prmt1 protein developed epileptic seizures and the KCNQ channels in their neurons featured a reduced level of methylation. However, increasing the amount of PIP2 in these neurons restored their excitability back to normal levels. The methylation of KCNQ channel proteins increases their affinity for PIP2, which is critical to open KCNQ channels. Kim et al. propose that these “opening” controllers balance the action of known “closers” of KCNQ channels to maintain neurons in a healthy condition. In future, Kim et al. plan to investigate whether methylation affects the activity of other ion channels controlled by PIP2. Such experiments will complement a more widespread investigation into other ways in which the Prtmt1 protein may control the activity of neurons. DOI:http://dx.doi.org/10.7554/eLife.17159.002
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Affiliation(s)
- Hyun-Ji Kim
- Department of Physiology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Myong-Ho Jeong
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Kyung-Ran Kim
- Department of Physiology and bioMembrane Plasticity Research Center, Seoul National University College of Medicine, Seoul, Korea.,Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea
| | - Chang-Yun Jung
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Seul-Yi Lee
- Department of Physiology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hanna Kim
- Department of Physiology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Jewoo Koh
- Department of Physiology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Tuan Anh Vuong
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Seungmoon Jung
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Hyunwoo Yang
- Department of Bio and Brain Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Su-Kyung Park
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Dahee Choi
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea.,Division of Life Sciences, Korea University, Seoul, Korea
| | - Sung Hun Kim
- Department of Neurology, College of Medicine, Kangwon National University, Chuncheon, Korea
| | - KyeongJin Kang
- Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Jong-Woo Sohn
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Joo Min Park
- Center for Cognition and Sociality, Institute for Basic Science, Daejeon, Korea
| | - Daejong Jeon
- Department of Neurology, Laboratory for Neurotherapeutics, Comprehensive Epilepsy Center, Seoul National University Hospital, Seoul, Korea.,Advanced Neural Technologies, Seoul, Republic of Korea
| | - Seung-Hoi Koo
- Division of Life Sciences, Korea University, Seoul, Korea
| | - Won-Kyung Ho
- Department of Physiology and bioMembrane Plasticity Research Center, Seoul National University College of Medicine, Seoul, Korea.,Neuroscience Research Institute, Seoul National University Medical Research Center, Seoul, Korea
| | - Jong-Sun Kang
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Seong-Tae Kim
- Department of Molecular Cell Biology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
| | - Hana Cho
- Department of Physiology, Samsung Biomedical Institute, Sungkyunkwan University School of Medicine, Suwon, Korea
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10
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Epand RM. Features of the Phosphatidylinositol Cycle and its Role in Signal Transduction. J Membr Biol 2016; 250:353-366. [PMID: 27278236 DOI: 10.1007/s00232-016-9909-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 05/26/2016] [Indexed: 01/03/2023]
Abstract
The phosphatidylinositol cycle (PI-cycle) has a central role in cell signaling. It is the major pathway for the synthesis of phosphatidylinositol and its phosphorylated forms. In addition, some lipid intermediates of the PI-cycle, including diacylglycerol and phosphatidic acid, are also important lipid signaling agents. The PI-cycle has some features that are important for the understanding of its role in the cell. As a cycle, the intermediates will be regenerated. The PI-cycle requires a large amount of metabolic energy. There are different steps of the cycle that occur in two different membranes, the plasma membrane and the endoplasmic reticulum. In order to complete the PI-cycle lipid must be transferred between the two membranes. The role of the Nir proteins in the process has recently been elucidated. The lipid intermediates of the PI-cycle are normally highly enriched with 1-stearoyl-2-arachidonoyl molecular species in mammals. This enrichment will be retained as long as the intermediates are segregated from other lipids of the cell. However, there is a significant fraction (>15 %) of lipids in the PI-cycle of normal cells that have other acyl chains. Phosphatidylinositol largely devoid of arachidonoyl chains are found in cancer cells. Phosphatidylinositol species with less unsaturation will not be as readily converted to phosphatidylinositol-3,4,5-trisphosphate, the lipid required for the activation of Akt with resulting effects on cell proliferation. Thus, the cyclical nature of the PI-cycle, its dependence on acyl chain composition and its requirement for lipid transfer between two membranes, explain many of the biological properties of this cycle.
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Affiliation(s)
- Richard M Epand
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada.
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11
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Bruntz RC, Lindsley CW, Brown HA. Phospholipase D signaling pathways and phosphatidic acid as therapeutic targets in cancer. Pharmacol Rev 2015; 66:1033-79. [PMID: 25244928 DOI: 10.1124/pr.114.009217] [Citation(s) in RCA: 161] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Phospholipase D is a ubiquitous class of enzymes that generates phosphatidic acid as an intracellular signaling species. The phospholipase D superfamily plays a central role in a variety of functions in prokaryotes, viruses, yeast, fungi, plants, and eukaryotic species. In mammalian cells, the pathways modulating catalytic activity involve a variety of cellular signaling components, including G protein-coupled receptors, receptor tyrosine kinases, polyphosphatidylinositol lipids, Ras/Rho/ADP-ribosylation factor GTPases, and conventional isoforms of protein kinase C, among others. Recent findings have shown that phosphatidic acid generated by phospholipase D plays roles in numerous essential cellular functions, such as vesicular trafficking, exocytosis, autophagy, regulation of cellular metabolism, and tumorigenesis. Many of these cellular events are modulated by the actions of phosphatidic acid, and identification of two targets (mammalian target of rapamycin and Akt kinase) has especially highlighted a role for phospholipase D in the regulation of cellular metabolism. Phospholipase D is a regulator of intercellular signaling and metabolic pathways, particularly in cells that are under stress conditions. This review provides a comprehensive overview of the regulation of phospholipase D activity and its modulation of cellular signaling pathways and functions.
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Affiliation(s)
- Ronald C Bruntz
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
| | - Craig W Lindsley
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
| | - H Alex Brown
- Department of Pharmacology (R.C.B., C.W.L., H.A.B.) and Vanderbilt Center for Neuroscience Drug Discovery (C.W.L.), Vanderbilt University Medical Center; Department of Chemistry, Vanderbilt Institute of Chemical Biology (C.W.L., H.A.B.); Vanderbilt Specialized Chemistry for Accelerated Probe Development (C.W.L.); and Department of Biochemistry, Vanderbilt-Ingram Cancer Center (H.A.B.), Vanderbilt University, Nashville, Tennessee
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12
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Increase in oxidative stress as measured by cerebrospinal fluid lipid peroxidation during treatment for childhood acute lymphoblastic leukemia. J Pediatr Hematol Oncol 2015; 37:e86-93. [PMID: 25222054 PMCID: PMC4423740 DOI: 10.1097/mph.0000000000000258] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Five-year survival from childhood acute lymphoblastic leukemia (ALL) approaches 90%, but 40% of survivors experience central nervous system (CNS) treatment-related cognitive problems. Despite considerable evidence for cognitive problems, less is known about mechanisms of neurological injury. Our purpose was to investigate oxidative stress, measured by lipid peroxidation, as a mechanism of CNS treatment-related neurological injury. The sample included 55 children (mean age at diagnosis=6.84 y, SD=3.40) who received intrathecal and intravenous chemotherapy for CNS-directed treatment according to Children's Oncology Group protocols. Glycerophospholipids were extracted from cerebrospinal fluid samples obtained at diagnosis and during intrathecal chemotherapy administration. Unoxidized and oxidized phosphatidylcholine (PC) and phosphatidylinositol (PI) were measured by normal phase high-performance liquid chromatography with diode array detection, and analyzed with a general linear model for repeated measures analysis of variance. Compared with the diagnostic cerebrospinal fluid sample, unoxidized and oxidized PC and PI increased significantly across treatment phases. Amount of intravenous methotrexate received was significantly correlated with oxidized PI, and age at time of ALL diagnosis was significantly associated with oxidized PC. These findings support our hypothesis that oxidative stress is a mechanism of neurological injury associated with CNS-directed treatment for ALL.
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Sakagami H, Katsumata O, Hara Y, Tamaki H, Fukaya M. Preferential localization of type I phosphatidylinositol 4-phosphate 5-kinase γ at the periactive zone of mouse photoreceptor ribbon synapses. Brain Res 2014; 1586:23-33. [PMID: 25152467 DOI: 10.1016/j.brainres.2014.08.051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 08/12/2014] [Accepted: 08/16/2014] [Indexed: 01/22/2023]
Abstract
Type I phosphatidylinositol 4-phosphate 5 kinase γ (PIP5KIγ) constitutes a major pathway for the generation of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) that regulates a variety of neuronal functions at both presynaptic and postsynaptic compartments. In this study, we examined the expression and localization of PIP5KIγ in the adult mouse retina. RT-PCR analysis revealed that PIP5KIγ_v2 was predominantly expressed in the retina while PIP5KIγ_v3 was also expressed faintly. Immunostaining of the adult mouse retina revealed intense PIP5KIγ-immunoreactivity in the inner and outer plexiform layers in a punctate manner. In the photoreceptor ribbon synapse, PIP5KIγ was highly concentrated at the periactive zone. These findings suggest that PIP5KIγ, especially PIP5KIγ_i2, is localized at the periactive zone, a functionally suitable compartment for the endocytosis of synaptic vesicles in photoreceptor ribbon synapses.
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Affiliation(s)
- Hiroyuki Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0374, Japan.
| | - Osamu Katsumata
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0374, Japan
| | - Yoshinobu Hara
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0374, Japan
| | - Hideaki Tamaki
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0374, Japan
| | - Masahiro Fukaya
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Kanagawa 252-0374, Japan
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14
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Bates RC, Fees CP, Holland WL, Winger CC, Batbayar K, Ancar R, Bergren T, Petcoff D, Stith BJ. Activation of Src and release of intracellular calcium by phosphatidic acid during Xenopus laevis fertilization. Dev Biol 2013; 386:165-80. [PMID: 24269904 DOI: 10.1016/j.ydbio.2013.11.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/24/2013] [Accepted: 11/08/2013] [Indexed: 01/03/2023]
Abstract
We report a new step in the fertilization in Xenopus laevis which has been found to involve activation of Src tyrosine kinase to stimulate phospholipase C-γ (PLC-γ) which increases inositol 1,4,5-trisphosphate (IP3) to release intracellular calcium ([Ca](i)). Molecular species analysis and mass measurements suggested that sperm activate phospholipase D (PLD) to elevate phosphatidic acid (PA). We now report that PA mass increased 2.7 fold by 1 min after insemination and inhibition of PA production by two methods inhibited activation of Src and PLCγ, increased [Ca](i) and other fertilization events. As compared to 14 other lipids, PA specifically bound Xenopus Src but not PLCγ. Addition of synthetic PA activated egg Src (an action requiring intact lipid rafts) and PLCγ as well as doubling the amount of PLCγ in rafts. In the absence of elevated [Ca](i), PA addition elevated IP3 mass to levels equivalent to that induced by sperm (but twice that achieved by calcium ionophore). Finally, PA induced [Ca](i) release that was blocked by an IP3 receptor inhibitor. As only PLD1b message was detected, and Western blotting did not detect PLD2, we suggest that sperm activate PLD1b to elevate PA which then binds to and activates Src leading to PLCγ stimulation, IP3 elevation and [Ca](i) release. Due to these and other studies, PA may also play a role in membrane fusion events such as sperm-egg fusion, cortical granule exocytosis, the elevation of phosphatidylinositol 4,5-bisphosphate and the large, late increase in sn 1,2-diacylglycerol in fertilization.
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Key Words
- 1,2-dicapryloyl-sn-glycero-3-phosphate
- 1,2-dioctanoyl-sn-glycero-3-[phospho-l-serine]
- 5-fluoro-2-indolyl des-chlorohalopemide
- DAG
- ELSD
- Exocytosis
- FIPI
- IP3
- LPA
- LPC
- Membrane fusion
- Membrane rafts
- PA
- PC
- PE
- PI
- PI3
- PI345P3
- PI34P2
- PI35P2
- PI4
- PI45P2
- PI5
- PKC
- PLC
- PLCγ
- PLD
- PS
- Phospholipase Cγ
- Phospholipase D
- RT-PCR
- S1P
- [Ca](i)
- dPA
- dPS
- evaporative light scattering detector
- inositol 1,4,5-trisphosphate
- intracellular calcium
- lysophosphatidic acid
- lysophosphatidylcholine
- phosphatidic acid
- phosphatidylcholine
- phosphatidylethanolamine
- phosphatidylinositol
- phosphatidylinositol 3,4,5-trisphosphate
- phosphatidylinositol 3,4-bisphosphate
- phosphatidylinositol 3,5-bisphosphate
- phosphatidylinositol 3-phosphate
- phosphatidylinositol 4,5-bisphosphate
- phosphatidylinositol 4-phosphate
- phosphatidylinositol 5-phosphate
- phosphatidylserine
- phospholipase C
- phospholipase C-γ
- phospholipase D
- protein kinase C
- reverse transcriptase polymerase chain reaction
- sn 1,2-diacylglycerol
- sphingosine-1-phosphate
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Affiliation(s)
- Ryan C Bates
- University of Colorado Denver, Denver, CO 80217-3364, USA
| | - Colby P Fees
- University of Colorado Denver, Denver, CO 80217-3364, USA
| | | | | | | | - Rachel Ancar
- University of Colorado Denver, Denver, CO 80217-3364, USA
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15
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Braunger JA, Kramer C, Morick D, Steinem C. Solid supported membranes doped with PIP2: influence of ionic strength and pH on bilayer formation and membrane organization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:14204-13. [PMID: 24199623 DOI: 10.1021/la402646k] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Phosphoinositides and in particular L-α-phosphatidylinositol-4,5-bisphosphate (PIP2) are key lipids controlling many cellular events and serve as receptors for a large number of intracellular proteins. To quantitatively analyze protein-PIP2 interactions in vitro in a time-resolved manner, planar membranes on solid substrates are highly desirable. Here, we describe an optimized protocol to form PIP2 containing planar solid supported membranes on silicon surfaces by vesicle spreading. Supported lipid bilayers (SLBs) were obtained by spreading POPC/PIP2 (92:8) small unilamellar vesicles onto hydrophilic silicon substrates at a low pH of 4.8. These membranes were capable of binding ezrin, resulting in large protein coverage as concluded from reflectometric interference spectroscopy and fluorescence microscopy. As deduced from fluorescence microscopy, only under low pH conditions, a homogeneously appearing distribution of fluorescently labeled PIP2 molecules in the membrane was achieved. Fluorescence recovery after photobleaching experiments revealed that PIP2 is not mobile in the bottom layer of the SLBs, while PIP2 is fully mobile in the top layer with diffusion coefficients of about 3 μm(2)/s. This diffusion coefficient was considerably reduced by a factor of about 3 if ezrin has been bound to PIP2 in the membrane.
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Affiliation(s)
- Julia A Braunger
- Institut für Organische und Biomolekulare Chemie, Georg-August Universität , Tammannstr. 2, 37077 Göttingen, Germany
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16
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Finkelstein M, Megnagi B, Ickowicz D, Breitbart H. Regulation of sperm motility by PIP2(4,5) and actin polymerization. Dev Biol 2013; 381:62-72. [DOI: 10.1016/j.ydbio.2013.06.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 04/17/2013] [Accepted: 06/10/2013] [Indexed: 11/24/2022]
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17
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Abstract
Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
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Affiliation(s)
- Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892, USA.
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18
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Trovò L, Ahmed T, Callaerts-Vegh Z, Buzzi A, Bagni C, Chuah M, Vandendriessche T, D'Hooge R, Balschun D, Dotti CG. Low hippocampal PI(4,5)P₂ contributes to reduced cognition in old mice as a result of loss of MARCKS. Nat Neurosci 2013; 16:449-55. [PMID: 23434911 DOI: 10.1038/nn.3342] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 01/18/2013] [Indexed: 02/03/2023]
Abstract
Cognitive and motor performances decline during aging. Although it is clear that such signs reflect synaptic compromise, the underlying mechanisms have not been defined. We found that the levels and activity of the synaptic plasticity modulators phosphatidylinositol-(4,5)-bisphosphate (PI(4,5)P₂) and phospholipase Cγ (PLCγ) were substantially reduced in hippocampal synaptic membranes from old mice. In addition, these membranes contained reduced levels of the PI(4,5)P₂-clustering molecule myristoylated alanine-rich C kinase substrate (MARCKS). Consistent with a cause-effect relationship, raising MARCKS levels in the brain of old mice led to increased synaptic membrane clustering of PI(4,5)P₂ and to PLCγ activation. MARCKS overexpression in the hippocampus of old mice or intraventricular perfusion of MARCKS peptide resulted in enhanced long-term potentiation and improved memory. These results reveal one of the mechanisms involved in brain dysfunction during aging.
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Affiliation(s)
- Laura Trovò
- VIB Center for the Biology of Disease, Leuven and Center for Human Genetics, University of Leuven (Katholieke University of Leuven), Leuven, Belgium
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19
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Coordinated signal integration at the M-type potassium channel upon muscarinic stimulation. EMBO J 2012; 31:3147-56. [PMID: 22643219 DOI: 10.1038/emboj.2012.156] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 04/25/2012] [Indexed: 01/08/2023] Open
Abstract
Several neurotransmitters, including acetylcholine, regulate neuronal tone by suppressing a non-inactivating low-threshold voltage-gated potassium current generated by the M-channel. Agonist dependent control of the M-channel is mediated by calmodulin, activation of anchored protein kinase C (PKC), and depletion of the phospholipid messenger phosphatidylinositol 4,5-bisphosphate (PIP2). In this report, we show how this trio of second messenger responsive events acts synergistically and in a stepwise manner to suppress activity of the M-current. PKC phosphorylation of the KCNQ2 channel subunit induces dissociation of calmodulin from the M-channel complex. The calmodulin-deficient channel has a reduced affinity towards PIP2. This pathway enhances the effect of concomitant reduction of PIP2, which leads to disruption of the M-channel function. These findings clarify how a common lipid cofactor, such as PIP2, can selectively regulate ion channels.
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20
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Dippe M, Ulbrich-Hofmann R. Phospholipid acylhydrolases trigger membrane degradation during fungal sporogenesis. Fungal Genet Biol 2011; 48:921-7. [DOI: 10.1016/j.fgb.2011.05.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 05/06/2011] [Accepted: 05/28/2011] [Indexed: 11/27/2022]
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21
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Finkelstein M, Etkovitz N, Breitbart H. Role and regulation of sperm gelsolin prior to fertilization. J Biol Chem 2010; 285:39702-9. [PMID: 20937821 DOI: 10.1074/jbc.m110.170951] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To acquire fertilization competence, spermatozoa should undergo several biochemical changes in the female reproductive tract, known as capacitation. The capacitated spermatozoon can interact with the egg zona pellucida resulting in the occurrence of the acrosome reaction, a process that allowed its penetration into the egg and fertilization. Sperm capacitation requires actin polymerization, whereas F-actin must disperse prior to the acrosome reaction. Here, we suggest that the actin-severing protein, gelsolin, is inactive during capacitation and is activated prior to the acrosome reaction. The release of bound gelsolin from phosphatidylinositol 4,5-bisphosphate (PIP(2)) by PBP10, a peptide containing the PIP(2)-binding domain of gelsolin, or by activation of phospholipase C, which hydrolyzes PIP(2), caused rapid Ca(2+)-dependent F-actin depolymerization as well as enhanced acrosome reaction. Using immunoprecipitation assays, we showed that the tyrosine kinase SRC and gelsolin coimmunoprecipitate, and activating SRC by adding 8-bromo-cAMP (8-Br-cAMP) enhanced the amount of gelsolin in this precipitate. Moreover, 8-Br-cAMP enhanced tyrosine phosphorylation of gelsolin and its binding to PIP(2(4,5)), both of which inactivated gelsolin, allowing actin polymerization during capacitation. This actin polymerization was blocked by inhibiting the Src family kinases, suggesting that gelsolin is activated under these conditions. These results are further supported by our finding that PBP10 was unable to cause complete F-actin breakdown in the presence of 8-Br-cAMP or vanadate. In conclusion, inactivation of gelsolin during capacitation occurs by its binding to PIP(2) and tyrosine phosphorylation by SRC. The release of gelsolin from PIP(2) together with its dephosphorylation enables gelsolin activation, resulting in the acrosome reaction.
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Affiliation(s)
- Maya Finkelstein
- The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan 52900, Israel
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22
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Holinstat M, Preininger AM, Milne SB, Hudson WJ, Brown HA, Hamm HE. Irreversible platelet activation requires protease-activated receptor 1-mediated signaling to phosphatidylinositol phosphates. Mol Pharmacol 2009; 76:301-13. [PMID: 19483102 PMCID: PMC2713123 DOI: 10.1124/mol.109.056622] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 05/29/2009] [Indexed: 01/25/2023] Open
Abstract
Thrombin induces platelet activation through an early, reversible stage of platelet aggregation, which is followed by a later, irreversible stage of platelet aggregation. Without intervention, events leading to pathological platelet activation can result in vessel occlusion, acute coronary syndrome, and stroke. Therefore, a better understanding of events leading to platelet-mediated clot formation may provide insight into new therapeutic targets. Once activated, protease activated receptors (PARs) are essential in regulating events leading to platelet aggregation. We have determined a signaling cascade through PAR1, which involves phosphatidylinositol (PI) kinases, phosphatidylinositol bisphosphate (PIP(2)), and Rap1 activation (independent of P2Y12) in the formation of a stable platelet aggregate. The putative phosphatidylinositol-3 kinase (PI3K) inhibitor LY294002 was found to reduce basal and PAR-stimulated PIP(2) levels by mass spectrometry and to inhibit PAR1-mediated stable platelet aggregation. Rap1 activation in platelets (during time points corresponding to the late, irreversible phase of aggregation) was found to require the PI signaling pathway. Perturbation of PI3K signaling by isoform-selective inhibitors had differential effects on Rap1 activation through PAR1 and PAR4. Hence, it is possible to disrupt lipid signaling pathways involved in stable clot formation without inhibiting early clot formation, offering a new potential target for antiplatelet therapy.
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Affiliation(s)
- Michael Holinstat
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, TN 37232-6600, USA
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23
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Rappley I, Myers DS, Milne SB, Ivanova PT, Lavoie MJ, Brown HA, Selkoe DJ. Lipidomic profiling in mouse brain reveals differences between ages and genders, with smaller changes associated with alpha-synuclein genotype. J Neurochem 2009; 111:15-25. [PMID: 19627450 DOI: 10.1111/j.1471-4159.2009.06290.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Advances in lipidomics technology have facilitated the precise detection, identification and profiling of lipid species within tissues. Mass spectrometry allows for identification of lipids as a function of the total number of carbons and double bonds in their acyl chains. Such detailed descriptions of lipid composition can provide a basis for further investigation of cell signaling and metabolic pathways, both physiological and pathological. Here, we applied phospholipid profiling to mouse models relevant to Parkinson's disease, using mice that were transgenic for human alpha-synuclein (alphaSyn) or deleted of endogenous alphaSyn. Proposed functions of alphaSyn include phospholipid binding, regulation of membrane composition, and regulation of vesicular pools. We investigated whether alphaSyn gene dosage interacts with differences in phospholipid composition across brain regions or with age-related changes in brain phospholipid composition. The most dramatic phospholipid changes were observed in alphaSyn wild-type animals as a function of age and gender. alphaSyn genotype-specific changes were also observed in aged, but not young, mice. Our results provide a detailed and systematic characterization of brain phospholipid composition in mice and identify age-related changes relevant both to Parkinson's disease and to normal aging.
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Affiliation(s)
- Irit Rappley
- Center for Neurologic Diseases, Harvard Medical School and Brigham & Women's Hospital, Boston, Massachusetts, USA
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24
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25
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Haga Y, Miwa N, Jahangeer S, Okada T, Nakamura SI. CtBP1/BARS is an activator of phospholipase D1 necessary for agonist-induced macropinocytosis. EMBO J 2009; 28:1197-207. [PMID: 19322195 PMCID: PMC2664659 DOI: 10.1038/emboj.2009.78] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 02/26/2009] [Indexed: 01/01/2023] Open
Abstract
Vesicular trafficking such as macropinocytosis is a dynamic process that requires coordinated interactions between specialized proteins and lipids. A recent report suggests the involvement of CtBP1/BARS in epidermal growth factor (EGF)-induced macropinocytosis. Detailed mechanisms as to how lipid remodelling is regulated during macropinocytosis are still undefined. Here, we show that CtBP1/BARS is a physiological activator of PLD1 required in agonist-induced macropinocytosis. EGF-induced macropinocytosis was specifically blocked by 1-butanol but not by 2-butanol. In addition, stimulation of cells by serum or EGF resulted in the association of CtBP1/BARS with PLD1. Finally, CtBP1/BARS activated PLD1 in a synergistic manner with other PLD activators, including ADP-ribosylation factors as demonstrated by in vitro and intact cell systems. The present results shed light on the molecular basis of how the ‘fission protein' CtBP1/BARS controls vesicular trafficking events including macropinocytosis.
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Affiliation(s)
- Yuki Haga
- Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe, Japan
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26
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Cockcroft S. Phosphatidic acid regulation of phosphatidylinositol 4-phosphate 5-kinases. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:905-12. [PMID: 19298865 DOI: 10.1016/j.bbalip.2009.03.007] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2009] [Revised: 03/03/2009] [Accepted: 03/04/2009] [Indexed: 11/18/2022]
Abstract
Phosphatidic acid (PA) production by receptor-stimulated phospholipase D is believed to play an important role in the regulation of cell function. The second messenger function of PA remains to be elucidated. PA can bind and affect the activities of different enzymes and here we summarise the current status of activation of Type I phosphatidylinositol 4-phosphate 5-kinase by PA. Type 1 phosphatidylinositol 4-phosphate 5-kinase is also regulated by ARF proteins as is phospholipase D and we discuss the contributions of ARF and PA towards phosphatidylinositol(4,5)bisphosphate synthesis at the plasma membrane.
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Affiliation(s)
- Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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27
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Halstead JR, Snel MH, Meeuws S, Jones DR, Divecha N. Assaying endogenous phosphatidylinositol-4-phosphate 5-kinase (PIP5K) activities. Methods Mol Biol 2009; 462:391-402. [PMID: 19160683 DOI: 10.1007/978-1-60327-115-8_25] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Phosphoinositides are a family of lipid second messengers interlinked by an extensive and highly regulated network of kinases and phosphatases. The modulation of phosphoinositide profiles can regulate numerous cancer-related pathways, including cell survival, cell proliferation, migration, integrin activation, and transcription. PtdIns(4,5)P2 is at the heart of phosphoinositide signaling; its levels are controlled by enzymes that synthesize it and those that degrade it. Phosphatidylinositol-4-phosphate 5-kinases (PIP5 K) phosphorylate PtdIns4P on the 5-position and constitute the major pathway for the generation of PtdIns(4,5)P2. We will discuss how to suppress the expression of human PIP5 Kbeta using RNAi and how to measure the activity and levels of the endogenous enzyme. We describe a method to immunoprecipitate the endogenous PIP5 Kbeta and to assay its activity. Western blotting with another panel of antibodies is then used to determine the levels of endogenous PIP5 Kbeta in the immunoprecipitates.
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Affiliation(s)
- Jonathan R Halstead
- Division of Cellular Biochemistry, The Netherlands Cancer Institute, Amsterdam
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28
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Caspase cleavage of phospholipase D1 in vitro alters its regulation and reveals a novel property of the "loop" region. Biochim Biophys Acta Mol Cell Biol Lipids 2008; 1781:376-82. [PMID: 18573349 DOI: 10.1016/j.bbalip.2008.05.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2008] [Revised: 05/19/2008] [Accepted: 05/26/2008] [Indexed: 11/20/2022]
Abstract
Phospholipase D (PLD) has been implicated in mediating vesicular transport, mitosis, differentiation and apoptosis. The product of PLD activity, phosphatidic acid (PA) has mitogenic potential and elevated PLD expression has been detected in many tumor cell lines. Several reports have demonstrated that distinct PLD domains regulate its activity and that truncated forms of PLD retain enzymatic activity. We hypothesized that during apoptosis caspase cleavage of PLDs could result in modification of their activities. To test this idea, we have used in vitro translation of PLD1 and PLD2 which generated active enzymes exhibiting properties mimicking those of the endogenous proteins. Here we demonstrate that PLD1 was rapidly cleaved in vitro by caspases-8, -3 and -7. In contrast, PLD2 cleavage was delayed and its activity was unaffected by incubation with caspase-3. Significantly, following caspase cleavage the response of PLD1 to regulatory stimuli was altered; it was no longer activated by PKC and instead exhibited an increased activity in response to small GTPases. Notably, this enhanced activity was due to cleavage of PLD1 in the "loop" domain, a region previously associated with negative regulatory function. Thus our data have identified a novel regulatory domain in PLD1.
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29
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Abstract
The two mammalian phosphatidylcholine (PC)-selective phospholipase D (PLD) enzymes remove the choline head group from PC to produce phosphatidic acid (PA). PA stimulates phosphatidylinositol(4)phosphate 5-kinases, can function as a binding site for membrane proteins, is required for certain membrane fusion or fission events and is an important precursor for the production of diacylglycerol (DAG). Both PA and DAG are lipids that favor negatively curved membranes rather than planar bilayers and can reduce the energetic barrier to membrane fission and fusion. Recent data provide a mechanistic explanation for the role PLDs play in some aspects of membrane traffic and provide an explanation for why some membrane fusion reactions require PA and some do not. PLDs also act as guanosine triphosphatase-activating proteins for dynamin and may participate with dynamin in the process of vesicle fission.
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Affiliation(s)
- Michael G Roth
- Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9038, USA.
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30
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Stace C, Manifava M, Delon C, Coadwell J, Cockcroft S, Ktistakis NT. PA binding of phosphatidylinositol 4-phosphate 5-kinase. ACTA ACUST UNITED AC 2007; 48:55-72. [PMID: 18167315 DOI: 10.1016/j.advenzreg.2007.11.008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Catherine Stace
- Signalling Programme, Babraham Institute, Babraham, Cambridge CB2 4AT, UK
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31
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Lam AD, Tryoen-Toth P, Tsai B, Vitale N, Stuenkel EL. SNARE-catalyzed fusion events are regulated by Syntaxin1A-lipid interactions. Mol Biol Cell 2007; 19:485-97. [PMID: 18003982 DOI: 10.1091/mbc.e07-02-0148] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Membrane fusion is a process that intimately involves both proteins and lipids. Although the SNARE proteins, which ultimately overcome the energy barrier for fusion, have been extensively studied, regulation of the energy barrier itself, determined by specific membrane lipids, has been largely overlooked. Our findings reveal a novel function for SNARE proteins in reducing the energy barrier for fusion, by directly binding and sequestering fusogenic lipids to sites of fusion. We demonstrate a specific interaction between Syntaxin1A and the fusogenic lipid phosphatidic acid, in addition to multiple polyphosphoinositide lipids, and define a polybasic juxtamembrane region within Syntaxin1A as its lipid-binding domain. In PC-12 cells, Syntaxin1A mutations that progressively reduced lipid binding resulted in a progressive reduction in evoked secretion. Moreover, amperometric analysis of fusion events driven by a lipid-binding-deficient Syntaxin1A mutant (5RK/A) demonstrated alterations in fusion pore dynamics, suggestive of an energetic defect in secretion. Overexpression of the phosphatidic acid-generating enzyme, phospholipase D1, completely rescued the secretory defect seen with the 5RK/A mutant. Moreover, knockdown of phospholipase D1 activity drastically reduced control secretion, while leaving 5RK/A-mediated secretion relatively unaffected. Altogether, these data suggest that Syntaxin1A-lipid interactions are a critical determinant of the energetics of SNARE-catalyzed fusion events.
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Affiliation(s)
- Alice D Lam
- Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA.
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Alb JG, Phillips SE, Wilfley LR, Philpot BD, Bankaitis VA. The pathologies associated with functional titration of phosphatidylinositol transfer protein α activity in mice. J Lipid Res 2007; 48:1857-72. [PMID: 17525475 DOI: 10.1194/jlr.m700145-jlr200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Phosphatidylinositol transfer proteins (PITPs) bind phosphatidylinositol (PtdIns) and phosphatidylcholine and play diverse roles in coordinating lipid metabolism/signaling with intracellular functions. The underlying mechanisms remain unclear. Genetic ablation of PITPalpha in mice results in neonatal lethality characterized by intestinal and hepatic steatosis, spinocerebellar neurodegeneration, and glucose homeostatic defects. We report that mice expressing a PITPalpha selectively ablated for PtdIns binding activity (Pitpalpha(T59D)), as the sole source of PITPalpha, exhibit phenotypes that recapitulate those of authentic PITPalpha nullizygotes. Analyses of mice with graded reductions in PITPalpha activity reveal proportionately graded reductions in lifespan, demonstrate that intestinal steatosis and hypoglycemia are apparent only when PITPalpha protein levels are strongly reduced (>or=90%), and correlate steatotic and glucose homeostatic defects with cerebellar inflammatory disease. Finally, reconstitution of PITPalpha expression in the small intestine substantially corrects the chylomicron retention disease and cerebellar inflammation of Pitpalpha(0/0) neonates, but does not rescue neonatal lethality in these animals. These data demonstrate that PtdIns binding is an essential functional property of PITPalpha in vivo, and suggest a causal linkage between defects in lipid transport and glucose homeostasis and cerebellar inflammatory disease. Finally, the data also demonstrate intrinsic neuronal deficits in PITPalpha-deficient mice that are independent of intestinal lipid transport defects and hypoglycemia.
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Affiliation(s)
- James G Alb
- Department of Cell and Developmental Biology, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7090, USA
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Lee MH, Sano H. Attenuation of the hypersensitive response by an ATPase associated with various cellular activities (AAA) protein through suppression of a small GTPase, ADP ribosylation factor, in tobacco plants. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2007; 51:127-39. [PMID: 17559512 DOI: 10.1111/j.1365-313x.2007.03124.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
ATPase associated with various cellular activities (AAA) proteins are commonly distributed among eukaryotes, and are involved in a multitude of cellular functions. NtAAA1 is one such example, being involved in pathogen response in tobacco plants. When its activity was suppressed in RNAi transgenic tobacco plants, an elevated resistance to the pathogenic bacterium Pseudomonas syringae was observed in comparison with the wild type. As AAA proteins function through interaction with specific partners, NtAAA1-interacting proteins were screened by the yeast two-hybrid assay, and one particular gene encoding a small GTPase, an ADP ribosylation factor, was identified and designated as NtARF. Its specific binding to NtAAA1 was confirmed by in vitro pull-down assay, and their interaction was predominant between active forms of NtARF and NtAAA1, each bound to GTP and ATP, respectively. Their physical interaction in vivo around the plasma membrane was shown by fluorescence resonance energy transfer assays, suggesting their role in membrane trafficking. Transgenic tobacco plants constitutively expressing NtARF under the control of a cauliflower mosaic virus 35S promoter exhibited spontaneous and wound-induced lesion formation, and enhanced resistance to pathogen attack. Expression of NtAAA1 in leaves of NtARF transgenic plants attenuated lesion and suppressed pathogen resistance. In wild-type tobacco plants, transcripts of NtAAA1 and NtARF could be induced by ethylene and salicylic acid, respectively. These results suggest that NtAAA1 balances plant resistance through suppression of NtARF, and that the molecular basis for the known antagonistic actions of ethylene and salicylic acid in defense response could be partly attributable to these two proteins.
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Affiliation(s)
- Mi-Hyun Lee
- Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Nara 630-0192, Japan
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Abstract
Phosphoinositides are minor phospholipid constituents of virtually every biological membrane yet they play fundamental roles in controlling membrane-bound signalling events. Phosphoinositides are produced from phosphatidylinositol (PtdIns) by phosphorylation of one or more of three positions (3, 4 and 5) of the inositol headgroup located at the membrane cytoplasmic interface by distinct families of inositol lipid kinases. Intriguingly, many of the kinase reactions are catalysed by more than one form of the kinases even in simple organisms and these enzymes often assume non-redundant functions. A similar diversity is seen with inositide phosphatases, the enzymes that dephosphorylate phosphoinositides with a certain degree of specificity and the impairments of which are often linked to human diseases. This degree of multiplicity at the enzyme level together with the universal roles of these lipids in cell regulation assumes that inositol lipids are spatially and functionally restricted in specific membrane compartments. Studying the compartmentalized roles of these lipids at the cellular level represents a major methodological challenge. Over the last 10 years significant progress has been made in creating reagents that can monitor inositol lipid changes in live cells with fluorescence or confocal microscopy. New methods are also being developed to manipulate these lipids in specific membrane compartments in a regulated fashion. This article recalls some historical aspects of inositide research and describes the new methodological advances highlighting their great potential as well as the problems one can encounter with their use.
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Affiliation(s)
- Tamas Balla
- National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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Xu X, Guo H, Wycuff DL, Lee M. Role of phosphatidylinositol-4-phosphate 5' kinase (ppk-1) in ovulation of Caenorhabditis elegans. Exp Cell Res 2007; 313:2465-75. [PMID: 17475243 PMCID: PMC1950138 DOI: 10.1016/j.yexcr.2007.03.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 03/15/2007] [Accepted: 03/19/2007] [Indexed: 11/21/2022]
Abstract
During Caenorhabditis elegans ovulation, the somatic gonad integrates signals from germ cells and propels a mature oocyte into the spermatheca for fertilization. Previous work suggests that phosphoinositide signaling plays important roles in C. elegans fertility. To fully understand inositol-1,4,5-trisphosphate (IP(3)) signaling in ovulation, we have examined the function of phosphatidylinositol-4-phosphate 5' kinase (PIP5K) in C. elegans. Our results show that the C. elegans PIP5K homolog, ppk-1, is essential for ovulation in C. elegans; ppk-1 is mainly expressed in somatic gonad, and depletion of ppk-1 expression causes defective ovulation, reduced gonad sheath contractility, and sterility. Increased IP(3) signaling compensates for ppk-1 (RNAi)-induced sterility, suggesting that ppk-1 is linked to IP(3) signaling. These results demonstrate that ppk-1 plays an essential role in IP(3) signaling and cytoskeleton organization in somatic gonad.
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Affiliation(s)
- Xiaojian Xu
- Department of Biology, Baylor University, One Bear Place 97388, Waco, TX 76798
| | - Haisu Guo
- Department of Biology, Baylor University, One Bear Place 97388, Waco, TX 76798
| | - Diane L. Wycuff
- Molecular Bioscience Center, Baylor University, One Bear Place 97046, Waco, TX 76798
| | - Myeongwoo Lee
- Department of Biology, Baylor University, One Bear Place 97388, Waco, TX 76798
- *All correspondence should be addressed to: Myeongwoo Lee, Ph.D., Tel) 254-710-2135, Fax) 254-710-2969, Email)
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Schulz TA, Prinz WA. Sterol transport in yeast and the oxysterol binding protein homologue (OSH) family. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:769-80. [PMID: 17434796 PMCID: PMC2034499 DOI: 10.1016/j.bbalip.2007.03.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2006] [Revised: 03/06/2007] [Accepted: 03/07/2007] [Indexed: 12/12/2022]
Abstract
Sterols such as cholesterol are a significant component of eukaryotic cellular membranes, and their unique physical properties influence a wide variety of membrane processes. It is known that the concentration of sterol within the membrane varies widely between organelles, and that the cell actively maintains this distribution through various transport processes. Vesicular pathways such as secretion or endocytosis may account for this traffic, but increasing evidence highlights the importance of nonvesicular routes as well. The structure of an oxysterol-binding protein homologue (OSH) in yeast (Osh4p/Kes1p) has recently been solved, identifying it as a sterol binding protein, and there is evidence consistent with the role of a cytoplasmic, nonvesicular sterol transporter. Yeast have seven such proteins, which appear to have distinct but overlapping functions with regard to maintaining intracellular sterol distribution and homeostasis. Control of sterol distribution can have far-reaching effects on membrane-related functions, and Osh proteins have been implicated in a variety of processes such as secretory vesicle budding from the Golgi and establishment of cell polarity. This review summarizes the current body of knowledge regarding this family and its potential functions, placing it in the context of known and hypothesized pathways of sterol transport in yeast.
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Affiliation(s)
- Timothy A Schulz
- Laboratory of Cell Biochemistry and Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, US Department of Health and Human Services, Bethesda, MD 20892, USA
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Oude Weernink PA, López de Jesús M, Schmidt M. Phospholipase D signaling: orchestration by PIP2 and small GTPases. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2007; 374:399-411. [PMID: 17245604 PMCID: PMC2020506 DOI: 10.1007/s00210-007-0131-4] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2006] [Accepted: 12/20/2006] [Indexed: 11/12/2022]
Abstract
Hydrolysis of phosphatidylcholine by phospholipase D (PLD) leads to the generation of the versatile lipid second messenger, phosphatidic acid (PA), which is involved in fundamental cellular processes, including membrane trafficking, actin cytoskeleton remodeling, cell proliferation and cell survival. PLD activity can be dramatically stimulated by a large number of cell surface receptors and is elaborately regulated by intracellular factors, including protein kinase C isoforms, small GTPases of the ARF, Rho and Ras families and, particularly, by the phosphoinositide, phosphatidylinositol 4,5-bisphosphate (PIP(2)). PIP(2) is well known as substrate for the generation of second messengers by phospholipase C, but is now also understood to recruit and/or activate a variety of actin regulatory proteins, ion channels and other signaling proteins, including PLD, by direct interaction. The synthesis of PIP(2) by phosphoinositide 5-kinase (PIP5K) isoforms is tightly regulated by small GTPases and, interestingly, by PA as well, and the concerted formation of PIP(2) and PA has been shown to mediate receptor-regulated cellular events. This review highlights the regulation of PLD by membrane receptors, and describes how the close encounter of PLD and PIP5K isoforms with small GTPases permits the execution of specific cellular functions.
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Affiliation(s)
| | | | - Martina Schmidt
- />Department of Molecular Pharmacology, University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
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Varnai P, Thyagarajan B, Rohacs T, Balla T. Rapidly inducible changes in phosphatidylinositol 4,5-bisphosphate levels influence multiple regulatory functions of the lipid in intact living cells. J Cell Biol 2006; 175:377-82. [PMID: 17088424 PMCID: PMC2064515 DOI: 10.1083/jcb.200607116] [Citation(s) in RCA: 284] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Accepted: 10/05/2006] [Indexed: 11/25/2022] Open
Abstract
Rapamycin (rapa)-induced heterodimerization of the FRB domain of the mammalian target of rapa and FKBP12 was used to translocate a phosphoinositide 5-phosphatase (5-ptase) enzyme to the plasma membrane (PM) to evoke rapid changes in phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) levels. Rapa-induced PM recruitment of a truncated type IV 5-ptase containing only the 5-ptase domain fused to FKBP12 rapidly decreased PM PtdIns(4,5)P(2) as monitored by the PLCdelta1PH-GFP fusion construct. This decrease was paralleled by rapid termination of the ATP-induced Ca(2+) signal and the prompt inactivation of menthol-activated transient receptor potential melastatin 8 (TRPM8) channels. Depletion of PM PtdIns(4,5)P(2) was associated with a complete blockade of transferrin uptake and inhibition of epidermal growth factor internalization. None of these changes were observed upon rapa-induced translocation of an mRFP-FKBP12 fusion protein that was used as a control. These data demonstrate that rapid inducible depletion of PM PtdIns(4,5)P(2) is a powerful tool to study the multiple regulatory roles of this phospholipid and to study differential sensitivities of various processes to PtdIns(4,5)P(2) depletion.
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Affiliation(s)
- Peter Varnai
- Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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Perez-Mansilla B, Ha VL, Justin N, Wilkins AJ, Carpenter CL, Thomas GMH. The differential regulation of phosphatidylinositol 4-phosphate 5-kinases and phospholipase D1 by ADP-ribosylation factors 1 and 6. Biochim Biophys Acta Mol Cell Biol Lipids 2006; 1761:1429-42. [PMID: 17071135 DOI: 10.1016/j.bbalip.2006.09.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2006] [Revised: 09/08/2006] [Accepted: 09/08/2006] [Indexed: 10/24/2022]
Abstract
Phosphatidylinositol 4-phosphate 5-kinases [PtdIns4P5Ks] synthesise the majority of cellular phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] and phospholipase D1 (PLD1) synthesises large amounts of phosphatidic acid (PtdOH). The activities of PtdIns4P5Ks and PLDs are thought to be coupled during cell signalling in order to support large simultaneous increases in both PtdIns(4,5)P(2) and PtdOH, since PtdOH activates PtdIns4P5Ks and PLD1 requires PtdIns(4,5)P(2) as a cofactor. However, little is known about the control of such a system. Membrane recruitment of ADP-ribosylation factors (Arfs) activates both PtdIns4P5Ks and PLDs, but it is not known if each enzyme is controlled in series by different Arfs or in parallel by a single form. We show through pull-down and vesicle sedimentation interaction assays that PtdIns4P5K activation may be facilitated by Arf-enhanced membrane association. However PtdIns4P5Ks discriminate poorly between near homogeneously myristoylated Arf1 and Arf6 although examples of all three known active isoforms (mouse alpha>beta, gamma) respond to these G-proteins. Conversely PLD1 genuinely prefers Arf1 and so the two lipid metabolising enzymes are differentially controlled. We propose that isoform selective Arf/PLD interaction and not Arf/PtdIns4P5K will be the critical trigger in the formation of distinct, optimal triples of Arf/PLDs/PtdIns4P5Ks and be the principle regulator of any coupled increases in the signalling lipids PtdIns(4,5)P(2) and PtdOH.
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Affiliation(s)
- Borja Perez-Mansilla
- Department of Physiology, University College London, Rockefeller Building, 21 University Street, London WC1E 6JJ, UK
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Abstract
Cytokinesis is a sequential process that occurs in three phases: assembly of the cytokinetic apparatus, furrow progression and fission (abscission) of the newly formed daughter cells. The ingression of the cleavage furrow is dependent on the constriction of an equatorial actomyosin ring in many cell types. Recent studies have demonstrated that this structure is highly dynamic and undergoes active polymerization and depolymerization throughout the furrowing process. Despite much progress in the identification of contractile ring components, little is known regarding the mechanism of its assembly and structural rearrangements. PIP2 (phosphatidylinositol 4,5-bisphosphate) is a critical regulator of actin dynamics and plays an essential role in cell motility and adhesion. Recent studies have indicated that an elevation of PIP2 at the cleavage furrow is a critical event for furrow stability. In this review we discuss the role of PIP2-mediated signalling in the structural maintenance of the contractile ring and furrow progression. In addition, we address the role of other phosphoinositides, PI(4)P (phosphatidylinositol 4-phosphate) and PIP3 (phosphatidylinositol 3,4,5-triphosphate) in these processes.
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Affiliation(s)
- Michael R Logan
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada H3A 2B2
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Hornberger TA, Chu WK, Mak YW, Hsiung JW, Huang SA, Chien S. The role of phospholipase D and phosphatidic acid in the mechanical activation of mTOR signaling in skeletal muscle. Proc Natl Acad Sci U S A 2006; 103:4741-6. [PMID: 16537399 PMCID: PMC1450240 DOI: 10.1073/pnas.0600678103] [Citation(s) in RCA: 233] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Signaling by the mammalian target of rapamycin (mTOR) has been reported to be necessary for mechanical load-induced growth of skeletal muscle. The mechanisms involved in the mechanical activation of mTOR signaling are not known, but several studies indicate that a unique [phosphotidylinositol-3-kinase (PI3K)- and nutrient-independent] mechanism is involved. In this study, we have demonstrated that a regulatory pathway for mTOR signaling that involves phospholipase D (PLD) and the lipid second messenger phosphatidic acid (PA) plays a critical role in the mechanical activation of mTOR signaling. First, an elevation in PA concentration was sufficient for the activation of mTOR signaling. Second, the isozymes of PLD (PLD1 and PLD2) are localized to the z-band in skeletal muscle (a critical site of mechanical force transmission). Third, mechanical stimulation of skeletal muscle with intermittent passive stretch ex vivo induced PLD activation, PA accumulation, and mTOR signaling. Finally, pharmacological inhibition of PLD blocked the mechanically induced increase in PA and the activation of mTOR signaling. Combined, these results indicate that mechanical stimuli activate mTOR signaling through a PLD-dependent increase in PA. Furthermore, we showed that mTOR signaling was partially resistant to rapamycin in muscles subjected to mechanical stimulation. Because rapamycin and PA compete for binding to the FRB domain on mTOR, these results suggest that mechanical stimuli activate mTOR signaling through an enhanced binding of PA to the FRB domain on mTOR.
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Affiliation(s)
- T. A. Hornberger
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
| | - W. K. Chu
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
| | - Y. W. Mak
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
| | - J. W. Hsiung
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
| | - S. A. Huang
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
| | - S. Chien
- Department of Bioengineering and Whitaker Institute of Biomedical Engineering, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0412
- *To whom correspondence should be addressed. E-mail:
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Henage LG, Exton JH, Brown HA. Kinetic analysis of a mammalian phospholipase D: allosteric modulation by monomeric GTPases, protein kinase C, and polyphosphoinositides. J Biol Chem 2006; 281:3408-17. [PMID: 16339153 PMCID: PMC3800466 DOI: 10.1074/jbc.m508800200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In mammalian cells, phospholipase D activity is tightly regulated by diverse cellular signals, including hormones, neurotransmitters, and growth factors. Multiple signaling pathways converge upon phospholipase D to modulate cellular actions, such as cell growth, shape, and secretion. We examined the kinetics of protein kinase C and G-protein regulation of mammalian phospholipase D1 (PLD1) in order to better understand interactions between PLD1 and its regulators. Activation by Arf-1, RhoA, Rac1, Cdc42, protein kinase Calpha, and phosphatidylinositol 4,5-bisphosphate displayed surface dilution kinetics, but these effectors modulated different kinetic parameters. PKCalpha activation of PLD1 involves N- and C-terminal PLD domains. Rho GTPases were binding activators, enhancing the catalytic efficiency of a purified PLD1 catalytic domain via effects on Km. Arf-1, a catalytic activator, stimulated PLD1 by enhancing the catalytic constant, kcat. A kinetic description of PLD1 activation by multiple modulators reveals a mechanism for apparent synergy between activators. Synergy was observed only when PLD1 was simultaneously stimulated by a binding activator and a catalytic activator. Surprisingly, synergistic activation was steeply dependent on phosphatidylinositol 4,5-bisphosphate and phosphatidylcholine. Together, these findings suggest a role for PLD1 as a signaling node, in which integration of convergent signals occurs within discrete locales of the cellular membrane.
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Affiliation(s)
- Lee G. Henage
- Department of Pharmacology, Institute for Chemical Biology, and Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37232-6600
| | - John H. Exton
- Department of Pharmacology, Institute for Chemical Biology, and Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37232-6600
| | - H. Alex Brown
- Department of Pharmacology, Institute for Chemical Biology, and Vanderbilt Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37232-6600
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Deng L, Sugiura R, Ohta K, Tada K, Suzuki M, Hirata M, Nakamura SI, Shuntoh H, Kuno T. Phosphatidylinositol-4-phosphate 5-kinase regulates fission yeast cell integrity through a phospholipase C-mediated protein kinase C-independent pathway. J Biol Chem 2005; 280:27561-8. [PMID: 15923187 DOI: 10.1074/jbc.m502660200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fission yeast its3-1 mutant is an allele of the essential gene its3+ that encodes a phosphatidylinositol-4-phosphate 5-kinase (PIP5K) that produces phosphatidylinositol 4,5-bisphosphate. We found that the its3-1 mutant is sensitive to micafungin, a (1,3)-beta-D-glucan synthase inhibitor, suggesting a cell wall integrity defect. Consistently, its3-1 mutation caused synthetic lethality with a (1,3)-beta-D-glucan synthase mutant, bgs1-i2, and its3-1 mutant cells showed aberrant localization of green fluorescent protein-Bgs1. Similar aberrant localization of green fluorescent protein-tagged Rgf1, a putative phosphatidylinositol 4,5-bisphosphate-binding guanine nucleotide exchange factor for Rho protein, in its3-1 mutants was observed, suggesting a defective Rgf1/Rho pathway. To unravel the molecular mechanism(s), putative downstream components of PIP5K signaling were analyzed. Unexpectedly, overexpression of phospholipase C (Plc1), but not that of protein kinase C (PKC; Pck1 and Pck2), suppressed the phenotypes of the its3-1 mutant. These findings indicate that PKCs are not involved in the suppression, and further analysis revealed that PKCs are not downstream of Plc1 in fission yeast. Also, the enzymatic activity of Plc1 is essential for the suppression of the phenotypes and for the viability of the its3-1 mutant. These findings suggest that Its3 PIP5K regulates cell integrity through a Plc1-mediated PKC-independent pathway, in addition to the Rho/PKC pathway.
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Affiliation(s)
- Lu Deng
- Division of Molecular Pharmacology and Pharmacogenomics, Department of Genome Sciences, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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Bairstow SF, Ling K, Anderson RA. Phosphatidylinositol phosphate kinase type Igamma directly associates with and regulates Shp-1 tyrosine phosphatase. J Biol Chem 2005; 280:23884-91. [PMID: 15849189 DOI: 10.1074/jbc.m500576200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyrosine phosphorylation plays a critical role in many regulatory aspects of cellular signaling, and dephosphorylation of phosphotyrosine residues is crucial for termination of signals initiated by tyrosine kinases. Previous work has shown that the tyrosine kinase Src phosphorylates Tyr644 on phosphatidylinositol phosphate kinase type I (PIPKI) gamma661 in a focal adhesion kinase-dependent manner. Phosphorylation of this residue is essential for high affinity binding of PIPKI gamma661 to the focal adhesion protein talin and for targeting of PIPKI gamma661 to focal adhesions. A yeast two-hybrid screen performed with the C-terminal 178-amino acid tail of PIPKI gamma661 identified an interaction with the phosphatase domain of the tyrosine phosphatase Shp-1. The interaction between PIPKI gamma661 and Shp-1 was confirmed via co-immunoprecipitation from HEK293 cell lysates. In addition, Src-phosphorylated PIPKI gamma661 is a substrate for Shp-1, and Shp-1 modulates both the association between PIPKI gamma661 and talin and the targeting of PIPKI gamma661 to focal adhesions in mammalian cells. Finally, we showed that Shp-1 phosphatase activity is inhibited by the product of PIPKI gamma661, phosphatidylinositol 4,5-bisphosphate, in vitro. These combined results suggest a model in which the reciprocal actions of Src tyrosine kinase and Shp-1 tyrosine phosphatase dynamically regulate the association between PIPKI gamma661 and talin.
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Affiliation(s)
- Shawn F Bairstow
- Department of Pharmacology, University of Wisconsin Medical School, Madison, Wisconsin 53706, USA
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45
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Asemu G, Dent MR, Singal T, Dhalla NS, Tappia PS. Differential changes in phospholipase D and phosphatidate phosphohydrolase activities in ischemia–reperfusion of rat heart. Arch Biochem Biophys 2005; 436:136-44. [PMID: 15752718 DOI: 10.1016/j.abb.2005.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2004] [Revised: 01/31/2005] [Indexed: 10/25/2022]
Abstract
Phospholipase D (PLD2) produces phosphatidic acid (PA), which is converted to 1,2 diacylglycerol (DAG) by phosphatidate phosphohydrolase (PAP2). Since PA and DAG regulate Ca(2+) movements, we examined PLD2 and PAP2 in the sarcolemma (SL) and sarcoplasmic reticular (SR) membranes from hearts subjected to ischemia and reperfusion (I-R). Although SL and SR PLD2 activities were unaltered after 30 min ischemia, 5 min reperfusion resulted in a 36% increase in SL PLD2 activity, whereas 30 min reperfusion resulted in a 30% decrease in SL PLD2 activity, as compared to the control value. SR PLD2 activity was decreased (39%) after 5 min reperfusion, but returned to control levels after 30 min reperfusion. Ischemia for 60 min resulted in depressed SL and SR PLD2 activities, characterized with reduced V(max) and increased K(m) values, which were not reversed during reperfusion. Although the SL PAP2 activity was decreased (31%) during ischemia and at 30 min reperfusion (28%), the SR PAP2 activity was unchanged after 30 min ischemia, but was decreased after 5 min reperfusion (25%) and almost completely recovered after 30 min reperfusion. A 60 min period of ischemia followed by reperfusion caused an irreversible depression of SL and SR PAP2 activities. Our results indicate that I-R induced cardiac dysfunction is associated with subcellular changes in PLD2 and PAP2 activities.
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Affiliation(s)
- Girma Asemu
- Institute of Cardiovascular Sciences, St. Boniface Hospital Research Centre, Department of Human Nutritional Sciences, Faculty of Human Ecology, University of Manitoba, Winnipeg, Canada R2H 2A6
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Abstract
Exocytosis is the process whereby intracellular fluid-filled vesicles fuse with the plasma membrane, incorporating vesicle proteins and lipids into the plasma membrane and releasing vesicle contents into the extracellular milieu. Exocytosis can occur constitutively or can be tightly regulated, for example, neurotransmitter release from nerve endings. The last two decades have witnessed the identification of a vast array of proteins and protein complexes essential for exocytosis. SNARE proteins fill the spotlight as probable mediators of membrane fusion, whereas proteins such as munc18/nsec1, NSF and SNAPs function as essential SNARE regulators. A central question that remains unanswered is how exocytic proteins and protein complexes are spatially regulated. Recent studies suggest that lipid rafts, cholesterol and sphingolipid-rich microdomains, enriched in the plasma membrane, play an essential role in regulated exocytosis pathways. The association of SNAREs with lipid rafts acts to concentrate these proteins at defined sites of the plasma membrane. Furthermore, cholesterol depletion inhibits regulated exocytosis, suggesting that lipid raft domains play a key role in the regulation of exocytosis. This review examines the role of lipid rafts in regulated exocytosis, from a passive role as spatial coordinator of exocytic proteins to a direct role in the membrane fusion reaction.
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Sundaram M, Cook HW, Byers DM. The MARCKS family of phospholipid binding proteins: regulation of phospholipase D and other cellular components. Biochem Cell Biol 2004; 82:191-200. [PMID: 15052337 DOI: 10.1139/o03-087] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Myristoylated alanine-rich C kinase substrate (MARCKS) and MARCKS-related protein (MRP) are essential proteins that are implicated in coordination of membrane-cytoskeletal signalling events, such as cell adhesion, migration, secretion, and phagocytosis in a variety of cell types. The most prominent structural feature of MARCKS and MRP is a central basic effector domain (ED) that binds F-actin, Ca2+-calmodulin, and acidic phospholipids; phosphorylation of key serine residues within the ED by protein kinase C (PKC) prevents the above interactions. While the precise roles of MARCKS and MRP have not been established, recent attention has focussed on the high affinity of the MARCKS ED for phosphatidylinositol 4,5-bisphosphate (PIP2), and a model has emerged in which calmodulin- or PKC-mediated regulation of these proteins at specific membrane sites could in turn control spatial availability of PIP2. The present review summarizes recent progress in this area and discusses how the above model might explain a role for MARCKS and MRP in activation of phospholipase D and other PIP2-dependent cellular processes.
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Affiliation(s)
- Meenakshi Sundaram
- Atlantic Research Centre, Department of Pediatrics, Dalhousie University, Halifax, NS, Canada
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Abstract
Phospholipase D catalyses the hydrolysis of the phosphodiester bond of glycerophospholipids to generate phosphatidic acid and a free headgroup. Phospholipase D activities have been detected in simple to complex organisms from viruses and bacteria to yeast, plants, and mammals. Although enzymes with broader selectivity are found in some of the lower organisms, the plant, yeast, and mammalian enzymes are selective for phosphatidylcholine. The two mammalian phospholipase D isoforms are regulated by protein kinases and GTP binding proteins of the ADP-ribosylation and Rho families. Mammalian and yeast phospholipases D are also potently stimulated by phosphatidylinositol 4,5-bisphosphate. This review discusses the identification, characterization, structure, and regulation of phospholipase D. Genetic and pharmacological approaches implicate phospholipase D in a diverse range of cellular processes that include receptor signaling, control of intracellular membrane transport, and reorganization of the actin cytoskeleton. Most ideas about phospholipase D function consider that the phosphatidic acid product is an intracellular lipid messenger. Candidate targets for phospholipase-D-generated phosphatidic acid include phosphatidylinositol 4-phosphate 5-kinases and the raf protein kinase. Phosphatidic acid can also be converted to two other lipid mediators, diacylglycerol and lyso phosphatidic acid. Coordinated activation of these phospholipase-D-dependent pathways likely accounts for the pleitropic roles for these enzymes in many aspects of cell regulation.
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Affiliation(s)
- Mark McDermott
- Department of Cell and Developmental Biology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 27599-7090, USA
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Routt SM, Bankaitis VA. Biological functions of phosphatidylinositol transfer proteins. Biochem Cell Biol 2004; 82:254-62. [PMID: 15052341 DOI: 10.1139/o03-089] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Phosphatidylinositol/phosphatidylcholine transfer proteins (PITPs) are ubiquitous and highly conserved proteins that are believed to regulate lipid-mediated signaling events. Their ubiquity and conservation notwithstanding, PITPs remain remarkably uninvestigated. Little is known about the coupling of specific PITPs to explicit cellular functions or the mechanisms by which PITPs interface with appropriate cellular functions. The available information indicates a role for these proteins in regulating the interface between lipid metabolism and membrane trafficking in yeast, signaling in plant development, the trafficking of specialized luminal cargo in mammalian enterocytes, and neurological function in mammals. Herein, we review recent advances in PITP biology and discuss as yet unresolved issues in this field.
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Affiliation(s)
- Sheri M Routt
- Department of Cell and Developmental Biology, School of Medicine, Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, 27599-7090, USA
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Yang SA, Carpenter CL, Abrams CS. Rho and Rho-kinase Mediate Thrombin-induced Phosphatidylinositol 4-Phosphate 5-Kinase Trafficking in Platelets. J Biol Chem 2004; 279:42331-6. [PMID: 15277528 DOI: 10.1074/jbc.m404335200] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylinositol 4-phosphate 5-kinase (PIP5K) catalyzes the rate-limiting step in the production of phosphatidylinositol 4,5-bisphosphate (PIP(2)), a signaling phospholipid that contributes to actin dynamics. We have shown in transfected tissue culture cells that PIP5K translocates from the cytosol to the plasma membrane following agonist-induced stimulation of Rho family GTPases. Nonetheless, it is unclear whether Rho GTPases induce PIP5K relocalization in platelets. We used PIP5K isoform-specific immunoblotting and lipid kinase assays to examine the intracellular localization of PIP5K in resting and activated platelets. Using differential centrifugation to separate the membrane skeleton, actin filaments and associated proteins, and cytoplasmic fractions, we found that PIP5K isoforms were translocated from cytosol to actin-rich fractions following stimulation of the thrombin receptor. PIP5K translocation was detectable within 30 s of stimulation and was complete by 2-5 min. This agonist-induced relocalization and activation of PIP5K was inhibited by 8-(4-parachlorophenylthio)-cAMP, a cAMP analogue that inhibits Rho and Rac. In contrast, 8-(4-parachlorophenylthio)-cGMP, a cGMP analogue that inhibits Rac but not Rho, did not affect PIP5K translocation and activation. This suggests that Rho GTPase may be an essential regulator of PIP5K in platelets. Consistent with this hypothesis, we found that C3 exotoxin (a Rho-specific inhibitor) and HA1077 (an inhibitor of the Rho effector, Rho-kinase) also eliminated PIP5K activation and trafficking into the membrane cytoskeleton. Thus, these data indicate that Rho GTPase and its effector Rho-kinase have an intimate relationship with the trafficking and activation of platelet PIP5K. Moreover, these data suggest that relocalization of platelet PIP5K following agonist stimulation may play an important role in regulating the assembly of the platelet cytoskeleton.
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Affiliation(s)
- Seun-Ah Yang
- Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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