1
|
Abstract
Virtually all aspects of T and B lymphocyte development, homeostasis, activation, and effector function are impacted by the interaction of their clonally distributed antigen receptors with antigens encountered in their respective environments. Antigen receptors mediate their effects by modulating intracellular signaling pathways that ultimately impinge on the cytoskeleton, bioenergetic pathways, transcription, and translation. Although these signaling pathways are rather well described at this point, especially those steps that are most receptor-proximal, how such pathways contribute to more quantitative aspects of lymphocyte function is still being elucidated. One of the signaling pathways that appears to be involved in this “tuning” process is controlled by the lipid kinase PI3K. Here we review recent key findings regarding both the triggering/enhancement of PI3K signals (via BCAP and ICOS) as well as their regulation (via PIK3IP1 and PHLPP) and how these signals integrate and determine cellular processes. Lymphocytes display tremendous functional plasticity, adjusting their metabolism and gene expression programs to specific conditions depending on their tissue of residence and the nature of the infectious threat to which they are responding. We give an overview of recent findings that have contributed to this model, with a focus on T cells, including what has been learned from patients with gain-of-function mutations in PI3K as well as lessons from cancer immunotherapy approaches.
Collapse
Affiliation(s)
- Benjamin Murter
- Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| | - Lawrence P Kane
- Department of Immunology, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15261, USA
| |
Collapse
|
2
|
Ulloa G, Hamati F, Dick A, Fitzgerald J, Mantell J, Verkade P, Collinson L, Arkill K, Larijani B, Poccia D. Lipid species affect morphology of endoplasmic reticulum: a sea urchin oocyte model of reversible manipulation. J Lipid Res 2019; 60:1880-1891. [PMID: 31548365 PMCID: PMC6824487 DOI: 10.1194/jlr.ra119000210] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 09/11/2019] [Indexed: 12/22/2022] Open
Abstract
The ER is a large multifunctional organelle of eukaryotic cells. Malfunction of the ER in various disease states, such as atherosclerosis, diabetes, cancer, Alzheimer’s and Parkinson’s and amyotrophic lateral sclerosis, often correlates with alterations in its morphology. The ER exhibits regionally variable membrane morphology that includes, at the extremes, large relatively flat surfaces and interconnected tubular structures highly curved in cross-section. ER morphology is controlled by shaping proteins that associate with membrane lipids. To investigate the role of these lipids, we developed a sea urchin oocyte model, a relatively quiescent cell in which the ER consists mostly of tubules. We altered levels of endogenous diacylglycerol (DAG), phosphatidylethanolamine (PtdEth), and phosphatidylcholine by microinjection of enzymes or lipid delivery by liposomes and evaluated shape changes with 2D and 3D confocal imaging and 3D electron microscopy. Decreases and increases in the levels of lipids such as DAG or PtdEth characterized by negative spontaneous curvature correlated with conversion to sheet structures or tubules, respectively. The effects of endogenous alterations of DAG were reversible upon exogenous delivery of lipids of negative spontaneous curvature. These data suggest that proteins require threshold amounts of such lipids and that localized deficiencies of the lipids could contribute to alterations of ER morphology. The oocyte modeling system should be beneficial to studies directed at understanding requirements of lipid species in interactions leading to alterations of organelle shaping.
Collapse
Affiliation(s)
| | - Fadi Hamati
- Department of Biology, Amherst College, Amherst, MA
| | | | | | - Judith Mantell
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Bristol, United Kingdom
| | | | - Kenton Arkill
- School of Medicine, Faculty of Medicine and Health Sciences, University of Nottingham Medical School, Nottingham, United Kingdom
| | - Banafshe Larijani
- Centre for Therapeutic Innovation, Cell Biophysics Laboratory, Department of Pharmacy and Pharmacology and Department of Physics, University of Bath, Claverton Down, Bath, United Kingdom, and Cell Biophysics Laboratory, Ikerbasque, Basque Foundation for Science, Research Centre for Experimental Marine Biology and Biotechnology (PiE) and Biophysics Institute (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain
| | | |
Collapse
|
3
|
Paddock MN, Field SJ, Cantley LC. Treating cancer with phosphatidylinositol-3-kinase inhibitors: increasing efficacy and overcoming resistance. J Lipid Res 2019; 60:747-752. [PMID: 30718284 PMCID: PMC6446698 DOI: 10.1194/jlr.s092130] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 01/25/2019] [Indexed: 11/20/2022] Open
Abstract
The discovery of the phosphatidylinositol-3-kinase (PI3K) pathway was a major advance in understanding growth factor signaling. The high frequency of PI3K pathway mutations in many cancers has encouraged a new field targeting cancer driver mutations. Although there have been many successes, targeting PI3K itself has proven challenging, in part because of its multiple isoforms with distinct roles. Despite promising preclinical results, development of PI3K inhibitors as pharmacologic anticancer agents has been limited by modest single-agent efficacy and significant adverse effects. If we could overcome these limitations, PI3K inhibitors would be a powerful cancer-fighting tool. Data from phase III clinical trials yields insight into some of the problems with PI3K inhibitors. Recent advances have shed light on the mechanisms of tumor resistance to PI3K inhibitors via feedback pathways that cause elevated insulin levels that then activate the same PI3K pathways that are the targets of inhibition. Improving our understanding of the complex regulatory feedback pathways that activate in response to PI3K inhibition will reveal ways to increase the efficacy of PI3K inhibitors and reduce adverse effects, increasing the usefulness of this class as a treatment option for multiple cancer types.
Collapse
Affiliation(s)
- Marcia N Paddock
- Meyer Cancer Center Weill Cornell Medicine, New York, NY 10021; Department of Medicine, Division of Hematology and Oncology, Weill Cornell Medicine, New York, NY 10021
| | - Seth J Field
- Department of Medicine, Division of Endocrinology and Metabolism, University of California, San Diego, La Jolla, CA 92093.
| | - Lewis C Cantley
- Meyer Cancer Center Weill Cornell Medicine, New York, NY 10021.
| |
Collapse
|
4
|
Record M, Silvente-Poirot S, Poirot M, Wakelam MJO. Extracellular vesicles: lipids as key components of their biogenesis and functions. J Lipid Res 2018; 59:1316-1324. [PMID: 29764923 PMCID: PMC6071772 DOI: 10.1194/jlr.e086173] [Citation(s) in RCA: 176] [Impact Index Per Article: 29.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Indexed: 12/15/2022] Open
Abstract
Intercellular communication has been known for decades to involve either direct contact between cells or to operate via circulating molecules, such as cytokines, growth factors, or lipid mediators. During the last decade, we have begun to appreciate the increasing importance of intercellular communication mediated by extracellular vesicles released by viable cells either from plasma membrane shedding (microvesicles, also named microparticles) or from an intracellular compartment (exosomes). Exosomes and microvesicles circulate in all biological fluids and can trigger biological responses at a distance. Their effects include a large variety of biological processes, such as immune surveillance, modification of tumor microenvironment, or regulation of inflammation. Extracellular vesicles can carry a large array of active molecules, including lipid mediators, such as eicosanoids, proteins, and nucleic acids, able to modify the phenotype of receiving cells. This review will highlight the role of the various lipidic pathways involved in the biogenesis and functions of microvesicles and exosomes.
Collapse
Affiliation(s)
- Michel Record
- UMR INSERM 1037-CRCT (Cancer Research Center of Toulouse), University of Toulouse III Paul Sabatier, Team "Cholesterol Metabolism and Therapeutic Innovations," Toulouse, France
| | - Sandrine Silvente-Poirot
- UMR INSERM 1037-CRCT (Cancer Research Center of Toulouse), University of Toulouse III Paul Sabatier, Team "Cholesterol Metabolism and Therapeutic Innovations," Toulouse, France
| | - Marc Poirot
- UMR INSERM 1037-CRCT (Cancer Research Center of Toulouse), University of Toulouse III Paul Sabatier, Team "Cholesterol Metabolism and Therapeutic Innovations," Toulouse, France
| | | |
Collapse
|
5
|
Benziane B, Borg ML, Tom RZ, Riedl I, Massart J, Björnholm M, Gilbert M, Chibalin AV, Zierath JR. DGKζ deficiency protects against peripheral insulin resistance and improves energy metabolism. J Lipid Res 2017; 58:2324-2333. [PMID: 29066466 DOI: 10.1194/jlr.m079723] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/16/2017] [Indexed: 12/25/2022] Open
Abstract
Diacylglycerol kinases (DGKs) regulate the balance between diacylglycerol (DAG) and phosphatidic acid. DGKζ is highly abundant in skeletal muscle and induces fiber hypertrophy. We hypothesized that DGKζ influences functional and metabolic adaptations in skeletal muscle and whole-body fuel utilization. DAG content was increased in skeletal muscle and adipose tissue, but unaltered in liver of DGKζ KO mice. Linear growth, body weight, fat mass, and lean mass were reduced in DGKζ KO versus wild-type mice. Conversely, male DGKζ KO and wild-type mice displayed a similar robust increase in plantaris weight after functional overload, suggesting that DGKζ is dispensable for muscle hypertrophy. Although glucose tolerance was similar, insulin levels were reduced in high-fat diet (HFD)-fed DGKζ KO versus wild-type mice. Submaximal insulin-stimulated glucose transport and p-Akt Ser473 were increased, suggesting enhanced skeletal muscle insulin sensitivity. Energy homeostasis was altered in DGKζ KO mice, as evidenced by an elevated respiratory exchange ratio, independent of altered physical activity or food intake. In conclusion, DGKζ deficiency increases tissue DAG content and leads to modest growth retardation, reduced adiposity, and protection against insulin resistance. DGKζ plays a role in the control of growth and metabolic processes, further highlighting specialized functions of DGK isoforms in type 2 diabetes pathophysiology.
Collapse
Affiliation(s)
- Boubacar Benziane
- Department of Physiology and Pharmacology Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Melissa L Borg
- Department of Physiology and Pharmacology Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Robby Z Tom
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Isabelle Riedl
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Julie Massart
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Marie Björnholm
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Marc Gilbert
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Alexander V Chibalin
- Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Juleen R Zierath
- Department of Physiology and Pharmacology Karolinska Institutet, 171 77 Stockholm, Sweden .,Department of Molecular Medicine and Surgery, Karolinska Institutet, 171 77 Stockholm, Sweden
| |
Collapse
|
6
|
Muftuoglu Y, Xue Y, Gao X, Wu D, Ha Y. Mechanism of substrate specificity of phosphatidylinositol phosphate kinases. Proc Natl Acad Sci U S A 2016; 113:8711-6. [PMID: 27439870 DOI: 10.1073/pnas.1522112113] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The phosphatidylinositol phosphate kinase (PIPK) family of enzymes is primarily responsible for converting singly phosphorylated phosphatidylinositol derivatives to phosphatidylinositol bisphosphates. As such, these kinases are central to many signaling and membrane trafficking processes in the eukaryotic cell. The three types of phosphatidylinositol phosphate kinases are homologous in sequence but differ in catalytic activities and biological functions. Type I and type II kinases generate phosphatidylinositol 4,5-bisphosphate from phosphatidylinositol 4-phosphate and phosphatidylinositol 5-phosphate, respectively, whereas the type III kinase produces phosphatidylinositol 3,5-bisphosphate from phosphatidylinositol 3-phosphate. Based on crystallographic analysis of the zebrafish type I kinase PIP5Kα, we identified a structural motif unique to the kinase family that serves to recognize the monophosphate on the substrate. Our data indicate that the complex pattern of substrate recognition and phosphorylation results from the interplay between the monophosphate binding site and the specificity loop: the specificity loop functions to recognize different orientations of the inositol ring, whereas residues flanking the phosphate binding Arg244 determine whether phosphatidylinositol 3-phosphate is exclusively bound and phosphorylated at the 5-position. This work provides a thorough picture of how PIPKs achieve their exquisite substrate specificity.
Collapse
|
7
|
Scott WJ, Hentemann MF, Rowley RB, Bull CO, Jenkins S, Bullion AM, Johnson J, Redman A, Robbins AH, Esler W, Fracasso RP, Garrison T, Hamilton M, Michels M, Wood JE, Wilkie DP, Xiao H, Levy J, Stasik E, Liu N, Schaefer M, Brands M, Lefranc J. Discovery and SAR of Novel 2,3-Dihydroimidazo[1,2-c]quinazoline PI3K Inhibitors: Identification of Copanlisib (BAY 80-6946). ChemMedChem 2016; 11:1517-30. [PMID: 27310202 PMCID: PMC5094563 DOI: 10.1002/cmdc.201600148] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/12/2016] [Indexed: 12/12/2022]
Abstract
The phosphoinositide 3‐kinase (PI3K) pathway is aberrantly activated in many disease states, including tumor cells, either by growth factor receptor tyrosine kinases or by the genetic mutation and amplification of key pathway components. A variety of PI3K isoforms play differential roles in cancers. As such, the development of PI3K inhibitors from novel compound classes should lead to differential pharmacological and pharmacokinetic profiles and allow exploration in various indications, combinations, and dosing regimens. A screening effort aimed at the identification of PI3Kγ inhibitors for the treatment of inflammatory diseases led to the discovery of the novel 2,3‐dihydroimidazo[1,2‐c]quinazoline class of PI3K inhibitors. A subsequent lead optimization program targeting cancer therapy focused on inhibition of PI3Kα and PI3Kβ. Herein, initial structure–activity relationship findings for this class and the optimization that led to the identification of copanlisib (BAY 80‐6946) as a clinical candidate for the treatment of solid and hematological tumors are described.
Collapse
Affiliation(s)
- William J Scott
- Global Development, Global Program Management, Bayer HealthCare Pharmaceuticals Inc., Whippany, NJ, 07981, USA.
| | | | - R Bruce Rowley
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Cathy O Bull
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Susan Jenkins
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Ann M Bullion
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | | | - Anikó Redman
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | | | - William Esler
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | | | | | - Mark Hamilton
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Martin Michels
- Global Drug Discovery, Project Management Drug Discovery, Bayer Pharma AG, 13353, Berlin, Germany
| | - Jill E Wood
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Dean P Wilkie
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Hong Xiao
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Joan Levy
- Former Bayer Research Center, West Haven, CT, 16516, USA
| | - Enrico Stasik
- Global Drug Discovery, TRG Oncology, Bayer Pharma AG, 13353, Berlin, Germany
| | - Ningshu Liu
- Global Drug Discovery, TRG Oncology, Bayer Pharma AG, 13353, Berlin, Germany
| | - Martina Schaefer
- Global Drug Discovery, Structural Biology, Bayer Pharma AG, 13353, Berlin, Germany
| | - Michael Brands
- Global Drug Discovery, Medicinal Chemistry Berlin, Bayer Pharma AG, 13353, Berlin, Germany
| | - Julien Lefranc
- Global Drug Discovery, Medicinal Chemistry Berlin, Bayer Pharma AG, 13353, Berlin, Germany.
| |
Collapse
|
8
|
Abstract
Type 2 diabetes is a complex disease. It results from a failure of the body to maintain energy homoeostasis. Multicellular organisms have evolved complex strategies to preserve a relatively stable internal nutrient environment, despite fluctuations in external nutrient availability. This complex strategy involves the co-ordinated responses of multiple organs to promote storage or mobilization of energy sources according to the availability of nutrients and cellular bioenergetics needs. The endocrine pancreas plays a central role in these processes by secreting insulin and glucagon. When this co-ordinated effort fails, hyperglycaemia and hyperlipidaemia develops, characterizing a state of metabolic imbalance and ultimately overt diabetes. Although diabetes is most likely a collection of diseases, scientists are starting to identify genetic components and environmental triggers. Genome-wide association studies revealed that by and large, gene variants associated with type 2 diabetes are implicated in pancreatic β-cell function, suggesting that the β-cell may be the weakest link in the chain of events that results in diabetes. Thus, it is critical to understand how environmental cues affect the β-cell. Phosphoinositides are important 'decoders' of environmental cues. As such, these lipids have been implicated in cellular responses to a wide range of growth factors, hormones, stress agents, nutrients and metabolites. Here we will review some of the well-established and potential new roles for phosphoinositides in β-cell function/dysfunction and discuss how our knowledge of phosphoinositide signalling could aid in the identification of potential strategies for treating or preventing type 2 diabetes.
Collapse
Affiliation(s)
- Lucia E Rameh
- Department of Medicine, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118, U.S.A.
| | - Jude T Deeney
- Department of Medicine, Boston University School of Medicine, 650 Albany Street, Boston, MA 02118, U.S.A
| |
Collapse
|
9
|
Liu K, Kunii N, Sakuma M, Yamaki A, Mizuno S, Sato M, Sakai H, Kado S, Kumagai K, Kojima H, Okabe T, Nagano T, Shirai Y, Sakane F. A novel diacylglycerol kinase α-selective inhibitor, CU-3, induces cancer cell apoptosis and enhances immune response. J Lipid Res 2016; 57:368-79. [PMID: 26768655 DOI: 10.1194/jlr.m062794] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Indexed: 02/02/2023] Open
Abstract
Diacylglycerol kinase (DGK) consists of 10 isozymes. The α-isozyme enhances the proliferation of cancer cells. However, DGKα facilitates the nonresponsive state of immunity known as T-cell anergy; therefore, DGKα enhances malignant traits and suppresses immune surveillance. The aim of this study was to identify a novel small molecule that selectively and potently inhibits DGKα activity. We screened a library containing 9,600 chemical compounds using a newly established high-throughput DGK assay. As a result, we have obtained a promising compound, 5-[(2E)-3-(2-furyl)prop-2-enylidene]-3-[(phenylsulfonyl)amino]2-thioxo-1,3-thiazolidin-4-one) (CU-3), which selectively inhibited DGKα with an IC50 value of 0.6 μM. CU-3 targeted the catalytic region, but not the regulatory region, of DGKα. CU-3 competitively reduced the affinity of DGKα for ATP, but not diacylglycerol or phosphatidylserine. Moreover, this compound induced apoptosis in HepG2 hepatocellular carcinoma and HeLa cervical cancer cells while simultaneously enhancing the interleukin-2 production of Jurkat T cells. Taken together, these results indicate that CU-3 is a selective and potent inhibitor for DGKα and can be an ideal anticancer drug candidate that attenuates cancer cell proliferation and simultaneously enhances immune responses including anticancer immunity.
Collapse
Affiliation(s)
- Ke Liu
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Naoko Kunii
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Megumi Sakuma
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Atsumi Yamaki
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Satoru Mizuno
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Mayu Sato
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Hiromichi Sakai
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| | - Sayaka Kado
- Graduate School of Science and Center for Analytical Instrumentation, Chiba University, Chiba 263-8522, Japan
| | - Kazuo Kumagai
- Drug Discovery Initiative, University of Tokyo, Tokyo 113-0033, Japan
| | - Hirotatsu Kojima
- Drug Discovery Initiative, University of Tokyo, Tokyo 113-0033, Japan
| | - Takayoshi Okabe
- Drug Discovery Initiative, University of Tokyo, Tokyo 113-0033, Japan
| | - Tetsuo Nagano
- Drug Discovery Initiative, University of Tokyo, Tokyo 113-0033, Japan
| | - Yasuhito Shirai
- Department of Applied Chemistry in Bioscience, Graduate School of Agricultural Science, Kobe University, Kobe 657-8501, Japan
| | - Fumio Sakane
- Department of Chemistry, Chiba University, Chiba 263-8522, Japan
| |
Collapse
|
10
|
Geng T, Sutter A, Harland MD, Law BA, Ross JS, Lewin D, Palanisamy A, Russo SB, Chavin KD, Cowart LA. SphK1 mediates hepatic inflammation in a mouse model of NASH induced by high saturated fat feeding and initiates proinflammatory signaling in hepatocytes. J Lipid Res 2015; 56:2359-71. [PMID: 26482537 DOI: 10.1194/jlr.m063511] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Indexed: 11/20/2022] Open
Abstract
Steatohepatitis occurs in up to 20% of patients with fatty liver disease and leads to its primary disease outcomes, including fibrosis, cirrhosis, and increased risk of hepatocellular carcinoma. Mechanisms that mediate this inflammation are of major interest. We previously showed that overload of saturated fatty acids, such as that which occurs with metabolic syndrome, induced sphingosine kinase 1 (SphK1), an enzyme that generates sphingosine-1-phosphate (S1P). While data suggest beneficial roles for S1P in some contexts, we hypothesized that it may promote hepatic inflammation in the context of obesity. Consistent with this, we observed 2-fold elevation of this enzyme in livers from humans with nonalcoholic fatty liver disease and also in mice with high saturated fat feeding, which recapitulated the human disease. Mice exhibited activation of NFκB, elevated cytokine production, and immune cell infiltration. Importantly, SphK1-null mice were protected from these outcomes. Studies in cultured cells demonstrated saturated fatty acid induction of SphK1 message, protein, and activity, and also a requirement of the enzyme for NFκB signaling and increased mRNA encoding TNFα and MCP1. Moreover, saturated fat-induced NFκB signaling and elevation of TNFα and MCP1 mRNA in HepG2 cells was blocked by targeted knockdown of S1P receptor 1, supporting a role for this lipid signaling pathway in inflammation in nonalcoholic fatty liver disease.
Collapse
Affiliation(s)
- Tuoyu Geng
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425
| | - Alton Sutter
- Surgery, Medical University of South Carolina, Charleston, SC 29425
| | - Michael D Harland
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425
| | - Brittany A Law
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425 Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29403
| | - Jessica S Ross
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425
| | - David Lewin
- Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC 29425
| | - Arun Palanisamy
- Surgery, Medical University of South Carolina, Charleston, SC 29425
| | - Sarah B Russo
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425
| | - Kenneth D Chavin
- Surgery, Medical University of South Carolina, Charleston, SC 29425
| | - L Ashley Cowart
- Departments of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425 Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29403
| |
Collapse
|
11
|
Abstract
Signaling through the phosphoinositide 3-kinase pathways mediates the actions of a plethora of hormones, growth factors, cytokines, and neurotransmitters upon their target cells following receptor occupation. Overactivation of these pathways has been implicated in a number of pathologies, in particular a range of malignancies. The tight regulation of signaling pathways necessitates the involvement of both stimulatory and terminating enzymes; inappropriate activation of a pathway can thus result from activation or inhibition of the two signaling arms. The focus of this review is to discuss, in detail, the activities of the identified families of phosphoinositide phosphatase expressed in humans, and how they regulate the levels of phosphoinositides implicated in promoting malignancy.
Collapse
Affiliation(s)
- Simon A Rudge
- Signalling Programme, Babraham Institute, Cambridge CB22 3AT, United Kingdom
| | - Michael J O Wakelam
- Signalling Programme, Babraham Institute, Cambridge CB22 3AT, United Kingdom
| |
Collapse
|
12
|
Abstract
The class I phosphoinositide 3-kinases (PI3Ks) are lipid kinases that transduce a host of cellular signals and regulate a broad range of essential functions including growth, proliferation, and migration. As such, PI3Ks have pivotal roles in diseases such as cancer, diabetes, primary immune disorders, and inflammation. These enzymes are activated downstream of numerous activating stimuli including receptor tyrosine kinases, G protein-coupled receptors (GPCRs), and the Ras superfamily of small G proteins. A major challenge is to decipher how each PI3K isoform is able to successfully synergize these inputs into their intended signaling function. This article highlights recent progress in characterizing the molecular mechanisms of PI3K isoform-specific activation pathways, as well as novel roles for PI3Ks in human diseases, specifically cancer and immune diseases.
Collapse
Affiliation(s)
- John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, 3800 Finnerty Drive, Victoria BC, V8P 5C2, Canada.
| | - Roger L Williams
- Medical Research Council (MRC) Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge, CB2 0QH, UK
| |
Collapse
|
13
|
Le TT, Yue S, Cheng JX. Shedding new light on lipid biology with coherent anti-Stokes Raman scattering microscopy. J Lipid Res 2010; 51:3091-102. [PMID: 20713649 PMCID: PMC2952550 DOI: 10.1194/jlr.r008730] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 08/16/2010] [Indexed: 12/31/2022] Open
Abstract
Despite the ubiquitous roles of lipids in biology, the detection of lipids has relied on invasive techniques, population measurements, or nonspecific labeling. Such difficulties can be circumvented by a label-free imaging technique known as coherent anti-Stokes Raman (CARS) microscopy, which is capable of chemically selective, highly sensitive, and high-speed imaging of lipid-rich structures with submicron three-dimensional spatial resolution. We review the broad applications of CARS microscopy to studies of lipid biology in cell cultures, tissue biopsies, and model organisms. Recent technical advances, limitations of the technique, and perspectives are discussed.
Collapse
Affiliation(s)
- Thuc T. Le
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907
| | - Shuhua Yue
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907
| | - Ji-Xin Cheng
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907
- Department of Chemistry, Purdue University, West Lafayette, IN 47907
| |
Collapse
|