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Cockcroft S. The expanding roles of PI4P and PI(4,5)P 2 at the plasma membrane: Role of phosphatidylinositol transfer proteins. Biochim Biophys Acta Mol Cell Biol Lipids 2024; 1869:159394. [PMID: 37714261 DOI: 10.1016/j.bbalip.2023.159394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 09/17/2023]
Abstract
Phosphoinositides are phosphorylated derivatives of phosphatidylinositol, a phospholipid that is synthesised at the endoplasmic reticulum. The plasma membrane contains the enzymes to phosphorylate phosphatidylinositol and is therefore rich in the phosphorylated derivatives, PI4P and PI(4,5)P2. PI(4,5)P2 is a substrate for phospholipase C and during cell signaling, PI(4,5)P2 levels are reduced. Here I discuss a family of proteins, phosphatidylinositol transfer proteins (PITPs) that can restore PI(4,5)P2 levels.
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Affiliation(s)
- Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, 21 University Street, London WC1E 6JJ, UK.
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2
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Redpath G, Deo N. Serotonin: an overlooked regulator of endocytosis and endosomal sorting? Biol Open 2022; 11:bio059057. [PMID: 35076063 PMCID: PMC8801889 DOI: 10.1242/bio.059057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 12/09/2021] [Indexed: 12/23/2022] Open
Abstract
Serotonin is a neurotransmitter and a hormone that is typically associated with regulating our mood. However, the serotonin transporter and receptors are expressed throughout the body, highlighting the much broader, systemic role of serotonin in regulating human physiology. A substantial body of data strongly implicates serotonin as a fundamental regulator of endocytosis and endocytic sorting. Serotonin has the potential to enhance endocytosis through three distinct mechanisms - serotonin signalling, serotonylation and insertion into the plasma membrane - although the interplay and relationship between these mechanisms has not yet been explored. Endocytosis is central to the cellular response to the extracellular environment, controlling receptor distribution on the plasma membrane to modulate signalling, neurotransmitter release and uptake, circulating protein and lipid cargo uptake, and amino acid internalisation for cell proliferation. Uncovering the range of cellular and physiological circumstances in which serotonin regulates endocytosis is of great interest for our understanding of how serotonin regulates mood, and also the fundamental understanding of endocytosis and its regulation throughout the body. This article has an associated Future Leader to Watch interview with the first author of the paper.
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Affiliation(s)
- Gregory Redpath
- EMBL Australia Node in Single Molecule Science, School of Medical Sciences and the ARC Centre of Excellence in Advanced Molecular Imaging, University of New South Wales, Sydney 2052, Australia
| | - Nikita Deo
- Department of Biochemistry, University of Otago, Dunedin 9016, New Zealand
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Katan M, Cockcroft S. Phospholipase C families: Common themes and versatility in physiology and pathology. Prog Lipid Res 2020; 80:101065. [PMID: 32966869 DOI: 10.1016/j.plipres.2020.101065] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/14/2020] [Accepted: 09/17/2020] [Indexed: 12/20/2022]
Abstract
Phosphoinositide-specific phospholipase Cs (PLCs) are expressed in all mammalian cells and play critical roles in signal transduction. To obtain a comprehensive understanding of these enzymes in physiology and pathology, a detailed structural, biochemical, cell biological and genetic information is required. In this review, we cover all these aspects to summarize current knowledge of the entire superfamily. The families of PLCs have expanded from 13 enzymes to 16 with the identification of the atypical PLCs in the human genome. Recent structural insights highlight the common themes that cover not only the substrate catalysis but also the mechanisms of activation. This involves the release of autoinhibitory interactions that, in the absence of stimulation, maintain classical PLC enzymes in their inactive forms. Studies of individual PLCs provide a rich repertoire of PLC function in different physiologies. Furthermore, the genetic studies discovered numerous mutated and rare variants of PLC enzymes and their link to human disease development, greatly expanding our understanding of their roles in diverse pathologies. Notably, substantial evidence now supports involvement of different PLC isoforms in the development of specific cancer types, immune disorders and neurodegeneration. These advances will stimulate the generation of new drugs that target PLC enzymes, and will therefore open new possibilities for treatment of a number of diseases where current therapies remain ineffective.
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Affiliation(s)
- Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Shamshad Cockcroft
- Department of Neuroscience, Physiology and Pharmacology, Division of Biosciences, University College London, 21 University Street, London WC1E 6JJ, UK.
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Effects of Dietary Threonine Levels on Intestinal Immunity and Antioxidant Capacity Based on Cecal Metabolites and Transcription Sequencing of Broiler. Animals (Basel) 2019; 9:ani9100739. [PMID: 31569385 PMCID: PMC6826648 DOI: 10.3390/ani9100739] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Revised: 09/18/2019] [Accepted: 09/24/2019] [Indexed: 01/15/2023] Open
Abstract
Simple Summary Threonine (Thr), an indispensable amino acid for animals and the third limiting amino acid of broilers, plays a vital role in the synthesis of gut mucosal proteins, which also has better effects on growth performance, biochemical indexes, antioxidant function, and gut morphology, as well as acting as a nutrient immunomodulator that affects the intestinal barrier function of broilers. However, it is not clear how it works in depth. The objective of the current study was to investigate the mechanism of effects of different dietary threonine levels on the antioxidant and immune capacity of broilers. Our findings suggest that a Thr level of 125% NRC (Nutrient Requirements of Poultry, 1994) recommendations had better effects on antioxidant and immune capacity, including resisting viruses and decreasing the abnormal proliferation of cells. As well as this, it also had better effects on maintaining the homeostasis of the body. Abstract This study aimed to determine the effects of different dietary threonine levels on the antioxidant and immune capacity and the immunity of broilers. A total of 432 one-day-old Arbor Acres (AA) broilers were randomly assigned to 4 groups, each with 6 replicates of 18 broilers. The amount of dietary threonine in the four treatments reached 85%, 100%, 125%, and 150% of the NRC (Nutrient Requirements of Poultry, 1994) recommendation for broilers (marked as THR85, THR100, THR125, and THR150). After 42 days of feeding, the cecum contents and jejunum mucosa were collected for metabolic analysis and transcriptional sequencing. The results indicated that under the condition of regular and non-disease growth of broilers, compared with that of the THR85 and THR150 groups, the metabolic profile of the THR125 group was significantly higher than that of the standard requirement group. Compared with the THR100 group, the THR125 group improved antioxidant ability and immunity of broilers and enhanced the ability of resisting viruses. The antioxidant gene CAT was upregulated. PLCD1, which is involved in immune signal transduction and plays a role in cancer suppression, was also upregulated. Carcinogenic or indirect genes PKM2, ACY1, HK2, and TBXA2 were down-regulated. The genes GPT2, glude2, and G6PC, which played an important role in maintaining homeostasis, were up-regulated. Therefore, the present study suggests that 125% of the NRC recommendations for Thr level had better effects on antioxidant and immune capacity, as well as maintaining the homeostasis of the body.
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Xiang Q, He X, Mu J, Mu H, Zhou D, Tang J, Xiao Q, Jiang Y, Ren G, Xiang T, Peng W. The phosphoinositide hydrolase phospholipase C delta1 inhibits epithelial-mesenchymal transition and is silenced in colorectal cancer. J Cell Physiol 2019; 234:13906-13916. [PMID: 30618183 DOI: 10.1002/jcp.28073] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2018] [Accepted: 12/18/2018] [Indexed: 12/21/2022]
Abstract
In this study, we found that the phospholipase C delta1 (PLCD1) protein expression is reduced in colorectal tumor tissues compared with paired surgical margin tissues. PLCD1-promoted CpG methylation was detected in 29/64 (45%) primary colorectal tumors, but not in nontumor tissues. The PLCD1 RNA expression was also reduced in three out of six cell lines, due to PLCD1 methylation. The ectopic expression of PLCD1 resulted in inhibited proliferation and attenuated migration of colorectal tumor cells, yet promoted colorectal tumor cell apoptosis in vitro. We also observed that PLCD1 suppressed proliferation and promoted apoptosis in vivo. In addition, PLCD1 induced G1/S phase cell cycle arrest. Furthermore, we found that PLCD1 led to the downregulation of several factors downstream of β-catenin, including c-Myc and cyclin D1, which are generally known to be promoters of tumorigenesis. This downregulation was caused by an upregulation of E-cadherin in colorectal tumor cells. Our findings provide insights into the role of PLCD1 as a tumor suppressor gene in colorectal cancer (CRC), and demonstrate that it plays significant roles in proliferation, migration, invasion, cell cycle progression, and epithelial-mesenchymal transition. On the basis of these results, tumor-specific methylation of PLCD1 could be used as a novel biomarker for early detection and prognostic prediction in CRC.
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Affiliation(s)
- Qin Xiang
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xiaoqian He
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Junhao Mu
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Haixi Mu
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Dishu Zhou
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jun Tang
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Qian Xiao
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Yu Jiang
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Guosheng Ren
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Tingxiu Xiang
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Weiyan Peng
- Chongqing Key Laboratory of Molecular Oncology and Epigenetics, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
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Grund T, Neumann ID. Neuropeptide S Induces Acute Anxiolysis by Phospholipase C-Dependent Signaling within the Medial Amygdala. Neuropsychopharmacology 2018; 43:1156-1163. [PMID: 28805209 PMCID: PMC5854792 DOI: 10.1038/npp.2017.169] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 08/04/2017] [Accepted: 08/07/2017] [Indexed: 12/11/2022]
Abstract
Neuropeptide S (NPS) is an important anxiolytic substance of the brain. However, the signaling pathways downstream of NPS receptor (NPSR) activation, underlying the behavioral effect of NPS, remain largely unknown. Here, we show that bilateral microinfusion of NPS (0.2 nmol/0.5 μl) into the medial amygdala (MeA) of male adult Wistar rats reduced anxiety-related behavior on both the elevated plus-maze and the open field. Moreover, as shown in amygdala tissue micropunches intracerebroventricular infusion of NPS (1 nmol/5 μl) (1) evoked phosphorylation and synthesis of CaMKIIα in relation to reference protein β-tubulin representing Ca2+ influx, and (2) induced phosphorylation of mitogen-activated protein kinase ERK1/2. The NPS-induced anxiolysis was prevented by local inhibition of phospholipase C signaling using U73122 (0.5 nmol/0.5 μl) in the MeA, indicating the behavioral relevance of this pathway. Conversely, local pharmacological blockade of adenylyl cyclase signaling using 2',5'-dideoxyadenosine (12.5 nmol/0.5 μl) failed to inhibit the anxiolytic effect of NPS infused into the MeA. Hence, NPS promotes acute anxiolysis within the MeA dependent on NPSR-mediated phospholipase C signaling. Taken together, our study extends the knowledge about the intracellular signaling mechanisms underlying the potent anxiolytic profile of NPS.
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Affiliation(s)
- Thomas Grund
- Department of Behavioural and Molecular Neurobiology, University of Regensburg, Regensburg, Germany
| | - Inga D Neumann
- Department of Behavioural and Molecular Neurobiology, University of Regensburg, Regensburg, Germany,Department of Behavioural and Molecular Neurobiology, University of Regensburg, Universitätsstraße 31, 93053 Regensburg, Germany, Tel: +49 941 943 3053, Fax: +49 941 943 3052, E-mail:
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King JR, Gillevet TC, Kabbani N. A G protein-coupled α7 nicotinic receptor regulates signaling and TNF-α release in microglia. FEBS Open Bio 2017; 7:1350-1361. [PMID: 28904864 PMCID: PMC5586346 DOI: 10.1002/2211-5463.12270] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 07/14/2017] [Indexed: 11/21/2022] Open
Abstract
Acetylcholine activation of α7 nicotinic acetylcholine receptors (α7 nAChRs) in microglia attenuates neuroinflammation and regulates TNF‐α release. We used lipopolysaccharide to model inflammation in the microglial cell line EOC20 and examined signaling by the α7 nAChR. Co‐immunoprecipitation experiments confirm that α7 nAChRs bind heterotrimeric G proteins in EOC20 cells. Interaction with Gαi mediates α7 nAChR signaling via enhanced intracellular calcium release and a decrease in cAMP, p38 phosphorylation, and TNF‐α release. These α7 nAChR effects were blocked by the inhibition of Gαi signaling via pertussis toxin, PLC activity with U73122, and α7 nAChR channel activity with the selective antagonist α‐bungarotoxin. Moreover, α7 nAChR signaling in EOC20 cells was significantly diminished by the expression of a dominant‐negative α7 nAChR, α7345‐8A, shown to be impaired in G protein binding. These findings indicate an essential role for G protein coupling in α7 nAChR function in microglia leading to the regulation of inflammation in the nervous system.
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Affiliation(s)
- Justin R King
- Interdisciplinary Program in Neuroscience Krasnow Institute for Advanced Study George Mason University Fairfax VA USA
| | - Trudy C Gillevet
- Interdisciplinary Program in Neuroscience Krasnow Institute for Advanced Study George Mason University Fairfax VA USA
| | - Nadine Kabbani
- School of Systems Biology Krasnow Institute for Advanced Study George Mason University Fairfax VA USA
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Mu H, Wang N, Zhao L, Li S, Li Q, Chen L, Luo X, Qiu Z, Li L, Ren G, Xu Y, Zhou X, Xiang T. Methylation of PLCD1 and adenovirus-mediated PLCD1 overexpression elicits a gene therapy effect on human breast cancer. Exp Cell Res 2015; 332:179-89. [PMID: 25655282 DOI: 10.1016/j.yexcr.2015.01.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 01/23/2015] [Accepted: 01/24/2015] [Indexed: 12/19/2022]
Abstract
Our previous study showed that PLCD1 significantly decreases cell proliferation and affects cell cycle progression in breast cancer cells. In the present study, we aimed to investigate its functional and molecular mechanisms, and whether or not can become a new target for gene therapies. We found reduced PLCD1 protein expression in breast tumor tissues compared with paired surgical margin tissues. PLCD1 promoter CpG methylation was detected in 55 of 96 (57%) primary breast tumors, but not in surgical-margin tissues and normal breast tissues. Ectopic expression of PLCD1 inhibited breast tumor cell proliferation in vivo by inducing apoptosis and suppressed tumor cell migration by regulating cytoskeletal reorganization proteins including RhoA and phospho-cofilin. Furthermore, we found that PLCD1 induced p53 accumulation, increased p27 and p21 protein levels, and cleaved PARP. Finally, we constructed an adenoviral vector expressing PLCD1 (AdH5-PLCD1), which exhibited strong cytotoxicity in breast cancer cells. Our findings provide insights into the development of PLCD1 gene therapies for breast cancer and perhaps, other human cancers.
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Affiliation(s)
- Haixi Mu
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China; Department of Endocrine and breast Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
| | - Na Wang
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Lijuan Zhao
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Shuman Li
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Qianqian Li
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Ling Chen
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xinrong Luo
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Zhu Qiu
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Lili Li
- Cancer Epigenetics Laboratory, Department of Clinical Oncology, Sir YK Pao Center for Cancer and Li Ka Shing Institute of Health Sciences, The Chinese University of Hong Kong and CUHK Shenzhen Research Institute, Hong Kong
| | - Guosheng Ren
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China; Department of Endocrine and breast Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China
| | - Yongzhu Xu
- Chongqing Health Service Center, Chongqing 400020, China
| | | | - Tingxiu Xiang
- Molecular Oncology and Epigenetics Laboratory, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China.
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Bolnick JM, Karana R, Chiang PJ, Kilburn BA, Romero R, Diamond MP, Smith SM, Armant DR. Apoptosis of alcohol-exposed human placental cytotrophoblast cells is downstream of intracellular calcium signaling. Alcohol Clin Exp Res 2014; 38:1646-53. [PMID: 24889927 DOI: 10.1111/acer.12417] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 02/22/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND Apoptosis is induced by ethanol (EtOH) in human placental trophoblast cells, possibly disrupting placentation and contributing to intrauterine growth restriction in fetal alcohol spectrum disorder (FASD). EtOH induces programmed cell death in several embryonic tissues by raising intracellular Ca(2+) . Therefore, the role of Ca(2+) signaling in EtOH-induced apoptosis was examined using human first trimester cytotrophoblast cell lines, examining the hypothesis that apoptosis is dependent on intracellular Ca(2+) signaling. METHODS Using HTR-8/SVneo and SW.71 cytotrophoblast cell lines, real-time intracellular Ca(2+) concentration was monitored by fluo-4 epifluorescence microscopy and apoptosis was assessed by flow cytometry of cells fluorescently labeled for DNA fragmentation (TUNEL) and annexin V binding. RESULTS Intracellular Ca(2+) concentrations increased synchronously in all cells within 10 seconds of exposure to 50 mM EtOH, but not at lower EtOH concentrations (10 to 25 mM) incapable of inducing apoptosis. Trophoblast cells treated with inhibitors of Ca(2+) signaling (BAPTA-AM, U73122, xestospongin D, BAPTA, SKF-96365) produced no intracellular Ca(2+) transients after exposure to 50 mM EtOH and were protected from cell death induced by EtOH. CONCLUSIONS EtOH-induced apoptosis in human cytotrophoblast cells, identified by DNA fragmentation and externalized phosphatidylserine, was dependent upon Ca(2+) signaling. Both intracellular Ca(2+) mobilization and extracellular Ca(2+) influx were required, as well as phosphatidylinositol signaling. Inhibition by SKF-96365 suggests that the capacitative Ca(2+) entry mechanism that utilizes TRPC channels was activated by EtOH. Apoptosis occurs downstream of Ca(2+) signaling in trophoblasts and may contribute to placental insufficiency and poor fetal growth associated with FASD.
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Affiliation(s)
- Jay M Bolnick
- Department of Obstetrics and Gynecology, Wayne State University, C.S. Mott Center for Human Growth and Development, Detroit, Michigan
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10
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Palmitoylation of human proteinase-activated receptor-2 differentially regulates receptor-triggered ERK1/2 activation, calcium signalling and endocytosis. Biochem J 2011; 438:359-67. [PMID: 21627585 DOI: 10.1042/bj20101958] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
hPAR(2) (human proteinase-activated receptor-2) is a member of the novel family of proteolytically activated GPCRs (G-protein-coupled receptors) termed PARs (proteinase-activated receptors). Previous pharmacological studies have found that activation of hPAR(2) by mast cell tryptase can be regulated by receptor N-terminal glycosylation. In order to elucidate other post-translational modifications of hPAR(2) that can regulate function, we have explored the functional role of the intracellular cysteine residue Cys(361). We have demonstrated, using autoradiography, that Cys(361) is the primary palmitoylation site of hPAR(2). The hPAR(2)C361A mutant cell line displayed greater cell-surface expression compared with the wt (wild-type)-hPAR(2)-expressing cell line. hPAR(2)C361A also showed a decreased sensitivity and efficacy (intracellular calcium signalling) towards both trypsin and SLIGKV. In stark contrast, hPAR(2)C361A triggered greater and more prolonged ERK (extracellular-signal-regulated kinase) phosphorylation compared with that of wt-hPAR(2) possibly through Gi, since pertussis toxin inhibited the ability of this receptor to activate ERK. Finally, flow cytometry was utilized to assess the rate and extent of receptor internalization following agonist challenge. hPAR(2)C361A displayed faster internalization kinetics following trypsin activation compared with wt-hPAR(2), whereas SLIGKV had a negligible effect on internalization for either receptor. In conclusion, palmitoylation plays an important role in the regulation of PAR(2) expression, agonist sensitivity, desensitization and internalization.
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11
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Klein RR, Bourdon DM, Costales CL, Wagner CD, White WL, Williams JD, Hicks SN, Sondek J, Thakker DR. Direct activation of human phospholipase C by its well known inhibitor u73122. J Biol Chem 2011; 286:12407-16. [PMID: 21266572 DOI: 10.1074/jbc.m110.191783] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phospholipase C (PLC) enzymes are an important family of regulatory proteins involved in numerous cellular functions, primarily through hydrolysis of the polar head group from inositol-containing membrane phospholipids. U73122 (1-(6-((17β-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione), one of only a few small molecules reported to inhibit the activity of these enzymes, has been broadly applied as a pharmacological tool to implicate PLCs in diverse experimental phenotypes. The purpose of this study was to develop a better understanding of molecular interactions between U73122 and PLCs. Hence, the effects of U73122 on human PLCβ3 (hPLCβ3) were evaluated in a cell-free micellar system. Surprisingly, U73122 increased the activity of hPLCβ3 in a concentration- and time-dependent manner; up to an 8-fold increase in enzyme activity was observed with an EC50=13.6±5 μm. Activation of hPLCβ3 by U73122 required covalent modification of cysteines as evidenced by the observation that enzyme activation was attenuated by thiol-containing nucleophiles, l-cysteine and glutathione. Mass spectrometric analysis confirmed covalent reaction with U73122 at eight cysteines, although maximum activation was achieved without complete alkylation; the modified residues were identified by LC/MS/MS peptide sequencing. Interestingly, U73122 (10 μm) also activated hPLCγ1 (>10-fold) and hPLCβ2 (∼2-fold); PLCδ1 was neither activated nor inhibited. Therefore, in contrast to its reported inhibitory potential, U73122 failed to inhibit several purified PLCs. Most of these PLCs were directly activated by U73122, and a simple mechanism for the activation is proposed. These results strongly suggest a need to re-evaluate the use of U73122 as a general inhibitor of PLC isozymes.
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Affiliation(s)
- Ryan R Klein
- Division of Molecular Pharmaceutics, UNC Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, NC 27599-7360, USA
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12
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Thévenod F. Catch me if you can! Novel aspects of cadmium transport in mammalian cells. Biometals 2010; 23:857-75. [DOI: 10.1007/s10534-010-9309-1] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Accepted: 02/16/2010] [Indexed: 12/13/2022]
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13
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Hu XT, Zhang FB, Fan YC, Shu XS, Wong AHY, Zhou W, Shi QL, Tang HM, Fu L, Guan XY, Rha SY, Tao Q, He C. Phospholipase C delta 1 is a novel 3p22.3 tumor suppressor involved in cytoskeleton organization, with its epigenetic silencing correlated with high-stage gastric cancer. Oncogene 2009; 28:2466-75. [PMID: 19448674 DOI: 10.1038/onc.2009.92] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Located at the important tumor suppressor locus, 3p22, PLCD1 encodes an enzyme that mediates regulatory signaling of energy metabolism, calcium homeostasis and intracellular movements. We identified PLCD1 as a downregulated gene in aerodigestive carcinomas through expression profiling and epigenetic characterization. We found that PLCD1 was expressed in all normal adult tissues but low or silenced in 84% (16/19) gastric cancer cell lines, well correlated with its CpG island (CGI) methylation status. Methylation was further detected in 62% (61/98) gastric primary tumors, but none of normal gastric mucosa tissues. PLCD1 methylation was significantly correlated with tumor high stage. Detailed methylation analysis of 37 CpG sites at the PLCD1 CGI by bisulfite genomic sequencing confirmed its methylation. PLCD1 silencing could be reversed by pharmacological demethylation with 5-aza-2'-deoxycytidine, indicating a direct epigenetic silencing. Ectopic expression of PLCD1 in silenced gastric tumor cells dramatically inhibited their clonogenicity and migration, possibly through downregulating MMP7 expression and hampering the reorganization of cytoskeleton through cofilin inactivation by phosphorylation. Thus, epigenetic inactivation of PLCD1 is common and tumor-specific in gastric cancer, and PLCD1 acts as a functional tumor suppressor involved in gastric carcinogenesis.
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Affiliation(s)
- X-T Hu
- Biomedical Research Center, Sir Run Run Shaw Hospital, Zhejiang University and Key Laboratory of Biotherapy of Zhejiang Province, Hangzhou, China
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14
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Thieman JR, Mishra SK, Ling K, Doray B, Anderson RA, Traub LM. Clathrin regulates the association of PIPKIgamma661 with the AP-2 adaptor beta2 appendage. J Biol Chem 2009; 284:13924-13939. [PMID: 19287005 DOI: 10.1074/jbc.m901017200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The AP-2 clathrin adaptor differs fundamentally from the related AP-1, AP-3, and AP-4 sorting complexes because membrane deposition does not depend directly on an Arf family GTPase. Instead phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) appears to act as the principal compartmental cue for AP-2 placement at the plasma membrane as well as for the docking of numerous other important clathrin coat components at the nascent bud site. This PtdIns(4,5)P(2) dependence makes type I phosphatidylinositol 4-phosphate 5-kinases (PIPKIs) lynchpin enzymes in the assembly of clathrin-coated structures at the cell surface. PIPKIgamma is the chief 5-kinase at nerve terminals, and here we show that the 26-amino acid, alternatively spliced C terminus of PIPKIgamma661 is an intrinsically unstructured polypeptide that binds directly to the sandwich subdomain of the AP-2 beta2 subunit appendage. An aromatic side chain-based, extended interaction motif that also includes the two bulky C-terminal residues of the short PIPKIgamma635 variant is necessary for beta2 appendage engagement. The clathrin heavy chain accesses the same contact surface on the AP-2 beta2 appendage, but because of additional clathrin binding sites located within the unstructured hinge segment of the beta2 subunit, clathrin binds the beta2 chain with a higher apparent affinity than PIPKIgamma661. A clathrin-regulated interaction with AP-2 could allow PIPKIgamma661 to be strategically positioned for regional PtdIns(4,5)P(2) generation during clathrin-coated vesicle assembly at the synapse.
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Affiliation(s)
- James R Thieman
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Sanjay K Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Kun Ling
- Department of Biochemistry and Molecular Biology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905
| | - Balraj Doray
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Richard A Anderson
- Department of Pharmacology, University of Wisconsin School of Medicine, Madison, Wisconsin 53706
| | - Linton M Traub
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261.
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15
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Kolman P, Pica A, Carvou N, Boyde A, Cockcroft S, Loesch A, Pizzey A, Simeoni M, Capasso G, Unwin RJ. Insulin uptake across the luminal membrane of the rat proximal tubule in vivo and in vitro. Am J Physiol Renal Physiol 2009; 296:F1227-37. [PMID: 19261743 PMCID: PMC2681358 DOI: 10.1152/ajprenal.90351.2008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We visualized insulin uptake in vivo across the apical membrane of the rat proximal tubule (PT) by confocal microscopy; we compared it with in vitro findings in a rat PT cell line (WKPT) using fluorescence microscopy and flow cytometry. Surface tubules were observed in vivo with a 633-nm single laser-illuminated real-time video-rate confocal scanning microscope in upright configuration for optical sectioning below the renal capsule. Fields were selected containing proximal and distal tubules; Cy5-labeled insulin was injected twice (the second time after ∼140 min) into the right jugular vein, and the fluorescence signal (at 650–670 nm) was recorded. Fluorescence was detected almost immediately at the brush-border membrane (BBM) of PT cells only, moving inside cells within 30–40 min. As a measure of insulin uptake, the ratio of the fluorescence signal after the second injection to the first doubled (ratio: 2.11 ± 0.26, mean ± SE, n = 10), indicating a “priming,” or stimulating, effect of insulin on its uptake mechanism at the BBM. This effect did not occur after pretreatment with intravenous lysine (ratio: 1.03 ± 0.07, n = 6; P < 0.01). Cy2- or Cy3-labeled insulin uptake in a PT cell line in vitro was monitored by 488-nm excitation fluorescence microscopy using an inverted microscope. Insulin localized toward the apical membrane of these cells. Semiquantitative analysis of insulin uptake by flow cytometry also demonstrated a priming effect (upregulation) on insulin internalization in the presence of increasing amounts of insulin, as was observed in vivo; moreover, this effect was not seen with, or affected by, the similarly endocytosed ligand β2-glycoprotein.
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Affiliation(s)
- Pavel Kolman
- Institute of Physical Engineering, Brno University of Technology, Brno, Czech Republic
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16
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Yaradanakul A, Feng S, Shen C, Lariccia V, Lin MJ, Yang J, Dong P, Yin HL, Albanesi JP, Hilgemann DW. Dual control of cardiac Na+ Ca2+ exchange by PIP(2): electrophysiological analysis of direct and indirect mechanisms. J Physiol 2007; 582:991-1010. [PMID: 17540705 PMCID: PMC2075271 DOI: 10.1113/jphysiol.2007.132712] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Cardiac Na(+)-Ca(2+) exchange (NCX1) inactivates in excised membrane patches when cytoplasmic Ca(2+) is removed or cytoplasmic Na(+) is increased. Exogenous phosphatidylinositol-4,5-bis-phosphate (PIP(2)) can ablate both inactivation mechanisms, while it has no effect on inward exchange current in the absence of cytoplasmic Na(+). To probe PIP(2) effects in intact cells, we manipulated PIP(2) metabolism by several means. First, we used cell lines with M1 (muscarinic) receptors that couple to phospholipase C's (PLCs). As expected, outward NCX1 current (i.e. Ca(2+) influx) can be strongly inhibited when M1 agonists induce PIP(2) depletion. However, inward currents (i.e. Ca(2+) extrusion) without cytoplasmic Na(+) can be increased markedly in parallel with an increase of cell capacitance (i.e. membrane area). Similar effects are incurred by cytoplasmic perfusion of GTPgammaS or the actin cytoskeleton disruptor latrunculin, even in the presence of non-hydrolysable ATP (AMP-PNP). Thus, G-protein signalling may increase NCX1 currents by destabilizing membrane cytoskeleton-PIP(2) interactions. Second, to increase PIP(2) we directly perfused PIP(2) into cells. Outward NCX1 currents increase as expected. But over minutes currents decline substantially, and cell capacitance usually decreases in parallel. Third, using BHK cells with stable NCX1 expression, we increased PIP(2) by transient expression of a phosphatidylinositol-4-phosphate-5-kinase (hPIP5KIbeta) and a PI4-kinase (PI4KIIalpha). NCX1 current densities were decreased by > 80 and 40%, respectively. Fourth, we generated transgenic mice with 10-fold cardiac-specific overexpression of PI4KIIalpha. This wortmannin-insensitive PI4KIIalpha was chosen because basal cardiac phosphoinositides are nearly insensitive to wortmannin, and surface membrane PI4-kinase activity, defined functionally in excised patches, is not blocked by wortmannin. Both phosphatidylinositol-4-phosphate (PIP) and PIP(2) were increased significantly, while NCX1 current densities were decreased by 78% with no loss of NCX1 expression. Most mice developed cardiac hypertrophy, and immunohistochemical analysis suggests that NCX1 is redistributed away from the outer sarcolemma. Cholera toxin uptake was increased 3-fold, suggesting that clathrin-independent endocytosis is enhanced. We conclude that direct effects of PIP(2) to activate NCX1 can be strongly modulated by opposing mechanisms in intact cells that probably involve membrane cytoskeleton remodelling and membrane trafficking.
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Affiliation(s)
- Alp Yaradanakul
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9040, USA
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17
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Bednarek EM, Schaheen L, Gaubatz J, Jorgensen EM, Fares H. The plasma membrane calcium ATPase MCA-3 is required for clathrin-mediated endocytosis in scavenger cells of Caenorhabditis elegans. Traffic 2007; 8:543-53. [PMID: 17343680 DOI: 10.1111/j.1600-0854.2007.00547.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Plasma membrane Ca2+ ATPases (PMCAs) maintain proper intracellular Ca2+ levels by extruding Ca2+ from the cytosol. PMCA genes and splice forms are expressed in tissue-specific patterns in vertebrates, suggesting that these isoforms may regulate specific biological processes. However, knockout mutants die as embryos or undergo cell death; thus, it is unclear whether other cell processes utilize PMCAs or whether these pumps are largely committed to the control of toxic levels of calcium. Here, we analyze the role of the PMCA gene, mca-3, in Caenorhabditis elegans. We report that partial loss-of-function mutations disrupt clathrin-mediated endocytosis in a class of scavenger cells called coelomocytes. Moreover, components of early endocytic machinery are mislocalized in mca-3 mutants, including phosphatidylinositol-4,5-bisphosphate, clathrin and the Eps15 homology (EH) domain protein RME-1. This defect in endocytosis in the coelomocytes can be reversed by lowering calcium. Together, these data support a function for PMCAs in the regulation of endocytosis in the C. elegans coelomocytes. In addition, they suggest that endocytosis can be blocked by high calcium levels.
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Affiliation(s)
- Ewa M Bednarek
- Department of Biology and Howard Hughes Medical Institute, University of Utah, Salt Lake City, UT 84112, USA
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