1
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Li W, Sano R, Apatira M, DeAnda F, Gururaja T, Yang M, Lundgaard G, Pan C, Liu J, Zhai Y, Yoon WH, Wang L, Tse C, Souers AJ, Lee CH. Bruton's Tyrosine Kinase Inhibitors with Distinct Binding Modes Reveal Differential Functional Impact on B-Cell Receptor Signaling. Mol Cancer Ther 2024; 23:35-46. [PMID: 37735104 PMCID: PMC10762339 DOI: 10.1158/1535-7163.mct-22-0642] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Revised: 04/17/2023] [Accepted: 09/14/2023] [Indexed: 09/23/2023]
Abstract
Small molecule inhibitors of Bruton's tyrosine kinase (BTK) have been approved for the treatment of multiple B-cell malignancies and are being evaluated for autoimmune and inflammatory diseases. Various BTK inhibitors (BTKi) have distinct potencies, selectivity profiles, and binding modes within the ATP-binding site. On the basis of the latter feature, BTKis can be classified into those that occupy the back-pocket, H3 pocket, and the hinge region only. Hypothesizing that differing binding modes may have differential impact on the B-cell receptor (BCR) signaling pathway, we evaluated the activities of multiple BTKis in B-cell lymphoma models in vitro and in vivo. We demonstrated that, although all three types of BTKis potently inhibited BTK-Y223 autophosphorylation and phospholipase C gamma 2 (PLCγ2)-Y1217 transphosphorylation, hinge-only binders were defective in inhibiting BTK-mediated calcium mobilization upon BCR activation. In addition, PLCγ2 activation was effectively blocked by back-pocket and H3 pocket binders but not by hinge-only binders. Further investigation using TMD8 cells deficient in Rac family small GTPase 2 (RAC2) revealed that RAC2 functioned as a bypass mechanism, allowing for residual BCR signaling and PLCγ2 activation when BTK kinase activity was fully inhibited by the hinge-only binders. These data reveal a kinase activity-independent function of BTK, involving RAC2 in transducing BCR signaling events, and provide mechanistic rationale for the selection of clinical candidates for B-cell lymphoma indications.
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Affiliation(s)
- Wei Li
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Renata Sano
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Mutiah Apatira
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Felix DeAnda
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | | | - Muhua Yang
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Greta Lundgaard
- Drug Discovery Science and Technology, AbbVie Inc., Lake County, Illinois
| | - Chin Pan
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Jing Liu
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Yongjiao Zhai
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Woo Hyun Yoon
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Longcheng Wang
- Oncology Discovery, AbbVie Inc., South San Francisco, California
| | - Chris Tse
- Oncology Discovery, AbbVie Inc., Lake County, Illinois
| | | | - Chih-Hung Lee
- Oncology Discovery, AbbVie Inc., South San Francisco, California
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2
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Kanemaru K, Nakamura Y. Activation Mechanisms and Diverse Functions of Mammalian Phospholipase C. Biomolecules 2023; 13:915. [PMID: 37371495 DOI: 10.3390/biom13060915] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2023] [Revised: 05/28/2023] [Accepted: 05/29/2023] [Indexed: 06/29/2023] Open
Abstract
Phospholipase C (PLC) plays pivotal roles in regulating various cellular functions by metabolizing phosphatidylinositol 4,5-bisphosphate in the plasma membrane. This process generates two second messengers, inositol 1,4,5-trisphosphate and diacylglycerol, which respectively regulate the intracellular Ca2+ levels and protein kinase C activation. In mammals, six classes of typical PLC have been identified and classified based on their structure and activation mechanisms. They all share X and Y domains, which are responsible for enzymatic activity, as well as subtype-specific domains. Furthermore, in addition to typical PLC, atypical PLC with unique structures solely harboring an X domain has been recently discovered. Collectively, seven classes and 16 isozymes of mammalian PLC are known to date. Dysregulation of PLC activity has been implicated in several pathophysiological conditions, including cancer, cardiovascular diseases, and neurological disorders. Therefore, identification of new drug targets that can selectively modulate PLC activity is important. The present review focuses on the structures, activation mechanisms, and physiological functions of mammalian PLC.
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Affiliation(s)
- Kaori Kanemaru
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
| | - Yoshikazu Nakamura
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, Chiba 278-8510, Japan
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3
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Dandamudi A, Akbar H, Cancelas J, Zheng Y. Rho GTPase Signaling in Platelet Regulation and Implication for Antiplatelet Therapies. Int J Mol Sci 2023; 24:ijms24032519. [PMID: 36768837 PMCID: PMC9917354 DOI: 10.3390/ijms24032519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 01/16/2023] [Accepted: 01/21/2023] [Indexed: 01/31/2023] Open
Abstract
Platelets play a vital role in regulating hemostasis and thrombosis. Rho GTPases are well known as molecular switches that control various cellular functions via a balanced GTP-binding/GTP-hydrolysis cycle and signaling cascade through downstream effectors. In platelets, Rho GTPases function as critical regulators by mediating signal transduction that drives platelet activation and aggregation. Mostly by gene targeting and pharmacological inhibition approaches, Rho GTPase family members RhoA, Rac1, and Cdc42 have been shown to be indispensable in regulating the actin cytoskeleton dynamics in platelets, affecting platelet shape change, spreading, secretion, and aggregation, leading to thrombus formation. Additionally, studies of Rho GTPase function using platelets as a non-transformed model due to their anucleated nature have revealed valuable information on cell signaling principles. This review provides an updated summary of recent advances in Rho GTPase signaling in platelet regulation. We also highlight pharmacological approaches that effectively inhibited platelet activation to explore their possible development into future antiplatelet therapies.
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Affiliation(s)
- Akhila Dandamudi
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
- Department of Pathology, University of Cincinnati Graduate School, Cincinnati, OH 45267, USA
| | - Huzoor Akbar
- Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, USA
| | - Jose Cancelas
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
- Hoxworth Blood Center, College of Medicine, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Yi Zheng
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229, USA
- Department of Pathology, University of Cincinnati Graduate School, Cincinnati, OH 45267, USA
- Correspondence: ; Tel.: +1-513-636-0595
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4
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Arthur R, Wathen A, Lemm EA, Stevenson FK, Forconi F, Linley AJ, Steele AJ, Packham G, Valle-Argos B. BTK-independent regulation of calcium signalling downstream of the B-cell receptor in malignant B-cells. Cell Signal 2022; 96:110358. [PMID: 35597428 DOI: 10.1016/j.cellsig.2022.110358] [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: 04/19/2022] [Revised: 05/13/2022] [Accepted: 05/14/2022] [Indexed: 11/20/2022]
Abstract
BTK inhibitors (BTKi) have dramatically improved outcomes for patients with chronic lymphocytic leukaemia (CLL) and some forms of B-cell lymphoma. However, new strategies are needed to enhance responses. Here we have performed a detailed analysis of the effects of BTKi on B-cell receptor (BCR)-induced signalling using primary malignant cells from CLL patients and B-lymphoma cell lines. Although BTK is considered as a key activator of PLCγ2, BTKi (ibrutinib and acalabrutinib) failed to fully inhibit calcium responses in CLL samples with strong BCR signalling capacity. This BTKi-resistant calcium signalling was sufficient to engage downstream calcium-dependent transcription and suppress CLL cell apoptosis and was entirely independent of BTK and not just its kinase activity as similar results were obtained using a BTK-degrading PROTAC. BTK-independent calcium signalling was also observed in two B-lymphoma cell lines where BTKi had little effect on the initial phase of the calcium response but did accelerate the subsequent decline in intracellular calcium. In contrast to BTKi, calcium responses were completely blocked by inhibition of SYK in CLL and lymphoma cells. Engagement of BTK-independent calcium responses was associated with BTK-independent phosphorylation of PLCγ2 on Y753 and Y759 in both CLL and lymphoma cells. Moreover, in CLL samples, inhibition of RAC, which can mediate BTK-independent activation of PLCγ2, cooperated with ibrutinib to suppress calcium responses. BTK-independent calcium signalling may limit the effectiveness of BTKi to suppress BCR signalling responses and our results suggest inhibition of SYK or dual inhibition of BTK and RAC as alternative strategies to strengthen pathway blockade.
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Affiliation(s)
- Rachael Arthur
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Alexander Wathen
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Elizabeth A Lemm
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Freda K Stevenson
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Francesco Forconi
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Adam J Linley
- Department of Molecular Physiology and Cell Signalling, University of Liverpool, Institute of Systems, Molecular and Integrative Biology, 5(th) Floor Nuffield Building, Crown Street, Liverpool L69 3BX, United Kingdom
| | - Andrew J Steele
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
| | - Graham Packham
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom.
| | - Beatriz Valle-Argos
- Cancer Sciences, Faculty of Medicine, University of Southampton, Southampton SO16 6YD, United Kingdom
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5
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Siraliev-Perez E, Stariha JTB, Hoffmann RM, Temple BRS, Zhang Q, Hajicek N, Jenkins ML, Burke JE, Sondek J. Dynamics of allosteric regulation of the phospholipase C-γ isozymes upon recruitment to membranes. eLife 2022; 11:77809. [PMID: 35708309 PMCID: PMC9203054 DOI: 10.7554/elife.77809] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 05/22/2022] [Indexed: 11/13/2022] Open
Abstract
Numerous receptor tyrosine kinases and immune receptors activate phospholipase C-γ (PLC-γ) isozymes at membranes to control diverse cellular processes including phagocytosis, migration, proliferation, and differentiation. The molecular details of this process are not well understood. Using hydrogen-deuterium exchange mass spectrometry, we show that PLC-γ1 is relatively inert to lipid vesicles that contain its substrate, phosphatidylinositol 4,5-bisphosphate (PIP2), unless first bound to the kinase domain of the fibroblast growth factor receptor (FGFR1). Exchange occurs throughout PLC-γ1 and is exaggerated in PLC-γ1 containing an oncogenic substitution (D1165H) that allosterically activates the lipase. These data support a model whereby initial complex formation shifts the conformational equilibrium of PLC-γ1 to favor activation. This receptor-induced priming of PLC-γ1 also explains the capacity of a kinase-inactive fragment of FGFR1 to modestly enhance the lipase activity of PLC-γ1 operating on lipid vesicles but not a soluble analog of PIP2 and highlights potential cooperativity between receptor engagement and membrane proximity. Priming is expected to be greatly enhanced for receptors embedded in membranes and nearly universal for the myriad of receptors and co-receptors that bind the PLC-γ isozymes.
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Affiliation(s)
- Edhriz Siraliev-Perez
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Jordan T B Stariha
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Reece M Hoffmann
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - Brenda R S Temple
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Qisheng Zhang
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States.,Division of Chemical Biology and Medicinal Chemistry, School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, United States.,Lineberger Comprehensive Cancer Center, School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Nicole Hajicek
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Meredith L Jenkins
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada
| | - John E Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, Canada.,Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, Canada
| | - John Sondek
- Department of Biochemistry and Biophysics, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States.,Lineberger Comprehensive Cancer Center, School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, United States.,Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
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6
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Rac Inhibition Causes Impaired GPVI Signalling in Human Platelets through GPVI Shedding and Reduction in PLCγ2 Phosphorylation. Int J Mol Sci 2022; 23:ijms23073746. [PMID: 35409124 PMCID: PMC8998833 DOI: 10.3390/ijms23073746] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/22/2022] [Accepted: 03/26/2022] [Indexed: 12/19/2022] Open
Abstract
Rac1 is a small Rho GTPase that is activated in platelets upon stimulation with various ligands, including collagen and thrombin, which are ligands for the glycoprotein VI (GPVI) receptor and the protease-activated receptors, respectively. Rac1-deficient murine platelets have impaired lamellipodia formation, aggregation, and reduced PLCγ2 activation, but not phosphorylation. The objective of our study is to investigate the role of Rac1 in GPVI-dependent human platelet activation and downstream signalling. Therefore, we used human platelets stimulated using GPVI agonists (collagen and collagen-related peptide) in the presence of the Rac1-specific inhibitor EHT1864 and analysed platelet activation, aggregation, spreading, protein phosphorylation, and GPVI clustering and shedding. We observed that in human platelets, the inhibition of Rac1 by EHT1864 had no significant effect on GPVI clustering on collagen fibres but decreased the ability of platelets to spread or aggregate in response to GPVI agonists. Additionally, in contrast to what was observed in murine Rac1-deficient platelets, EHT1864 enhanced GPVI shedding in platelets and reduced the phosphorylation levels of PLCγ2 following GPVI activation. In conclusion, Rac1 activity is required for both human and murine platelet activation in response to GPVI-ligands, but Rac1's mode of action differs between the two species.
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7
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Joseph RE, Lowe J, Fulton DB, Engen JR, Wales TE, Andreotti AH. The Conformational State of the BTK Substrate PLCγ Contributes to Ibrutinib Resistance. J Mol Biol 2022; 434:167422. [PMID: 34954235 PMCID: PMC8924901 DOI: 10.1016/j.jmb.2021.167422] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/06/2021] [Accepted: 12/16/2021] [Indexed: 12/17/2022]
Abstract
Mutations in PLCγ, a substrate of the tyrosine kinase BTK, are often found in patients who develop resistance to the BTK inhibitor Ibrutinib. However, the mechanisms by which these PLCγ mutations cause Ibrutinib resistance are unclear. Under normal signaling conditions, BTK mediated phosphorylation of Y783 within the PLCγ cSH2-linker promotes the intramolecular association of this site with the adjacent cSH2 domain resulting in active PLCγ. Thus, the cSH2-linker region in the center of the regulatory gamma specific array (γSA) of PLCγ is a key feature controlling PLCγ activity. Even in the unphosphorylated state this linker exists in a conformational equilibrium between free and bound to the cSH2 domain. The position of this equilibrium is optimized within the properly regulated PLCγ enzyme but may be altered in the context of mutations. We therefore assessed the conformational status of four resistance associated mutations within the PLCγ γSA and find that they each alter the conformational equilibrium of the γSA leading to a shift toward active PLCγ. Interestingly, two distinct modes of mutation induced activation are revealed by this panel of Ibrutinib resistance mutations. These findings, along with the recently determined structure of fully autoinhibited PLCγ, provide new insight into the nature of the conformational change that occurs within the γSA regulatory region to affect PLCγ activation. Improving our mechanistic understanding of how B cell signaling escapes Ibrutinib treatment via mutations in PLCγ will aid in the development of strategies to counter drug resistance.
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Affiliation(s)
- Raji E Joseph
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - Jacques Lowe
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA
| | - D Bruce Fulton
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA. https://twitter.com/dbfulton
| | - John R Engen
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA. https://twitter.com/jrengen
| | - Thomas E Wales
- Department of Chemistry and Chemical Biology, Northeastern University, Boston, MA 02115, USA.
| | - Amy H Andreotti
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA 50011, USA.
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8
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Shaffer AL, Phelan JD, Wang JQ, Huang D, Wright GW, Kasbekar M, Choi J, Young RM, Webster DE, Yang Y, Zhao H, Yu X, Xu W, Roulland S, Ceribelli M, Zhang X, Wilson KM, Chen L, McKnight C, Klumpp-Thomas C, Thomas CJ, Häupl B, Oellerich T, Rae Z, Kelly MC, Ahn IE, Sun C, Gaglione EM, Wilson WH, Wiestner A, Staudt LM. Overcoming Acquired Epigenetic Resistance to BTK Inhibitors. Blood Cancer Discov 2021; 2:630-647. [PMID: 34778802 DOI: 10.1158/2643-3230.bcd-21-0063] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/17/2021] [Accepted: 08/31/2021] [Indexed: 12/14/2022] Open
Abstract
The use of Bruton tyrosine kinase (BTK) inhibitors to block B-cell receptor (BCR)-dependent NF-κB activation in lymphoid malignancies has been a major clinical advance, yet acquired therapeutic resistance is a recurring problem. We modeled the development of resistance to the BTK inhibitor ibrutinib in the activated B-cell (ABC) subtype of diffuse large B-cell lymphoma, which relies on chronic active BCR signaling for survival. The primary mode of resistance was epigenetic, driven in part by the transcription factor TCF4. The resultant phenotypic shift altered BCR signaling such that the GTPase RAC2 substituted for BTK in the activation of phospholipase Cγ2, thereby sustaining NF-κB activity. The interaction of RAC2 with phospholipase Cγ2 was also increased in chronic lymphocytic leukemia cells from patients with persistent or progressive disease on BTK inhibitor treatment. We identified clinically available drugs that can treat epigenetic ibrutinib resistance, suggesting combination therapeutic strategies. Significance In diffuse large B-cell lymphoma, we show that primary resistance to BTK inhibitors is due to epigenetic rather than genetic changes that circumvent the BTK blockade. We also observed this resistance mechanism in chronic lymphocytic leukemia, suggesting that epigenetic alterations may contribute more to BTK inhibitor resistance than currently thought.See related commentary by Pasqualucci, p. 555. This article is highlighted in the In This Issue feature, p. 549.
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Affiliation(s)
- Arthur L Shaffer
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - James D Phelan
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - James Q Wang
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - DaWei Huang
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - George W Wright
- Biometric Research Program, Division of Cancer Diagnosis and Treatment, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Monica Kasbekar
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Jaewoo Choi
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Ryan M Young
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Daniel E Webster
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Yandan Yang
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Hong Zhao
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Xin Yu
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Weihong Xu
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Sandrine Roulland
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Michele Ceribelli
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.,Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Xiaohu Zhang
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Kelli M Wilson
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Lu Chen
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Crystal McKnight
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Carleen Klumpp-Thomas
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Craig J Thomas
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland.,Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland
| | - Björn Häupl
- Department of Medicine II, Hematology/Oncology, Goethe University, Frankfurt; German Cancer Consortium/German Cancer Research Center, Heidelberg; and Department of Molecular Diagnostics and Translational Proteomics, Frankfurt Cancer Institute, Frankfurt, Germany
| | - Thomas Oellerich
- Department of Medicine II, Hematology/Oncology, Goethe University, Frankfurt; German Cancer Consortium/German Cancer Research Center, Heidelberg; and Department of Molecular Diagnostics and Translational Proteomics, Frankfurt Cancer Institute, Frankfurt, Germany
| | - Zachary Rae
- Cancer Research Technology Program, Single-Cell Analysis Facility, Frederick National Laboratory for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Michael C Kelly
- Cancer Research Technology Program, Single-Cell Analysis Facility, Frederick National Laboratory for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Inhye E Ahn
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Clare Sun
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Erika M Gaglione
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Wyndham H Wilson
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Adrian Wiestner
- Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland
| | - Louis M Staudt
- Lymphoid Malignancies Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
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9
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Löber J, Hitzing C, Münchhalfen M, Engels N. Vav family proteins constitute disparate branching points for distinct BCR signaling pathways. Eur J Immunol 2020; 50:1912-1928. [PMID: 32671844 DOI: 10.1002/eji.202048621] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 05/18/2020] [Accepted: 07/10/2020] [Indexed: 01/16/2023]
Abstract
Antigen recognition by B-cell antigen receptors (BCRs) activates distinct intracellular signaling pathways that control the differentiation fate of activated B lymphocytes. BCR-proximal signaling enzymes comprise protein tyrosine kinases, phosphatases, and plasma membrane lipid-modifying enzymes, whose function is furthermore coordinated by catalytically inert adaptor proteins. Here, we show that an additional class of enzymatic activity provided by guanine-nucleotide exchange factors (GEFs) of the Vav family controls BCR-proximal Ca2+ mobilization, cytoskeletal actin reorganization, and activation of the PI3 kinase/Akt pathway. Whereas Vav1 and Vav3 supported all of those signaling processes to different extents in a human B-cell model system, Vav2 facilitated Actin remodeling, and activation of Akt but did not promote Ca2+ signaling. On BCR activation, Vav1 was directly recruited to the phosphorylated BCR and to the central adaptor protein SLP65 via its Src homology 2 domain. Pharmacological inhibition or genetic inactivation of the substrates of Vav GEFs, small G proteins of the Rho/Rac family, impaired BCR-induced Ca2+ mobilization, probably because phospholipase Cγ2 requires activated Rac proteins for optimal activity. Our findings show that Vav family members are key relays of the BCR signalosome that differentially control distinct signaling pathways both in a catalysis-dependent and -independent manner.
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Affiliation(s)
- Jens Löber
- Institute of Cellular & Molecular Immunology, University Medical Center Göttingen, Göttingen, Germany
| | - Christoffer Hitzing
- Institute of Cellular & Molecular Immunology, University Medical Center Göttingen, Göttingen, Germany
| | - Matthias Münchhalfen
- Institute of Cellular & Molecular Immunology, University Medical Center Göttingen, Göttingen, Germany
| | - Niklas Engels
- Institute of Cellular & Molecular Immunology, University Medical Center Göttingen, Göttingen, Germany
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10
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Abstract
Cell migration is an essential process, both in unicellular organisms such as amoeba and as individual or collective motility in highly developed multicellular organisms like mammals. It is controlled by a variety of activities combining protrusive and contractile forces, normally generated by actin filaments. Here, we summarize actin filament assembly and turnover processes, and how respective biochemical activities translate into different protrusion types engaged in migration. These actin-based plasma membrane protrusions include actin-related protein 2/3 complex-dependent structures such as lamellipodia and membrane ruffles, filopodia as well as plasma membrane blebs. We also address observed antagonisms between these protrusion types, and propose a model - also inspired by previous literature - in which a complex balance between specific Rho GTPase signaling pathways dictates the protrusion mechanism employed by cells. Furthermore, we revisit published work regarding the fascinating antagonism between Rac and Rho GTPases, and how this intricate signaling network can define cell behavior and modes of migration. Finally, we discuss how the assembly of actin filament networks can feed back onto their regulators, as exemplified for the lamellipodial factor WAVE regulatory complex, tightly controlling accumulation of this complex at specific subcellular locations as well as its turnover.
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11
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Wist M, Meier L, Gutman O, Haas J, Endres S, Zhou Y, Rösler R, Wiese S, Stilgenbauer S, Hobeika E, Henis YI, Gierschik P, Walliser C. Noncatalytic Bruton's tyrosine kinase activates PLCγ 2 variants mediating ibrutinib resistance in human chronic lymphocytic leukemia cells. J Biol Chem 2020; 295:5717-5736. [PMID: 32184360 DOI: 10.1074/jbc.ra119.011946] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/26/2020] [Indexed: 12/25/2022] Open
Abstract
Treatment of patients with chronic lymphocytic leukemia (CLL) with inhibitors of Bruton's tyrosine kinase (BTK), such as ibrutinib, is limited by primary or secondary resistance to this drug. Examinations of CLL patients with late relapses while on ibrutinib, which inhibits BTK's catalytic activity, revealed several mutations in BTK, most frequently resulting in the C481S substitution, and disclosed many mutations in PLCG2, encoding phospholipase C-γ2 (PLCγ2). The PLCγ2 variants typically do not exhibit constitutive activity in cell-free systems, leading to the suggestion that in intact cells they are hypersensitive to Rac family small GTPases or to the upstream kinases spleen-associated tyrosine kinase (SYK) and Lck/Yes-related novel tyrosine kinase (LYN). The sensitivity of the PLCγ2 variants to BTK itself has remained unknown. Here, using genetically-modified DT40 B lymphocytes, along with various biochemical assays, including analysis of PLCγ2-mediated inositol phosphate formation, inositol phospholipid assessments, fluorescence recovery after photobleaching (FRAP) static laser microscopy, and determination of intracellular calcium ([Ca2+] i ), we show that various CLL-specific PLCγ2 variants such as PLCγ2S707Y are hyper-responsive to activated BTK, even in the absence of BTK's catalytic activity and independently of enhanced PLCγ2 phospholipid substrate supply. At high levels of B-cell receptor (BCR) activation, which may occur in individual CLL patients, catalytically-inactive BTK restored the ability of the BCR to mediate increases in [Ca2+] i Because catalytically-inactive BTK is insensitive to active-site BTK inhibitors, the mechanism involving the noncatalytic BTK uncovered here may contribute to preexisting reduced sensitivity or even primary resistance of CLL to these drugs.
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Affiliation(s)
- Martin Wist
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Laura Meier
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Orit Gutman
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Jennifer Haas
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sascha Endres
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yuan Zhou
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Reinhild Rösler
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Sebastian Wiese
- Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University Medical Center, 89081 Ulm, Germany
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, 89081 Ulm, Germany
| | - Elias Hobeika
- Institute of Immunology, Ulm University Medical Center, 89081 Ulm, Germany
| | - Yoav I Henis
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Peter Gierschik
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
| | - Claudia Walliser
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, 89081 Ulm, Germany.
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12
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Hajicek N, Keith NC, Siraliev-Perez E, Temple BRS, Huang W, Zhang Q, Harden TK, Sondek J. Structural basis for the activation of PLC-γ isozymes by phosphorylation and cancer-associated mutations. eLife 2019; 8:e51700. [PMID: 31889510 PMCID: PMC7004563 DOI: 10.7554/elife.51700] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 12/30/2019] [Indexed: 12/14/2022] Open
Abstract
Direct activation of the human phospholipase C-γ isozymes (PLC-γ1, -γ2) by tyrosine phosphorylation is fundamental to the control of diverse biological processes, including chemotaxis, platelet aggregation, and adaptive immunity. In turn, aberrant activation of PLC-γ1 and PLC-γ2 is implicated in inflammation, autoimmunity, and cancer. Although structures of isolated domains from PLC-γ isozymes are available, these structures are insufficient to define how release of basal autoinhibition is coupled to phosphorylation-dependent enzyme activation. Here, we describe the first high-resolution structure of a full-length PLC-γ isozyme and use it to underpin a detailed model of their membrane-dependent regulation. Notably, an interlinked set of regulatory domains integrates basal autoinhibition, tyrosine kinase engagement, and additional scaffolding functions with the phosphorylation-dependent, allosteric control of phospholipase activation. The model also explains why mutant forms of the PLC-γ isozymes found in several cancers have a wide spectrum of activities, and highlights how these activities are tuned during disease.
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Affiliation(s)
- Nicole Hajicek
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Nicholas C Keith
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Edhriz Siraliev-Perez
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Brenda RS Temple
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
- R L Juliano Structural Bioinformatics Core FacilityThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Weigang Huang
- Division of Chemical Biology and Medicinal ChemistryThe University of North Carolina at Chapel HillChapel HillUnited States
| | - Qisheng Zhang
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
- Division of Chemical Biology and Medicinal ChemistryThe University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer CenterThe University of North Carolina at Chapel HillChapel HillUnited States
| | - T Kendall Harden
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
| | - John Sondek
- Department of PharmacologyThe University of North Carolina at Chapel HillChapel HillUnited States
- Department of Biochemistry and BiophysicsThe University of North Carolina at Chapel HillChapel HillUnited States
- Lineberger Comprehensive Cancer CenterThe University of North Carolina at Chapel HillChapel HillUnited States
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13
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Kuramasu A, Wakabayashi M, Inui M, Yanai K. Distinct Roles of Small GTPases Rac1 and Rac2 in Histamine H 4 Receptor-Mediated Chemotaxis of Mast Cells. J Pharmacol Exp Ther 2018; 367:9-19. [PMID: 30021868 DOI: 10.1124/jpet.118.249706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 07/12/2018] [Indexed: 11/22/2022] Open
Abstract
Histamine induces chemotaxis of mast cells through the H4 receptor. However, little is known about the precise intracellular signaling pathway that mediates this process. In this study, we identified small GTPases Rac1 and Rac2 as intracellular binding partners of the H4 receptor and characterized their roles in H4 receptor signaling. We showed that histamine induced Rac GTPase activation via the H4 receptor. A Rac inhibitor NSC23766 attenuated chemotaxis of mast cells toward histamine, as well as histamine-induced calcium mobilization and extracellular signal-regulated kinase (ERK) activation. Histamine-induced migration of mast cells was also sensitive to PD98059, an inhibitor of the mitogen-activated protein kinase kinase, indicating that the Rac-ERK pathway was involved in chemotaxis through the H4 receptor. Inhibition of phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K) by LY294002 suppressed the histamine-induced chemotaxis and activation of Rac GTPases, suggesting that PI3K regulates chemotaxis upstream of Rac activation. Specific knockdown of Rac1 and Rac2 by short-hairpin RNA revealed that both Rac GTPases are necessary for histamine-induced migration. Downregulation of Rac1 and Rac2 led to attenuated response in calcium mobilization and ERK activation, respectively. These observations suggested that Rac1 and Rac2 have distinct and essential roles in intracellular signaling downstream of H4 receptor-PI3K in histamine-induced chemotaxis of mast cells.
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Affiliation(s)
- Atsuo Kuramasu
- Department of Pharmacology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan (A.K., M.I.); and Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan (M.W., K.Y.)
| | - Mie Wakabayashi
- Department of Pharmacology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan (A.K., M.I.); and Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan (M.W., K.Y.)
| | - Makoto Inui
- Department of Pharmacology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan (A.K., M.I.); and Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan (M.W., K.Y.)
| | - Kazuhiko Yanai
- Department of Pharmacology, Yamaguchi University Graduate School of Medicine, Ube, Yamaguchi, Japan (A.K., M.I.); and Department of Pharmacology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan (M.W., K.Y.)
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14
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Walliser C, Wist M, Hermkes E, Zhou Y, Schade A, Haas J, Deinzer J, Désiré L, Li SSC, Stilgenbauer S, Milner JD, Gierschik P. Functional characterization of phospholipase C-γ 2 mutant protein causing both somatic ibrutinib resistance and a germline monogenic autoinflammatory disorder. Oncotarget 2018; 9:34357-34378. [PMID: 30344948 PMCID: PMC6188132 DOI: 10.18632/oncotarget.26173] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 09/08/2018] [Indexed: 12/17/2022] Open
Abstract
Depending on its occurrence in the germline or somatic context, a single point mutation, S707Y, of phospholipase C-γ2 (PLCγ2) gives rise to two distinct human disease states: acquired resistance of chronic lymphocytic leukemia cells (CLL) to inhibitors of Brutons´s tyrosine kinase (Btk) and dominantly inherited autoinflammation and PLCγ2-associated antibody deficiency and immune dysregulation, APLAID, respectively. The functional relationships of the PLCγ2S707Y mutation to other PLCG2 mutations causing (i) Btk inhibitor resistance of CLL cells and (ii) the APLAID-related human disease PLCγ2-associated antibody deficiency and immune dysregulation, PLAID, revealing different clinical characteristics including cold-induced urticaria, respectively, are currently incompletely understood. Here, we show that PLCγ2S707 point mutants displayed much higher activities at 37° C than the CLL Btk inhibitor resistance mutants R665W and L845F and the two PLAID mutants, PLCγ2Δ19 and PLCγ2Δ20-22. Combinations of CLL Btk inhibitor resistance mutations synergized to enhance PLCγ2 activity, with distinct functional consequences for different temporal orders of the individual mutations. Enhanced activity of PLCγ2S707Y was not observed in a cell-free system, suggesting that PLCγ2 activation in intact cells is dependent on regulatory rather than mutant-enzyme-inherent influences. Unlike the two PLAID mutants, PLCγ2S707Y was insensitive to activation by cooling and retained marked hyperresponsiveness to activated Rac upon cooling. In contrast to the PLAID mutants, which are insensitive to activation by endogenously expressed EGF receptors, the S707Y mutation markedly enhanced the stimulatory effect of EGF, explaining some of the pathophysiological discrepancies between immune cells of PLAID and APLAID patients in response to receptor-tyrosine-kinase activation.
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Affiliation(s)
- Claudia Walliser
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Martin Wist
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Elisabeth Hermkes
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Yuan Zhou
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Anja Schade
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Jennifer Haas
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | - Julia Deinzer
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
| | | | - Shawn S C Li
- Department of Biochemistry and The Siebens-Drake Medical Research Institute, Schulich School of Medicine, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, Ulm 89070, Germany
| | - Joshua D Milner
- Laboratory of Allergic Diseases, NIAID, NIH, Bethesda, MD 20892, USA
| | - Peter Gierschik
- Institute of Pharmacology and Toxicology, Ulm University Medical Center, Ulm 89070, Germany
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15
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The Role of Phospholipase C Signaling in Macrophage-Mediated Inflammatory Response. J Immunol Res 2018; 2018:5201759. [PMID: 30057916 PMCID: PMC6051040 DOI: 10.1155/2018/5201759] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 10/06/2017] [Accepted: 11/05/2017] [Indexed: 12/15/2022] Open
Abstract
Macrophages are crucial members of the mononuclear phagocyte system essential to protect the host from invading pathogens and are central to the inflammatory response with their ability to acquire specialized phenotypes of inflammatory (M1) and anti-inflammatory (M2) and to produce a pool of inflammatory mediators. Equipped with a broad range of receptors, such as Toll-like receptor 4 (TLR4), CD14, and Fc gamma receptors (FcγRs), macrophages can efficiently recognize and phagocytize invading pathogens and secrete cytokines by triggering various secondary signaling pathways. Phospholipase C (PLC) is a family of enzymes that hydrolyze phospholipids, the most significant of which is phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2]. Cleavage at the internal phosphate ester generates two second messengers, inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG), both of which mediate in diverse cellular functions including the inflammatory response. Recent studies have shown that some PLC isoforms are involved in multiple stages in TLR4-, CD14-, and FcγRs-mediated activation of nuclear factor kappa B (NF-κB), mitogen-activated protein kinase (MAPK), and interferon regulatory factors (IRFs), all of which are associated with the regulation of the inflammatory response. Therefore, secondary signaling by PLC is implicated in the pathogenesis of numerous inflammatory diseases. This review provides an overview of our current knowledge on how PLC signaling regulates the macrophage-mediated inflammatory response.
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16
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Walliser C, Hermkes E, Schade A, Wiese S, Deinzer J, Zapatka M, Désiré L, Mertens D, Stilgenbauer S, Gierschik P. The Phospholipase Cγ2 Mutants R665W and L845F Identified in Ibrutinib-resistant Chronic Lymphocytic Leukemia Patients Are Hypersensitive to the Rho GTPase Rac2 Protein. J Biol Chem 2016; 291:22136-22148. [PMID: 27542411 PMCID: PMC5063995 DOI: 10.1074/jbc.m116.746842] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Revised: 08/18/2016] [Indexed: 12/29/2022] Open
Abstract
Mutations in the gene encoding phospholipase C-γ2 (PLCγ2) have been shown to be associated with resistance to targeted therapy of chronic lymphocytic leukemia (CLL) with the Bruton's tyrosine kinase inhibitor ibrutinib. The fact that two of these mutations, R665W and L845F, imparted upon PLCγ2 an ∼2-3-fold ibrutinib-insensitive increase in the concentration of cytosolic Ca2+ following ligation of the B cell antigen receptor (BCR) led to the assumption that the two mutants exhibit constitutively enhanced intrinsic activity. Here, we show that the two PLCγ2 mutants are strikingly hypersensitive to activation by Rac2 such that even wild-type Rac2 suffices to activate the mutant enzymes upon its introduction into intact cells. Enhanced "basal" activity of PLCγ2 in intact cells is shown using the pharmacologic Rac inhibitor EHT 1864 and the PLCγ2F897Q mutation mediating Rac resistance to be caused by Rac-stimulated rather than by constitutively enhanced PLCγ2 activity. We suggest that R665W and L845F be referred to as allomorphic rather than hypermorphic mutations of PLCG2 Rerouting of the transmembrane signals emanating from BCR and converging on PLCγ2 through Rac in ibrutinib-resistant CLL cells may provide novel drug treatment strategies to overcome ibrutinib resistance mediated by PLCG2 mutations or to prevent its development in ibrutinib-treated CLL patients.
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MESH Headings
- Adenine/analogs & derivatives
- Amino Acid Substitution
- Animals
- COS Cells
- Chlorocebus aethiops
- Drug Resistance, Neoplasm/drug effects
- Drug Resistance, Neoplasm/genetics
- Humans
- Leukemia, Lymphocytic, Chronic, B-Cell/drug therapy
- Leukemia, Lymphocytic, Chronic, B-Cell/enzymology
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Mutation, Missense
- Neoplasm Proteins/antagonists & inhibitors
- Neoplasm Proteins/genetics
- Neoplasm Proteins/metabolism
- Phospholipase C gamma/antagonists & inhibitors
- Phospholipase C gamma/genetics
- Phospholipase C gamma/metabolism
- Piperidines
- Pyrazoles/pharmacology
- Pyrimidines/pharmacology
- Pyrones/pharmacology
- Quinolines/pharmacology
- Receptors, Antigen, B-Cell/genetics
- Receptors, Antigen, B-Cell/metabolism
- Signal Transduction/drug effects
- Signal Transduction/genetics
- rac GTP-Binding Proteins/genetics
- rac GTP-Binding Proteins/metabolism
- RAC2 GTP-Binding Protein
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Affiliation(s)
| | | | - Anja Schade
- From the Institute of Pharmacology and Toxicology and
| | - Sebastian Wiese
- the Core Unit Mass Spectrometry and Proteomics, Medical Faculty, Ulm University, 89081 Ulm, Germany
| | - Julia Deinzer
- From the Institute of Pharmacology and Toxicology and
| | - Marc Zapatka
- the Division of Molecular Genetics, German Cancer Research Center (DKFZ), 69121 Heidelberg, Germany, and
| | - Laurent Désiré
- the Diaxonhit, 63-65 Boulevard Masséna, 75013 Paris, France
| | - Daniel Mertens
- Department of Internal Medicine III, Ulm University Medical Center, 89070 Ulm, Germany
| | - Stephan Stilgenbauer
- Department of Internal Medicine III, Ulm University Medical Center, 89070 Ulm, Germany
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17
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Münzer P, Walker-Allgaier B, Geue S, Geuss E, Hron G, Rath D, Eißler D, Winter S, Schaeffeler E, Meinert M, Schaller M, Greinacher A, Schwab M, Geisler T, Kleinschnitz C, Lang F, Gawaz M, Borst O. PDK1 Determines Collagen-Dependent Platelet Ca
2+
Signaling and Is Critical to Development of Ischemic Stroke In Vivo. Arterioscler Thromb Vasc Biol 2016; 36:1507-16. [DOI: 10.1161/atvbaha.115.307105] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Accepted: 05/16/2016] [Indexed: 01/12/2023]
Abstract
Objective—
Activation of platelets by subendothelial collagen results in an increase of cytosolic Ca
2+
concentration ([Ca
2+
]
i
) and is followed by platelet activation and thrombus formation that may lead to vascular occlusion. The present study determined the role of phosphoinositide-dependent protein kinase 1 (PDK1) in collagen-dependent platelet Ca
2+
signaling and ischemic stroke in vivo.
Approach and Results—
Platelet activation with collagen receptor glycoprotein VI agonists collagen-related peptide or convulxin resulted in a significant increase in PDK1 activity independent of second-wave signaling. PDK1 deficiency was associated with reduced platelet phospholipase Cγ2–dependent inositol-1,4,5-trisphosphate production and intracellular [Ca
2+
]
i
in response to stimulation with collagen-related peptide or convulxin. The defective increase of [Ca
2+
]
i
resulted in a substantial defect in activation-dependent platelet secretion and aggregation on collagen-related peptide stimulation. Furthermore, Rac1 activation and spreading, adhesion to collagen, and thrombus formation under high arterial shear rates were significantly diminished in PDK1-deficient platelets. Mice with PDK1-deficient platelets were protected against arterial thrombotic occlusion after FeCl
3
-induced mesenteric arterioles injury and ischemic stroke in vivo. These mice had significantly reduced brain infarct volumes, with a significantly increased survival of 7 days after transient middle cerebral artery occlusion without increase of intracerebral hemorrhage. Tail bleeding time was prolonged in
pdk1
−/−
mice, reflecting an important role of PDK1 in primary hemostasis.
Conclusions—
PDK1 is required for Ca
2+
-dependent platelet activation on stimulation of collagen receptor glycoprotein VI, arterial thrombotic occlusion, and ischemic stroke in vivo.
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Affiliation(s)
- Patrick Münzer
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Britta Walker-Allgaier
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Sascha Geue
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Eva Geuss
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Gregor Hron
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Dominik Rath
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Daniela Eißler
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Stefan Winter
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Elke Schaeffeler
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Monika Meinert
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Martin Schaller
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Andreas Greinacher
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Matthias Schwab
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Tobias Geisler
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Christoph Kleinschnitz
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Florian Lang
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Meinrad Gawaz
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
| | - Oliver Borst
- From the Department of Cardiology and Cardiovascular Medicine (P.M., B.W.-A., S.G., D.R., D.E., T.G., M.G., O.B.), Department of Physiology (B.W.-A., F.L.), Department of Evolutionary Biology of Invertebrates, Institute for Evolution and Ecology (M.M.), Department of Dermatology (M.S.), and Department of Clinical Pharmacology (M.S.), University of Tübingen, Tübingen, Germany; Department of Neurology, University of Würzburg, Würzburg, Germany (E.G., C.K.); Institute for Immunology and Transfusion
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18
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Cool-temperature-mediated activation of phospholipase C-γ2 in the human hereditary disease PLAID. Cell Signal 2016; 28:1237-1251. [PMID: 27196803 DOI: 10.1016/j.cellsig.2016.05.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Revised: 05/10/2016] [Accepted: 05/12/2016] [Indexed: 12/24/2022]
Abstract
Deletions in the gene encoding signal-transducing inositol phospholipid-specific phospholipase C-γ2 (PLCγ2) are associated with the novel human hereditary disease PLAID (PLCγ2-associated antibody deficiency and immune dysregulation). PLAID is characterized by a rather puzzling concurrence of augmented and diminished functions of the immune system, such as cold urticaria triggered by only minimal decreases in temperature, autoimmunity, and immunodeficiency. Understanding of the functional effects of the genomic alterations at the level of the affected enzyme, PLCγ2, is currently lacking. PLCγ2 is critically involved in coupling various cell surface receptors to regulation of important functions of immune cells such as mast cells, B cells, monocytes/macrophages, and neutrophils. PLCγ2 is unique by carrying three Src (SH) and one split pleckstrin homology domain (spPH) between the two catalytic subdomains (spPHn-SH2n-SH2c-SH3-spPHc). Prevailing evidence suggests that activation of PLCγ2 is primarily due to loss of SH-region-mediated autoinhibition and/or enhanced plasma membrane translocation. Here, we show that the two PLAID PLCγ2 mutants lacking portions of the SH region are strongly (>100-fold), rapidly, and reversibly activated by cooling by only a few degrees. We found that the mechanism(s) underlying PLCγ2 PLAID mutant activation by cool temperatures is distinct from a mere loss of SH-region-mediated autoinhibition and dependent on both the integrity and the pliability of the spPH domain. The results suggest a new mechanism of PLCγ activation with unique thermodynamic features and assign a novel regulatory role to its spPH domain. Involvement of this mechanism in other human disease states associated with cooling such as exertional asthma and certain acute coronary events appears an intriguing possibility.
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19
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The Novel Functions of the PLC/PKC/PKD Signaling Axis in G Protein-Coupled Receptor-Mediated Chemotaxis of Neutrophils. J Immunol Res 2015; 2015:817604. [PMID: 26605346 PMCID: PMC4641950 DOI: 10.1155/2015/817604] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 10/05/2015] [Indexed: 12/16/2022] Open
Abstract
Chemotaxis, a directional cell migration guided by extracellular chemoattractant gradients, plays an essential role in the recruitment of neutrophils to sites of inflammation. Chemotaxis is mediated by the G protein-coupled receptor (GPCR) signaling pathway. Extracellular stimuli trigger activation of the PLC/PKC/PKD signaling axis, which controls several signaling pathways. Here, we concentrate on the novel functions of PLC/PKC/PKD signaling in GPCR-mediated chemotaxis of neutrophils.
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20
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Regulatory role of guanine nucleotide exchange factor (GEF) Dock180 phosphorylation on Tyr/Ser in mediation of gastric mucosal Rac1 activation in response to Helicobacter pylori and ghrelin. Inflammopharmacology 2015; 23:111-8. [PMID: 25957600 DOI: 10.1007/s10787-015-0235-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 04/28/2015] [Indexed: 01/26/2023]
Abstract
A small GTPase, Rac1, is recognized as an important modulator of the inflammatory responses to bacterial lipopolysaccharide (LPS) by affecting the processes of phospholipase C activation. The activation of Rac1 involves the exchange of GDP for GTP and is catalyzed by the guanine nucleotide exchange factors (GEFs). Here, we report on the gastric mucosal GEF, Dock180, activation in response to H. pylori PS, and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to up-regulation in Dock180 phosphorylation on Tyr and Ser that is accompanied by a massive rise in Rac1-GTP level, while the effect of ghrelin, manifested by a drop in Dock180 phosphorylation on Ser, is associated with a decrease in Rac1-GTP formation. Furthermore, we demonstrate that phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is accompanied by Dock180 membrane translocation, while phosphorylation of the membrane-localized Dock180 on Ser represents the stimulatory contribution of protein kinase Cδ (PKCδ) to Dock180 activation. Moreover, we reveal that the interaction between Dock180 and PKCδ is dependent on Dock180 Tyr phosphorylation as well as the activity of PKCδ. Thus, our findings point to the involvement of PKCδ in the LPS-induced up-regulation of Dock180 activation, and suggest the modulatory mechanism of ghrelin influence on the gastric mucosal inflammatory responses to H. pylori.
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21
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Abstract
Rho GTPases are critical for platelet function. Although the roles of RhoA, Rac and Cdc42 are characterized, platelets express other Rho GTPases, whose activities are less well understood. This review summarizes our understanding of the roles of platelet Rho GTPases and focuses particularly on the functions of Rif and RhoG. In human platelets, Rif interacts with cytoskeleton regulators including formins mDia1 and mDia3, whereas RhoG binds SNARE-complex proteins and cytoskeletal regulators ELMO and DOCK1. Knockout mouse studies suggest that Rif plays no critical functions in platelets, likely due to functional overlap with other Rho GTPases. In contrast, RhoG is essential for normal granule secretion downstream of the collagen receptor GPVI. The central defect in RhoG-/- platelets is reduced dense granule secretion, which impedes integrin activation and aggregation and limits platelet recruitment to growing thrombi under shear, translating into reduced thrombus formation in vivo. Potential avenues for future work on Rho GTPases in platelets are also highlighted, including identification of the key regulator for platelet filopodia formation and investigation of the role of the many Rho GTPase regulators in platelet function in both health and disease.
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22
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Walliser C, Tron K, Clauss K, Gutman O, Kobitski AY, Retlich M, Schade A, Röcker C, Henis YI, Nienhaus GU, Gierschik P. Rac-mediated Stimulation of Phospholipase Cγ2 Amplifies B Cell Receptor-induced Calcium Signaling. J Biol Chem 2015; 290:17056-72. [PMID: 25903139 DOI: 10.1074/jbc.m115.645739] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 12/21/2022] Open
Abstract
The Rho GTPase Rac is crucially involved in controlling multiple B cell functions, including those regulated by the B cell receptor (BCR) through increased cytosolic Ca(2+). The underlying molecular mechanisms and their relevance to the functions of intact B cells have thus far remained unknown. We have previously shown that the activity of phospholipase Cγ2 (PLCγ2), a key constituent of the BCR signalosome, is stimulated by activated Rac through direct protein-protein interaction. Here, we use a Rac-resistant mutant of PLCγ2 to functionally reconstitute cultured PLCγ2-deficient DT40 B cells and to examine the effects of the Rac-PLCγ2 interaction on BCR-mediated changes of intracellular Ca(2+) and regulation of Ca(2+)-regulated and nuclear-factor-of-activated-T-cell-regulated gene transcription at the level of single, intact B cells. The results show that the functional Rac-PLCγ2 interaction causes marked increases in the following: (i) sensitivity of B cells to BCR ligation; (ii) BCR-mediated Ca(2+) release from intracellular stores; (iii) Ca(2+) entry from the extracellular compartment; and (iv) nuclear translocation of the Ca(2+)-regulated nuclear factor of activated T cells. Hence, Rac-mediated stimulation of PLCγ2 activity serves to amplify B cell receptor-induced Ca(2+) signaling.
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Affiliation(s)
- Claudia Walliser
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Kyrylo Tron
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Karen Clauss
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Orit Gutman
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - Andrei Yu Kobitski
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany
| | - Michael Retlich
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Anja Schade
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany
| | - Carlheinz Röcker
- the Institute of Biophysics, University of Ulm, 89069 Ulm, Germany
| | - Yoav I Henis
- the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel
| | - G Ulrich Nienhaus
- the Institute of Applied Physics and Center for Functional Nanostructures, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany, the Institute of Toxicology and Genetics, Karlsruhe Institute of Technology, 76344 Eggenstein-Leopoldshafen, Germany, and the Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Peter Gierschik
- From the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, 89070 Ulm, Germany,
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23
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Slomiany BL, Slomiany A. Mechanism of Rac1-induced amplification in gastric mucosal phospholipase Cγ2 activation in response to Helicobacter pylori: modulatory effect of ghrelin. Inflammopharmacology 2015; 23:101-9. [PMID: 25796615 DOI: 10.1007/s10787-015-0231-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Accepted: 03/04/2015] [Indexed: 12/27/2022]
Abstract
Membrane recruitment followed by targeted phosphorylation of specific Tyr and Ser residues and the interaction with Rac GTPases are the crucial parts of an elaborate mechanism of PLCγ2 activation essential for its role in linking the specific receptor responses to a variety of hormones and bacterial endotoxins with the intended intracellular targets. Here, we explored the involvement of Rac in mediation of PLCγ2 activation associated with gastric mucosal inflammatory responses to H. pylori LPS and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the membrane translocation of Rac1 as well as PLCγ2, while the effect of ghrelin is manifested by elevation in the membrane PLCγ2 activation and suppression in Rac1 translocation. However, blocking the LPS-induced Rac1 translocation, while detrimental to the PLCγ2 activation, has no effect on its membrane translocation. We reveal further that PLCγ2, localized in the membrane in association with Rac1 following the LPS stimulation, exhibits a marked increase in phosphorylation on Ser, while the modulatory effect of ghrelin, manifested by a drop in Rac1 translocation, is associated with a distinct decrease in PLCγ2 phosphorylation on Ser. Thus, the results suggest that H. pylori-elicited increase in gastric mucosal PLCγ2 phosphorylation on Ser serves as an essential platform for Rac1 colocalization and amplification in PLCγ2 activation.
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Affiliation(s)
- B L Slomiany
- Research Center C875, Rutgers School of Dental Medicine Rutgers, The State University of New Jersey, 110 Bergen Street, PO Box 1709, Newark, NJ, 07103-2400, USA,
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24
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Wang X, Hills LB, Huang YH. Lipid and Protein Co-Regulation of PI3K Effectors Akt and Itk in Lymphocytes. Front Immunol 2015; 6:117. [PMID: 25821452 PMCID: PMC4358224 DOI: 10.3389/fimmu.2015.00117] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/02/2015] [Indexed: 12/21/2022] Open
Abstract
The phosphoinositide 3-kinase (PI 3-kinase, PI3K) pathway transduces signals critical for lymphocyte function. PI3K generates the phospholipid PIP3 at the plasma membrane to recruit proteins that contain pleckstrin homology (PH) domains – a conserved domain found in hundreds of mammalian proteins. PH domain–PIP3 interactions allow for rapid signal propagation and confer a spatial component to these signals. The kinases Akt and Itk are key PI3K effectors that bind PIP3 via their PH domains and mediate vital processes – such as survival, activation, and differentiation – in lymphocytes. Here, we review the roles and regulation of PI3K signaling in lymphocytes with a specific emphasis on Akt and Itk. We also discuss these and other PH domain-containing proteins as they relate more broadly to immune cell function. Finally, we highlight the emerging view of PH domains as multifunctional protein domains that often bind both lipid and protein substrates to exert their effects.
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Affiliation(s)
- Xinxin Wang
- California Institute for Biomedical Research , La Jolla, CA , USA
| | - Leonard Benjamin Hills
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA
| | - Yina Hsing Huang
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA ; Department of Pathology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA
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25
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Elvers M. RhoGAPs and Rho GTPases in platelets. Hamostaseologie 2015; 36:168-77. [PMID: 25639730 DOI: 10.5482/hamo-14-09-0046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 01/13/2015] [Indexed: 01/03/2023] Open
Abstract
Platelet cytoskeletal reorganization is essential for platelet adhesion and thrombus formation in hemostasis and thrombosis. The Rho GTPases RhoA, Rac1 and Cdc42 are the main players in cytoskeletal dynamics of platelets responsible for the formation of filopodia and lamellipodia to strongly increase the platelet surface upon activation. They are involved in platelet activation and aggregate formation including platelet secretion, integrin activation and arterial thrombus formation. The activity of Rho GTPases is tightly controlled by different proteins such as GTPase-activating proteins (GAPs). GAPs stimulate GTP hydrolysis to terminate Rho signaling. The role and impact of GAPs in platelets is not well-defined and many of the RhoGAPs identified are not known to be present in platelets or to have any function in platelets. The recently identified RhoGAPs Oligophrenin1 (OPHN1) and Nadrin regulate the activity of RhoA, Rac1 and Cdc42 and subsequent platelet cytoskeletal reorganization, platelet activation and thrombus formation. In the last years, the analysis of genetically modified mice helped to gain the understanding of Rho GTPases and their regulators in cytoskeletal rearrangements and other Rho mediated cellular processes in platelets.
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Affiliation(s)
- Margitta Elvers
- Margitta Elvers, Ph.D., Department of Clinical and Experimental Hemostasis, Hemotherapy and Transfusion Medicine, Heinrich-Heine-University Duesseldorf, Moorenstr. 5, 40225 Duesseldorf, Germany, Tel. +49/(0)211/81-08851, Fax -17498., E-mail:
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26
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Sicart A, Katan M, Egea G, Sarri E. PLCγ1 participates in protein transport and diacylglycerol production triggered by cargo arrival at the Golgi. Traffic 2015; 16:250-66. [PMID: 25491205 DOI: 10.1111/tra.12246] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 11/26/2014] [Accepted: 11/26/2014] [Indexed: 02/02/2023]
Abstract
Diacylglycerol (DAG) is required for membrane traffic and structural organization at the Golgi. DAG is a lipid metabolite of several enzymatic reactions present at this organelle, but the mechanisms by which they are regulated are still unknown. Here, we show that cargo arrival at the Golgi increases the recruitment of the DAG-sensing constructs C1-PKCθ-GFP and the PKD-wt-GFP. The recruitment of both constructs was reduced by PLCγ1 silencing. Post-Golgi trafficking of transmembrane and soluble proteins was impaired in PLCγ1-silenced cells. Under basal conditions, PLCγ1 contributed to the maintenance of the pool of DAG associated with the Golgi and to the structural organization of the organelle. Finally, we show that cytosolic phospholipase C (PLC) can hydrolyse phosphatidylinositol 4-phosphate in isolated Golgi membranes. Our results indicate that PLCγ1 is part of the molecular mechanism that couples cargo arrival at the Golgi with DAG production to co-ordinate the formation of transport carriers for post-Golgi traffic.
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Affiliation(s)
- Adrià Sicart
- Departament de Biologia Cel·lular, Immunologia i Neurociències, Facultat de Medicina, Universitat de Barcelona, C/ Casanova, 143, 08036, Barcelona, Spain; Current address: Vlaams Instituut voor Biotechnologie (VIB), Centre for the Biology of Disease and KU Leuven, Department of Human Genetics, Campus Gasthuisberg, 3000 Leuven, Belgium
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27
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Koss H, Bunney TD, Behjati S, Katan M. Dysfunction of phospholipase Cγ in immune disorders and cancer. Trends Biochem Sci 2014; 39:603-11. [PMID: 25456276 DOI: 10.1016/j.tibs.2014.09.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/19/2014] [Accepted: 09/24/2014] [Indexed: 12/15/2022]
Abstract
The surge in genetic and genomic investigations over the past 5 years has resulted in many discoveries of causative variants relevant to disease pathophysiology. Although phospholipase C (PLC) enzymes have long been recognized as important components in intracellular signal transmission, it is only recently that this approach highlighted their role in disease development through gain-of-function mutations. In this review we describe the new findings that link the PLCγ family to immune disorders and cancer, and illustrate further efforts to elucidate the molecular mechanisms that underpin their dysfunction.
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Affiliation(s)
- Hans Koss
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK; Division of Molecular Structure, Medical Research Council (MRC) National Institute for Medical Research, London, UK
| | - Tom D Bunney
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK.
| | - Sam Behjati
- Cancer Genome Project, Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, UK
| | - Matilda Katan
- Institute of Structural and Molecular Biology, Division of Biosciences, University College London, London, UK.
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28
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Role of amplification in phospholipase Cγ2 activation in modulation of gastric mucosal inflammatory responses to Helicobacter pylori: effect of ghrelin. Inflammopharmacology 2014; 23:37-45. [PMID: 25362585 DOI: 10.1007/s10787-014-0220-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Accepted: 10/18/2014] [Indexed: 12/21/2022]
Abstract
Phosphoinositide-specific phospholipase C (PLC) enzymes are crucial elements of signal transduction pathways that provide a common link of communication integrating specific receptor responses to a variety of hormones, growth factors, and bacterial endotoxins with the intended intracellular targets. Here, we examined the involvement of PLC in modulation of gastric mucosal inflammatory responses to Helicobacter pylori LPS by peptide hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the activation and membrane translocation of the γ2 isoform of PLC, phosphorylated on Tyr as well as Ser, while the effect of ghrelin is reflected in the translocation and phosphorylation of membrane-associated PLCγ2 on Tyr mainly. Moreover, we demonstrate that PLCγ2 phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is intimately linked to PLCγ2 membrane localization, while the LPS-induced phosphorylation of membrane-recruited PLCγ2 on Ser displays dependence on protein kinase Cδ (PKCδ) and leads to the amplification in PLCγ2 activation. Thus, our findings link the extent of H. pylori-elicited gastric mucosal inflammatory involvement to the PKCδ-mediated amplification in PLCγ2 activation through phosphorylation on Ser.
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29
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Timsah Z, Ahmed Z, Lin CC, Melo FA, Stagg LJ, Leonard PG, Jeyabal P, Berrout J, O'Neil RG, Bogdanov M, Ladbury JE. Competition between Grb2 and Plcγ1 for FGFR2 regulates basal phospholipase activity and invasion. Nat Struct Mol Biol 2014; 21:180-8. [DOI: 10.1038/nsmb.2752] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Accepted: 12/02/2013] [Indexed: 12/23/2022]
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30
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Alexander SPH, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Spedding M, Peters JA, Harmar AJ. The Concise Guide to PHARMACOLOGY 2013/14: enzymes. Br J Pharmacol 2013; 170:1797-867. [PMID: 24528243 PMCID: PMC3892293 DOI: 10.1111/bph.12451] [Citation(s) in RCA: 415] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. Enzymes are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, nuclear hormone receptors, catalytic receptors and transporters. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.
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Affiliation(s)
- Stephen PH Alexander
- School of Life Sciences, University of Nottingham Medical SchoolNottingham, NG7 2UH, UK
| | - Helen E Benson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Elena Faccenda
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Adam J Pawson
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | - Joanna L Sharman
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
| | | | - John A Peters
- Neuroscience Division, Medical Education Institute, Ninewells Hospital and Medical School, University of DundeeDundee, DD1 9SY, UK
| | - Anthony J Harmar
- The University/BHF Centre for Cardiovascular Science, University of EdinburghEdinburgh, EH16 4TJ, UK
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31
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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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32
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Cao C, Wang Z, Niu C, Desneux N, Gao X. Transcriptome profiling of Chironomus kiinensis under phenol stress using Solexa sequencing technology. PLoS One 2013; 8:e58914. [PMID: 23527048 PMCID: PMC3604134 DOI: 10.1371/journal.pone.0058914] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 02/08/2013] [Indexed: 12/25/2022] Open
Abstract
Phenol is a major pollutant in aquatic ecosystems due to its chemical stability, water solubility and environmental mobility. To date, little is known about the molecular modifications of invertebrates under phenol stress. In the present study, we used Solexa sequencing technology to investigate the transcriptome and differentially expressed genes (DEGs) of midges (Chironomus kiinensis) in response to phenol stress. A total of 51,518,972 and 51,150,832 clean reads in the phenol-treated and control libraries, respectively, were obtained and assembled into 51,014 non-redundant (Nr) consensus sequences. A total of 6,032 unigenes were classified by Gene Ontology (GO), and 18,366 unigenes were categorized into 238 Kyoto Encyclopedia of Genes and Genomes (KEGG) categories. These genes included representatives from almost all functional categories. A total of 10,724 differentially expressed genes (P value <0.05) were detected in a comparative analysis of the expression profiles between phenol-treated and control C. kiinensis including 8,390 upregulated and 2,334 downregulated genes. The expression levels of 20 differentially expressed genes were confirmed by real-time RT-PCR, and the trends in gene expression that were observed matched the Solexa expression profiles, although the magnitude of the variations was different. Through pathway enrichment analysis, significantly enriched pathways were identified for the DEGs, including metabolic pathways, aryl hydrocarbon receptor (AhR), pancreatic secretion and neuroactive ligand-receptor interaction pathways, which may be associated with the phenol responses of C. kiinensis. Using Solexa sequencing technology, we identified several groups of key candidate genes as well as important biological pathways involved in the molecular modifications of chironomids under phenol stress.
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Affiliation(s)
- Chuanwang Cao
- Department of Forest Protection, Northeast Forestry University, Harbin, China
| | - Zhiying Wang
- Department of Forest Protection, Northeast Forestry University, Harbin, China
| | - Changying Niu
- Hubei Key Laboratory of Utilization of Insect Resources and Sustainable Control of Pests, Huazhong Agricultural University, Wuhan, China
| | - Nicolas Desneux
- French National Institute for Agricultural Research (INRA), Sophia-Antipolis, France
| | - Xiwu Gao
- Department of Entomology, China Agricultural University, Beijing, China
- * E-mail:
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Abstract
The Rho family of GTP binding proteins, also commonly referred to as the Rho GTPases, are master regulators of the platelet cytoskeleton and platelet function. These low-molecular-weight or 'small' GTPases act as signaling switches in the spatial and temporal transduction, and amplification of signals from platelet cell surface receptors to the intracellular signaling pathways that drive platelet function. The Rho GTPase family members RhoA, Cdc42 and Rac1 have emerged as key regulators in the dynamics of the actin cytoskeleton in platelets and play key roles in platelet aggregation, secretion, spreading and thrombus formation. Rho GTPase regulators, including GEFs and GAPs and downstream effectors, such as the WASPs, formins and PAKs, may also regulate platelet activation and function. In this review, we provide an overview of Rho GTPase signaling in platelet physiology. Previous studies of Rho GTPases and platelets have had a shared history, as platelets have served as an ideal, non-transformed cellular model to characterize Rho function. Likewise, recent studies of the cell biology of Rho GTPase family members have helped to build an understanding of the molecular regulation of platelet function and will continue to do so through the further characterization of Rho GTPases as well as Rho GAPs, GEFs, RhoGDIs and Rho effectors in actin reorganization and other Rho-driven cellular processes.
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Affiliation(s)
- J E Aslan
- Department of Biomedical Engineering and Cell & Developmental Biology, School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA.
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Abstract
Phospholipase C (PLC) converts phosphatidylinositol 4,5-bisphosphate (PIP(2)) to inositol 1,4,5-trisphosphate (IP(3)) and diacylglycerol (DAG). DAG and IP(3) each control diverse cellular processes and are also substrates for synthesis of other important signaling molecules. PLC is thus central to many important interlocking regulatory networks. Mammals express six families of PLCs, each with both unique and overlapping controls over expression and subcellular distribution. Each PLC also responds acutely to its own spectrum of activators that includes heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca(2+), and phospholipids. Mammalian PLCs are autoinhibited by a region in the catalytic TIM barrel domain that is the target of much of their acute regulation. In combination, the PLCs act as a signaling nexus that integrates numerous signaling inputs, critically governs PIP(2) levels, and regulates production of important second messengers to determine cell behavior over the millisecond to hour timescale.
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Affiliation(s)
- Ganesh Kadamur
- Department of Pharmacology, Molecular Biophysics Graduate Program and Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Patel S, Huang YW, Reheman A, Pluthero FG, Chaturvedi S, Mukovozov IM, Tole S, Liu GY, Li L, Durocher Y, Ni H, Kahr WHA, Robinson LA. The cell motility modulator Slit2 is a potent inhibitor of platelet function. Circulation 2012; 126:1385-95. [PMID: 22865890 DOI: 10.1161/circulationaha.112.105452] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Vascular injury and atherothrombosis involve vessel infiltration by inflammatory leukocytes, migration of medial vascular smooth muscle cells to the intimal layer, and ultimately acute thrombosis. A strategy to simultaneously target these pathological processes has yet to be identified. The secreted protein, Slit2, and its transmembrane receptor, Robo-1, repel neuronal migration in the developing central nervous system. More recently, it has been appreciated that Slit2 impairs chemotaxis of leukocytes and vascular smooth muscle cells toward diverse inflammatory attractants. The effects of Slit2 on platelet function and thrombus formation have never been explored. METHODS AND RESULTS We detected Robo-1 expression in human and murine platelets and megakaryocytes and confirmed its presence via immunofluorescence microscopy and flow cytometry. In both static and shear microfluidic assays, Slit2 impaired platelet adhesion and spreading on diverse extracellular matrix substrates by suppressing activation of Akt. Slit2 also prevented platelet activation on exposure to ADP. In in vivo studies, Slit2 prolonged bleeding times in murine tail bleeding assays. Using intravital microscopy, we found that after mesenteric arteriolar and carotid artery injury, Slit2 delayed vessel occlusion time and prevented the stable formation of occlusive arteriolar thrombi. CONCLUSIONS These data demonstrate that Slit2 is a powerful negative regulator of platelet function and thrombus formation. The ability to simultaneously block multiple events in vascular injury may allow Slit2 to effectively prevent and treat thrombotic disorders such as myocardial infarction and stroke.
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Affiliation(s)
- Sajedabanu Patel
- The Hospital for Sick Children, 555 University Ave, Toronto, ON, Canada M5G 1X8
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Scheffzek K, Welti S. Pleckstrin homology (PH) like domains - versatile modules in protein-protein interaction platforms. FEBS Lett 2012; 586:2662-73. [PMID: 22728242 DOI: 10.1016/j.febslet.2012.06.006] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 06/07/2012] [Accepted: 06/08/2012] [Indexed: 12/21/2022]
Abstract
The initial reports on pleckstrin homology (PH) domains almost 20 years ago described them as sequence feature of proteins involved in signal transduction processes. Investigated at first along the phospholipid binding properties of a small subset of PH representatives, the PH fold turned out to appear as mediator of phosphotyrosine and polyproline peptide binding to other signaling proteins. While phospholipid binding now seems rather the exception among PH-like domains, protein-protein interactions established as more and more important feature of these modules. In this review we focus on the PH superfold as a versatile protein-protein interaction platform and its three-dimensional integration in an increasing number of available multidomain structures.
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Affiliation(s)
- Klaus Scheffzek
- Division Biological Chemistry, Biocenter, Innsbruck Medical University, Innrain 80/82, A-6020 Innsbruck, Austria.
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37
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Montresor A, Toffali L, Constantin G, Laudanna C. Chemokines and the signaling modules regulating integrin affinity. Front Immunol 2012; 3:127. [PMID: 22654882 PMCID: PMC3360201 DOI: 10.3389/fimmu.2012.00127] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 05/03/2012] [Indexed: 01/05/2023] Open
Abstract
Integrin-mediated adhesion is a general concept referring to a series of adhesive phenomena including tethering–rolling, affinity, valency, and binding stabilization altogether controlling cell avidity (adhesiveness) for the substrate. Arrest chemokines modulate each aspect of integrin activation, although integrin affinity regulation has been recognized as the prominent event in rapid leukocyte arrest induced by chemokines. A variety of inside-out and outside-in signaling mechanisms have been related to the process of integrin-mediated adhesion in different cellular models, but only few of them have been clearly contextualized to rapid integrin affinity modulation by arrest chemokines in primary leukocytes. Complex signaling processes triggered by arrest chemokines and controlling leukocyte integrin activation have been described for ras-related rap and for rho-related small GTPases. We summarize the role of rap and rho small GTPases in the regulation of rapid integrin affinity in primary leukocytes and provide a modular view of these pro-adhesive signaling events. A potential, albeit still speculative, mechanism of rho-mediated regulation of cytoskeletal proteins controlling the last step of integrin activation is also discussed. We also discuss data suggesting a functional integration between the rho- and rap-modules of integrin activation. Finally we examine the universality of signaling mechanisms regulating integrin triggering by arrest chemokines.
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Affiliation(s)
- Alessio Montresor
- Division of General Pathology, Department of Pathology, University of Verona Verona, Italy
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Cross-talk between mitogenic Ras/MAPK and survival PI3K/Akt pathways: a fine balance. Biochem Soc Trans 2012; 40:139-46. [PMID: 22260680 DOI: 10.1042/bst20110609] [Citation(s) in RCA: 347] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In the present paper, we describe multiple levels of cross-talk between the PI3K (phosphoinositide 3-kinase)/Akt and Ras/MAPK (mitogen-activated protein kinase) signalling pathways. Experimental data and computer simulations demonstrate that cross-talk is context-dependent and that both pathways can activate or inhibit each other. Positive influence of the PI3K pathway on the MAPK pathway is most effective at sufficiently low doses of growth factors, whereas negative influence of the MAPK pathway on the PI3K pathway is mostly pronounced at high doses of growth factors. Pathway cross-talk endows a cell with emerging capabilities for processing and decoding signals from multiple receptors activated by different combinations of extracellular cues.
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Wagner S, Arnold F, Wu Z, Schubert A, Walliser C, Tadagaki K, Jockers R, Mertens T, Michel D. The 7-transmembrane protein homologue UL78 of the human cytomegalovirus forms oligomers and traffics between the plasma membrane and different intracellular compartments. Arch Virol 2012; 157:935-49. [PMID: 22327422 DOI: 10.1007/s00705-012-1246-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Accepted: 12/29/2011] [Indexed: 12/22/2022]
Abstract
The human cytomegalovirus (HCMV) UL78 ORF is considered to encode an orphan 7-transmembrane receptor. However, until now, the UL78 protein (pUL78) has not been characterized. Here, we have investigated the expression of pUL78 and found it mainly associated with the endoplasmic reticulum. However, we provide evidence that pUL78 is also localized on the cell surface from where it is quickly endocytosed. Colocalization with adaptin and EEA-1 implies that at least a small amount of pUL78 is transported to the trans Golgi network and early endosomes. Using a bimolecular fluorescence complementation assay and co-immunoprecipitation experiments, we were able to find homomeric and heteromeric structure formations of pUL78 and the US28 protein, respectively. However, the absence of pUL78 had no effect on the accumulation of inositol phosphate triggered by the US28 protein. In summary, our results suggest that the UL78 protein of HCMV traffics between the cell surface and cytoplasm, from where it might be recycled via early endosomes.
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Affiliation(s)
- Svenja Wagner
- Institut für Virologie, Universitätsklinikum Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
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Goggs R, Poole AW. Platelet signaling-a primer. J Vet Emerg Crit Care (San Antonio) 2012; 22:5-29. [PMID: 22316389 DOI: 10.1111/j.1476-4431.2011.00704.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 11/25/2011] [Indexed: 12/28/2022]
Abstract
OBJECTIVE To review the receptors and signal transduction pathways involved in platelet plug formation and to highlight links between platelets, leukocytes, endothelium, and the coagulation system. DATA SOURCES Original studies, review articles, and book chapters in the human and veterinary medical fields. DATA SYNTHESIS Platelets express numerous surface receptors. Critical among these are glycoprotein VI, the glycoprotein Ib-IX-V complex, integrin α(IIb) β(3) , and the G-protein-coupled receptors for thrombin, ADP, and thromboxane. Activation of these receptors leads to various important functional events, in particular activation of the principal adhesion receptor α(IIb) β(3) . Integrin activation allows binding of ligands such as fibrinogen, mediating platelet-platelet interaction in the process of aggregation. Signals activated by these receptors also couple to 3 other important functional events, secretion of granule contents, change in cell shape through cytoskeletal rearrangement, and procoagulant membrane expression. These processes generate a stable thrombus to limit blood loss and promote restoration of endothelial integrity. CONCLUSIONS Improvements in our understanding of how platelets operate through their signaling networks are critical for diagnosis of unusual primary hemostatic disorders and for rational antithrombotic drug design.
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Affiliation(s)
- Robert Goggs
- School of Physiology and Pharmacology, Faculty of Medical and Veterinary Sciences, University of Bristol, UK.
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41
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Abstract
The physiological effects of many extracellular neurotransmitters, hormones, growth factors, and other stimuli are mediated by receptor-promoted activation of phospholipase C (PLC) and consequential activation of inositol lipid signaling pathways. These signaling responses include the classically described conversion of phosphatidylinositol(4,5)P(2) to the Ca(2+)-mobilizing second messenger inositol(1,4,5)P(3) and the protein kinase C-activating second messenger diacylglycerol as well as alterations in membrane association or activity of many proteins that harbor phosphoinositide binding domains. The 13 mammalian PLCs elaborate a minimal catalytic core typified by PLC-d to confer multiple modes of regulation of lipase activity. PLC-b isozymes are activated by Gaq- and Gbg-subunits of heterotrimeric G proteins, and activation of PLC-g isozymes occurs through phosphorylation promoted by receptor and non-receptor tyrosine kinases. PLC-e and certain members of the PLC-b and PLC-g subclasses of isozymes are activated by direct binding of small G proteins of the Ras, Rho, and Rac subfamilies of GTPases. Recent high resolution three dimensional structures together with biochemical studies have illustrated that the X/Y linker region of the catalytic core mediates autoinhibition of most if not all PLC isozymes. Activation occurs as a consequence of removal of this autoinhibition.
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Stefanini L, Boulaftali Y, Ouellette TD, Holinstat M, Désiré L, Leblond B, Andre P, Conley PB, Bergmeier W. Rap1-Rac1 circuits potentiate platelet activation. Arterioscler Thromb Vasc Biol 2011; 32:434-41. [PMID: 22075250 DOI: 10.1161/atvbaha.111.239194] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE The goal of this study was to investigate the potential crosstalk between Rap1 and Rac1, 2 small GTPases central to platelet activation, particularly downstream of the collagen receptor GPVI. METHODS AND RESULTS We compared the activation response of platelets with impaired Rap signaling (double knock-out; deficient in both the guanine nucleotide exchange factor, CalDAG-GEFI, and the Gi-coupled receptor for ADP, P2Y12), to that of wild-type platelets treated with a small-molecule Rac inhibitor, EHT 1864 (wild-type /EHT). We found that Rac1 is sequentially activated downstream of Rap1 on stimulation via GPVI. In return, Rac1 provides important feedback for both CalDAG-GEFI- and P2Y12-dependent activation of Rap1. When analyzing platelet responses controlled by Rac1, we observed (1) impaired lamellipodia formation, clot retraction, and granule release in both double knock-out and EHT 1864-treated wild-type platelets; and (2) reduced calcium store release in EHT 1864-treated wild-type but not double knock-out platelets. Consistent with the latter finding, we identified 2 pools of Rac1, one activated immediately downstream of GPVI and 1 activated downstream of Rap1. CONCLUSIONS We demonstrate important crosstalk between Rap1 and Rac1 downstream of GPVI. Whereas Rap1 signaling directly controls sustained Rac1 activation, Rac1 affects CalDAG-GEFI- and P2Y12-dependent Rap1 activation via its role in calcium mobilization and granule/ADP release, respectively.
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Affiliation(s)
- Lucia Stefanini
- Dept. of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, 98 Manning Drive, 306a Mary Ellen Jones Building, Chapel Hill, NC 27599, USA
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Harden TK, Waldo GL, Hicks SN, Sondek J. Mechanism of activation and inactivation of Gq/phospholipase C-β signaling nodes. Chem Rev 2011; 111:6120-9. [PMID: 21988240 PMCID: PMC3626114 DOI: 10.1021/cr200209p] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- T Kendall Harden
- Department of Pharmacology and the Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
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Abe K, Fuchs H, Boersma A, Hans W, Yu P, Kalaydjiev S, Klaften M, Adler T, Calzada-Wack J, Mossbrugger I, Rathkolb B, Rozman J, Prehn C, Maraslioglu M, Kametani Y, Shimada S, Adamski J, Busch DH, Esposito I, Klingenspor M, Wolf E, Wurst W, Gailus-Durner V, Katan M, Marschall S, Soewarto D, Wagner S, de Angelis MH. A novel N-ethyl-N-nitrosourea-induced mutation in phospholipase Cγ2 causes inflammatory arthritis, metabolic defects, and male infertility in vitro in a murine model. ACTA ACUST UNITED AC 2011; 63:1301-11. [PMID: 21305534 DOI: 10.1002/art.30280] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE It is difficult to identify a single causative factor for inflammatory arthritis because of the multifactorial nature of the disease. This study was undertaken to dissect the molecular complexity of systemic inflammatory disease, utilizing a combined approach of mutagenesis and systematic phenotype screening in a murine model. METHODS In a large-scale N-ethyl-N-nitrosourea mutagenesis project, the Ali14 mutant mouse strain was established because of dominant inheritance of spontaneous swelling and inflammation of the hind paws. Genetic mapping and subsequent candidate gene sequencing were conducted to find the causative gene, and systematic phenotyping of Ali14/+ mice was performed in the German Mouse Clinic. RESULTS A novel missense mutation in the phospholipase Cγ2 gene (Plcg2) was identified in Ali14/+ mice. Because of the hyperreactive external entry of calcium observed in cultured B cells and other in vitro experiments, the Ali14 mutation is thought to be a novel gain-of-function allele of Plcg2. Findings from systematic screening of Ali14/+ mice demonstrated various phenotypic changes: an abnormally high T cell:B cell ratio, up-regulation of Ig, alterations in body composition, and a reduction in cholesterol and triglyceride levels in peripheral blood. In addition, spermatozoa from Ali14/+ mice failed to fertilize eggs in vitro, despite the normal fertility of the Ali14/+ male mice in vivo. CONCLUSION These results suggest that the Plcg2-mediated pathways play a crucial role in various metabolic and sperm functions, in addition to initiating and maintaining the immune system. These findings may indicate the importance of the Ali14/+ mouse strain as a model for systemic inflammatory diseases and inflammation-related metabolic changes in humans.
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Affiliation(s)
- Koichiro Abe
- Tokai University School of Medicine, Kanagawa, Japan.
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Sequential phosphorylation of SLP-76 at tyrosine 173 is required for activation of T and mast cells. EMBO J 2011; 30:3160-72. [PMID: 21725281 DOI: 10.1038/emboj.2011.213] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Accepted: 06/03/2011] [Indexed: 02/03/2023] Open
Abstract
Cooperatively assembled signalling complexes, nucleated by adaptor proteins, integrate information from surface receptors to determine cellular outcomes. In T and mast cells, antigen receptor signalling is nucleated by three adaptors: SLP-76, Gads and LAT. Three well-characterized SLP-76 tyrosine phosphorylation sites recruit key components, including a Tec-family tyrosine kinase, Itk. We identified a fourth, evolutionarily conserved SLP-76 phosphorylation site, Y173, which was phosphorylated upon T-cell receptor stimulation in primary murine and Jurkat T cells. Y173 was required for antigen receptor-induced phosphorylation of phospholipase C-γ1 (PLC-γ1) in both T and mast cells, and for consequent downstream events, including activation of the IL-2 promoter in T cells, and degranulation and IL-6 production in mast cells. In intact cells, Y173 phosphorylation depended on three, ZAP-70-targeted tyrosines at the N-terminus of SLP-76 that recruit and activate Itk, a kinase that selectively phosphorylated Y173 in vitro. These data suggest a sequential mechanism whereby ZAP-70-dependent priming of SLP-76 at three N-terminal sites triggers reciprocal regulatory interactions between Itk and SLP-76, which are ultimately required to couple active Itk to its substrate, PLC-γ1.
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Membrane environment exerts an important influence on rac-mediated activation of phospholipase Cγ2. Mol Cell Biol 2011; 31:1240-51. [PMID: 21245382 DOI: 10.1128/mcb.01408-10] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We performed analyses of the molecular mechanisms involved in the regulation of phospholipase Cγ2 (PLCγ2). We identified several regions in the PLCγ-specific array, γSA, that contribute to autoinhibition in the basal state by occlusion of the catalytic domain. While the activation of PLCγ2 by Rac2 requires stable translocation to the membrane, the removal of the domains required for membrane translocation in the context of an enzyme with impaired autoinhibition generated constitutive, highly active PLC in cells. We further tested the possibility that the interaction of PLCγ2 with its activator protein Rac2 was sufficient for activation through the release of autoinhibition. However, we found that Rac2 binding in the absence of lipid surfaces was not able to activate PLCγ2. Together with other observations, these data suggest that an important consequence of Rac2 binding and translocation to the membrane is that membrane proximity, on its own or together with Rac2, has a role in the release of autoinhibition, resulting in interfacial activation.
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Kwiatkowska K. One lipid, multiple functions: how various pools of PI(4,5)P(2) are created in the plasma membrane. Cell Mol Life Sci 2010; 67:3927-46. [PMID: 20559679 PMCID: PMC11115911 DOI: 10.1007/s00018-010-0432-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Revised: 06/01/2010] [Accepted: 06/02/2010] [Indexed: 01/25/2023]
Abstract
Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P(2)] is a minor lipid of the inner leaflet of the plasma membrane that controls the activity of numerous proteins and serves as a source of second messengers. This multifunctionality of PI(4,5)P(2) relies on mechanisms ensuring transient appearance of PI(4,5)P(2) clusters in the plasma membrane. One such mechanism involves phosphorylation of PI(4)P to PI(4,5)P(2) by the type I phosphatidylinositol-4-phosphate 5-kinases (PIP5KI) at discrete membrane locations coupled with PI(4)P delivery/synthesis at the plasma membrane. Simultaneously, both PI(4)P and PI(4,5)P(2) participate in anchoring PIP5KI at the plasma membrane via electrostatic bonds. PIP5KI isoforms are also selectively recruited and activated at the plasma membrane by Rac1, talin, or AP-2 to generate PI(4,5)P(2) in ruffles and lamellipodia, focal contacts, and clathrin-coated pits. In addition, PI(4,5)P(2) can accumulate at sphingolipid/cholesterol-based rafts following activation of distinct membrane receptors or be sequestered in a reversible manner due to electrostatic constrains posed by proteins like MARCKS.
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Affiliation(s)
- Katarzyna Kwiatkowska
- Laboratory of Plasma Membrane Receptors, Nencki Institute of Experimental Biology, 3 Pasteur St., 02-093 Warsaw, Poland.
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48
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Gresset A, Hicks SN, Harden TK, Sondek J. Mechanism of phosphorylation-induced activation of phospholipase C-gamma isozymes. J Biol Chem 2010; 285:35836-47. [PMID: 20807769 DOI: 10.1074/jbc.m110.166512] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The lipase activity of most phospholipases C (PLCs) is basally repressed by a highly degenerate and mostly disordered X/Y linker inserted within the catalytic domain. Release of this auto-inhibition is driven by electrostatic repulsion between the plasma membrane and the electronegative X/Y linker. In contrast, PLC-γ isozymes (PLC-γ1 and -γ2) are structurally distinct from other PLCs because multiple domains are present in their X/Y linker. Moreover, although many tyrosine kinases directly phosphorylate PLC-γ isozymes to enhance their lipase activity, the underlying molecular mechanism of this activation remains unclear. Here we define the mechanism for the unique regulation of PLC-γ isozymes by their X/Y linker. Specifically, we identify the C-terminal SH2 domain within the X/Y linker as the critical determinant for auto-inhibition. Tyrosine phosphorylation of the X/Y linker mediates high affinity intramolecular interaction with the C-terminal SH2 domain that is coupled to a large conformational rearrangement and release of auto-inhibition. Consequently, PLC-γ isozymes link phosphorylation to phospholipase activation by elaborating upon primordial regulatory mechanisms found in other PLCs.
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Affiliation(s)
- Aurelie Gresset
- Department of Pharmacology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7365, USA
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Phosphorylation of CLEC-2 is dependent on lipid rafts, actin polymerization, secondary mediators, and Rac. Blood 2010; 115:2938-46. [PMID: 20154214 DOI: 10.1182/blood-2009-12-257212] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The C-type lectin-like receptor 2 (CLEC-2) activates platelets through Src and Syk tyrosine kinases via a single cytoplasmic YxxL motif known as a hem immunoreceptor tyrosine-based activation motif (hemITAM). Here, we demonstrate using sucrose gradient ultracentrifugation and methyl-beta-cyclodextrin treatment that CLEC-2 translocates to lipid rafts upon ligand engagement and that translocation is essential for hemITAM phosphorylation and signal initiation. HemITAM phosphorylation, but not translocation, is also critically dependent on actin polymerization, Rac1 activation, and release of ADP and thromboxane A(2) (TxA(2)). The role of ADP and TxA(2) in mediating phosphorylation is dependent on ligand engagement and rac activation but is independent of platelet aggregation. In contrast, tyrosine phosphorylation of the GPVI-FcRgamma-chain ITAM, which has 2 YxxL motifs, is independent of actin polymerization and secondary mediators. These results reveal a unique series of proximal events in CLEC-2 phosphorylation involving actin polymerization, secondary mediators, and Rac activation.
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Gutman O, Walliser C, Piechulek T, Gierschik P, Henis YI. Differential regulation of phospholipase C-beta2 activity and membrane interaction by Galphaq, Gbeta1gamma2, and Rac2. J Biol Chem 2010; 285:3905-3915. [PMID: 20007712 PMCID: PMC2823533 DOI: 10.1074/jbc.m109.085100] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2009] [Indexed: 01/15/2023] Open
Abstract
We combined fluorescence recovery after photobleaching (FRAP) beam-size analysis with biochemical assays to investigate the mechanisms of membrane recruitment and activation of phospholipase C-beta(2) (PLCbeta(2)) by G protein alpha(q) and betagamma dimers. We show that activation by alpha(q) and betagamma differ from activation by Rac2 and from each other. Stimulation by alpha(q) enhanced the plasma membrane association of PLCbeta(2), but not of PLCbeta(2)Delta, which lacks the alpha(q)-interacting region. Although alpha(q) resembled Rac2 in increasing the contribution of exchange to the FRAP of PLCbeta(2) and in enhancing its membrane association, the latter effect was weaker than with Rac2. Moreover, the membrane recruitment of PLCbeta(2) by alpha(q) occurred by enhancing PLCbeta(2) association with fast-diffusing (lipid-like) membrane components, whereas stimulation by Rac2 led to interactions with slow diffusing membrane sites. On the other hand, activation by betagamma shifted the FRAP of PLCbeta(2) and PLCbeta(2)Delta to pure lateral diffusion 3- to 5-fold faster than lipids, suggesting surfing-like diffusion along the membrane. We propose that these different modes of PLCbeta(2) membrane recruitment may accommodate contrasting functional needs to hydrolyze phosphatidylinositol 4,5-bisphosphate (PtdInsP(2)) in localized versus dispersed populations. PLCbeta(2) activation by Rac2, which leads to slow lateral diffusion and much faster exchange, recruits PLCbeta(2) to act locally on PtdInsP(2) at specific domains. Activation by alpha(q) leads to lipid-like diffusion of PLCbeta(2) accompanied by exchange, enabling the sampling of larger, yet limited, areas prior to dissociation. Finally, activation by betagamma recruits PLCbeta(2) to the membrane by transient interactions, leading to fast "surfing" diffusion along the membrane, sampling large regions for dispersed PtdInsP(2) populations.
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Affiliation(s)
- Orit Gutman
- From the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, and
| | - Claudia Walliser
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Thomas Piechulek
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - Peter Gierschik
- the Institute of Pharmacology and Toxicology, University of Ulm Medical Center, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
| | - Yoav I Henis
- From the Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel, and.
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