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Zerihun M, Rubin SJS, Silnitsky S, Qvit N. An Update on Protein Kinases as Therapeutic Targets-Part II: Peptides as Allosteric Protein Kinase C Modulators Targeting Protein-Protein Interactions. Int J Mol Sci 2023; 24:17504. [PMID: 38139336 PMCID: PMC10743673 DOI: 10.3390/ijms242417504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 12/11/2023] [Accepted: 12/12/2023] [Indexed: 12/24/2023] Open
Abstract
Human protein kinases are highly-sought-after drug targets, historically harnessed for treating cancer, cardiovascular disease, and an increasing number of autoimmune and inflammatory conditions. Most current treatments involve small molecule protein kinase inhibitors that interact orthosterically with the protein kinase ATP-binding pocket. As a result, these compounds are often poorly selective and highly toxic. Part I of this series reviews the role of PKC isoforms in various human diseases, featuring cancer and cardiovascular disease, as well as translational examples of PKC modulation applied to human health and disease. In the present Part II, we discuss alternative allosteric binding mechanisms for targeting PKC, as well as novel drug platforms, such as modified peptides. A major goal is to design protein kinase modulators with enhanced selectivity and improved pharmacological properties. To this end, we use molecular docking analysis to predict the mechanisms of action for inhibitor-kinase interactions that can facilitate the development of next-generation PKC modulators.
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Affiliation(s)
- Mulate Zerihun
- The Azrieli Faculty of Medicine in the Galilee, Bar-Ilan University, Henrietta Szold St. 8, P.O. Box 1589, Safed 1311502, Israel; (M.Z.); (S.S.)
| | - Samuel J. S. Rubin
- Department of Medicine, School of Medicine, Stanford University, 300 Pasteur Drive, Stanford, CA 94305, USA;
| | - Shmuel Silnitsky
- The Azrieli Faculty of Medicine in the Galilee, Bar-Ilan University, Henrietta Szold St. 8, P.O. Box 1589, Safed 1311502, Israel; (M.Z.); (S.S.)
| | - Nir Qvit
- The Azrieli Faculty of Medicine in the Galilee, Bar-Ilan University, Henrietta Szold St. 8, P.O. Box 1589, Safed 1311502, Israel; (M.Z.); (S.S.)
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Zhou L, Matsushima GK. Tyro3, Axl, Mertk receptor-mediated efferocytosis and immune regulation in the tumor environment. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2021; 361:165-210. [PMID: 34074493 DOI: 10.1016/bs.ircmb.2021.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Three structurally related tyrosine receptor cell surface kinases, Tyro3, Axl, and Mertk (TAM) have been recognized to modulate immune function, tissue homeostasis, cardiovasculature, and cancer. The TAM receptor family appears to operate in adult mammals across multiple cell types, suggesting both widespread and specific regulation of cell functions and immune niches. TAM family members regulate tissue homeostasis by monitoring the presence of phosphatidylserine expressed on stressed or apoptotic cells. The detection of phosphatidylserine on apoptotic cells requires intermediary molecules that opsonize the dying cells and tether them to TAM receptors on phagocytes. This complex promotes the engulfment of apoptotic cells, also known as efferocytosis, that leads to the resolution of inflammation and tissue healing. The immune mechanisms dictating these processes appear to fall upon specific family members or may involve a complex of different receptors acting cooperatively to resolve and repair damaged tissues. Here, we focus on the role of TAM receptors in triggering efferocytosis and its consequences in the regulation of immune responses in the context of inflammation and cancer.
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Affiliation(s)
- Liwen Zhou
- UNC Neuroscience Center, University of North Carolina-CH, Chapel Hill, NC, United States
| | - Glenn K Matsushima
- UNC Neuroscience Center, University of North Carolina-CH, Chapel Hill, NC, United States; UNC Department of Microbiology & Immunology, University of North Carolina-CH, Chapel Hill, NC, United States; UNC Integrative Program for Biological & Genome Sciences, University of North Carolina-CH, Chapel Hill, NC, United States.
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Voices from the dead: The complex vocabulary and intricate grammar of dead cells. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 116:1-90. [PMID: 31036289 DOI: 10.1016/bs.apcsb.2019.02.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Of the roughly one million cells per second dying throughout the body, the vast majority dies by apoptosis, the predominant form of regulated cell death in higher organisms. Long regarded as mere waste, apoptotic cells are now recognized as playing a prominent and active role in homeostatic maintenance, especially resolution of inflammation, and in the sculpting of tissues during development. The activities associated with apoptotic cells are continually expanding, with more recent studies demonstrating their ability to modulate such vital functions as proliferation, survival, differentiation, metabolism, migration, and angiogenesis. In each case, the role of apoptotic cells is active, exerting their effects via new activities acquired during the apoptotic program. Moreover, the capacity to recognize and respond to apoptotic cells is not limited to professional phagocytes. Most, if not all, cells receive and integrate an array of signals from cells dying in their vicinity. These signals comprise a form of biochemical communication. As reviewed in this chapter, this communication is remarkably sophisticated; each of its three critical steps-encoding, transmission, and decoding of the apoptotic cell's "message"-is endowed with exquisite robustness. Together, the abundance and intricacy of the variables at each step comprise the vocabulary and grammar of the language by which dead cells achieve their post-mortem voice. The combinatorial complexity of the resulting communication network permits dying cells, through the signals they emit and the responses those signals elicit, to partake of an expanded role in homeostasis, acting as both sentinels of environmental change and agents of adaptation.
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Kimani SG, Kumar S, Davra V, Chang YJ, Kasikara C, Geng K, Tsou WI, Wang S, Hoque M, Boháč A, Lewis-Antes A, De Lorenzo MS, Kotenko SV, Birge RB. Normalization of TAM post-receptor signaling reveals a cell invasive signature for Axl tyrosine kinase. Cell Commun Signal 2016; 14:19. [PMID: 27595981 PMCID: PMC5011882 DOI: 10.1186/s12964-016-0142-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Accepted: 08/26/2016] [Indexed: 12/11/2022] Open
Abstract
Background Tyro3, Axl, and Mertk (TAMs) are a family of three conserved receptor tyrosine kinases that have pleiotropic roles in innate immunity and homeostasis and when overexpressed in cancer cells can drive tumorigenesis. Methods In the present study, we engineered EGFR/TAM chimeric receptors (EGFR/Tyro3, EGFR/Axl, and EGF/Mertk) with the goals to interrogate post-receptor functions of TAMs, and query whether TAMs have unique or overlapping post-receptor activation profiles. Stable expression of EGFR/TAMs in EGFR-deficient CHO cells afforded robust EGF inducible TAM receptor phosphorylation and activation of downstream signaling. Results Using a series of unbiased screening approaches, that include kinome-view analysis, phosphor-arrays, RNAseq/GSEA analysis, as well as cell biological and in vivo readouts, we provide evidence that each TAM has unique post-receptor signaling platforms and identify an intrinsic role for Axl that impinges on cell motility and invasion compared to Tyro3 and Mertk. Conclusion These studies demonstrate that TAM show unique post-receptor signatures that impinge on distinct gene expression profiles and tumorigenic outcomes. Electronic supplementary material The online version of this article (doi:10.1186/s12964-016-0142-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stanley G Kimani
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Sushil Kumar
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Viralkumar Davra
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Yun-Juan Chang
- Rutgers, Biomedical and Health Sciences, OIT/High Performance and Research Computing, 185 South Orange Ave, Newark, NJ, 07103, USA
| | - Canan Kasikara
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Ke Geng
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Wen-I Tsou
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Shenyan Wang
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Mainul Hoque
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Genomics Research Program, Rutgers- New Jersey Medical School, 185 South Orange Ave, Newark, NJ, 07103, USA
| | - Andrej Boháč
- Department of Organic Chemistry, Comenius University in Bratislava, Faculty of Natural Sciences, Mlynská dolina, Ilkovičova 6, 842 15, Bratislava, Slovakia.,Biomagi, Ltd, Mamateyova 26, 851 04, Bratislava, Slovakia
| | - Anita Lewis-Antes
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Mariana S De Lorenzo
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Sergei V Kotenko
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA
| | - Raymond B Birge
- Rutgers, Department of Microbiology, Biochemistry and Molecular Genetics, Cancer Center, Rutgers- New Jersey Medical School, 205 South Orange Ave, Newark, NJ, 07103, USA.
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Suppression of macrophage-mediated phagocytosis of apoptotic cells by soluble β-glucan due to a failure of PKC-βII translocation. Int Immunopharmacol 2016; 31:195-9. [DOI: 10.1016/j.intimp.2015.12.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2015] [Revised: 12/18/2015] [Accepted: 12/21/2015] [Indexed: 11/17/2022]
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McCubbrey AL, Nelson JD, Stolberg VR, Blakely PK, McCloskey L, Janssen WJ, Freeman CM, Curtis JL. MicroRNA-34a Negatively Regulates Efferocytosis by Tissue Macrophages in Part via SIRT1. THE JOURNAL OF IMMUNOLOGY 2015; 196:1366-75. [PMID: 26718338 DOI: 10.4049/jimmunol.1401838] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 11/19/2015] [Indexed: 01/22/2023]
Abstract
Apoptotic cell (AC) clearance (efferocytosis) is an evolutionarily conserved process essential for immune health, particularly to maintain self-tolerance. Despite identification of many recognition receptors and intracellular signaling components of efferocytosis, its negative regulation remains incompletely understood and has not previously been known to involve microRNAs (miRs). In this article, we show that miR-34a (gene ID 407040), well recognized as a p53-dependent tumor suppressor, mediates coordinated negative regulation of efferocytosis by resident murine and human tissue macrophages (Mø). The miR-34a expression varied greatly between Mø from different tissues, correlating inversely with their capacity for AC uptake. Transient or genetic knockdown of miR-34a increased efferocytosis, whereas miR-34a overexpression decreased efferocytosis, without altering recognition of live, necrotic, or Ig-opsonized cells. The inhibitory effect of miR-34a was mediated both by reduced expression of Axl, a receptor tyrosine kinase known to recognize AC, and of the deacetylase silent information regulator T1, which had not previously been linked to efferocytosis by tissue Mø. Exposure to AC downregulated Mø miR-34a expression, resulting in a positive feedback loop that increased subsequent capacity to engulf AC. These findings demonstrate that miR-34a both specifically regulates and is regulated by efferocytosis. Given the ability of efferocytosis to polarize ingesting Mø uniquely and to reduce their host-defense functions, dynamic negative regulation by miR-34a provides one means of fine-tuning Mø behavior toward AC in specific tissue environments with differing potentials for microbial exposure.
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Affiliation(s)
- Alexandra L McCubbrey
- Graduate Program in Immunology, University of Michigan Health System, Ann Arbor, MI 48109
| | - Joshua D Nelson
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109
| | | | - Pennelope K Blakely
- Department of Neurology, University of Michigan Health System, Ann Arbor, MI 48109
| | - Lisa McCloskey
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109
| | - William J Janssen
- Division of Pulmonary Sciences and Critical Care Medicine, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO 80045; Department of Medicine, National Jewish Health, Denver, CO 80262; and
| | - Christine M Freeman
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109; Research Service, VA Ann Arbor Healthcare System, Ann Arbor, MI 48105
| | - Jeffrey L Curtis
- Graduate Program in Immunology, University of Michigan Health System, Ann Arbor, MI 48109; Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48109; Pulmonary and Critical Care Medicine Section, VA Ann Arbor Healthcare System, Ann Arbor, MI 48105
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McCubbrey AL, Sonstein J, Ames TM, Freeman CM, Curtis JL. Glucocorticoids relieve collectin-driven suppression of apoptotic cell uptake in murine alveolar macrophages through downregulation of SIRPα. THE JOURNAL OF IMMUNOLOGY 2012; 189:112-9. [PMID: 22615206 DOI: 10.4049/jimmunol.1200984] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The lung environment actively inhibits apoptotic cell (AC) uptake by alveolar macrophages (AMøs) via lung collectin signaling through signal regulatory protein α (SIRPα). Even brief glucocorticoid (GC) treatment during maturation of human blood monocyte-derived or murine bone marrow-derived macrophages (Møs) increases their AC uptake. Whether GCs similarly impact differentiated tissue Møs and the mechanisms for this rapid response are unknown and important to define, given the widespread therapeutic use of inhaled GCs. We found that the GC fluticasone rapidly and dose-dependently increased AC uptake by murine AMøs without a requirement for protein synthesis. Fluticasone rapidly suppressed AMø expression of SIRPα mRNA and surface protein, and also activated a more delayed, translation-dependent upregulation of AC recognition receptors that was not required for the early increase in AC uptake. Consistent with a role for SIRPα suppression in rapid GC action, murine peritoneal Møs that had not been exposed to lung collectins showed delayed, but not rapid, increase in AC uptake. However, pretreatment of peritoneal Møs with the lung collectin surfactant protein D inhibited AC uptake, and fluticasone treatment rapidly reversed this inhibition. Thus, GCs act not only by upregulating AC recognition receptors during Mø maturation but also via a novel rapid downregulation of SIRPα expression by differentiated tissue Møs. Release of AMøs from inhibition of AC uptake by lung collectins may, in part, explain the beneficial role of inhaled GCs in inflammatory lung diseases, especially emphysema, in which there is both increased lung parenchymal cell apoptosis and defective AC uptake by AMøs.
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Affiliation(s)
- Alexandra L McCubbrey
- Graduate Program in Immunology, University of Michigan Health System, Ann Arbor, MI 48109, USA
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Curtis JL, Todt JC, Hu B, Osterholzer JJ, Freeman CM. Tyro3 receptor tyrosine kinases in the heterogeneity of apoptotic cell uptake. Front Biosci (Landmark Ed) 2009; 14:2631-46. [PMID: 19273223 DOI: 10.2741/3401] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Mononuclear phagocytes comprise a mobile, broadly dispersed and highly adaptable system that lies at the very epicenter of host defense against pathogens and the interplay of the innate and adaptive arms of immunity. Understanding the molecular mechanisms that control the response of mononuclear phagocytes to apoptotic cells and the anti-inflammatory consequences of that response is an important goal with implications for multiple areas of biomedical sciences. This review details current understanding of the heterogeneity of apoptotic cell uptake by different members of the mononuclear phagocyte family in humans and mice. It also recounts the unique role of the Tyro3 family of receptor tyrosine kinases, best characterized for Mertk, in the signal transduction leading both to apoptotic cell ingestion and the anti-inflammatory effects that result.
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Affiliation(s)
- Jeffrey L Curtis
- Pulmonary and Critical Care Medicine, Department of Veterans Affairs Healthsystem and University of Michigan Health System, Ann Arbor, MI 48105, USA.
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Linger RMA, Keating AK, Earp HS, Graham DK. TAM receptor tyrosine kinases: biologic functions, signaling, and potential therapeutic targeting in human cancer. Adv Cancer Res 2008; 100:35-83. [PMID: 18620092 DOI: 10.1016/s0065-230x(08)00002-x] [Citation(s) in RCA: 539] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Tyro-3, Axl, and Mer constitute the TAM family of receptor tyrosine kinases (RTKs) characterized by a conserved sequence within the kinase domain and adhesion molecule-like extracellular domains. This small family of RTKs regulates an intriguing mix of processes, including cell proliferation/survival, cell adhesion and migration, blood clot stabilization, and regulation of inflammatory cytokine release. Genetic or experimental alteration of TAM receptor function can contribute to a number of disease states, including coagulopathy, autoimmune disease, retinitis pigmentosa, and cancer. In this chapter, we first provide a comprehensive review of the structure, regulation, biologic functions, and downstream signaling pathways of these receptors. In addition, we discuss recent evidence which suggests a role for TAM receptors in oncogenic mechanisms as family members are overexpressed in a spectrum of human cancers and have prognostic significance in some. Possible strategies for targeted inhibition of the TAM family in the treatment of human cancer are described. Further research will be necessary to evaluate the full clinical implications of TAM family expression and activation in cancer.
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Affiliation(s)
- Rachel M A Linger
- Department of Pediatrics, University of Colorado at Denver and Health Sciences Center, Aurora, CO, USA
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Todt JC, Hu B, Curtis JL. The scavenger receptor SR-A I/II (CD204) signals via the receptor tyrosine kinase Mertk during apoptotic cell uptake by murine macrophages. J Leukoc Biol 2008; 84:510-8. [PMID: 18511575 DOI: 10.1189/jlb.0307135] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Apoptotic cells (AC) must be cleared by macrophages (Mø) to resolve inflammation effectively. Mertk and scavenger receptor A (SR-A) are two of many receptors involved in AC clearance. As SR-A lacks enzymatic activity or evident intracellular signaling motifs, yet seems to signal in some cell types, we hypothesized that SR-A signals via Mer receptor tyrosine kinase (Mertk), which contains a multisubstrate docking site. We induced apoptosis in murine thymocytes by dexamethasone and used Western blotting and immunoprecipitation to analyze the interaction of Mertk and SR-A in the J774A.1 (J774) murine Mø cell line and in peritoneal Mø of wild-type mice and SR-A-/- mice. Phagocytosis (but not adhesion) of AC by J774 was inhibited by anti-SR-A or function-blocking SR-A ligands. In resting J774, SR-A was associated minimally with unphosphorylated (monomeric) Mertk; exposure to AC induced a time-dependent increase in association of SR-A with Mertk in a direct or indirect manner. Anti-SR-A inhibited AC-induced phosphorylation of Mertk and of phospholipase Cgamma2, essential steps in AC ingestion. Relative to tissue Mø of wild-type mice, AC-induced Mertk phosphorylation was reduced and delayed in tissue Mø of SR-A-/- mice, as was in vitro AC ingestion at early time-points. Thus, during AC uptake by murine Mø, SR-A is essential for optimal phosphorylation of Mertk and subsequent signaling required for AC ingestion. These data support the Mertk/SR-A complex as a potential target to manipulate AC clearance and hence, resolution of inflammation and infections.
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Affiliation(s)
- Jill C Todt
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
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Tibrewal N, Wu Y, D'mello V, Akakura R, George TC, Varnum B, Birge RB. Autophosphorylation docking site Tyr-867 in Mer receptor tyrosine kinase allows for dissociation of multiple signaling pathways for phagocytosis of apoptotic cells and down-modulation of lipopolysaccharide-inducible NF-kappaB transcriptional activation. J Biol Chem 2007; 283:3618-3627. [PMID: 18039660 DOI: 10.1074/jbc.m706906200] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Efficient clearance of apoptotic cells is essential for tissue homeostasis, allowing for cellular turnover without inflammatory consequences. The Mer (Nyk and c-Eyk) receptor tyrosine kinase (Mertk) is involved in two aspects of apoptotic cell clearance by acting as a receptor for Gas6, a gamma-carboxylated phosphatidylserine-binding protein that bridges apoptotic and viable cells. First, Mertk acts in a bona fide engulfment pathway in concert with alphavbeta5 integrin by regulating cytoskeletal assemblages, and second, it acts as a negative regulator for inflammation by down-modulating pro-inflammatory signals mediated from bacterial lipopolysaccharide-Toll-like receptor 4 (TLR4) signaling, and hence recapitulating anti-inflammatory immune modulation by apoptotic cells. Here we describe Mertk post-receptor events that govern phagocytosis and cytoskeletal signaling are principally mediated by autophosphorylation site Tyr-867. Using the Mertk Y867F mutant and pharmacological inhibitors, we show that Tyr-867 is required for phosphatidylinositol 3-kinase and phospholipase Cgamma2 activation; their activation in turn elicits protein kinase C-dependent signals that act on the actin cytoskeleton. Although Mertk(Y867F) blocked the tyrosine phosphorylation of FAK on Tyr-861 and p130(cas) and also abrogated the phagocytosis of apoptotic cells, this mutant did not suppress lipopolysaccharide-inducible NF-kappaB transcription, nor was NF-kappaB activation dependent on the protein kinase C inhibitor, calphostin C. Finally, unlike the cytoskeletal events associated with Tyr-867 autophosphorylation, the trans-inhibition of NF-kappaB occurred in a postnuclear-dependent fashion independent of cytosolic IkappaB phosphorylation and p65/RelA sequestration. Taken together, these data suggest that Mertk has distinct and separable effects for phagocytosis and for resolving inflammation, providing a molecular rationale for how immune licensing and inflammation can be dissociated from phagocytosis in a single phagocytic receptor.
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Affiliation(s)
- Nitu Tibrewal
- Department of Biochemistry & Molecular Biology, University of Medicine and Dentistry of New Jersey (UMDNJ)-New Jersey Medical School, Newark New Jersey 07103
| | - Yi Wu
- Department of Biochemistry & Molecular Biology, University of Medicine and Dentistry of New Jersey (UMDNJ)-New Jersey Medical School, Newark New Jersey 07103
| | - Veera D'mello
- Department of Biochemistry & Molecular Biology, University of Medicine and Dentistry of New Jersey (UMDNJ)-New Jersey Medical School, Newark New Jersey 07103
| | - Reiko Akakura
- Department of Biochemistry & Molecular Biology, University of Medicine and Dentistry of New Jersey (UMDNJ)-New Jersey Medical School, Newark New Jersey 07103
| | | | - Brian Varnum
- Inflammation Department, Amgen Pharmaceuticals, Amgen, Inc., Thousand Oaks, California 91320
| | - Raymond B Birge
- Department of Biochemistry & Molecular Biology, University of Medicine and Dentistry of New Jersey (UMDNJ)-New Jersey Medical School, Newark New Jersey 07103.
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Ladrech S, Wang J, Simonneau L, Puel JL, Lenoir M. Macrophage contribution to the response of the rat organ of Corti to amikacin. J Neurosci Res 2007; 85:1970-9. [PMID: 17497672 DOI: 10.1002/jnr.21335] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Transdifferentiation of nonsensory supporting cells into sensory hair cells occurs naturally in the damaged avian inner ear. Such transdifferentiation was achieved experimentally in the cochlea of deaf guinea pigs through Atoh 1 gene transfection. Supporting cells may therefore serve as targets for transdifferentiation therapy. Supporting cells rapidly degenerate after hair cell disappearance, however, limiting the therapeutic window for gene transfer. We studied the time course of ultrastructural and phenotypical changes occurring in Deiters cells (hair cell supporting cells) after ototoxic treatment in the rat. The presence of macrophages in the cochlea was also investigated, to study any deleterious effects they may have on pathologic tissues. One week after treatment most hair cells had disappeared. Deiters cells no longer expressed the glial marker vimentin but instead displayed typical hair cell markers, the calcium binding proteins calbindin and parvalbumin. This suggests that a process of transdifferentiation of Deiters cells into hair cells was activated. By 3 weeks post-treatment, however, the Deiters cells began to degenerate and by 10 weeks post-treatment the organ of Corti was degraded fully. Interestingly, a marked increase in macrophage density was seen after the end of amikacin treatment to 10 weeks post-treatment. This suggests chronic inflammation is involved in epithelium degeneration. Consequently, early treatments with anti-inflammatory factors might promote supporting cell survival, thus improving the efficacy of more specific strategies aimed to regenerate hair cells from nonsensory cells.
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Affiliation(s)
- Sabine Ladrech
- INSERM, U.583, Laboratoire de Physiopathologie et Thérapie des Déficits Sensoriels et Moteurs, Montpellier, France
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Griger Z, Páyer E, Kovács I, Tóth BI, Kovács L, Sipka S, Bíró T. Protein kinase C-β and -δ isoenzymes promote arachidonic acid production and proliferation of MonoMac-6 cells. J Mol Med (Berl) 2007; 85:1031-42. [PMID: 17549442 DOI: 10.1007/s00109-007-0209-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2006] [Revised: 02/08/2007] [Accepted: 03/30/2007] [Indexed: 10/23/2022]
Abstract
In this study, we investigated the putative roles of certain protein kinase C (PKC) isoenzymes in the regulation of proliferation and arachidonic acid (AA) release in the human monocytoid MonoMac-6 cell line. Experiments employing specific PKC inhibitors and molecular biological methods (RNA-interference, recombinant overexpression) revealed that the two dominantly expressed isozymes, i.e., the "conventional" cPKCbeta and the "novel" nPKCdelta, promote AA production and cellular proliferation. In addition, using different phospholipase A(2) (PLA(2)) inhibitors, we were able to show that the calcium-independent iPLA(2) as well as diacylglycerol lipase (but not the cytosolic PLA(2)) function as "downstream" targets of cPKCbeta and nPKCdelta. In addition, we have also found that, among the other existing PKC isoforms, cPKCalpha plays a minor inhibitory role, whereas nPKCvarepsilon and aPKCzeta apparently do not regulate these cellular processes. In conclusion, in this paper we provide the first evidence that certain PKC isoforms play pivotal, specific, and (at least partly) antagonistic roles in the regulation of AA production and cellular proliferation of human monocytoid MonoMac-6 cells.
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Affiliation(s)
- Zoltán Griger
- Department of Physiology, University of Debrecen, Research Center for Molecular Medicine, Medical and Health Science Center, Nagyerdei krt. 98., 4032, Debrecen, Hungary
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Ma HT, Lin WW, Zhao B, Wu WT, Huang W, Li Y, Jones NL, Kruth HS. Protein kinase C β and δ isoenzymes mediate cholesterol accumulation in PMA-activated macrophages. Biochem Biophys Res Commun 2006; 349:214-20. [PMID: 16930534 DOI: 10.1016/j.bbrc.2006.08.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2006] [Accepted: 08/05/2006] [Indexed: 10/24/2022]
Abstract
Previously, we showed that PMA activation of human monocyte-derived macrophages stimulates macropinocytosis (i.e., fluid-phase endocytosis) of LDL and transforms these macrophages into foam cells. The current study aimed to learn which PKC isoenzymes mediate cholesterol accumulation in PMA-activated human macrophages incubated with LDL. Cholesterol accumulation by PMA-activated macrophages incubated with LDL was nearly completely inhibited (>85%) by the pan PKC inhibitors Go6850, Go6983, and RO 32-0432, but only was inhibited about 50% by the classical group PKC inhibitor, Go6976. This indicated that cholesterol accumulation was mediated by both a classical group and some other PKC isoenzyme. PKC beta was determined to be the classical group isoenzyme that mediated PMA-stimulated cholesterol accumulation. A pseudosubstrate myristoylated peptide inhibitor of PKC alpha and beta showed partial inhibition (congruent with 50%) of cholesterol accumulation. However, a small molecule inhibitor of PKC alpha, HBDDE, show minimal inhibition of cholesterol accumulation while a small molecule inhibitor of PKC beta, LY333513, could completely account for the inhibition of cholesterol accumulation by the classical group PKC isoenzyme. Thus, our findings show that beta and some other PKC isoenzyme, most likely delta, mediate cholesterol accumulation when macropinocytosis of LDL is stimulated in PMA-activated human monocyte-derived macrophages.
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Affiliation(s)
- Hong-Tao Ma
- Section of Experimental Atherosclerosis, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1422, USA
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15
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Liu Y, Furuta K, Teshima R, Shirata N, Sugimoto Y, Ichikawa A, Tanaka S. Critical Role of Protein Kinase C βII in Activation of Mast Cells by Monomeric IgE. J Biol Chem 2005; 280:38976-81. [PMID: 16183638 DOI: 10.1074/jbc.m506351200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Accumulating evidence suggests that IgE-mediated activation of mast cells occurs even in the absence of antigen, which is referred to as "monomeric IgE" responses. Although monomeric IgE was found to induce a wide variety of responses, such as up-regulation of the FcepsilonRI, survival, cytokine production, histamine synthesis, and adhesion to fibronectin, it remains to be clarified how mast cells are activated in the absence of antigen. It has been controversial whether monomeric IgE responses are mediated by a similar signaling mechanism to antigen stimulation, although recent studies suggest that IgE can induce the FcepsilonRI aggregation even in the absence of antigen. In this study, we focused on the role of conventional protein kinase C (cPKC), since this response is suppressed by a specific inhibitor for cPKC. Monomeric IgE-induced Ca(2+) influx was not observed in a mouse mastocytoma cell line, which lacks the expression of PKCbetaII, although Ca(2+) influx induced by cross-linking of the FcepsilonRI was intact. Transfection of PKCbetaII cDNA was found to restore the Ca(2+) influx induced by monomeric IgE in this cell line. Furthermore, the dominant negative form of PKCbetaII (PKCbetaII/T500V) significantly suppressed the Ca(2+) influx, histamine synthesis, and interleukin-6 production in another mouse mast cell line, which is highly sensitive to monomeric IgE. Expression of PKCbetaII/T500V was found not to affect the antigen-induced responses. These results suggest that PKCbetaII plays a critical role in monomeric IgE responses, but not in antigen responses.
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Affiliation(s)
- Ying Liu
- Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
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16
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Huynh MLN, Malcolm KC, Kotaru C, Tilstra JA, Westcott JY, Fadok VA, Wenzel SE. Defective apoptotic cell phagocytosis attenuates prostaglandin E2 and 15-hydroxyeicosatetraenoic acid in severe asthma alveolar macrophages. Am J Respir Crit Care Med 2005; 172:972-9. [PMID: 16040786 DOI: 10.1164/rccm.200501-035oc] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
RATIONALE Clearance of apoptotic cells is crucial to the resolution of inflammation and development of fibrosis, but the process is not well understood in normal or diseased human lungs. OBJECTIVES To determine phagocytosis of apoptotic cells by primary human alveolar macrophages and whether defects in uptake of apoptotic cells are associated with decreases in antiinflammatory/antifibrotic mediators. METHODS Human bronchoalveolar lavage macrophages (AMphis) from normal control subjects and subjects with mild-moderate or severe asthma were examined in vitro for phagocytosis of apoptotic human T-cell line Jurkats and secretion of inflammatory mediators. MEASUREMENTS AND MAIN RESULTS AMphis from normal subjects and patients with mild-moderate asthma were able to phagocytose apoptotic cells in response to LPS, resulting in an induction of the antifibrotic and/or antiinflammatory eicosanoids, prostaglandin E2 (PGE2) and 15-hydroxyeicosatetraenoic acid (HETE). In contrast, AMphis from patients with severe asthma had defective LPS-stimulated uptake of apoptotic cells, with associated failure to induce PGE2 and 15-HETE. In addition, LPS-stimulated basal levels of tumor necrosis factor alpha and granulocyte-macrophage colony-stimulating factor were reduced in all patients with asthma, whereas PGE2 and 15-HETE were reduced only in patients with severe asthma. Dexamethasone enhanced specific uptake of apoptotic cells in all subjects, while suppressing inflammatory mediator secretion. CONCLUSIONS A decrease in AMphis LPS-responsiveness in severe asthma is manifested by defective apoptotic cell uptake and reduces secretion of inflammatory mediators. This may contribute to the chronicity of inflammation and remodeling in lungs of patients with asthma.
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Affiliation(s)
- Mai-Lan N Huynh
- Division of Pulmonary Sciences and Critical Care Medicine, University of Colorado Health Sciences Center, National Jewish Medical and Research Center, Denver, CO 80206, USA.
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17
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Serezani CHC, Aronoff DM, Jancar S, Mancuso P, Peters-Golden M. Leukotrienes enhance the bactericidal activity of alveolar macrophages against Klebsiella pneumoniae through the activation of NADPH oxidase. Blood 2005; 106:1067-75. [PMID: 15718414 PMCID: PMC1895163 DOI: 10.1182/blood-2004-08-3323] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Leukotrienes (LTs) are lipid mediators that participate in inflammatory diseases and innate immune function. We sought to investigate the importance of LTs in regulating the microbicidal activity of alveolar macrophages (AMs) and the molecular mechanisms by which this occurs. The role of LTs in enhancing AM microbicidal activity was evaluated pharmacologically and genetically using in vitro challenge with Klebsiella pneumoniae. Exogenous LTs increased AM microbicidal activity in a dose- and receptor-dependent manner, and endogenous production of LTs was necessary for optimal killing. Leukotriene B4 (LTB4) was more potent than cysteinyl LTs. An important role for nicotinamide adenine dinucleotide (NADPH) oxidase in LT-induced microbicidal activity was indicated by the fact that bacterial killing was abrogated by the NADPH oxidase inhibitor diphenyleneiodonium (DPI; 10 microM) and in AMs derived from gp91phox-deficient mice. By contrast, LT-induced microbicidal activity was independent of the generation of nitric oxide. LTs increased H2O2 production, and LTB4 was again the more potent agonist. Both classes of LTs elicited translocation of p47phox to the cell membrane, and LTB4 induced phosphorylation of p47phox in a manner dependent on protein kinase C-delta (PKC-delta) activity. In addition, the enhancement of microbicidal activity by LTs was also dependent on PKC-delta activity. Our results demonstrate that LTs, especially LTB4, enhanceAM microbicidal activity through the PKC-delta-dependent activation of NADPH oxidase.
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Affiliation(s)
- Carlos H C Serezani
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109-0642, USA
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18
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Jennings JH, Linderman DJ, Hu B, Sonstein J, Curtis JL. Monocytes recruited to the lungs of mice during immune inflammation ingest apoptotic cells poorly. Am J Respir Cell Mol Biol 2004; 32:108-17. [PMID: 15563692 PMCID: PMC2267037 DOI: 10.1165/rcmb.2004-0108oc] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Apoptotic cells must be cleared to resolve inflammation, but few resident alveolar macrophages (AMo) from normal lungs ingest apoptotic cells. We examined how Mo ingestion of apoptotic cells is altered during immune inflammation induced by intratracheal challenge of primed C57BL/6 mice using sheep red blood cells. Resident AMo were labeled in situ before challenge using intravenous PKH26 to distinguish them from recruited monocytes. Using flow cytometry, we identified phagocytosis of fluorescently-labeled apoptotic thymocytes by alveolar mononuclear phagocytes in vitro and in vivo, and measured surface molecule expression. Intratracheal challenge induced rapid recruitment of monocytes, peaking at Day 3 and decreasing thereafter, whereas numbers of resident AMo did not change significantly. At all times, the percentage of phagocytes ingesting apoptotic thymocytes in vitro was greater among resident AMo (28-45%) than among recruited monocytes (9-19%), but was low in both cell types relative to ingestion of immunoglobulin-opsonized targets. There was also a nonsignificant trend toward lower ingestion by monocytes in vivo. MerTK, a receptor tyrosine kinase crucial for apoptotic cell phagocytosis, was expressed by resident AMo, but not by recruited monocytes. Relative to resident AMo, monocytes recruited to the alveolus ingest apoptotic cells meagerly, possibly due to absence of MerTK expression.
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Affiliation(s)
- Jeffrey H Jennings
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48105, USA
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19
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Punturieri A, Alviani RS, Polak T, Copper P, Sonstein J, Curtis JL. Specific engagement of TLR4 or TLR3 does not lead to IFN-beta-mediated innate signal amplification and STAT1 phosphorylation in resident murine alveolar macrophages. THE JOURNAL OF IMMUNOLOGY 2004; 173:1033-42. [PMID: 15240691 PMCID: PMC2701405 DOI: 10.4049/jimmunol.173.2.1033] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The innate immune response must be mobilized promptly yet judiciously via TLRs to protect the lungs against pathogens. Stimulation of murine peritoneal macrophage (PMphi) TLR4 or TLR3 by pathogen-associated molecular patterns (PAMPs) typically induces type I IFN-beta, leading to autocrine activation of the transcription factor STAT1. Because it is unknown whether STAT1 plays a similar role in the lungs, we studied the response of resident alveolar macrophages (AMphi) or control PMphi from normal C57BL/6 mice to stimulation by PAMPs derived from viruses (polyriboinosinic:polyribocytidylic acid, specific for TLR3) or bacteria (Pam(3)Cys, specific for TLR2, and repurified LPS, specific for TLR4). AMphi did not activate STAT1 by tyrosine phosphorylation on Y701 following stimulation of any of these three TLRs, but readily did so in response to exogenous IFN-beta. This unique AMphi response was not due to altered TLR expression, or defective immediate-early gene response, as measured by expression of TNF-alpha and three beta chemokines. Instead, AMphi differed from PMphi in not producing bioactive IFN-beta, as confirmed by ELISA and by the failure of supernatants from TLR-stimulated AMphi to induce STAT1 phosphorylation in PMphi. Consequently, AMphi did not produce the microbicidal effector molecule NO following TLR4 or TLR3 stimulation unless exogenous IFN-beta was also added. Thus, murine AMphi respond to bacterial or viral PAMPs by producing inflammatory cytokines and chemokines, but because they lack the feed-forward amplification typically mediated by autocrine IFN-beta secretion and STAT1 activation, require exogenous IFN to mount a second phase of host defense.
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Affiliation(s)
- Antonello Punturieri
- Pulmonary and Critical Care Medicine Section, and Research Service, Department of Veterans Affairs Medical Center, Ann Arbor, MI 48105, USA.
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20
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De Simone R, Ajmone-Cat MA, Minghetti L. Atypical antiinflammatory activation of microglia induced by apoptotic neurons: possible role of phosphatidylserine-phosphatidylserine receptor interaction. Mol Neurobiol 2004; 29:197-212. [PMID: 15126686 DOI: 10.1385/mn:29:2:197] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2003] [Accepted: 10/03/2003] [Indexed: 11/11/2022]
Abstract
In the central nervous system (CNS), apoptosis plays an important role during development and is a primary pathogenic mechanism in several adult neurodegenerative diseases. A main feature of apoptotic cell death is the efficient and fast removal of dying cells by macrophages and nonprofessional phagocytes, without eliciting inflammation in the surrounding tissue. Apoptotic cells undergo several membrane changes, including the externalization of so-called "eat me" signals whose cognate receptors are present on professional phagocytes. Among these signals, the aminophospholipid phosphatidylserine (PS) appears to have a crucial and unique role in preventing the classical pro-inflammatory activation of macrophages, thus ensuring the silent and safe removal of apoptotic cells. Although extensively studied in the peripheral organs, the process of recognition and removal of apoptotic cells in the brain has only recently begun to be unraveled. Here, we summarize the evidence suggesting that upon interaction with PS-expressing apoptotic neurons, microglia may no longer promote the inflammatory cascade, but rather facilitate the elimination of damaged neurons through antiinflammatory and neuroprotective functions. We propose that the anti-inflammatory microglial phenotype induced through the activation of the specific PS receptor (PtdSerR), expressed by resting and activated microglial cells, could be relevant to the final outcome of neurodegenerative diseases, in which apoptosis seems to play a crucial role.
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Affiliation(s)
- Roberta De Simone
- Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Italy
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21
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Todt JC, Hu B, Curtis JL. The receptor tyrosine kinase MerTK activates phospholipase C gamma2 during recognition of apoptotic thymocytes by murine macrophages. J Leukoc Biol 2004; 75:705-13. [PMID: 14704368 PMCID: PMC2441598 DOI: 10.1189/jlb.0903439] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Apoptotic leukocytes must be cleared efficiently by macrophages (Mø). Apoptotic cell phagocytosis by Mø requires the receptor tyrosine kinase (RTK) MerTK (also known as c-Mer and Tyro12), the phosphatidylserine receptor (PS-R), and the classical protein kinase C (PKC) isoform betaII, which translocates to Mø membrane and cytoskeletal fractions in a PS-R-dependent manner. How these molecules cooperate to induce phagocytosis is unknown. As the phosphatidylinositol-specific phospholipase (PI-PLC) gamma2 is downstream of RTKs in some cell types and can activate classical PKCs, we hypothesized that MerTK signals via PLC gamma2. To test this hypothesis, we examined the interaction of MerTK and PLC gamma2 in resident, murine peritoneal (P)Mø and in the murine Mø cell line J774A.1 (J774) following exposure to apoptotic thymocytes. We found that as with PMø, J774 phagocytosis of apoptotic thymocytes was inhibited by antibody against MerTK. Western blotting and immunoprecipitation showed that exposure to apoptotic cells produced three time-dependent changes in PMø and J774: tyrosine phosphorylation of MerTK; association of PLC gamma2 with MerTK; and tyrosine phosphorylation of PLC gamma2. Cross-linking MerTK using antibody also induced phosphorylation of PLC gamma2 and its association with MerTK. A PI-PLC appears to be required for phagocytosis of apoptotic cells, as the PI-PLC inhibitor Et-18-OCH3 and the PLC inhibitor U73122, but not the inactive control U73343, blocked phagocytosis without impairing adhesion. On apoptotic cell adhesion to Mø, MerTK signals at least in part via PLC gamma2.
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Affiliation(s)
- Jill C. Todt
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
| | - Bin Hu
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
| | - Jeffrey L. Curtis
- Division of Pulmonary & Critical Care Medicine, Department of Internal Medicine, University of Michigan Health Care System, Ann Arbor, MI, USA
- Comprehensive Cancer Center, University of Michigan Health Care System, Ann Arbor, MI, USA
- Graduate Program in Immunology, University of Michigan Health Care System, Ann Arbor, MI, USA
- Pulmonary & Critical Care Medicine Section, Medical Service, Department of Veterans Affairs Care System, Ann Arbor, MI, USA
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22
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Hu B, Jennings JH, Sonstein J, Floros J, Todt JC, Polak T, Curtis JL. Resident murine alveolar and peritoneal macrophages differ in adhesion of apoptotic thymocytes. Am J Respir Cell Mol Biol 2003; 30:687-93. [PMID: 14527926 PMCID: PMC4138126 DOI: 10.1165/rcmb.2003-0255oc] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Apoptotic cells must be cleared efficiently by macrophages (Mø) to prevent autoimmunity, yet their ingestion impairs Mø microbicidal function. The principal murine resident lung phagocyte, the alveolar Mø (AMø), is specifically deficient at apoptotic cell ingestion, both in vitro and in vivo, compared with resident peritoneal Mø (PMø). To further characterize this deficiency, we assayed static adhesion in vitro using apoptotic thymocytes and resident AMø and PMø from normal C57BL/6 mice. Adhesion of apoptotic thymocytes by both types of Mø was rapid, specific, and cold-sensitive. Antibody against the receptor tyrosine kinase MerTK (Tyro12) blocked phagocytosis but not adhesion in both types of Mø. Surfactant protein A increased adhesion and phagocytosis by AMø, but not to the levels seen using PMø. Adhesion was largely cation-independent for PMø and calcium-dependent for AMø. Adhesion was not inhibited in either Mø type by mAbs against beta1 or beta3 integrins or scavenger receptor I/II (CD204), but AMø adhesion was inhibited by specific mAbs against CD11c/CD18. Thus, resident murine tissue Mø from different tissues depend on qualitatively disparate receptor systems to bind apoptotic cells. The decreased capacity of murine AMø to ingest apoptotic cells is only partially explained by reduced initial adhesion.
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Affiliation(s)
- Bin Hu
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Health System, Ann Arbor, MI 48105-2303, USA
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23
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Idiopathic Pulmonary Fibrosis. Proceedings of the 1st Annual Pittsburgh International Lung Conference. October 2002. Am J Respir Cell Mol Biol 2003; 29:S1-105. [PMID: 12936907 DOI: 10.1165/rcmb.2003-0159su] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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24
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Ajmone-Cat MA, De Simone R, Nicolini A, Minghetti L. Effects of phosphatidylserine on p38 mitogen activated protein kinase, cyclic AMP responding element binding protein and nuclear factor-kappaB activation in resting and activated microglial cells. J Neurochem 2003; 84:413-6. [PMID: 12559004 DOI: 10.1046/j.1471-4159.2003.01562.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In the last few years, the interaction between phosphatidylserine (PS), a phospholipid that becomes permanently exposed on the external cell surface in the early phases of apoptosis, and its specific receptor (PtdSerR) has emerged as a crucial event for the engulfing of apoptotic cells and for preventing the acquisition of pro-inflammatory functions by peripheral macrophages. Recently, we demonstrated that PtdSerR is expressed in microglial cultures purified from neonatal rat brain, and that PS-liposomes, used to mimic apoptotic cells, strongly reduce the lipopolysaccharide (LPS)-induced release of inflammatory mediators. Here, we show that in resting microglia, PS-liposomes induce cyclic AMP responding element binding protein (CREB) phosphorylation but do not activate nuclear factor-kappaB (NF-kappaB) and p38 mitogen-activated protein kinase (p38), in line with the non-inflammatory consequences of the recognition and removal of apoptotic cells by macrophages. In LPS-activated microglia, PS-liposomes did not affect NF-kappaB activation but inhibited the phosphorylation of p38 and delayed that of CREB. To our knowledge, this is the first biochemical evidence of the molecular signaling evoked by PS/PtdSerR interaction possibly related to repression of pro-inflammatory activities in microglial cells.
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Affiliation(s)
- M A Ajmone-Cat
- Laboratory of Pathophysiology, Istituto Superiore di Sanità, Rome, Italy
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