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Du R, Wang P, Tian N. CD3ζ-Mediated Signaling Protects Retinal Ganglion Cells in Glutamate Excitotoxicity of the Retina. Cells 2024; 13:1006. [PMID: 38920637 PMCID: PMC11201742 DOI: 10.3390/cells13121006] [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: 03/30/2024] [Revised: 05/28/2024] [Accepted: 06/06/2024] [Indexed: 06/27/2024] Open
Abstract
Excessive levels of glutamate activity could potentially damage and kill neurons. Glutamate excitotoxicity is thought to play a critical role in many CNS and retinal diseases. Accordingly, glutamate excitotoxicity has been used as a model to study neuronal diseases. Immune proteins, such as major histocompatibility complex (MHC) class I molecules and their receptors, play important roles in many neuronal diseases, while T-cell receptors (TCR) are the primary receptors of MHCI. We previously showed that a critical component of TCR, CD3ζ, is expressed by mouse retinal ganglion cells (RGCs). The mutation of CD3ζ or MHCI molecules compromises the development of RGC structure and function. In this study, we investigated whether CD3ζ-mediated molecular signaling regulates RGC death in glutamate excitotoxicity. We show that mutation of CD3ζ significantly increased RGC survival in NMDA-induced excitotoxicity. In addition, we found that several downstream molecules of TCR, including Src (proto-oncogene tyrosine-protein kinase) family kinases (SFKs) and spleen tyrosine kinase (Syk), are expressed by RGCs. Selective inhibition of an SFK member, Hck, or Syk members, Syk or Zap70, significantly increased RGC survival in NMDA-induced excitotoxicity. These results provide direct evidence to reveal the underlying molecular mechanisms that control RGC death under disease conditions.
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Affiliation(s)
- Rui Du
- Department of Ophthalmology and Visual Science, University of Utah School of Medicine, Salt Lake City, UT 84132, USA; (R.D.); (P.W.)
| | - Ping Wang
- Department of Ophthalmology and Visual Science, University of Utah School of Medicine, Salt Lake City, UT 84132, USA; (R.D.); (P.W.)
| | - Ning Tian
- Department of Ophthalmology and Visual Science, University of Utah School of Medicine, Salt Lake City, UT 84132, USA; (R.D.); (P.W.)
- Department of Neurobiology, University of Utah, Salt Lake City, UT 84132, USA
- Department of Biomedical Engineering, University of Utah, Salt Lake City, UT 84132, USA
- Veterans Affairs Medical Center, Salt Lake City, UT 84148, USA
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2
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Ubil E, Zahid KR. Structure and functions of Mer, an innate immune checkpoint. Front Immunol 2023; 14:1244170. [PMID: 37936688 PMCID: PMC10626544 DOI: 10.3389/fimmu.2023.1244170] [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: 06/22/2023] [Accepted: 10/09/2023] [Indexed: 11/09/2023] Open
Abstract
Immunotherapy is a promising therapeutic tool that promotes the elimination of cancerous cells by a patient's own immune system. However, in the clinical setting, the number of cancer patients benefitting from immunotherapy is limited. Identification and targeting of other immune subsets, such as tumor-associated macrophages, and alternative immune checkpoints, like Mer, may further limit tumor progression and therapy resistance. In this review, we highlight the key roles of macrophage Mer signaling in immune suppression. We also summarize the role of pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes in tumor onset and progression and how Mer structure and activation can be targeted therapeutically to alter activation state. Preclinical and clinical studies focusing on Mer kinase inhibition have demonstrated the potential of targeting this innate immune checkpoint, leading to improved anti-tumor responses and patient outcomes.
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Affiliation(s)
- Eric Ubil
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL, United States
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3
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Lieffrig SA, Gyimesi G, Mao Y, Finnemann SC. Clearance phagocytosis by the retinal pigment epithelial during photoreceptor outer segment renewal: Molecular mechanisms and relation to retinal inflammation. Immunol Rev 2023; 319:81-99. [PMID: 37555340 PMCID: PMC10615845 DOI: 10.1111/imr.13264] [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: 05/15/2023] [Accepted: 07/18/2023] [Indexed: 08/10/2023]
Abstract
Mammalian photoreceptor outer segment renewal is a highly coordinated process that hinges on timed cell signaling between photoreceptor neurons and the adjacent retinal pigment epithelial (RPE). It is a strictly rhythmic, synchronized process that underlies in part circadian regulation. We highlight findings from recently developed methods that quantify distinct phases of outer segment renewal in retinal tissue. At light onset, outer segments expose the conserved "eat-me" signal phosphatidylserine exclusively at their distal, most aged tip. A coordinated two-receptor efferocytosis process follows, in which ligands bridge outer segment phosphatidylserine with the RPE receptors αvβ5 integrin, inducing cytosolic signaling toward Rac1 and focal adhesion kinase/MERTK, and with MERTK directly, additionally inhibiting RhoA/ROCK and thus enabling F-actin dynamics favoring outer segment fragment engulfment. Photoreceptors and RPE persist for life with each RPE cell in the eye servicing dozens of overlying photoreceptors. Thus, RPE cells phagocytose more often and process more material than any other cell type. Mutant mice with impaired outer segment renewal largely retain functional photoreceptors and retinal integrity. However, when anti-inflammatory signaling in the RPE via MERTK or the related TYRO3 is lacking, catastrophic inflammation leads to immune cell infiltration that swiftly destroys the retina causing blindness.
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Affiliation(s)
- Stephanie A. Lieffrig
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
| | - Gavin Gyimesi
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
| | | | - Silvia C. Finnemann
- Center for Cancer, Genetic Diseases and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY
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4
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Kelvin JM, Chimenti ML, Zhang DY, Williams EK, Moore SG, Humber GM, Baxter TA, Birnbaum LA, Qui M, Zecca H, Thapa A, Jain J, Jui NT, Wang X, Fu H, Du Y, Kemp ML, Lam WA, Graham DK, DeRyckere D, Dreaden EC. Development of constitutively synergistic nanoformulations to enhance chemosensitivity in T-cell leukemia. J Control Release 2023; 361:470-482. [PMID: 37543290 PMCID: PMC10544718 DOI: 10.1016/j.jconrel.2023.07.045] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 06/27/2023] [Accepted: 07/28/2023] [Indexed: 08/07/2023]
Abstract
Advances in multiagent chemotherapy have led to recent improvements in survival for patients with acute lymphoblastic leukemia (ALL); however, a significant fraction do not respond to frontline chemotherapy or later relapse with recurrent disease, after which long-term survival rates remain low. To develop new, effective treatment options for these patients, we conducted a series of high-throughput combination drug screens to identify chemotherapies that synergize in a lineage-specific manner with MRX-2843, a small molecule dual MERTK and FLT3 kinase inhibitor currently in clinical testing for treatment of relapsed/refractory leukemias and solid tumors. Using experimental and computational approaches, we found that MRX-2843 synergized strongly-and in a ratio-dependent manner-with vincristine to inhibit both B-ALL and T-ALL cell line expansion. Based on these findings, we developed multiagent lipid nanoparticle formulations of these drugs that not only delivered defined drug ratios intracellularly in T-ALL, but also improved anti-leukemia activity following drug encapsulation. Synergistic and additive interactions were recapitulated in primary T-ALL patient samples treated with MRX-2843 and vincristine nanoparticle formulations, suggesting their clinical relevance. Moreover, the nanoparticle formulations reduced disease burden and prolonged survival in an orthotopic murine xenograft model of early thymic precursor T-ALL (ETP-ALL), with both agents contributing to therapeutic activity in a dose-dependent manner. In contrast, nanoparticles containing MRX-2843 alone were ineffective in this model. Thus, MRX-2843 increased the sensitivity of ETP-ALL cells to vincristine in vivo. In this context, the additive particles, containing a higher dose of MRX-2843, provided more effective disease control than the synergistic particles. In contrast, particles containing an even higher, antagonistic ratio of MRX-2843 and vincristine were less effective. Thus, both the drug dose and the ratio-dependent interaction between MRX-2843 and vincristine significantly impacted therapeutic activity in vivo. Together, these findings present a systematic approach to high-throughput combination drug screening and multiagent drug delivery that maximizes the therapeutic potential of combined MRX-2843 and vincristine in T-ALL and describe a novel translational agent that could be used to enhance therapeutic responses to vincristine in patients with T-ALL. This broadly generalizable approach could also be applied to develop other constitutively synergistic combination products for the treatment of cancer and other diseases.
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Affiliation(s)
- James M Kelvin
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA
| | - Madison L Chimenti
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA
| | - Dan Y Zhang
- Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA; Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Evelyn K Williams
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA
| | - Samuel G Moore
- Systems Mass Spectrometry Core Facility, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Gabrielle M Humber
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA
| | - Travon A Baxter
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA
| | - Lacey A Birnbaum
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA
| | - Min Qui
- Department of Pharmacology and Chemical Biology, Emory Chemical Biology Discovery Center, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Henry Zecca
- Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Aashis Thapa
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA
| | - Juhi Jain
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA; Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA
| | - Nathan T Jui
- Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA; Department of Chemistry, Emory University, Atlanta, GA 30322, USA
| | - Xiaodong Wang
- Center for Integrative Chemical Biology and Drug Discovery, Division of Chemical Biology and Medicinal Chemistry, Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27514, USA
| | - Haian Fu
- Department of Pharmacology and Chemical Biology, Emory Chemical Biology Discovery Center, Emory University School of Medicine, Atlanta, GA 30322, USA; Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - Yuhong Du
- Department of Pharmacology and Chemical Biology, Emory Chemical Biology Discovery Center, Emory University School of Medicine, Atlanta, GA 30322, USA; Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - Melissa L Kemp
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA; Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA; Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - Wilbur A Lam
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA; Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA; Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA; Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA; Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA
| | - Douglas K Graham
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA; Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA
| | - Deborah DeRyckere
- Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA; Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA.
| | - Erik C Dreaden
- Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30322, USA; Department of Pediatrics, Emory School of Medicine, Atlanta, GA 30322, USA; Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA; Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta, Atlanta, GA 30322, USA; Winship Cancer Institute of Emory University, Atlanta, GA 30322, USA.
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5
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Engelmann J, Zarrer J, Gensch V, Riecken K, Berenbrok N, Luu TV, Beitzen-Heineke A, Vargas-Delgado ME, Pantel K, Bokemeyer C, Bhamidipati S, Darwish IS, Masuda E, Burstyn-Cohen T, Alberto EJ, Ghosh S, Rothlin C, Hesse E, Taipaleenmäki H, Ben-Batalla I, Loges S. Regulation of bone homeostasis by MERTK and TYRO3. Nat Commun 2022; 13:7689. [PMID: 36509738 PMCID: PMC9744875 DOI: 10.1038/s41467-022-33938-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 10/07/2022] [Indexed: 12/14/2022] Open
Abstract
The fine equilibrium of bone homeostasis is maintained by bone-forming osteoblasts and bone-resorbing osteoclasts. Here, we show that TAM receptors MERTK and TYRO3 exert reciprocal effects in osteoblast biology: Osteoblast-targeted deletion of MERTK promotes increased bone mass in healthy mice and mice with cancer-induced bone loss, whereas knockout of TYRO3 in osteoblasts shows the opposite phenotype. Functionally, the interaction of MERTK with its ligand PROS1 negatively regulates osteoblast differentiation via inducing the VAV2-RHOA-ROCK axis leading to increased cell contractility and motility while TYRO3 antagonizes this effect. Consequently, pharmacologic MERTK blockade by the small molecule inhibitor R992 increases osteoblast numbers and bone formation in mice. Furthermore, R992 counteracts cancer-induced bone loss, reduces bone metastasis and prolongs survival in preclinical models of multiple myeloma, breast- and lung cancer. In summary, MERTK and TYRO3 represent potent regulators of bone homeostasis with cell-type specific functions and MERTK blockade represents an osteoanabolic therapy with implications in cancer and beyond.
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Affiliation(s)
- Janik Engelmann
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Jennifer Zarrer
- Molecular Skeletal Biology Laboratory, Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute of Musculoskeletal Medicine, University Hospital, LMU Munich, Martinsried, Germany
- Musculoskeletal University Center Munich, University Hospital, LMU Munich, Martinsried, Germany
| | - Victoria Gensch
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Kristoffer Riecken
- Department of Stem Cell Transplantation, Research Department Cell and Gene Therapy, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Nikolaus Berenbrok
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - The Vinh Luu
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Antonia Beitzen-Heineke
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Maria Elena Vargas-Delgado
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - Klaus Pantel
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Carsten Bokemeyer
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | - Ihab S Darwish
- Rigel Pharmaceuticals, Inc., South San Francisco, CA, USA
| | - Esteban Masuda
- Rigel Pharmaceuticals, Inc., South San Francisco, CA, USA
| | - Tal Burstyn-Cohen
- Faculty of Dental Medicine, Institute for Dental Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Emily J Alberto
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
| | - Sourav Ghosh
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, USA
| | - Carla Rothlin
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT, USA
- Department of Pharmacology, Yale University School of Medicine, New Haven, CT, USA
| | - Eric Hesse
- Institute of Musculoskeletal Medicine, University Hospital, LMU Munich, Martinsried, Germany
- Musculoskeletal University Center Munich, University Hospital, LMU Munich, Martinsried, Germany
| | - Hanna Taipaleenmäki
- Molecular Skeletal Biology Laboratory, Department of Trauma, Hand and Reconstructive Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
- Institute of Musculoskeletal Medicine, University Hospital, LMU Munich, Martinsried, Germany
- Musculoskeletal University Center Munich, University Hospital, LMU Munich, Martinsried, Germany
| | - Isabel Ben-Batalla
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany.
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany.
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
| | - Sonja Loges
- Department of Oncology, Hematology and Bone Marrow Transplantation with Section Pneumology, Hubertus Wald Comprehensive Cancer Center Hamburg, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- Department of Tumor Biology, Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
- DKFZ-Hector Cancer Institute at the University Medical Center Mannheim, Mannheim, Germany.
- Division of Personalized Medical Oncology (A420), German Cancer Research Center (DKFZ), Heidelberg, Germany.
- Department of Personalized Oncology, University Hospital Mannheim, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany.
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6
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Acute RhoA/Rho Kinase Inhibition Is Sufficient to Restore Phagocytic Capacity to Retinal Pigment Epithelium Lacking the Engulfment Receptor MerTK. Cells 2021; 10:cells10081927. [PMID: 34440696 PMCID: PMC8394172 DOI: 10.3390/cells10081927] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2021] [Revised: 07/26/2021] [Accepted: 07/26/2021] [Indexed: 12/27/2022] Open
Abstract
The diurnal phagocytosis of spent photoreceptor outer segment fragments (POS) by retinal pigment epithelial (RPE) cells is essential for visual function. POS internalization by RPE cells requires the assembly of F-actin phagocytic cups beneath surface-tethered POS and Mer tyrosine kinase (MerTK) signaling. The activation of the Rho family GTPase Rac1 is necessary for phagocytic cup formation, and Rac1 is activated normally in MerTK-deficient RPE. We show here that mutant RPE lacking MerTK and wild-type RPE deprived of MerTK ligand both fail to form phagocytic cups regardless of Rac1 activation. However, in wild-type RPE in vivo, a decrease in RhoA activity coincides with the daily phagocytosis burst, while RhoA activity in MerTK-deficient RPE is constant. Elevating RhoA activity blocks phagocytic cup formation and phagocytosis by wild-type RPE. Conversely, inhibiting RhoA effector Rho kinases (ROCKs) rescues both F-actin assembly and POS internalization of primary RPE if MerTK or its ligand are lacking. Most strikingly, acute ROCK inhibition is sufficient to induce the formation and acidification of endogenous POS phagosomes by MerTK-deficient RPE ex vivo. Altogether, RhoA pathway inactivation is a necessary and sufficient downstream effect of MerTK phagocytic signaling such that the acute manipulation of cytosolic ROCK activity suffices to restore phagocytic capacity to MerTK-deficient RPE.
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7
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Sakti DH, Cornish EE, Mustafic N, Zaheer A, Retsas S, Rajagopalan S, Chung CW, Ewans L, McCluskey P, Nash BM, Jamieson RV, Grigg JR. MERTK retinopathy: biomarkers assessing vision loss. Ophthalmic Genet 2021; 42:706-716. [PMID: 34289798 DOI: 10.1080/13816810.2021.1955278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE Mer tyrosine kinase-retinitis pigmentosa (MERTK-RP) causes a primary defect in the retinal pigment epithelium, which subsequently affects rod and cone photoreceptors. The study aims to identify the most appropriate MERTK-RP biomarkers to measure disease progression for deciding the optimum therapeutic trial intervention time. MATERIALS AND METHODS Patients' data from baseline (BL) and last follow-up (LFU) were reviewed. Best corrected visual acuity (BCVA), spectral domain-optical coherence tomography (SD-OCT), ultra-widefield fundus autofluorescence (UWF-FAF) patterns, kinetic perimetry (KP), and electroretinography (ERG) parameters were analyzed. RESULTS Five patients were included with the mean age of 17.7 ± 14.4 years old (6.7-42.3) at BL and mean BCVA follow-up of 8.4 ± 5.1 years. Mean BCVA at BL and LFU were 0.84 ± 0.86 LogMAR and 1.14 ± 0.86 LogMAR, respectively. The BCVA decline rate was 0.05 ± 0.03 LogMAR units/year. Ellipzoid zones (EZ) were measurable in eight eyes with mean BL length of 1293.75 ± 421.07 µm and reduction of 140.95 ± 69.28 µm/year and mean BL CMT of 174.2 ± 37.52 µm with the rate of 11.2 ± 12.77 µm declining/year. Full-field ERG (ffERG) and pattern ERG (pERG) were barely recordable. UWF-FAF showed central macular hyper-autofluorescence (hyperAF). KP (III4e and V4e) was normal in two eyes, restricted nasally in four eyes, superior wedge defect in two eyes and undetectable in two eyes. The four restricted nasally KPs became worse, while the others stayed almost unchanged. CONCLUSIONS This cohort showed early visual loss, moderately rapid EZ reduction and macular hyperAF. EZ, CMT, and BCVA were consistently reduced. Relative rapid decline in these biomarkers reflecting visual function suggests an early and narrow timespan for intervention.
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Affiliation(s)
- Dhimas H Sakti
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Department of Ophthalmology, Faculty of Medicine, Public Health and Nursing; Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - Elisa E Cornish
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia
| | - Nina Mustafic
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Afsah Zaheer
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Stephanie Retsas
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Sulekha Rajagopalan
- Department of Clinical Genetics, Liverpool Hospital, Liverpool BC, NSW, Australia
| | - Clara Wt Chung
- Department of Clinical Genetics, Liverpool Hospital, Liverpool BC, NSW, Australia.,School of Women's & Children's Health, University of NSW, Sydney, NSW, Australia
| | - Lisa Ewans
- Department of Clinical Genetics, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.,Faculty of Medicine and Health Central Clinical School, Sydney Medical School, University of Sydney, Sydney, NSW, Australia
| | - Peter McCluskey
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia
| | - Benjamin M Nash
- Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia.,Disciplines of Genomic Medicine & Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Sydney Genome Diagnostics, Western Sydney Genetics Program, the Children's Hospital at Westmead, Sydney, NSW, Australia
| | - Robyn V Jamieson
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia.,Disciplines of Genomic Medicine & Child and Adolescent Health, Sydney Medical School, University of Sydney, Sydney, NSW, Australia.,Department of Clinical Genetics, Western Sydney Genetics Program, the Children's Hospital at Westmead, Sydney, NSW, Australia
| | - John R Grigg
- Save Sight Institute, Faculty of Medicine and Health, The University of Sydney, Sydney, NSW, Australia.,Eye Genetics Research Unit, Children's Medical Research Institute, the Children's Hospital at Westmead, Save Sight Institute, University of Sydney, Sydney, NSW, Australia
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8
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Having an Old Friend for Dinner: The Interplay between Apoptotic Cells and Efferocytes. Cells 2021; 10:cells10051265. [PMID: 34065321 PMCID: PMC8161178 DOI: 10.3390/cells10051265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/12/2021] [Accepted: 05/17/2021] [Indexed: 02/02/2023] Open
Abstract
Apoptosis, the programmed and intentional death of senescent, damaged, or otherwise superfluous cells, is the natural end-point for most cells within multicellular organisms. Apoptotic cells are not inherently damaging, but if left unattended, they can lyse through secondary necrosis. The resulting release of intracellular contents drives inflammation in the surrounding tissue and can lead to autoimmunity. These negative consequences of secondary necrosis are avoided by efferocytosis—the phagocytic clearance of apoptotic cells. Efferocytosis is a product of both apoptotic cells and efferocyte mechanisms, which cooperate to ensure the rapid and complete removal of apoptotic cells. Herein, we review the processes used by apoptotic cells to ensure their timely removal, and the receptors, signaling, and cellular processes used by efferocytes for efferocytosis, with a focus on the receptors and signaling driving this process.
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MERTK-Dependent Ensheathment of Photoreceptor Outer Segments by Human Pluripotent Stem Cell-Derived Retinal Pigment Epithelium. Stem Cell Reports 2021; 14:374-389. [PMID: 32160519 PMCID: PMC7066375 DOI: 10.1016/j.stemcr.2020.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Revised: 02/06/2020] [Accepted: 02/10/2020] [Indexed: 11/22/2022] Open
Abstract
Maintenance of a healthy photoreceptor-retinal pigment epithelium (RPE) interface is essential for vision. At the center of this interface, apical membrane protrusions stemming from the RPE ensheath photoreceptor outer segments (POS), and are possibly involved in the recycling of POS through phagocytosis. The molecules that regulate POS ensheathment and its relationship to phagocytosis remain to be deciphered. By means of ultrastructural analysis, we revealed that Mer receptor tyrosine kinase (MERTK) ligands, GAS6 and PROS1, rather than αVβ5 integrin receptor ligands, triggered POS ensheathment by human embryonic stem cell (hESC)-derived RPE. Furthermore, we found that ensheathment is required for POS fragmentation before internalization. Consistently, POS ensheathment, fragmentation, and internalization were abolished in MERTK mutant RPE, and rescue of MERTK expression in retinitis pigmentosa (RP38) patient RPE counteracted these defects. Our results suggest that loss of ensheathment due to MERTK dysfunction might contribute to vision impairment in RP38 patients. POS are ensheathed in vitro by human embryonic stem cell-derived RPE POS ensheathment is upregulated by MERTK ligands: GAS6 and PROS1 αVβ5 integrin receptor ligands do not stimulate POS ensheathment MERTK is essential for POS ensheathment and fragmentation before internalization
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10
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Zheng DJ, Abou Taka M, Heit B. Role of Apoptotic Cell Clearance in Pneumonia and Inflammatory Lung Disease. Pathogens 2021; 10:134. [PMID: 33572846 PMCID: PMC7912081 DOI: 10.3390/pathogens10020134] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 01/25/2021] [Accepted: 01/26/2021] [Indexed: 02/07/2023] Open
Abstract
Pneumonia and inflammatory diseases of the pulmonary system such as chronic obstructive pulmonary disease and asthma continue to cause significant morbidity and mortality globally. While the etiology of these diseases is highly different, they share a number of similarities in the underlying inflammatory processes driving disease pathology. Multiple recent studies have identified failures in efferocytosis-the phagocytic clearance of apoptotic cells-as a common driver of inflammation and tissue destruction in these diseases. Effective efferocytosis has been shown to be important for resolving inflammatory diseases of the lung and the subsequent restoration of normal lung function, while many pneumonia-causing pathogens manipulate the efferocytic system to enhance their growth and avoid immunity. Moreover, some treatments used to manage these patients, such as inhaled corticosteroids for chronic obstructive pulmonary disease and the prevalent use of statins for cardiovascular disease, have been found to beneficially alter efferocytic activity in these patients. In this review, we provide an overview of the efferocytic process and its role in the pathophysiology and resolution of pneumonia and other inflammatory diseases of the lungs, and discuss the utility of existing and emerging therapies for modulating efferocytosis as potential treatments for these diseases.
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Affiliation(s)
- David Jiao Zheng
- Department of Microbiology and Immunology, Center for Human Immunology, The University of Western Ontario, London, ON N0M 2N0, Canada; (D.J.Z.); (M.A.T.)
| | - Maria Abou Taka
- Department of Microbiology and Immunology, Center for Human Immunology, The University of Western Ontario, London, ON N0M 2N0, Canada; (D.J.Z.); (M.A.T.)
| | - Bryan Heit
- Department of Microbiology and Immunology, Center for Human Immunology, The University of Western Ontario, London, ON N0M 2N0, Canada; (D.J.Z.); (M.A.T.)
- Robarts Research Institute, London, ON N6A 5K8, Canada
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11
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Kwon W, Freeman SA. Phagocytosis by the Retinal Pigment Epithelium: Recognition, Resolution, Recycling. Front Immunol 2020; 11:604205. [PMID: 33281830 PMCID: PMC7691529 DOI: 10.3389/fimmu.2020.604205] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Tissue-resident phagocytes are responsible for the routine binding, engulfment, and resolution of their meals. Such populations of cells express appropriate surface receptors that are tailored to recognize the phagocytic targets of their niche and initiate the actin polymerization that drives internalization. Tissue-resident phagocytes also harbor enzymes and transporters along the endocytic pathway that orchestrate the resolution of ingested macromolecules from the phagolysosome. Solutes fluxed from the endocytic pathway and into the cytosol can then be reutilized by the phagocyte or exported for their use by neighboring cells. Such a fundamental metabolic coupling between resident phagocytes and the tissue in which they reside is well-emphasized in the case of retinal pigment epithelial (RPE) cells; specialized phagocytes that are responsible for the turnover of photoreceptor outer segments (POS). Photoreceptors are prone to photo-oxidative damage and their long-term health depends enormously on the disposal of aged portions of the outer segment. The phagocytosis of the POS by the RPE is the sole means of this turnover and clearance. RPE are themselves mitotically quiescent and therefore must resolve the ingested material to prevent their toxic accumulation in the lysosome that otherwise leads to retinal disorders. Here we describe the sequence of events underlying the healthy turnover of photoreceptors by the RPE with an emphasis on the signaling that ensures the phagocytosis of the distal POS and on the transport of solutes from the phagosome that supersedes its resolution. While other systems may utilize different receptors and transporters, the biophysical and metabolic manifestations of such events are expected to apply to all tissue-resident phagocytes that perform regular phagocytic programs.
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Affiliation(s)
- Whijin Kwon
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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12
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Lakkaraju A, Umapathy A, Tan LX, Daniele L, Philp NJ, Boesze-Battaglia K, Williams DS. The cell biology of the retinal pigment epithelium. Prog Retin Eye Res 2020; 78:100846. [PMID: 32105772 PMCID: PMC8941496 DOI: 10.1016/j.preteyeres.2020.100846] [Citation(s) in RCA: 185] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/19/2020] [Accepted: 02/23/2020] [Indexed: 02/07/2023]
Abstract
The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.
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Affiliation(s)
- Aparna Lakkaraju
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Li Xuan Tan
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Lauren Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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13
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Shelby SJ. A course-based undergraduate research experience in biochemistry that is suitable for students with various levels of preparedness. BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION : A BIMONTHLY PUBLICATION OF THE INTERNATIONAL UNION OF BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 47:220-227. [PMID: 30794348 DOI: 10.1002/bmb.21227] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/01/2019] [Indexed: 06/09/2023]
Abstract
Due to resource limitations at predominantly undergraduate institutions, research opportunities for non-senior students can be limited. To provide opportunities for a variety of students to gain exposure to research, a course-based undergraduate research experience (CURE) was designed and conducted. Coupled inquiry was used to allow underclassmen and upperclassmen to participate. Students first utilized a bioinformatics approach to develop hypotheses concerning protein interactions with the receptor Mer tyrosine kinase (MERTK). Students designed experiments to identify specific sites of interactions with SH2-domain proteins utilizing an assortment of basic biochemical techniques. The semester culminated in students testing their hypotheses and producing manuscripts. Underclassmen that participated in the course also benefitted from mentor-mentee relationships developed with upperclassmen due to the collaborative nature of the course. The structure of the course also allows for further studies to be conducted based on novel findings and is highly adaptable to receptor tyrosine kinases found in other tissue types. © 2019 International Union of Biochemistry and Molecular Biology, 47(3):220-227, 2019.
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Affiliation(s)
- Shameka J Shelby
- Department of Chemistry, Biochemistry, and Physics, Florida Southern College, Lakeland, Florida 33801
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14
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Evans AL, Blackburn JWD, Taruc K, Kipp A, Dirk BS, Hunt NR, Barr SD, Dikeakos JD, Heit B. Antagonistic Coevolution of MER Tyrosine Kinase Expression and Function. Mol Biol Evol 2017; 34:1613-1628. [PMID: 28369510 DOI: 10.1093/molbev/msx102] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
TYRO3, AXL, and MERTK (TAM) receptors are a family of receptor tyrosine kinases that maintain homeostasis through the clearance of apoptotic cells, and when defective, contribute to chronic inflammatory and autoimmune diseases such as atherosclerosis, multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, and Crohn's disease. In addition, certain enveloped viruses utilize TAM receptors for immune evasion and entry into host cells, with several viruses preferentially hijacking MERTK for these purposes. Despite the biological importance of TAM receptors, little is understood of their recent evolution and its impact on their function. Using evolutionary analysis of primate TAM receptor sequences, we identified strong, recent positive selection in MERTK's signal peptide and transmembrane domain that was absent from TYRO3 and AXL. Reconstruction of hominid and primate ancestral MERTK sequences revealed three nonsynonymous single nucleotide polymorphisms in the human MERTK signal peptide, with a G14C mutation resulting in a predicted non-B DNA cruciform motif, producing a significant decrease in MERTK expression with no significant effect on MERTK trafficking or half-life. Reconstruction of MERTK's transmembrane domain identified three amino acid substitutions and four amino acid insertions in humans, which led to significantly higher levels of self-clustering through the creation of a new interaction motif. This clustering counteracted the effect of the signal peptide mutations through enhancing MERTK avidity, whereas the lower MERTK expression led to reduced binding of Ebola virus-like particles. The decreased MERTK expression counterbalanced by increased avidity is consistent with antagonistic coevolution to evade viral hijacking of MERTK.
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Affiliation(s)
- Amanda L Evans
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Jack W D Blackburn
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Kyle Taruc
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Angela Kipp
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Brennan S Dirk
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Nina R Hunt
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Stephen D Barr
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Jimmy D Dikeakos
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
| | - Bryan Heit
- Department of Microbiology and Immunology and the Centre for Human Immunology, The University of Western Ontario, London, Canada
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15
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Peng RM, Hong J, Jin Y, Sun YZ, Sun YQ, Zhang P. Mertk gene expression and photoreceptor outer segment phagocytosis by cultured rat bone marrow mesenchymal stem cells. Mol Vis 2017; 23:8-19. [PMID: 28210098 PMCID: PMC5287449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 01/26/2017] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND Bone marrow mesenchymal stem cells (BM-MSCs) are multipotential stem cells that have been used for a broad spectrum of indications. Several investigations have used BM-MSCs to promote photoreceptor survival and suggested that BM-MSCs are a potential source of cell replacement therapy for some forms of retinal degeneration. PURPOSE To investigate the expression of the MER proto-oncogene, tyrosine kinase (Mertk), involved in the disruption of RPE phagocytosis and the onset of autosomal recessive retinitis pigmentosa in rat BM-MSCs and to compare phagocytosis of the photoreceptor outer segment (POS) by BM-MSCs and RPE cells in vitro. METHODS MSCs were isolated from the bone marrow of Brown Norway rats. Reverse transcription-PCR (RT-PCR) and western blot analyses were used to examine the expression of Mertk. The phagocytized POS was detected with double fluorescent labeling, transmission electron microscopy, and scanning electron microscopy. RESULTS Mertk expression did not differ among the first three passages of BM-MSCs. Mertk gene expression was greater in the BM-MSCs than the RPE cells. Mertk protein expression in the BM-MSCs was similar to that in the RPE cells in the primary passage and was greater than that in the RPE cells in the other two passages. BM-MSCs at the first three passages phagocytized the POS more strongly than the RPE cells. The process of BM-MSC phagocytosis was similar to that of the RPE cells. CONCLUSIONS BM-MSCs may be an effective cell source for treating retinal degeneration in terms of phagocytosis of the POS.
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Affiliation(s)
- Rong-mei Peng
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, China
| | - Jing Hong
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, China
| | - Ying Jin
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, China
| | - Yu-zhao Sun
- Department of Ophthalmology, China Medical University, the First Affiliated Hospital, Shenyang, China
| | - Yi-qian Sun
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, China
| | - Pei Zhang
- Department of Ophthalmology, Peking University Third Hospital, Beijing, China Key Laboratory of Vision Loss and Restoration, Ministry of Education, Beijing, China
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16
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Yao J, Jia L, Khan N, Lin C, Mitter SK, Boulton ME, Dunaief JL, Klionsky DJ, Guan JL, Thompson DA, Zacks DN. Deletion of autophagy inducer RB1CC1 results in degeneration of the retinal pigment epithelium. Autophagy 2016; 11:939-53. [PMID: 26075877 DOI: 10.1080/15548627.2015.1041699] [Citation(s) in RCA: 90] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Autophagy regulates cellular homeostasis and response to environmental stress. Within the retinal pigment epithelium (RPE) of the eye, the level of autophagy can change with both age and disease. The purpose of this study is to determine the relationship between reduced autophagy and age-related degeneration of the RPE. The gene encoding RB1CC1/FIP200 (RB1-inducible coiled-coil 1), a protein essential for induction of autophagy, was selectively knocked out in the RPE by crossing Best1-Cre mice with mice in which the Rb1cc1 gene was flanked with Lox-P sites (Rb1cc1(flox/flox)). Ex vivo and in vivo analyses, including western blot, immunohistochemistry, transmission electron microscopy, fundus photography, optical coherence tomography, fluorescein angiography, and electroretinography were performed to assess the structure and function of the retina as a function of age. Deletion of Rb1cc1 resulted in multiple autophagy defects within the RPE including decreased conversion of LC3-I to LC3-II, accumulation of autophagy-targeted precursors, and increased numbers of mitochondria. Age-dependent degeneration of the RPE occurred, with formation of atrophic patches, subretinal migration of activated microglial cells, subRPE deposition of inflammatory and oxidatively damaged proteins, subretinal drusenoid deposits, and occasional foci of choroidal neovascularization. There was secondary loss of photoreceptors overlying the degenerated RPE and reduction in the electroretinogram. These observations are consistent with a critical role of autophagy in the maintenance of normal homeostasis in the aging RPE, and indicate that disruption of autophagy leads to retinal phenotypes associated with age-related degeneration.
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Key Words
- AMD, age-related macular degeneration
- ANOVA, analysis of variance
- Bru, Bruch's membrane
- CKO, conditional knockout
- CTSD, cathepsin D
- ERG, electroretinogram
- FIP200
- GCL, ganglion cell layer
- INL, inner nuclear layer
- IS, inner segment
- LAP, LC3-associated phagocytosis
- MTOR, mechanistic target of rapamycin
- OCT, optical coherence tomography
- ONL, outer nuclear layer
- OS, outer segment
- PBS, phosphate-buffered saline
- POS, photoreceptor outer segments
- RB1CC1, RB1-inducible coiled-coil 1
- RPE, retinal pigment epithelium
- age-related macular degeneration
- photoreceptor
- retina
- retinal pigment epithelium
- siRNA, small interfering ribonucleic acid.
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Affiliation(s)
- Jingyu Yao
- a Department of Ophthalmology and Visual Sciences ; University of Michigan ; Ann Arbor , MI USA
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17
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Sethna S, Chamakkala T, Gu X, Thompson TC, Cao G, Elliott MH, Finnemann SC. Regulation of Phagolysosomal Digestion by Caveolin-1 of the Retinal Pigment Epithelium Is Essential for Vision. J Biol Chem 2016; 291:6494-506. [PMID: 26814131 DOI: 10.1074/jbc.m115.687004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Indexed: 01/09/2023] Open
Abstract
Caveolin-1 associates with the endo/lysosomal machinery of cells in culture, suggesting that it functions at these organelles independently of its contribution to cell surface caveolae. Here we explored mice lacking caveolin-1 specifically in the retinal pigment epithelium (RPE). The RPE supports neighboring photoreceptors via diurnal phagocytosis of spent photoreceptor outer segment fragments. Like mice lacking caveolin-1 globally, (RPE)CAV1(-/-) mice developed a normal RPE and neural retina but showed reduced rod photoreceptor light responses, indicating that lack of caveolin-1 affects photoreceptor function in a non-cell-autonomous manner. (RPE)CAV1(-/-) RPE in situ showed normal particle engulfment but delayed phagosome clearance and reversed diurnal profiles of levels and activities of lysosomal enzymes. Therefore, eliminating caveolin-1 specifically impairs phagolysosomal degradation by the RPE in vivo. Endogenous caveolin-1 was recruited to maturing phagolysosomes in RPE cells in culture. Consistent with these in vivo data, a moderate increase (to ∼ 2.5-fold) or decrease (by half) of caveolin-1 protein levels in RPE cells in culture was sufficient to accelerate or impair phagolysosomal digestion, respectively. A mutant form of caveolin-1 that fails to reach the cell surface augmented degradation like wild-type caveolin-1. Acidic lysosomal pH and increased protease activity are essential for digestion. We show that halving caveolin-1 protein levels significantly alkalinized lysosomal pH and decreased lysosomal enzyme activities. Taken together, our results reveal a novel role for intracellular caveolin-1 in modulating phagolysosomal function. Moreover, they show, for the first time, that organellar caveolin-1 significantly affects tissue functionality in vivo.
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Affiliation(s)
- Saumil Sethna
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458
| | - Tess Chamakkala
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458
| | - Xiaowu Gu
- the Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | - Timothy C Thompson
- the Department of Genitourinary Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Guangwen Cao
- the Department of Genitourinary Medical Oncology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030
| | - Michael H Elliott
- the Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, and
| | - Silvia C Finnemann
- From the Department of Biological Sciences, Center for Cancer Genetic Diseases and Gene Regulation, Fordham University, Bronx, New York 10458,
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18
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Shelby SJ, Feathers KL, Ganios AM, Jia L, Miller JM, Thompson DA. MERTK signaling in the retinal pigment epithelium regulates the tyrosine phosphorylation of GDP dissociation inhibitor alpha from the GDI/CHM family of RAB GTPase effectors. Exp Eye Res 2015; 140:28-40. [PMID: 26283020 DOI: 10.1016/j.exer.2015.08.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 08/10/2015] [Accepted: 08/10/2015] [Indexed: 10/25/2022]
Abstract
Photoreceptor outer segments (OS) in the vertebrate retina undergo a process of continual renewal involving shedding of disc membranes that are cleared by phagocytic uptake into the retinal pigment epithelium (RPE). In dystrophic Royal College of Surgeons (RCS) rats, OS phagocytosis is blocked by a mutation in the gene encoding the receptor tyrosine kinase MERTK. To identify proteins tyrosine-phosphorylated downstream of MERTK in the RPE, MALDI-mass spectrometry with peptide-mass fingerprinting was used in comparative studies of RCS congenic and dystrophic rats. At times corresponding to peak phagocytic activity, the RAB GTPase effector GDP dissociation inhibitor alpha (GDI1) was found to undergo tyrosine phosphorylation only in congenic rats. In cryosections of native RPE/choroid, GDI1 colocalized with MERTK and the intracellular tyrosine-kinase SRC. In cultured RPE-J cells, and in transfected heterologous cells, MERTK stimulated SRC-mediated tyrosine phosphorylation of GDI1. In OS-fed RPE-J cells, GDI1 colocalized with MERTK and SRC on apparent phagosomes located near the apical membrane. In addition, both GDI1 and RAB5, a regulator of vesicular transport, colocalized with ingested OS. Taken together, these findings identify a novel role of MERTK signaling in membrane trafficking in the RPE that is likely to subserve mechanisms of phagosome formation.
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Affiliation(s)
- Shameka J Shelby
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA; Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Kecia L Feathers
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Anna M Ganios
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA
| | - Lin Jia
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Jason M Miller
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA
| | - Debra A Thompson
- Department of Biological Chemistry, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA; Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, 1000 Wall St., Ann Arbor, MI 48105, USA.
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19
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Gupta A, Mohanty P, Bhatnagar S. Integrative analysis of ocular complications in atherosclerosis unveils pathway convergence and crosstalk. J Recept Signal Transduct Res 2014; 35:149-64. [PMID: 25055025 DOI: 10.3109/10799893.2014.942462] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Atherosclerosis is a life-threatening disease and a major cause of mortalities worldwide. While many of the atherosclerotic sequelae are reflected as microvascular effects in the eye, the molecular mechanisms of their development is not yet known. In this study, we employed a systems biology approach to unveil the most significant events and key molecular mediators of ophthalmic sequelae caused by atherosclerosis. Literature mining was used to identify the proteins involved in both atherosclerosis and ophthalmic diseases. A protein-protein interaction (PPI) network was prepared using the literature-mined seed nodes. Network topological analysis was carried out using Cytoscape, while network nodes were annotated using database for annotation, visualization and integrated discovery in order to identify the most enriched pathways and processes. Network analysis revealed that mitogen-activated protein kinase 1 (MAPK1) and protein kinase C occur with highest betweenness centrality, degree and closeness centrality, thus reflecting their functional importance to the network. Our analysis shows that atherosclerosis-associated ophthalmic complications are caused by the convergence of neurotrophin signaling pathways, multiple immune response pathways and focal adhesion pathway on the MAPK signaling pathway. The PPI network shares features with vasoregression, a process underlying multiple vascular eye diseases. Our study presents a first clear and composite picture of the components and crosstalk of the main pathways of atherosclerosis-induced ocular diseases. The hub bottleneck nodes highlight the presence of molecules important for mediating the ophthalmic complications of atherosclerosis and contain five established drug targets for future therapeutic modulation efforts.
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Affiliation(s)
- Akanksha Gupta
- Division of Biotechnology, Netaji Subhas Institute of Technology , New Delhi , India
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20
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Yao J, Jia L, Shelby SJ, Ganios AM, Feathers K, Thompson DA, Zacks DN. Circadian and noncircadian modulation of autophagy in photoreceptors and retinal pigment epithelium. Invest Ophthalmol Vis Sci 2014; 55:3237-46. [PMID: 24781939 DOI: 10.1167/iovs.13-13336] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
PURPOSE Autophagy in photoreceptors and the RPE promotes homeostasis and survival. The purpose of this study is to determine the daily pattern of changes in autophagy and factors contributing to its regulation in the outer retina. METHODS Levels of autophagy markers in the retina and RPE were evaluated over a 24-hour period. To assess the role of phagocytosis in stimulating autophagy in the RPE, cultured RPE-J cells were incubated with isolated photoreceptor outer segments and levels of autophagy markers were measured. Electron microscopy was performed on retina sections and RPE-J cells to assess formation of double-membraned vesicles consistent with autophagosomes. RESULTS In wild-type C57BL/6 mice maintained under normal cycling light conditions, autophagy in photoreceptor cells and the RPE exhibited a bimodal pattern of activation. In photoreceptors, shifts between light and dark evoked a sharp decrease in autophagy that was followed by a time-dependent increase. In photoreceptors, translocation of transducin and arrestin from the outer to inner segment appeared to contribute to the light-dependent upregulation of autophagy. In contrast, the cyclic variations in RPE autophagy were independent of lighting conditions, and are triggered, at least in part, by ingestion of outer segments. CONCLUSIONS Activation of autophagy in the outer retina exhibits a bimodal pattern that correlates with shifts in transduction proteins within the photoreceptor and by circadian ingestion of outer segments in the RPE. These dynamic shifts suggest a critical role for this pathway in maintaining homeostasis, with further study needed to define the mechanisms underlying the regulation of this phenomenon.
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Affiliation(s)
- Jingyu Yao
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Lin Jia
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Shameka J Shelby
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Anna M Ganios
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Kecia Feathers
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - Debra A Thompson
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, United States
| | - David N Zacks
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States
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Mazzoni F, Safa H, Finnemann SC. Understanding photoreceptor outer segment phagocytosis: use and utility of RPE cells in culture. Exp Eye Res 2014; 126:51-60. [PMID: 24780752 DOI: 10.1016/j.exer.2014.01.010] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 01/10/2014] [Accepted: 01/13/2014] [Indexed: 12/21/2022]
Abstract
RPE cells are the most actively phagocytic cells in the human body. In the eye, RPE cells face rod and cone photoreceptor outer segments at all times but contribute to shedding and clearance phagocytosis of distal outer segment tips only once a day. Analysis of RPE phagocytosis in situ has succeeded in identifying key players of the RPE phagocytic mechanism. Phagocytic processes comprise three distinct phases, recognition/binding, internalization, and digestion, each of which is regulated separately by phagocytes. Studies of phagocytosis by RPE cells in culture allow specifically analyzing and manipulating these distinct phases to identify their molecular mechanisms. Here, we compare similarities and differences of primary, immortalized, and stem cell-derived RPE cells in culture to RPE cells in situ with respect to phagocytic function. We discuss in particular potential pitfalls of RPE cell culture phagocytosis assays. Finally, we point out considerations for phagocytosis assay development for future studies.
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Affiliation(s)
- Francesca Mazzoni
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
| | - Hussein Safa
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA
| | - Silvia C Finnemann
- Department of Biological Sciences, Center for Cancer, Genetic Diseases, and Gene Regulation, Fordham University, Bronx, NY 10458, USA.
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Mustafi D, Kevany BM, Genoud C, Bai X, Palczewski K. Photoreceptor phagocytosis is mediated by phosphoinositide signaling. FASEB J 2013; 27:4585-95. [PMID: 23913857 DOI: 10.1096/fj.13-237537] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Circadian oscillations in peripheral tissues, such as the retinal compartment of the eye, are critical to anticipating changing metabolic demands. Circadian shedding of retinal photoreceptor cell discs with subsequent phagocytosis by the neighboring retinal pigmented epithelium (RPE) is essential for removal of toxic metabolites and lifelong survival of these postmitotic neurons. Defects in photoreceptor phagocytosis can lead to severe retinal pathology, but the biochemical mechanisms remain poorly defined. By first documenting a 2.8-fold burst of photoreceptor phagocytosis events in the mouse eye in the morning compared with the afternoon by serial block face imaging, we established time points to assess transcriptional readouts by RNA sequencing (RNA-Seq). We identified 365 oscillating protein-coding transcripts that implicated the phosphoinositide lipid signaling network mediating the discrete steps of photoreceptor phagocytosis. Moreover, examination of overlapping cistromic sites by core clock transcription factors and promoter elements of these effector genes provided a functional basis for the circadian cycling of these transcripts. RNA-Seq also revealed oscillating expression of 16 long intergenic noncoding RNAs and key histone modifying enzymes critical for circadian gene expression. Our phenotypic and genotypic characterization reveals a complex global landscape of overlapping and temporally controlled networks driving the essential circadian process in the eye.
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Affiliation(s)
- Debarshi Mustafi
- 1Department of Pharmacology, School of Medicine, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106-4965, USA.
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Bulloj A, Duan W, Finnemann SC. PI 3-kinase independent role for AKT in F-actin regulation during outer segment phagocytosis by RPE cells. Exp Eye Res 2013; 113:9-18. [PMID: 23669303 DOI: 10.1016/j.exer.2013.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2012] [Revised: 04/15/2013] [Accepted: 05/01/2013] [Indexed: 12/24/2022]
Abstract
Daily phagocytosis of photoreceptor outer segment fragments (POS) by the retinal pigment epithelium (RPE) is essential for vision. RPE cells use an uptake machinery that is highly similar to the one macrophages use to phagocytose apoptotic cells. In both forms of phagocytosis, particle binding induces phagocyte signaling that is required for F-actin assembly and re-arrangement beneath bound particles. Macrophage binding of apoptotic cells stimulates PI3 kinases (PI3K) and AKT kinases (AKT), which may be downstream of PI3K, and PI3K inhibition decreases engulfment. Here, we used specific inhibitory agents to investigate whether and how PI3K and AKT contribute to RPE phagocytosis. Either PI3K or AKT inhibition eliminated AKT activation by RPE cells in response to POS and increased the numbers of POS bound by RPE cells. Analyzing the quality of bound POS, we found a higher fraction of POS associated with F-actin phagocytic cups and myosin II in RPE receiving AKT inhibitor. In these cells, individual POS also recruited more F-actin and myosin II than POS in control cells. In contrast, PI3K inhibition did not alter frequency of phagocytic cups but individual cups contained less F-actin (but similar levels of myosin II) compared to control cups. Annexin AII, another phagocytic cup protein of RPE cells, associated with bound POS regardless of inhibitor treatment. POS engulfment proceeded normally if cells already carried surface-bound POS when receiving inhibitors. However, PI3K inhibition during POS binding blocked subsequent POS engulfment. In striking contrast, AKT inhibition had no effect on POS engulfment. Taken together, these results suggest distinct regulatory roles of PI3K and AKT during POS phagocytosis by RPE cells.
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Affiliation(s)
- Ayelen Bulloj
- Department of Biological Sciences, Center for Cancer, Genetic Diseases and Gene Regulation, Fordham University, Larkin Hall, 441 East Fordham Road, Bronx, NY 10458, USA
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