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Hage-Sleiman R, Hamze AB, El-Hed AF, Attieh R, Kozhaya L, Kabbani S, Dbaibo G. Ceramide inhibits PKCθ by regulating its phosphorylation and translocation to lipid rafts in Jurkat cells. Immunol Res 2017; 64:869-86. [PMID: 26798039 DOI: 10.1007/s12026-016-8787-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Protein kinase C theta (PKCθ) is a novel, calcium-independent member of the PKC family of kinases that was identified as a central player in T cell signaling and proliferation. Upon T cell activation by antigen-presenting cells, PKCθ gets phosphorylated and activated prior to its translocation to the immunological synapse where it couples with downstream effectors. PKCθ may be regulated by ceramide, a crucial sphingolipid that is known to promote differentiation, growth arrest, and apoptosis. To further investigate the mechanism, we stimulated human Jurkat T cells with either PMA or anti-CD3/anti-CD28 antibodies following induction of ceramide accumulation by adding exogenous ceramide, bacterial sphingomyelinase, or Fas ligation. Our results suggest that ceramide regulates the PKCθ pathway through preventing its critical threonine 538 (Thr538) phosphorylation and subsequent activation, thereby inhibiting the kinase's translocation to lipid rafts. Moreover, this inhibition is not likely to be a generic effect of ceramide on membrane reorganization. Other lipids, namely dihydroceramide, palmitate, and sphingosine, did not produce similar effects on PKCθ. Addition of the phosphatase inhibitors okadaic acid and calyculin A reversed the inhibition exerted by ceramide, and this suggests involvement of a ceramide-activated protein phosphatase. Such previously undescribed mechanism of regulation of PKCθ raises the possibility that ceramide, or one of its derivatives, and may prove valuable in novel therapeutic approaches for disorders involving autoimmunity or excessive inflammation-where PKCθ plays a critical role.
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Affiliation(s)
- Rouba Hage-Sleiman
- Department of Biology, Faculty of Sciences, Lebanese University, Hadath, Lebanon
| | - Asmaa B Hamze
- Department of Biomedical Science, Faculty of Health Sciences, Global University, Batrakiyye, Beirut, Lebanon
| | - Aimée F El-Hed
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Randa Attieh
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Lina Kozhaya
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Sarah Kabbani
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon
| | - Ghassan Dbaibo
- Department of Pediatrics and Adolescent Medicine, Center for Infectious Diseases Research, Department of Biochemistry and Molecular Genetics, Faculty of Medicine, American University of Beirut, PO Box 11-0236 Riad El Solh, Beirut, Lebanon.
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Ozay EI, Gonzalez-Perez G, Torres JA, Vijayaraghavan J, Lawlor R, Sherman HL, Garrigan DT, Burnside AS, Osborne BA, Tew GN, Minter LM. Intracellular Delivery of Anti-pPKCθ (Thr538) via Protein Transduction Domain Mimics for Immunomodulation. Mol Ther 2016; 24:2118-2130. [PMID: 27633441 DOI: 10.1038/mt.2016.177] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Accepted: 09/07/2016] [Indexed: 12/12/2022] Open
Abstract
Targeting cellular proteins with antibodies, to better understand cellular signaling pathways in the context of disease modulation, is a fast-growing area of investigation. Humanized antibodies are increasingly gaining attention for their therapeutic potential, but the collection of cellular targets is limited to those secreted from cells or expressed on the cell surface. This approach leaves a wealth of intracellular proteins unexplored as putative targets for antibody binding. Protein kinase Cθ (PKCθ) is essential to T cell activation, proliferation, and differentiation, and its phosphorylation at specific residues is required for its activity. Here we report on the design, synthesis, and characterization of a protein transduction domain mimic capable of efficiently delivering an antibody against phosphorylated PKCθ (Thr538) into human peripheral mononuclear blood cells and altering expression of downstream indicators of T cell activation and differentiation. We used a humanized, lymphocyte transfer model of graft-versus-host disease, to evaluate the durability of protein transduction domain mimic:Anti-pPKCθ modulation, when delivered into human peripheral mononuclear blood cells ex vivo. We demonstrate that protein transduction domain mimic:Antibody complexes can be readily introduced with high efficacy into hard-to-transfect human peripheral mononuclear blood cells, eliciting a biological response sufficient to alter disease progression. Thus, protein transduction domain mimic:Antibody delivery may represent an efficient ex vivo approach to manipulating cellular responses by targeting intracellular proteins.
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Affiliation(s)
- E Ilker Ozay
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Gabriela Gonzalez-Perez
- Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, Columbia University, New York, New York, USA
| | - Joe A Torres
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Jyothi Vijayaraghavan
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Rebecca Lawlor
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Heather L Sherman
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Daniel T Garrigan
- Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Amy S Burnside
- Institute for Applied Life Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Barbara A Osborne
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA.,Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Gregory N Tew
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA.,Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA.,Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts, USA
| | - Lisa M Minter
- Program in Molecular and Cellular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, USA.,Department of Veterinary and Animal Sciences, University of Massachusetts Amherst, Amherst, Massachusetts, USA
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Brezar V, Tu WJ, Seddiki N. PKC-Theta in Regulatory and Effector T-cell Functions. Front Immunol 2015; 6:530. [PMID: 26528291 PMCID: PMC4602307 DOI: 10.3389/fimmu.2015.00530] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 09/28/2015] [Indexed: 01/20/2023] Open
Abstract
One of the major goals in immunology research is to understand the regulatory mechanisms that underpin the rapid switch on/off of robust and efficient effector (Teffs) or regulatory (Tregs) T-cell responses. Understanding the molecular mechanisms underlying the regulation of such responses is critical for the development of effective therapies. T-cell activation involves the engagement of T-cell receptor and co-stimulatory signals, but the subsequent recruitment of serine/threonine-specific protein Kinase C-theta (PKC-θ) to the immunological synapse (IS) is instrumental for the formation of signaling complexes, which ultimately lead to a transcriptional network in T cells. Recent studies demonstrated that major differences between Teffs and Tregs occurred at the IS where its formation induces altered signaling pathways in Tregs. These pathways are characterized by reduced recruitment of PKC-θ, suggesting that PKC-θ inhibits Tregs suppressive function in a negative feedback loop. As the balance of Teffs and Tregs has been shown to be central in several diseases, it was not surprising that some studies revealed that PKC-θ plays a major role in the regulation of this balance. This review will examine recent knowledge on the role of PKC-θ in T-cell transcriptional responses and how this protein can impact on the function of both Tregs and Teffs.
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Affiliation(s)
- Vedran Brezar
- INSERM U955, Équipe 16 and Faculté de Médecine, Université Paris Est , Créteil , France ; Vaccine Research Institute (VRI) , Créteil , France
| | - Wen Juan Tu
- Faculty of Education, Science, Technology and Maths, University of Canberra , Canberra, ACT , Australia
| | - Nabila Seddiki
- INSERM U955, Équipe 16 and Faculté de Médecine, Université Paris Est , Créteil , France ; Vaccine Research Institute (VRI) , Créteil , France
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Abstract
The protein kinases C (PKCs) are a family of serine/threonine kinases involved in regulating multiple essential cellular processes such as survival, proliferation, and differentiation. Of particular interest is the novel, calcium-independent PKCθ which plays a central role in immune responses. PKCθ shares structural similarities with other PKC family members, mainly consisting of an N-terminal regulatory domain and a C-terminal catalytic domain tethered by a hinge region. This isozyme, however, is unique in that it translocates to the immunological synapse between a T cell and an antigen-presenting cell (APC) upon T cell receptor-peptide MHC recognition. Thereafter, PKCθ interacts physically and functionally with downstream effectors to mediate T cell activation and differentiation, subsequently leading to inflammation. PKCθ-specific perturbations have been identified in several diseases, most notably autoimmune disorders, and hence the modulation of its activity presents an attractive therapeutic intervention. To that end, many inhibitors of PKCs and PKCθ have been developed and tested in preclinical and clinical studies. And although selectivity remains a challenge, results are promising for the future development of effective PKCθ inhibitors that would greatly advance the treatment of several T-cell mediated diseases.
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