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Gopalakrishnan S, Uma SK, Mohan G, Mohan A, Shanmugam G, Kumar VTV, J S, Chandrika SK, Vasudevan D, Nori SRC, Sathi SN, George S, Maliekal TT. SSTP1, a Host Defense Peptide, Exploits the Immunomodulatory IL6 Pathway to Induce Apoptosis in Cancer Cells. Front Immunol 2021; 12:740620. [PMID: 34867962 PMCID: PMC8639500 DOI: 10.3389/fimmu.2021.740620] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 10/27/2021] [Indexed: 12/30/2022] Open
Abstract
While the immunomodulatory pathways initiated in immune cells contribute to therapeutic response, their activation in cancer cells play a role in cancer progression. Also, many of the aberrantly expressed immunomodulators on cancer cells are considered as therapeutic targets. Here, we introduce host defense peptide (HDP), a known immuomodulator, as a therapeutic agent to target them. The cationic host defense peptides (HDPs), an integral part of the innate immune system, possess membranolytic activity, which imparts antimicrobial and antitumor efficacy to it. They act as immunomodulators by activating the immune cells. Though their antimicrobial function has been recently reassigned to immunoregulation, their antitumor activity is still attributed to its membranolytic activity. This membrane pore formation ability, which is proportional to the concentration of the peptide, also leads to side effects like hemolysis, limiting their therapeutic application. So, despite the identification of a variety of anticancer HDPs, their clinical utility is limited. Though HDPs are shown to exert the immunomodulatory activity through specific membrane targets on immune cells, their targets on cancer cells are unknown. We show that SSTP1, a novel HDP identified by shotgun cloning, binds to the active IL6/IL6Rα/gp130 complex on cancer cells, rearranging the active site residues. In contrast to the IL6 blockers inhibiting JAK/STAT activity, SSTP1 shifts the proliferative IL6/JAK/STAT signaling to the apoptotic IL6/JNK/AP1 pathway. In IL6Rα-overexpressing cancer cells, SSTP1 induces apoptosis at low concentration through JNK pathway, without causing significant membrane disruption. We highlight the importance of immunomodulatory pathways in cancer apoptosis, apart from its established role in immune cell regulation and cancer cell proliferation. Our study suggests that identification of the membrane targets for the promising anticancer HDPs might lead to the identification of new drugs for targeted therapy.
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Affiliation(s)
- Shyla Gopalakrishnan
- Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
- Interdisciplinary Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Soumya Krishnan Uma
- Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Gayathri Mohan
- Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
- Regional Centre for Biotechnology, Faridabad, India
| | - Amrutha Mohan
- Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
- Manipal Academy of Higher Education, Manipal, India
| | - Geetha Shanmugam
- Cancer Research, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Vineeth T. V. Kumar
- Interdisciplinary Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Sreekumar J
- Statistics, Section of Extension and Social Science, The Indian Council of Agricultural Research (ICAR) Central Tuber Crops Research Institute, Thiruvananthapuram, India
| | - Sivakumar K. Chandrika
- Genomics Core Facility, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | | | - Sai Ravi Chandra Nori
- Interdisciplinary Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Shijulal Nelson Sathi
- Interdisciplinary Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
| | - Sanil George
- Interdisciplinary Biology, Rajiv Gandhi Centre for Biotechnology, Thiruvananthapuram, India
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Denessiouk KA, Denesyuk AI, Johnson MS. Negative modulation of signal transduction via interleukin splice variation. Proteins 2008; 71:751-70. [PMID: 17979192 DOI: 10.1002/prot.21756] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Interleukin 6 (IL-6) belongs to a large group of secreted proteins called cytokines functioning to mediate and regulate immunity, inflammation, and hematopoiesis with direct effects on cell proliferation, apoptosis, and differentiation. Along with the IL-6 protein, two of its splice variants, IL-6delta2 and IL-6delta4, were reported to be transcribed or expressed in vivo in human, and the mRNAs of IL-6delta3 and IL-6delta5 had been observed in mouse. While the existence of different splice variants of IL-6 has been shown, very little is known on how the structural modifications of IL-6 resulting from the formation of the different splice variants may alter cytokine functions. We have analyzed the potential effects splicing would have on interactions with the cell surface receptor complex. We (1) constructed three-dimensional structures of the IL-6 splice variants, IL-6delta2, IL-6delta3, and IL-6delta4, with the assumption that an interleukin splice variant as a folded protein should retain a functional hydrophobic core; (2) reconstructed the ternary structural complexes consisting of the modeled IL-6 splice variants, the IL-6 receptor molecule (IL-6R) and the dimeric signal-transducing protein, gp130, and (3) analyzed all complexes and made comparisons with the X-ray structure of the wild-type IL-6 complex. We identified three separate sites on IL-6 where interactions are made with IL-6R and with each of the two copies of gp130. The structural consequences of losing an exon lead to a unique pattern of lost interaction with different components of the receptor complex. Thus, in IL-6 and its splice variants, the exons appear to have compartmentalized roles contributing to the combined function of the cytokine. The modeled interactions suggest that splice variants could act as antagonists, and that IL-6delta2, missing the signal peptide, would be a cytoplasmic protein and be released and interact with nearby cell-surface receptors when cells are damaged. We argue that in the case of IL-6, helix E may act as a "silent secondary structure," which only has an active role when it substitutes for a part of the hydrophobic core, for example, replacing helix A in IL-6delta2.
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Affiliation(s)
- Konstantin A Denessiouk
- Department of Biochemistry and Pharmacy, Abo Akademi University, Artillerigatan 6 A, 20521 Turku, Finland
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St-Laurent G, Archambault D. Molecular cloning, phylogenetic analysis and expression of beluga whale (Delphinapterus leucas) interleukin 6. Vet Immunol Immunopathol 2000; 73:31-44. [PMID: 10678396 DOI: 10.1016/s0165-2427(99)00150-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Interleukin 6 (IL-6) is a cytokine produced primarily by the monocytes/macrophages with regulatory effects in hematopoiesis, acute phase response, and multiple aspects of the immune response. IL-6 exerts its activity through its binding to specific high affinity receptors at the surface of target cells. As yet, no molecular data have been reported for the beluga whale IL-6. In this study, we cloned and determined the entire beluga whale IL-6-encoding cDNA sequence by reverse transcription-polymerase chain reaction (RT-PCR) sequencing, and analysed its genetic relationship with those from several mammalian species including human, rodent, ruminant, carnivore and other marine species. The identity levels of beluga whale IL-6 nucleic and deduced amino acid sequences with those from these mammalian species ranged from 62.3 to 97.3%, and 42.9 to 95.6%, respectively. Phylogenetic analysis based on amino acid sequences showed that the beluga whale IL-6 was most closely related to that of the killer whale. Thereafter, beluga whale IL-6-encoding sequence was successfully expressed in Escherichia coli by using the pTHIOHisA expression vector for the production of a recombinant fusion protein. The immunogenicity of the recombinant fusion protein was then confirmed as determined by the production of a beluga whale IL-6-specific rabbit antiserum.
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Affiliation(s)
- G St-Laurent
- University of Québec at Montréal, Department of Biological Sciences, Canada
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Simpson RJ, Hammacher A, Smith DK, Matthews JM, Ward LD. Interleukin-6: structure-function relationships. Protein Sci 1997; 6:929-55. [PMID: 9144766 PMCID: PMC2143693 DOI: 10.1002/pro.5560060501] [Citation(s) in RCA: 270] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Interleukin-6 (IL-6) is a multifunctional cytokine that plays a central role in host defense due to its wide range of immune and hematopoietic activities and its potent ability to induce the acute phase response. Overexpression of IL-6 has been implicated in the pathology of a number of diseases including multiple myeloma, rheumatoid arthritis, Castleman's disease, psoriasis, and post-menopausal osteoporosis. Hence, selective antagonists of IL-6 action may offer therapeutic benefits. IL-6 is a member of the family of cytokines that includes interleukin-11, leukemia inhibitory factor, oncostatin M, cardiotrophin-1, and ciliary neurotrophic factor. Like the other members of this family, IL-6 induces growth or differentiation via a receptor-system that involves a specific receptor and the use of a shared signaling subunit, gp130. Identification of the regions of IL-6 that are involved in the interactions with the IL-6 receptor, and gp130 is an important first step in the rational manipulation of the effects of this cytokine for therapeutic benefit. In this review, we focus on the sites on IL-6 which interact with its low-affinity specific receptor, the IL-6 receptor, and the high-affinity converter gp130. A tentative model for the IL-6 hexameric receptor ligand complex is presented and discussed with respect to the mechanism of action of the other members of the IL-6 family of cytokines.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antigens, CD/chemistry
- Antigens, CD/physiology
- Arthritis, Rheumatoid/immunology
- Castleman Disease/immunology
- Chromosome Mapping
- Chromosomes, Human, Pair 7
- Cytokines/physiology
- Female
- Growth Hormone/chemistry
- Humans
- Interleukin-6/biosynthesis
- Interleukin-6/chemistry
- Interleukin-6/physiology
- Models, Biological
- Models, Structural
- Molecular Sequence Data
- Multiple Myeloma/immunology
- Osteoporosis, Postmenopausal/immunology
- Protein Structure, Secondary
- Psoriasis/immunology
- Receptors, Interleukin/chemistry
- Receptors, Interleukin/physiology
- Receptors, Interleukin-6
- Receptors, Somatotropin/chemistry
- Sequence Alignment
- Sequence Homology, Amino Acid
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Affiliation(s)
- R J Simpson
- Joint Protein Structure Laboratory, Ludwig Institute for Cancer Research, (Melbourne Tumour Biology Branch), Parkville, Victoria, Australia.
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Grotzinger J, Kurapkat G, Wollmer A, Kalai M, Rose-John S. The family of the IL-6-Type cytokines: Specificity and promiscuity of the receptor complexes. Proteins 1997. [DOI: 10.1002/(sici)1097-0134(199701)27:1<96::aid-prot10>3.0.co;2-d] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Brakenhoff JP, Bos HK, Grötzinger J, Rose-John S, Aarden LA. Identification of residues in the putative 5th helical region of human interleukin-6, important for activation of the IL-6 signal transducer, gp130. FEBS Lett 1996; 395:235-40. [PMID: 8898103 DOI: 10.1016/0014-5793(96)00974-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have previously shown that L58 in the putative 5th helical region of human interleukin-6 (IL-6) is important for activation of the IL-6 signal transducer gp130 [de Hon et al. (1995) FEBS Lett. 369, 187-191]. To further explore the importance of individual residues in this region for gp130 activation we have now combined Ala substitutions of residues E52, S53, S54, K55, E56, L58 and E60 with other substitutions in IL-6, known to affect gp130 activation (Q160E and T163P). The combination mutant protein with L58A completely lost the capacity to induce the proliferation of XG-1 myeloma cells, and could effectively antagonize wild type IL-6 activity on these cells. Moreover, the data suggest that besides L58, S54 particularly, but also E52, S53, K55 and E56 contribute to gp130 activation.
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MESH Headings
- Alanine
- Antigens, CD/drug effects
- Antigens, CD/physiology
- Cell Division/drug effects
- Cloning, Molecular
- Cytokine Receptor gp130
- Escherichia coli
- Humans
- Interleukin-6/chemistry
- Interleukin-6/pharmacology
- Kinetics
- Leukemia, Erythroblastic, Acute
- Membrane Glycoproteins/drug effects
- Membrane Glycoproteins/physiology
- Models, Molecular
- Multiple Myeloma
- Mutagenesis, Site-Directed
- Point Mutation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Recombinant Proteins/chemistry
- Recombinant Proteins/pharmacology
- Signal Transduction
- Tumor Cells, Cultured
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Affiliation(s)
- J P Brakenhoff
- Department of Autoimmune Diseases, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, University of Amsterdam, The Netherlands
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Ehlers M, Grötzinger J, Fischer M, Bos HK, Brakenhoff JP, Rose-John S. Identification of single amino acid residues of human IL-6 involved in receptor binding and signal initiation. J Interferon Cytokine Res 1996; 16:569-76. [PMID: 8877726 DOI: 10.1089/jir.1996.16.569] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The pleiotropic cytokine interleukin-6 (IL-6) has been predicted to be a protein with four antiparallel alpha-helices. On target cells, IL-6 interacts with a specific ligand binding receptor subunit (IL-6R), and this complex associates with the signal-transducing subunit gp130. Human IL-6 acts on human and murine cells, whereas murine IL-6 is only active on murine cells. The construction of chimeric human/murine IL-6 proteins has allowed us to define a region (residues 77-95, region 2c) within the human IL-6 protein that is important for IL-6R binding and a region (residues 50-55, region 2a2) that is important for IL-6R dependent gp130 interaction. Guided by sequence alignment and molecular modeling, we have constructed several IL-6 variants with point mutations in these regions and have tested them for receptor binding and signal initiation. Within region 2c, phenylalanine 78 was involved in receptor binding, whereas lysine 54 within region 2a2 participated in gp130 activation. Furthermore, some IL-6 variants with lysine 54 replacements could be used to construct muteins that retained receptor binding but failed to activate gp130. Such IL-6 muteins were efficient IL-6 receptor antagonists.
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Affiliation(s)
- M Ehlers
- 1st Department of Medicine, Johannes Gutenberg-University of Mainz, Germany
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