Staphylococcal superantigen-like protein 10 (SSL10) binds to human immunoglobulin G (IgG) and inhibits complement activation via the classical pathway |
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| Authors: | Saotomo Itoh Eri Hamada Go Kamoshida Ryosuke Yokoyama Takemasa Takii Kikuo Onozaki Tsutomu Tsuji |
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| Institution: | 1. Department of Microbiology, Hoshi University, School of Pharmacy and Pharmaceutical Sciences, Tokyo 142-8501, Japan;2. Department of Molecular Health Sciences, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan;1. Department of Laboratory Medicine, Laboratory of Hematology, Radboud University Medical Center, Geert Grooteplein 10, 6525 GA Nijmegen, The Netherlands;2. Department of Vascular Medicine, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;3. Department for Health Evidence, Radboud University Medical Center, Geert Grooteplein 21, 6525 EZ Nijmegen, The Netherlands;4. Department of General Internal Medicine, Radboud University Medical Center, Geert Grooteplein 8, 6525 GA Nijmegen, The Netherlands;1. Laboratory of Pharmacology, Faculty of Pharmacy, Osaka Ohtani University, 3-11-1 Nishikiori-Kita, Tonda-bayashi, Osaka 584-8540, Japan;3. From the Center for Infectious and Inflammatory Disease, Institute of Biosciences and Technology, Texas A&M Health Science Center and;4. the Division of Infectious Disease, Department of Medicine, University of Texas Medical School, Houston, Texas 77030;1. Institute of Surgical Research, University of Szeged, Szeged, Hungary;2. Department of Immunology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan;3. Choju Medical Institute, Fukushimura Hospital, Toyohashi, Japan;1. Department of Pathology, Microbiology & Immunology, Vanderbilt University Medical Center, Nashville, TN, 37232, USA;2. Graduate Program in Microbiology & Immunology, Vanderbilt University, Nashville, TN, 37232, USA |
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| Abstract: | Staphylococcal superantigen-like (SSL) proteins are a family of exoproteins that share structural similarity with staphylococcal superantigens but exhibit no superantigenic activity. It was previously reported that two members (SSL5 and SSL7) bound to serum components and cell adhesion molecules involved in host immune response; however, the other family members have not been functionally characterized. In this study, we attempted to isolate SSL10-binding proteins from human serum and found that recombinant His-tagged SSL10 bound two major polypeptides of ～50 and ～25 kDa after affinity purification and SDS-polyacrylamide gel electrophoresis. These polypeptides were identified as heavy and light chains of human IgG by peptide mass fingerprinting analysis. The specific interaction between recombinant SSL10 and human IgG was confirmed by far Western blot analysis using immobilized SSL10 and pull-down analysis using SSL10-conjugated Sepharose. Surface plasmon resonance analysis revealed that the dissociation equilibrium constant for the interaction between human IgG and recombinant SSL10 was estimated to be 220 nM. We also found that recombinant SSL10 inhibited the binding of complement component C1q to IgG-Sepharose and hemolysis of IgG-sensitized sheep erythrocytes via the classical complement activation pathway. These results suggest that SSL10 may play a role in the evasion of Staphylococcus aureus from the host immune system via interfering complement activation. |
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