The scavenger receptor cysteine-rich (SRCR) family comprises a group of membrane-attached or secreted proteins that contain one or more modules/domains structurally similar to the membrane distal domain of type I macrophage scavenger receptor. Although no all-inclusive biological function has been ascribed to the SRCR family, some of these receptors have been shown to recognize pathogen-associated molecular patterns (PAMP) of bacteria, fungi, or other microbes. SSc5D is a recently described soluble SRCR receptor produced by monocytes/macrophages and T lymphocytes, consisting of an N-terminal portion, which contains five SRCR modules, and a large C-terminal mucin-like domain. Toward establishing a global common role for SRCR domains, we interrogated whether the set of five SRCR domains of SSc5D displayed pattern recognition receptor (PRR) properties. For that purpose, we have expressed in a mammalian expression system the N-terminal SRCR-containing moiety of SSc5D (N-SSc5D), thus excluding the mucin-like domain likely by nature to bind microorganisms, and tested the capacity of the SRCR functional groups to physically interact with bacteria. Using conventional protein-bacteria binding assays, we showed that N-SSc5D had a superior capacity to bind to Escherichia coli strains RS218 and IHE3034 compared with that of the extracellular domains of the SRCR proteins CD5 and CD6 (sCD5 and sCD6, respectively), and similar E. coli-binding properties as Spα, a proven PRR of the SRCR family. We have further designed a more sensitive, real-time, and label-free surface plasmon resonance (SPR)-based assay and examined the capacity of N-SSc5D, Spα, sCD5, and sCD6 to bind to different bacteria. We demonstrated that N-SSc5D compares with Spα in the capacity to bind to E. coli and Listeria monocytogenes, and further that it can distinguish between pathogenic E. coli RS218 and IHE3034 strains and the non-pathogenic laboratory E. coli strain BL21(DE3). Our work thus advocates the utility of SPR-based assays as sensitive tools for the rapid screening of interactions between immune-related receptors and PAMP-bearing microbes. The analysis of our results suggests that SRCR domains of different members of the family have a differential capacity to interact with bacteria, and further that the same receptor can discriminate between different bacteria strains and species.

i3S Instituto de Investigação e Inovação em Saúde Universidade do Porto Porto Portugal; IBMC Instituto de Biologia Molecular e Celular Porto Portugal

i3S Instituto de Investigação e Inovação em Saúde Universidade do Porto Porto Portugal; IBMC Instituto de Biologia Molecular e Celular Porto Portugal; ICBAS Instituto de Ciências Biomédicas Abel Salazar Universidade do Porto Porto Portugal

Institute of Photonics and Electronics of the Czech Academy of Sciences Prague Czech Republic

MRC Human Immunology Unit Nuffield Department of Clinical Medicine Weatherall Institute of Molecular Medicine University of Oxford Oxford UK

Front Immunol. 2017 Mar 28;8:366. doi: 10.3389/fimmu.2017.00366. PubMed

Zobrazit více v PubMed

Blander JM, Sander LE. Beyond pattern recognition: five immune checkpoints for scaling the microbial threat. Nat Rev Immunol (2012) 12:215–25.10.1038/nri3167 PubMed DOI

Martínez VG, Moestrup SK, Holmskov U, Mollenhauer J, Lozano F. The conserved scavenger receptor cysteine-rich superfamily in therapy and diagnosis. Pharmacol Rev (2011) 63:967–1000.10.1124/pr.111.004523 PubMed DOI

Sarrias MR, Grønlund J, Padilla O, Madsen J, Holmskov U, Lozano F. The scavenger receptor cysteine-rich (SRCR) domain: an ancient and highly conserved protein module of the innate immune system. Crit Rev Immunol (2004) 24:1–37.10.1615/CritRevImmunol.v24.i1.10 PubMed DOI

Carmo AM, Sreenu VB. A systematic and thorough search for domains of the scavenger receptor cysteine-rich group B family in the human genome. In: Mahdavi MA, editor. Bioinformatics – Trends and Methodologies. Rijeka, Croatia: InTech; (2011). p. 195–210.

Sarrias MR, Padilla O, Monreal Y, Carrascal M, Abian J, Vives J, et al. Biochemical characterization of recombinant and circulating human Spalpha. Tissue Antigens (2004) 63:335–44.10.1111/j.0001-2815.2004.00193.x PubMed DOI

Sarrias MR, Farnós M, Mota R, Sánchez-Barbero F, Ibáñez A, Gimferrer I, et al. CD6 binds to pathogen-associated molecular patterns and protects from LPS-induced septic shock. Proc Natl Acad Sci U S A (2007) 104:11724–9.10.1073/pnas.0702815104 PubMed DOI PMC

Fabriek BO, van Bruggen R, Deng DM, Ligtenberg AJ, Nazmi K, Schornagel K, et al. The macrophage scavenger receptor CD163 functions as an innate immune sensor for bacteria. Blood (2009) 113:887–92.10.1182/blood-2008-07-167064 PubMed DOI

Prakobphol A, Xu F, Hoang VM, Larsson T, Bergstrom J, Johansson I, et al. Salivary agglutinin, which binds Streptococcus mutans and Helicobacter pylori, is the lung scavenger receptor cysteine-rich protein gp-340. J Biol Chem (2000) 275:39860–6.10.1074/jbc.M006928200 PubMed DOI

Sarrias MR, Roselló S, Sánchez-Barbero F, Sierra JM, Vila J, Yélamos J, et al. A role for human Sp alpha as a pattern recognition receptor. J Biol Chem (2005) 280:35391–8.10.1074/jbc.M505042200 PubMed DOI

Vera J, Fenutría R, Cañadas O, Figueras M, Mota R, Sarrias MR, et al. The CD5 ectodomain interacts with conserved fungal cell wall components and protects from zymosan-induced septic shock-like syndrome. Proc Natl Acad Sci U S A (2009) 106:1506–11.10.1073/pnas.0805846106 PubMed DOI PMC

Martínez VG, Escoda-Ferran C, Tadeu Simões I, Arai S, Orta Mascaró M, Carreras E, et al. The macrophage soluble receptor AIM/Api6/CD5L displays a broad pathogen recognition spectrum and is involved in early response to microbial aggression. Cell Mol Immunol (2014) 11:343–54.10.1038/cmi.2014.12 PubMed DOI PMC

Gonçalves CM, Castro MA, Henriques T, Oliveira MI, Pinheiro HC, Oliveira C, et al. Molecular cloning and analysis of SSc5D, a new member of the scavenger receptor cysteine-rich superfamily. Mol Immunol (2009) 46:2585–96.10.1016/j.molimm.2009.05.006 PubMed DOI

Balakrishnan L, Bhattacharjee M, Ahmad S, Nirujogi RS, Renuse S, Subbannayya Y, et al. Differential proteomic analysis of synovial fluid from rheumatoid arthritis and osteoarthritis patients. Clin Proteomics (2014) 11:1.10.1186/1559-0275-11-6 PubMed DOI PMC

Miró-Julià C, Roselló S, Martínez VG, Fink DR, Escoda-Ferran C, Padilla O, et al. Molecular and functional characterization of mouse S5D-SRCRB: a new group B member of the scavenger receptor cysteine-rich superfamily. J Immunol (2011) 186:2344–54.10.4049/jimmunol.1000840 PubMed DOI

Miró-Julià C, Escoda-Ferran C, Carrasco E, Moeller JB, Vadekaer DF, Gao X, et al. Expression of the innate defense receptor S5D-SRCRB in the urogenital tract. Tissue Antigens (2014) 83:273–85.10.1111/tan.12330 PubMed DOI

Homola J. Surface plasmon resonance sensors for detection of chemical and biological species. Chem Rev (2008) 108:462–93.10.1021/cr068107d PubMed DOI

Bergwerff AA, van Knapen F. Surface plasmon resonance biosensors for detection of pathogenic microorganisms: strategies to secure food and environmental safety. J AOAC Int (2006) 89:826–31. PubMed

Homola J, Dostálek J, Chen S, Rasooly A, Jiang S, Yee SS. Spectral surface plasmon resonance biosensor for detection of staphylococcal enterotoxin B in milk. Int J Food Microbiol (2002) 75:61–9.10.1016/S0168-1605(02)00010-7 PubMed DOI

Taylor AD, Ladd J, Yu Q, Chen S, Homola J, Jiang S. Quantitative and simultaneous detection of four foodborne bacterial pathogens with a multi-channel SPR sensor. Biosens Bioelectron (2006) 22:752–8.10.1016/j.bios.2006.03.012 PubMed DOI

Oliveira MI, Gonçalves CM, Pinto M, Fabre S, Santos AM, Lee SF, et al. CD6 attenuates early and late signaling events, setting thresholds for T-cell activation. Eur J Immunol (2012) 42:195–205.10.1002/eji.201040528 PubMed DOI PMC

Davis SJ, Ward HA, Puklavec MJ, Willis AC, Williams AF, Barclay AN. High level expression in Chinese hamster ovary cells of soluble forms of CD4 T lymphocyte glycoprotein including glycosylation variants. J Biol Chem (1990) 265:10410–8. PubMed

Pimková K, Bocková M, Hegnerová K, Suttnar J, Cermák J, Homola J, et al. Surface plasmon resonance biosensor for the detection of VEGFR-1 – a protein marker of myelodysplastic syndromes. Anal Bioanal Chem (2012) 402:381–7.10.1007/s00216-011-5395-3 PubMed DOI

Homola J. Surface Plasmon Resonance Based Sensors. Berlin: Springer-Verlag; (2006).

Kneidl J, Löffler B, Erat MC, Kalinka J, Peters G, Roth J, et al. Soluble CD163 promotes recognition, phagocytosis and killing of Staphylococcus aureus via binding of specific fibronectin peptides. Cell Microbiol (2012) 14:914–36.10.1111/j.1462-5822.2012.01766.x PubMed DOI

van der Merwe PA. Surface plasmon resonance. In: Harding S, Chowdry B, editors. Protein-Ligand Interactions: Hydrodynamics and Calorimetry. Oxford, UK: Oxford Univ Press; (2001). p. 137–70.

Chung KH, Park JS, Hwang HS, Kim JC, Lee KY. Detection and kinetics of mucosal pathogenic bacteria binding with polysaccharides. J Microbiol Biotechnol (2007) 17:1191–7. PubMed

Bérubé LR, Schur MK, Latta RK, Hirama T, McKenzie CR, Jarrell HC. Phosphatidyl choline-mediated inhibition of Streptococcus pneumoniae adherence to type II pneumocytes in vitro. Microb Pathog (1999) 26:65–75.10.1006/mpat.1998.0254 PubMed DOI

Salminen A, Loimaranta V, Joosten JA, Khan AS, Hacker J, Pieters RJ, et al. Inhibition of P-fimbriated Escherichia coli adhesion by multivalent galabiose derivatives studied by a live-bacteria application of surface plasmon resonance. J Antimicrob Chemother (2007) 60:495–501.10.1093/jac/dkm251 PubMed DOI

Bustanji Y, Arciola CR, Conti M, Mandello E, Montanaro L, Samorí B. Dynamics of the interaction between a fibronectin molecule and a living bacterium under mechanical force. Proc Natl Acad Sci U S A (2003) 100:13292–7.10.1073/pnas.1735343100 PubMed DOI PMC

Pinto M, Carmo AM. CD6 as a therapeutic target in autoimmune diseases: successes and challenges. BioDrugs (2013) 27:191–202.10.1007/s40259-013-0027-4 PubMed DOI