| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
2.1 Molecular Interface1
,
,,
,,
* Lawson Health Research Institute,
Department of Microbiology and Immunology, and
Bacterial Pathogenesis Research Group, University of Western Ontario, and
The FOCIS Centre for Clinical Immunology and Immunotherapeutics and Robarts Research Institute, London, Ontario, Canada; and
¶ Boston Biomedical Research Institute, Watertown, MA 02472
Superantigens activate large fractions of T cells through unconventional interactions with both TCR 
-chain V domains (Vs) and MHC class II molecules. The bacterial superantigen streptococcal pyrogenic exotoxin C (SpeC) primarily stimulates human V2+ T cells. Herein, we have analyzed the SpeC-V2.1 interaction by mutating all SpeC residues that make contact with V2.1 and have determined the energetic and functional consequences of these mutations. Our comprehensive approach, including mutagenesis, functional readouts from both bulk T cell populations, and an engineered V2.1+ Jurkat T cell, as well as surface plasmon resonance binding analysis, has defined the SpeC "functional epitope" for TCR engagement. Although only two SpeC residues (Tyr15 and Arg181) are critical for activation of virtually all human CD3+ T cells, a larger cluster of four hot spot residues are required for interaction with V2.1. Three of these residues (Tyr15, Phe75, and Arg181) concentrate their binding energy on the CDR2 loop residue Ser52a, a noncanonical residue insertion found only in V2 and V4 chains. Plasticity of this loop is important for recognition by SpeC. Although SpeC interacts with the V2.1 hypervariable CDR3 loop, our data indicate these contacts have little to no influence on the functional interaction with V2.1. These studies also provide a molecular basis for selectivity and cross-reactivity of SpeC-TCR recognition and reveal a degree of fine specificity in these interactions, whereby certain SpeC mutants are capable of distinguishing between different alleles of the same V domain subfamily.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported by Canadian Institutes of Health Research (CIHR) operating grants (to J.K.M. and J.M.) and National Institutes of Health Grant AI55882 (to E.J.S.). C.B. was supported by a fellowship from the Ontario Research and Development Fund, J.M. holds a Canada Research Chair in Transplantation and Immunobiology, and J.K.M. holds a New Investigator award from the CIHR.
2 Current address: Section of Haemato-Oncology, The Institute of Cancer Research, Chester Beatty Laboratories, 237 Fulham Road SW3 6JB, London, U.K.
3 Address correspondence and reprint requests to Dr. John K. McCormick, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada N6A 5C1. E-mail address: john.mccormick{at}schulich.uwo.ca
4 Abbreviations used in this paper: SAg, superantigen; p/MHC, peptide-MHC; SE, staphylococcal enterotoxin; Spe, streptococcal pyrogenic exotoxin; HV, hypervariable region; FR, framework region; SPR, surface plasmon resonance; TEV, tobacco etch virus.
This article has been cited by other articles:
|
|
 |
|
  K. J. Kasper, W. Xi, A. K. M. Nur-ur Rahman, M. M. Nooh, M. Kotb, E. J. Sundberg, J. Madrenas, and J. K. McCormick Molecular Requirements for MHC Class II {alpha}-Chain Engagement and Allelic Discrimination by the Bacterial Superantigen Streptococcal Pyrogenic Exotoxin C J. Immunol., September 1, 2008; 181(5): 3384 - 3392. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
