Antigen presentation by MHC class II molecules represents a key step in the development of T cell mediated autoimmune diseases. The peptide repertoire presented to CD4 T cells is shaped by the action of HLA-DM, a protein with an MHC-like fold that acts as an enzyme which accelerates peptide exchange. The major goals of the project are to define the mechanism by which DM catalyzes peptide exchange and to examine whether low affinity peptides involved in autoimmune processes can be selectively removed by increasing the editing function of DM. We have identified four small molecules that accelerate DM-catalyzed peptide exchange and increase the activity of this enzyme. These small molecules represent unique tools to examine relevant structural and biological properties of DM. The focus of Aim 1 is to determine the structural basis of DM-catalyzed peptide exchange.
We aim to determine the structure of DM with one of the small molecule accelerators in order to define the small molecule binding site and the conformational change that increases the activity of the enzyme. This structural information will be used to design functional experiments on the catalytic mechanism. We also aim to crystallize the complex of DM with DR/peptide and will examine whether the small molecule accelerators promote the formation of crystals suitable for structure determination by shifting the equilibrium to an active conformation of DM. The focus of Aim 2 is to determine whether low affinity peptides can be selectively removed from MHC class II molecules by increasing the editing function of DM with small molecule accelerators. This question is relevant because T cells specific for low affinity self-peptides can escape tolerance induction and cause autoimmune diseases. For a systematic assessment of the peptide repertoire, we will analyze peptides eluted from MHC class II molecules by mass spectrometry and determine the binding properties of peptides whose abundance is significantly affected by the small molecules. In the B10.PL mouse model of multiple sclerosis, disease is mediated by CD4 T cells specific for the low affinity Ac(1-11 ) peptide of myelin basic protein (MBP) since T cells specific for high affinity determinants are subjected to central and peripheral tolerance mechanisms. T cell experiments will assess whether small molecule accelerators of DM prevent presentation of this self peptide to CD4 T cells. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI057493-04
Application #
7154119
Study Section
Immunobiology Study Section (IMB)
Program Officer
Esch, Thomas R
Project Start
2003-12-01
Project End
2008-11-30
Budget Start
2006-12-01
Budget End
2007-11-30
Support Year
4
Fiscal Year
2007
Total Cost
$364,813
Indirect Cost
Name
Dana-Farber Cancer Institute
Department
Type
DUNS #
076580745
City
Boston
State
MA
Country
United States
Zip Code
02215
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Schulze, Monika-Sarah E D; Wucherpfennig, Kai W (2012) The mechanism of HLA-DM induced peptide exchange in the MHC class II antigen presentation pathway. Curr Opin Immunol 24:105-11
Anders, Anne-Kathrin; Call, Melissa J; Schulze, Monika-Sarah E D et al. (2011) HLA-DM captures partially empty HLA-DR molecules for catalyzed removal of peptide. Nat Immunol 12:54-61
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Grotenbreg, Gijsbert M; Nicholson, Melissa J; Fowler, Kevin D et al. (2007) Empty class II major histocompatibility complex created by peptide photolysis establishes the role of DM in peptide association. J Biol Chem 282:21425-36
Nicholson, Melissa J; Moradi, Babak; Seth, Nilufer P et al. (2006) Small molecules that enhance the catalytic efficiency of HLA-DM. J Immunol 176:4208-20