Molecular studies of memory B cell activation have been hampered by their relative scarcity and lack of effective technical approaches to unveil the distinctive activation pathways employed by memory versus naive B cells. Most memory B cells express IgG-containing B cell receptors, while naive B cells express IgM/IgD. Relative to IgM/IgD, IgG/IgE receptors have an extended cytoplasmic tail that contains conserved phosphotyrosine (pTyr) motifs and confers enhanced survival and proliferation. This proposal utilizes cutting edge proteomic approaches, gene silencing methods and mouse models to elucidate differences in IgM/IgD- versus IgG-based signaling. As tyrosine kinase/phosphatase activity is known to be critical for BCR signaling, our analysis is focused on determining differences in induced tyrosine phosphorylation of downstream substrates by IgG versus IgM/IgD receptors. Based upon our pilot studies we expect to discover three classes of novel pTyr residues: (1) Novel pTyr sites on known BCR signaling effectors;(2) pTyr sites on known proteins not previously associated with BCR signaling intermediates;and (3) pTyr sites on novel proteins. Proteins bearing these novel pTyr sites will be functionally characterized using gene silencing methods in B cell lines and primary IgG-expressing B cells. Further mass spectrometry methods will be applied to characterize proteins binding to the novel pTyr residues. Determining the functional importance and signaling properties of these effectors should greatly aid our understanding of how IgG expression directs memory B cell propagation and differentiation.

Public Health Relevance

Project Narrative The efficacy of many vaccines depends upon the antigen-specific activation of long-lived memory B cells to rapidly differentiate into high-affinity antibody producing cells upon pathogen re-exposure. In chronic autoimmune diseases, production of pathogenic antibody may also be derived from the propagation and subsequent differentiation of memory B cells. Despite their importance, molecular studies of memory B cell activation have been hampered by their relative scarcity and lack of effective technical approaches to unveil the distinctive activation pathways employed by memory versus naove B cells. Most memory B cells express IgG-containing B cell receptors, while naove B cells express IgM/IgD. This proposal utilizes cutting edge proteomic approaches, gene silencing methods and mouse models to identify and evaluate differences in IgM/IgD- versus IgG-based signaling. As tyrosine kinase/phosphatase activity is known to be critical for BCR signaling, our analysis is focused on determining differences in induced tyrosine phosphorylation of downstream substrates by IgG versus IgM/IgD receptors. Determining the functional importance and signaling properties of these effectors should greatly aid our understanding of how IgG expression directs memory B cell propagation and differentiation.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21AI084883-02
Application #
8077304
Study Section
Special Emphasis Panel (ZRG1-IMM-J (02))
Program Officer
Ferguson, Stacy E
Project Start
2010-06-01
Project End
2012-05-31
Budget Start
2011-06-01
Budget End
2012-05-31
Support Year
2
Fiscal Year
2011
Total Cost
$189,090
Indirect Cost
Name
Sanford-Burnham Medical Research Institute
Department
Type
DUNS #
020520466
City
La Jolla
State
CA
Country
United States
Zip Code
92037