DESCRIPTION Of RESEARCH
We investigate molecular mechanisms of B cell activation that regulate humoral immunity and pathogenesis of B cell-mediated diseases. B cells are unique in their ability to make protective antibodies against pathogens. Overactive B cells are often associated with lymphoma/leukemia and autoimmune disorders. B cells respond to environmental cues by migrating in and out of circulation and lymphoid tissues, binding to antigens, and engaging with other components of the immune system. This requires considerable morphological, molecular and cytoskeletal reorganization of the B cell membrane. Dynamic remodeling of the B cell membrane and the underlying actin cytoskeleton also facilitates recruitment and organization of key signaling components to their subcellular sites of action. We have combined cutting edge technologies including electron microscopy, superresolution live cell imaging, intravital multiphoton imaging, quantitative proteomics and genetic knockout mice to study the role of membrane-cytoskeleton remodeling proteins in the regulation of B cell function. We have found that Ezrin, a member of the Ezrin-Radixin-Moesin (ERM) family of membrane-actin cytoskeleton crosslinkers, regulates multiple facets of B cell function, such as proliferation, differentiation, migration, and antibody production. Upon encountering antigens or chemokine gradients, Ezrin undergoes rapid and reversible dephosphorylation at a conserved phosphorylation site. This modification is not only important for antigen-induced lipid raft coalescence, but also for microvillar and lamellipodial dynamics that regulate B cell migration. Structural analysis of Ezrin enabled us to discover a novel role for it as a spatial adaptor that couples the proximal B cell antigen receptor (BCR) signalosome with endosomal signaling pathways. This study re-defined the existing paradigm for the function of ERM proteins in lymphocyte activation. To investigate physiological relevance of these functions during the B cell immune response, we generated mice with conditional B cell-specific deletion of Ezrin. Superresolution imaging of the BCR on live Ezrin-deficient B cells revealed a direct linear relationship between the size of BCR clusters and magnitude of antibody production.Using mass spectrometry-based proteomics we demonstrated that Ezrin interacts with the unconventional myosin family protein Myo18aα, which in turn co-segregates with BCR clusters upon antigen stimulation, suggesting collaborative regulation of BCR dynamics by Ezrin-Actin-Myosin complexes. We are currently investigating Ezrin-mediated regulation of B cell activation in the pathogenesis of B cell autoimmunity and malignancy.
Debasis Pore, Ph.D., Postdoctoral Fellow
Gospel Enyindah-Asonye, B.S., Graduate Student
Dharaniya Sakthivel, B.S, Graduate Student
Neha Desai, Undergraduate Research Student
Sarah Veatch, Ph.D., University of Michigan
Andrea McClatchey, Ph.D., Massachusetts General Hospital and Harvard University
Bernd Wollscheid, Ph.D., Swiss Federal Research Institute, Zurich
Chao-Yie Yang, Ph.D., University of Michigan
Brian Hill, M.D., Ph.D., Hematologic Oncology and Blood Disorders
Mitchell Smith, M.D., Hematologic Oncology and Blood Disorders
James Phillips, Ph.D., Translational Hematology and Oncology Research
Daniel Lindner, Ph.D., Translational Hematology and Oncology Research
Alexandru Almasan, Ph.D., Cancer Biology
Feng Lin, Ph.D., Immunology
Molecular mechanisms of B cell activation and differentiation in health and disease.
Selected Recent Publications
Parameswaran, N. and Gupta, N. 2013. Review: Re-defining ERM function in lymphocyte activation and migration. Immunol. Rev. (Special Issue: The Cytoskeleton), 256:63-79.
Pore, D., Parameswaran, N., Matsui, K., Stone, M.B., Saotome, I., McClatchey, A.I., Veatch, S.L., and Gupta, N. 2013. Ezrin tunes the strength of humoral immunity. J. Immunol., 191:4048-4058.
Parameswaran, N., Enyindah-Asonye, G., Liggett, L., Shah, N., Bagheri, N., and Gupta, N. 2013. Spatial coupling of JNK activation to the B cell antigen receptor by tyrosine-phosphorylated ezrin. J. Immunol. 190:2017-2026.
Kish, D.D., Gorbachev, A.V., Parameswaran, N., Gupta, N., and Fairchild, R.F. 2012. Neutrophil expression of FasL and perforin directs effector CD8 T cell infiltration into antigen-challenged skin. J. Immunol. 189:2191-2202.
Matsui, K., Parameswaran, N., Bagheri, N., Willard, B., and Gupta, N. 2011. Proteomics analysis of the ezrin interactome in B cells reveals a novel association with Myo18aa. J. Proteome Res. 10:3983-3992.
Parameswaran, N., Matsui, K., and Gupta, N. 2011. Conformational switching in ezrin regulates chemokine-induced morphological and cytoskeletal changes required for B cell migration. J. Immunol. 186:4088-4097.