B lymphocytes play a critical role in host defenses; however critical mechanisms of their activation and differentiation are poorly understood. For example, intracellular Ca2+ is recognized as being central, yet relatively little is known about how it is regulated. Much of what we know about Ca2+ in lymphocytes has been learned from studies of T cells. For example, Ca2+-Release Activated Calcium (CRAC) channels, which are believed to be their major, and possibly only, antigen receptor-operated Ca2+ channel in T cells, has been studied in great detail, but it has not yet been described in primary B cells. In fact, limited previous studies and our preliminary data demonstrate that the mechanisms of Ca2+ signaling in B cells are more complex than described for T cells, and whether CRAC channels play a similar indispensable role in B cell immunological functions now seems unlikely. We show that B cells utilize CRAC channels, but also additional Ca2+-permeant Non-Selective Cation Channels (NSCC). We further demonstrate that these NSCCs are activated by stimuli associated with innate immune responses including viral and bacterial agonists of Toll like receptors (TLR) called Pathogen-Associated Molecular Patterns (PAMPs), and by mechanical forces. These responses are not observed in T cells. We speculate that these dissimilarities between B and T cells reflect the fundamental difference in the way that these two lymphocyte populations recognize antigens. B cells recognize antigens directly through contact with immunoglobulin molecules at their surface. In contrast, antigen recognition by T cells is indirect and depends upon permissive interactions with antigen presenting cells (APC's). As a safeguard against autoimmunity, recognition of antigen alone is not sufficient to trigger activation; a second signal indicating the presence or absence of danger - TLR ligands such as double-stranded RNA, LPS, LTA, unmethylated CpG DNA that are unique to pathogens - is required. Much of the decision making for a T cell is made by the APC, while the B cell is on its own in terms of integrating costimulatory information and this will require the more complex signaling that we have uncovered. One of the central underlying ideas of this application, therefore, is that appropriate responses of B cells will reflect the coordinated activation of distinct Ca2+ permeant (NSC and CRAC) channels by the overlapping pathways activated by the BCR and innate stimuli. We will use single cell patch clamp recording and calcium imaging methods to biophysically define these channels activated by BCR and innate stimuli, but also a novel modification of this approach to unravel the complex intracellular signaling pathways that coordinate their activation and functions. Our results will have fundamental importance for understanding the basis of immune competence, immune deficiency, and autoimmunity.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI060921-03
Application #
7172920
Study Section
Cellular and Molecular Immunology - B (CMI)
Program Officer
Miller, Lara R
Project Start
2005-02-01
Project End
2010-01-31
Budget Start
2007-02-01
Budget End
2008-01-31
Support Year
3
Fiscal Year
2007
Total Cost
$375,716
Indirect Cost
Name
University of Pennsylvania
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Liu, Xiaohong; Berry, Corbett T; Ruthel, Gordon et al. (2016) T Cell Receptor-induced Nuclear Factor ?B (NF-?B) Signaling and Transcriptional Activation Are Regulated by STIM1- and Orai1-mediated Calcium Entry. J Biol Chem 291:8440-52
Han, Ziying; Madara, Jonathan J; Herbert, Andrew et al. (2015) Calcium Regulation of Hemorrhagic Fever Virus Budding: Mechanistic Implications for Host-Oriented Therapeutic Intervention. PLoS Pathog 11:e1005220
Rao, Sheila; Liu, Xiaohong; Freedman, Bruce D et al. (2013) Spleen tyrosine kinase (Syk)-dependent calcium signals mediate efficient CpG-induced exocytosis of tumor necrosis factor ? (TNF?) in innate immune cells. J Biol Chem 288:12448-58
Psathas, James N; Doonan, Patrick J; Raman, Pichai et al. (2013) The Myc-miR-17-92 axis amplifies B-cell receptor signaling via inhibition of ITIM proteins: a novel lymphomagenic feed-forward loop. Blood 122:4220-9
Lu, Jianhong; Qu, Yonggang; Liu, Yuliang et al. (2013) Host IQGAP1 and Ebola virus VP40 interactions facilitate virus-like particle egress. J Virol 87:7777-80
Babich, Alexander; Li, Shuixing; O'Connor, Roddy S et al. (2012) F-actin polymerization and retrograde flow drive sustained PLC?1 signaling during T cell activation. J Cell Biol 197:775-87
Zhu, Peimin; Liu, Xiaohong; Treml, Laura S et al. (2009) Mechanism and regulatory function of CpG signaling via scavenger receptor B1 in primary B cells. J Biol Chem 284:22878-87
King, Leslie B; Freedman, Bruce D (2009) B-lymphocyte calcium influx. Immunol Rev 231:265-77
Carrizosa, Esteban; Gomez, Timothy S; Labno, Christine M et al. (2009) Hematopoietic lineage cell-specific protein 1 is recruited to the immunological synapse by IL-2-inducible T cell kinase and regulates phospholipase Cgamma1 Microcluster dynamics during T cell spreading. J Immunol 183:7352-61
Shaffer, Meredith H; Dupree, Renell S; Zhu, Peimin et al. (2009) Ezrin and moesin function together to promote T cell activation. J Immunol 182:1021-32

Showing the most recent 10 out of 13 publications