Microbiology and Immunology
Uniformed Services University of the Health Sciences
Department of Microbiology and Immunology
4301 Jones Bridge Road
Bethesda, Maryland 20814-4799
Phone: (301) 295-3402
FAX: (301) 295-1545
Brian C. Schaefer, Ph.D.
Ph.D., Harvard University, 1995
Research: NF-κB signaling in T cell activation and in vivo immunity
Our research is focused on investigating signaling events that regulate antigen-dependent lymphocyte activation, with particular emphasis on T cell receptor (TCR) activation of NF-κB. Our experimental approach combines imaging technologies with biochemistry, cell biology, and in vivo models. We are currently focusing on the following major projects:
Figure 1. The TCR to NF-κB pathway. Following TCR activation, PKCθ is recruited to the immunological synapse. Activated PKCθ phosphorylates CARMA1, resulting in formation of the CARMA1, BCL10, MALT1 (CBM) complex. The CBM complex transmits activating signals that ultimately result in ubiquitination (U) and degradation of the NF-κB inhibitor, IκBa. Following IκBα proteolysis, NF-κB translocates to the nucleus and activates transcription of genes required for T cell proliferation and differentiation.
Figure 2. PKC? and Bcl10 redistribution after TCR stimulation. Conalbumin-loaded antigen presenting cells (APC) stimulate D10 T cells, triggering PKC? (red) translocation to the immunological synapse and Bcl10 (green) clustering in the cytoplasm of T cells.
Figure 3. TCR-activated CD4 T cell with cytoplasmic Bcl10 clusters that co-localize with LC3+ autophagosomes. Bcl10 (green) and LC3 (red) signals combine to produce yellow at the region of overlap. Blue is cell surface anti-CD4. The fluorescence image is overlayed on a grayscale DIC image.
1. Elucidating the molecular mechanisms and subcellular organization of T cell receptor-regulated NF-?B signaling intermediates.
Our published studies (Schaefer et al PNAS 2004; Rossman et al MBC 2006; Langel et al JBC 2008; Paul et al Immunity 2012) have documented that TCR stimulation results in the dramatic subcellular redistribution of key NF-?B signaling intermediates into large cytosolic aggregates and/or vesicular structures. Our most recent data suggest that these structures represent a cytoplasmic "signalosome" that is a key site of signal transmission and regulation. The long-term goal of these studies is to reveal the molecular mechanisms responsible for transmitting activating signals from the TCR to NF-?B. This project also includes elucidating mechanisms whereby dysregulation of NF-?B signaling cascades contributes to various forms of cancer.
2. Identifying and characterizing regulatory mechanisms that modulate TCR signals to NF-κB.
Following activation, signaling cascades must be deactivated to restore homeostasis. The mechanisms that modulate the TCR-to-NF-κB cytoplasmic signaling cascade are not yet well understood. We observed that post-TCR stimulation, the NF-κB signaling protein Bcl10 co-localizes with LC3, a marker of autophagosomes (Fig. 3), followed by Bcl10 degradation in autolysosomes. Our recent study (Paul et al Immunity 2012) provides evidence that selective autophagy is a key mechanism of degradation of Bcl10. This autophagy mechanism limits signal transmission from the TCR to NF-κB, We are currently attempting to identify novel molecules that participate in the mechanism which restricts TCR actvation of NF-κB.
3. Investigation of the role of immune cells and NF-κB signaling in functional recovery from traumatic brain injury (TBI).
In this project, we are testing the hypothesis that NF-κB-dependent immune responses are a major determinant of functional recovery, post-TBI. Our goals are to define the contribution of specific NF-κB signaling pathways and NF-κB dependent immune mechanisms to TBI outcomes. Modulation of NF-κB activation and/or specific NF-κB dependent immune responses is a potentially powerful approach for developing effective therapeutic interventions for brain injury, and to promote neuroregeneration.
Mouna Lagraoui, Ph.D.
Sean Maynard, M.S.
Left-to-right: Anuj Kashyap, Ashley Shaloo, Michael Washington, Joe Latoche, Sean Maynard, Natalia Cartwright, Brian Schaefer, Mouna Lagraou
Ayesha Liem, Ph.D.
Natalia Cartwright, Ph.D.
Lara Kingeter, Ph.D.
Felicia Langel, Ph.D.
Jeremy Rossman, Ph.D.
Nidhi Jain, M.S.
Left-to-right: Anuj Kashyap, Suman Paul, Sean Maynard, Michael Washington, Ashley Shaloo, Natalia Cartwright, Ayesha Liem
Paul S, Kashyap AK, Jia W, He YW, Schaefer BC. Selective Autophagy of the Adaptor Protein Bcl10 Modulates T Cell Receptor Activation of NF-κB. Immunity. 2012; 36:947-58.
Cartwright NG, Kashyap AK, Schaefer BC. An active kinase domain is required for retention of PKCθ at the T cell immunological synapse. Mol Biol Cell. 2011; 22:3491-7.
Kingeter LM, Paul S, Maynard SK, Cartwright NG, Schaefer BC. Cutting edge: TCR ligation triggers digital activation of NF-κB. J Immunol. 2010; 185:4520-4.
Kingeter LM and Schaefer BC. Malt1 and cIAP2-Malt1 as effectors of NF-κB activation: Kissing cousins or distant relatives? Cell Signal. 2010; 22:9-22.
Kingeter LM and Schaefer BC. Expanding the multicolor capabilities of basic confocal microscopes by employing red and near-infrared quantum dot conjugates. BMC Biotech. 2009; 9:49.
Langel FD, Jain NA, Rossman JS, Kingeter LM, Kashyap AK, and Schaefer BC. Multiple protein domains mediate interaction between Bcl10 and MALT1. J. Biol. Chem. 2008; 283: 32419-31.
Kingeter LM and Schaefer BC. Loss of PKCtheta, Bcl10, or Malt1 selectively impairs proliferation and NF-κB activation in the CD4+ T cell subset. J. Immunol. 2008; 181:6244-54.
Rossman JS, Stoicheva NG, Langel FD, Patterson GH, Lippincott-Schwartz J, and Schaefer BC. POLKADOTS are foci of functional interactions between cytosolic intermediates in T cell receptor-induced activation of NF-κB. Mol. Biol. Cell 2006; 17:2166-76.
Schaefer BC, Kappler JW, Kupfer A, and Marrack P. Complex and dynamic redistribution of NF-kB signaling intermediates in response to T cell receptor stimulation. Proc. Natl. Acad. Sci. USA. 2004; 101:1004-9.