Members of the transcription factor NF-?B and inhibitor I?B families are the key regulators of diverse array of cell signaling pathways that have profound impact on cell physiology, in particular, immuno-modulation, survival and proliferation of cell. NF-?B1 (also called p105/p50) and NF-?B2 (also called p100/p52) belong to both the NF-?B and I?B families. p105 and p100 are the precursors which processed into smaller products, p50 and p52, members of the NF-?B family. Precursors function as inhibitors of NF-?B, including their own processed products. Processing must be tightly regulated to generate appropriate ratio of unprocessed and processed forms. Many human diseases, such as autoimmune diseases and cancer, are linked to unregulated processing of p100 and p105. p105 and p100 divulge highly complex regulatory events in the NF-?B signaling module by generating all of NF-?B p50 and p52 proteins and inhibiting nearly half of all five NF-?B proteins. Like the prototypical I?B inhibitors, I?B?,-? and -?, p105 and p100 inhibitors also undergo complete degradation releasing NF-?B transcription factors. However, complete degradation events are difficult to observe in the backdrop of the processing events and thus are less appreciated. Processing of p105 is constitutive whereas that of p100 is inducible. This proposal aims to study the biochemical mechanisms of processing and complete degradation and coupling between these two events. Our hypothesis, derived from our preliminary results and published reports, is that the fundamental regulation of processing or lack of it is guided by several competing inter- and intra-domain interactions in p105 and p100, and these interactions can be altered by signaling. We propose that p105-self interaction induces a structural state that is conducive to constitutive processing whereas p100 attains that state only through signaling. We further propose that as the fully assembled NF-?B inhibitory complexes, the processing sites of p105 and p100 are masked. p105 and p100 in these assembled complexes must undergo complete degradation by cell signaling to liberate bound NF-?B. We will test our hypothesis by i) determining the three-dimensional structures of p105/p100 bound to NF-?B using x- ray crystallography, ii) identifying interaction strategies and energies of the p105/p100:NF-?B complexes, and finally, iii) studying the processing and degradation of the precursors.

Public Health Relevance

Our proposed research has the potential to unravel the long-standing question of how the two NF-kappaB precursor proteins carry out dual functions both as transcription factors and inhibitors of NF-kB. Misregulation of both these proteins are strongly linked to auto-immune diseases and cancer. Current therapy against multiple myeloma function as an inhibitor of aberrant NF-kB activation. Our work will play a major role identifying new and better inhibitors.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI064326-08
Application #
8460811
Study Section
Special Emphasis Panel (ZRG1-BCMB-R (02))
Program Officer
Mallia, Conrad M
Project Start
2005-02-15
Project End
2016-04-30
Budget Start
2013-05-01
Budget End
2014-04-30
Support Year
8
Fiscal Year
2013
Total Cost
$327,825
Indirect Cost
$116,325
Name
University of California San Diego
Department
Chemistry
Type
Schools of Arts and Sciences
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
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Fusco, Amanda J; Huang, De-Bin; Miller, Dustyn et al. (2009) NF-kappaB p52:RelB heterodimer recognizes two classes of kappaB sites with two distinct modes. EMBO Rep 10:152-9
Huxford, Tom; Ghosh, Gourisankar (2009) A structural guide to proteins of the NF-kappaB signaling module. Cold Spring Harb Perspect Biol 1:a000075
Shih, Vincent F-S; Kearns, Jeffrey D; Basak, Soumen et al. (2009) Kinetic control of negative feedback regulators of NF-kappaB/RelA determines their pathogen- and cytokine-receptor signaling specificity. Proc Natl Acad Sci U S A 106:9619-24
Moorthy, Anu K; Savinova, Olga V; Ho, Jessica Q et al. (2006) The 20S proteasome processes NF-kappaB1 p105 into p50 in a translation-independent manner. EMBO J 25:1945-56