BIOCHEMISTRY

Dr. David Samols

Professor

• Biochemistry Trainer: YES
  
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• Phone: 216-368-3520
  
• Fax: 216-368-3419
  
• Office: W426
  
• Lab: RT400
  
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Department of Biochemistry
10900 Euclid Avenue
Cleveland, OH 44106-4935

Pub Med:

Dr. David Samols

The mammalian response to inflammation; Function and regulation of the acute phase reactant, C-reactive protein

In mammals, tissue damage or infection leads to a cytokine induced reorchestration of gene expression in the liver resulting in a change in the concentration of a group of serum proteins called the acute phase reactants. The focus of the work in the Samols lab is to understand the dramatic change in abundance of the prototypic acute phase protein, C-reactive protein (CRP) as well as its in vivo function. CRP is a very sensitive reflector of inflammatory status. It is associated with innate immunity and is presumed to play an important role in host defense systems. In humans, CRP is synthesized at very low levels in the absence of inflammatory stimuli but synthesis can increase 100-1000 fold under certain acute inflammatory conditions. Even minimal elevations of circulating CRP are associated with, and predict, a large number of conditions that can be generally classified as “failure to thrive”. Understanding the details of the interplay between defined transcription factors on the CRP promoter will likely explain cytokine-mediated synergy in transcriptional activation of the gene and provide insight into the mechanism of activation of other acute phase protein genes as well.

CRP expression is regulated by cytokines IL-6 and IL-1 through the participation of transcription factors C/EBP, STAT3 and NFκB (rel proteins). Our studies focus on the unique combinations of interactions on the promoter. We have found that the binding of C/EBPβ is critical for cytokine responsiveness and that rel proteins participate in an indirect manner to synergistically activate the transcriptional process. Our data point to a mechanism in which rel proteins, c-rel and p50, alter the conformation of C/EBP? such that the latter shows high affinity and strong transcriptional stimulation activity when bound to its normally poor binding site on the promoter. Thus, protein:protein contacts are altering protein:DNA contacts and c-rel and p50 are acting as coactivators rather than transcription factors.

In a separate project we focus on the function of CRP. Based on in vitro studies, three hallmark properties of CRP have been described; 1) its ability to bind phosphocholine-containing compounds, 2) its ability to bind C1q and activate the classical complement cascade and 3) its ability to interact with IgG receptors on leukocytes. We have created transgenic mice which express CRP driven by a PEPCK promoter in an attempt to determine if these in vitro properties are important in vivo. We have used these mice in three inflammatory models: a model of systemic inflammation employing mediators of septic shock, a model of local inflammation employing pulmonary alveolitis induced with chemokines, and a model of immune-mediated inflammation employing antigen-induced arthritis. In all three, CRP had marked anti-inflammatory properties. We have further created transgenic mice expressing variants of CRP which are either incapable of binding phosphocholine or activating complement. We are currently repeating our models in these strains to begin to determine if in vitro properties correlate with in vivo function.

Selected References

• Samols, D., A. Agrawal and I. Kushner. “Acute Phase Proteins (2002)”  In: Oppenheim, J. J. and Feldman, M. (Eds.).Cytokine Reference On-Line, , Academic Press, Harcourt, London, UK, Website: www.academicpress.com/cytokinereference

• Black, S., I. Kushner and D. Samols. (2004) Minireview: “C-reactive Protein” J.Biol. Chem 279.48487-48490.

• Black, S, A. Wilson and D. Samols (2005) “An intact phosphocholine binding site is necessary for transgenic rabbit CRP to protect mice against challenge with platelet activating factor” J. Immunol 175.  1192-1196.

• Kushner, I, D. Rzewnicki and D. Samols. (2006) “What does minor elevation of C-reactive protein signify” Am J. Med. 119, 166.e17-166.e28.

• Cha-Molstad, H. D. Young, I. Kushner, D. Samols, (2007) “C-Rel facilitates C/EBP-beta binding on the C-reactive protein gene promoter” Mol. Immunol. 44. 2933-42.

Biography

Dr. Samols received his PhD in Cell Biology at the University of Chicago and did postdoctoral training at the Roche Institute of Molecular Biology and at the Institute of Molecular Biology at the University of Oregon. He is currently a Professor of Biochemistry