Degree Name
PhD (Doctor of Philosophy)
Program
Biomedical Sciences
Date of Award
5-2020
Committee Chair or Co-Chairs
Dr. Douglas Thewke
Committee Members
Cecilia A. McIntosh, Chuanfu Li, Krishna Singh, Valentin Yakubenko
Abstract
C-reactive protein (CRP) is an acute phase protein of the innate immune system that has been evolutionarily conserved. Human CRP is known to exist in two different pentameric conformations; native CRP and non-native CRP that possess differential ligand recognition functions. The structure of CRP evolved from arthropods to humans, in terms of subunit composition, disulfide bonds, and glycosylation pattern. Along with change in structure, the gene expression pattern of CRP also evolved from a constitutive protein in lower invertebrates to an acute phase protein in humans. The objective of this study was to determine the function of a non-native pentameric CRP, that binds to atherogenic LDL, in atherosclerosis and compare the ligand recognition functions of human pentameric CRP with an evolutionary distant CRP for understanding the evolution of the structure of CRP. Additionally, in vitro reporter gene assays were used to gain further insight into the regulation of human CRP gene expression by an IL-6 inducible transcription factor, STAT3. We observed that CRP, in its non-native pentameric conformation, binds to atherogenic LDL and slows the progression of atherosclerosis in a site-specific manner in high fat diet fed LDLR-/- mice. Further, we observed that the ligand recognition function of CRP from an evolutionary conserved species, Limulus polyphemus, is different than that of native pentameric human CRP, but overlaps that of non-native pentameric human CRP. Lastly, we screened the proximal 300 bp region of the CRP promoter and identified a novel STAT3 binding site at position -134 located upstream of the previously identified, transcriptionally active STAT3 site at -108. In conclusion, non-native pentameric human CRP is an atheroprotective molecule whose ligand recognition functions exhibit similarity with CRP from an evolutionarily distant species. IL-6 mediated transcriptional regulation of human CRP is modulated, in part, by STAT3 binding to two distinct positions on the CRP promoter.
Document Type
Dissertation - unrestricted
Recommended Citation
Pathak, Asmita, "Protection Against Atherosclerosis by A Non-native Pentameric CRP that Shares its Ligand Recognition Functions with an Evolutionarily Distant CRP" (2020). Electronic Theses and Dissertations. Paper 3759. https://dc.etsu.edu/etd/3759
Copyright
Copyright by the authors.