Interaction between complement receptor gC1qR and hepatitis C virus core protein inhibits T-lymphocyte proliferation
David J. Kittlesen, … , Thomas J. Braciale, Young S. Hahn
David J. Kittlesen, … , Thomas J. Braciale, Young S. Hahn
Published November 15, 2000
Citation Information: J Clin Invest. 2000;106(10):1239-1249. https://doi.org/10.1172/JCI10323.
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Article

Interaction between complement receptor gC1qR and hepatitis C virus core protein inhibits T-lymphocyte proliferation

Abstract

Hepatitis C virus (HCV) is an important human pathogen that is remarkably efficient at establishing persistent infection. The HCV core protein is the first protein expressed during the early phase of HCV infection. Our previous work demonstrated that the HCV core protein suppresses host immune responses, including anti-viral cytotoxic T-lymphocyte responses in a murine model. To investigate the mechanism of HCV core-mediated immunosuppression, we searched for host proteins capable of associating with the core protein using a yeast two-hybrid system. Using the core protein as bait, we screened a human T cell–enriched expression library and identified a gene encoding the gC1q receptor (gC1qR). C1q is a ligand of gC1qR and is involved in the early host defense against infection. Like C1q, HCV core can inhibit T-cell proliferative responses in vitro. This core-induced anti–T-cell proliferation is reversed by addition of anti-gC1qR Ab in a T-cell proliferation assay. Furthermore, biochemical analysis of the interaction between core and gC1qR indicates that HCV core binds the region spanning amino acids 188 to 259 of gC1qR, a site distinct from the binding region of C1q. The inhibition of T-cell responsiveness by HCV core may have important implications for HCV persistence in humans.

Authors

David J. Kittlesen, Kimberly A. Chianese-Bullock, Zhi Qiang Yao, Thomas J. Braciale, Young S. Hahn

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Figure 1

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Physical association between HCV core protein and the gC1qR. (a) Identif...
Physical association between HCV core protein and the gC1qR. (a) Identification of interaction between core and gC1qR. Structure of gC1qR is drawn as a box, and the C1q-binding site is indicated as a filled box. Six independent clones interacting with core are represented as a line with a location within the gC1qR. (b) Quantification of interaction between HCV core and the gC1qR. Yeast cells of strain Y187 were cotransformed with plasmids encoding the DNA-binding and -activation domains of the GAL4 transcriptional complex as fusion proteins with the following bait-prey protein combinations: (first bar) pAS2.1 parental vector (GAL4 DNA-binding domain without any carboxy-terminal fusion construct) + pGAD10/gC1qR (GAL4 transcriptional activation domain as the amino-terminal end of a fusion protein with the human gC1q receptor); (second bar) pAS2.1/core 1–124 (GAL4 DNA-binding domain as the amino-terminal end of a fusion protein with the HCV core protein amino acids 1 to 124) + pGAD10/gC1qR; (third bar) pAS2.1/core 1–124 + pGAD10; (fourth bar) pAS2.1/core 1–124 + pGAD10/CRAT1 (a parental GAL4 activation domain vector encoding an irrelevant prey protein as a carboxy-terminal fusion construct); and (fifth bar) pAS2.1/HE4Z (GAL4 DNA-binding domain as amino-terminal end of fusion protein construct with an irrelevant bait protein) + pGAD10/gC1qR. Yeast cells were grown in media maintaining selection for each of the plasmid pairs. Cells were harvested and tested for GAL4 gene activity, indicating association between bait and prey fusion constructs, using a standard method (26). (c) Binding assay for core and gC1qR interaction. Yeast two-hybrid was performed as described above using gC1qR (bait) and core (prey) constructs: (first bar) pAS2.1/gC1qR + pACT2; (second bar) pAS2.1 + pACT2/core; and (third bar) pAS2.1/gC1qR + pACT2/core. aa, amino acid.