# Entry and post entry effect of NTCP receptor on HBV life cycle

> **NIH NIH R21** · RHODE ISLAND HOSPITAL · 2020 · $241,500

## Abstract

Project Summary/Abstract
 Identification of sodium taurocholate cotransporting polypeptide (NTCP) as a functional hepatitis
B virus (HBV) receptor solved a longstanding puzzle and represented a major breakthrough in the field.
Silencing NTCP expression impairs HBV infectivity in primary human hepatocytes and differentiated
HepaRG cell line, whereas NTCP overexpression in HepG2 cell line confers HBV susceptibility.
Curiously, HepG2/NTCP cells can be efficiently infected by cell culture-derived HBV (cHBV) of
genotype D, but not by patient serum-derived HBV (sHBV) of genotype C. In this regard genotype D is
unique in lacking 11 residues between the N-terminal myristyolation signal and the NTCP binding motif
in the large (L) envelope protein. Another abnormality is that cHBV infected HepG2/NTCP cells, but not
HepaRG cells, overproduce hepatitis B e antigen (HBeAg) relative to hepatitis B surface antigen
(HBsAg). We found that NTCP overexpression in the absence of infection increased HBV RNAs,
replicative DNA, and proteins. In this regard NTCP is a liver-specific transporter of conjugated bile
acids, some of which are ligands and activators of transcription factor FXRα. FXRα stimulates
transcription of the 3.5-kb HBV RNA, which drives genome replication and HBeAg but not HBsAg
expression. In this R21 grant application we will clarify both the receptor function of NTCP and its
transcriptional impact. In Aim 1 we will compare cHBV infectivity between genotype D and non-D
genotypes in HepG2/NTCP cells, and establish the impact of the 11 residues in L protein on cHBV
infectivity through site-directed mutagenesis. Aim 2 will employ a HepG2 cell line with inducible NTCP
expression to estimate the post-entry effect of NTCP on HBV RNA, DNA, and HBsAg/HBeAg ratio
following cHBV infection, and on HBV DNA replication and protein production driven by an integrated
HBV genome. Aim 3 will verify whether NTCP promotes HBV RNA transcription through bile acids and
transcription factor FXRα. This will be achieved by depleting bile acids from culture medium, by NTCP
mutants impaired in bile acid transport, and by FXRα silencing. The proposed studies should clarify
whether relative to HepaRG cells, HepG2/NTCP cells are poorly susceptible to sHBV infection, or to
non-D HBV genotypes. This should spur the search for additional host factors for efficient HBV infection
in cell culture. A role of NTCP in up regulating HBV RNA transcription, an early step in viral life cycle,
makes it an attractive therapeutic target for chronic HBV carriers.
!

## Key facts

- **NIH application ID:** 9822959
- **Project number:** 5R21AI142456-02
- **Recipient organization:** RHODE ISLAND HOSPITAL
- **Principal Investigator:** Jisu Li
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $241,500
- **Award type:** 5
- **Project period:** 2018-11-14 → 2021-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9822959

## Citation

> US National Institutes of Health, RePORTER application 9822959, Entry and post entry effect of NTCP receptor on HBV life cycle (5R21AI142456-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9822959. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*