Abstract

Hepatitis B virus (HBV) infections are among the major public health concerns worldwide with more than 250 million of chronically ill individuals. Many of them are additionally infected with the Hepatitis D virus, a satellite virus to HBV. Chronic infection frequently leads to serious liver diseases including cirrhosis and hepatocellular carcinoma, the most common type of liver cancer. Although current antiviral therapies can control HBV replication and slow down disease progress, there is an unmet medical need to identify therapies to cure this chronic infectious disease. Lately, a noteworthy progress in fighting against HBV has been made by identification of the high-affinity hepatic host receptor for HBV and HDV, namely Na+/taurocholate cotransporting polypeptide (NTCP, gene symbol SLC10A1). Next to its primary function as hepatic uptake transporter for bile acids, NTCP is essential for the cellular entry of HBV and HDV into hepatocytes. Due to this high-ranking discovery, NTCP has become a valuable target for drug development strategies for HBV/HDV-infected patients. In this review, we will focus on a newly predicted three-dimensional NTCP model that was generated using computational approaches and discuss its value in understanding the NTCP’s membrane topology, substrate and virus binding taking place in plasma membranes. We will review existing data on structural, functional, and biological consequences of amino acid residue changes and mutations that lead to loss of NTCP’s transport and virus receptor functions. Finally, we will discuss new directions for future investigations aiming at development of new NTCP-based HBV entry blockers that inhibit HBV tropism in human hepatocytes.

Highlights

  • Hepatitis B virus (HBV) infections are one of the major health issues worldwide

  • HBV infection is strictly associated with the development and progression of hepatocellular carcinoma, a primary liver cancer and a major cause of death in patients suffering from cirrhosis, an end-stage liver disease [3]

  • Membrane (TMD) helices [18,23] with an extracellular glycosylated amino terminus and a numerous homology models have been generated for hASBT and hNTCP, giving a first

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Summary

Introduction

Hepatitis B virus (HBV) infections are one of the major health issues worldwide. The virus causes liver infection, which often leads to acute and chronic hepatic diseases such as fulminant hepatic failure and cirrhosis [1,2]. In 2015 the World Health Organization estimated that more than 250 million people around the globe were chronically infected, which resulted in almost 900,000 deaths every year due to HBV-related liver diseases [4]. Since this is the seventh highest cause of worldwide mortality, reducing HBV infections and improving the patients’ treatment is currently aimed in many countries [5,6]. A deep understanding of three-dimensional structure, topology, cellular expression, and physical interactions of target proteins in this process is essential

NTCP’s Protein Sequence Is Evolutionary Conserved
Prediction of Human NTCP Structure
Prediction of Humangenerally
NTCP Primary Function
Protein Engineering as a Valuable Approach to Study NTCP Functions
Conclusions and Future Research
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