Sodium taurocholate cotransporting polypeptide

Definition

Sodium taurocholate cotransporting polypeptide (NTCP) is a membrane protein that facilitates the uptake of bile acids, specifically sodium taurocholate, into hepatocytes in the liver. This protein plays a critical role in the hepatic uptake of bile acids and is also recognized as a receptor for certain viruses, which utilize NTCP to gain entry into liver cells.

5 Must Know Facts For Your Next Test

1. NTCP is primarily expressed on the basolateral membrane of hepatocytes, allowing for the efficient uptake of bile acids from the portal circulation.
2. The interaction between NTCP and certain viruses, such as Hepatitis B virus (HBV) and Hepatitis D virus (HDV), highlights its importance not just in bile acid transport but also in viral pathogenesis.
3. The function of NTCP is sodium-dependent, meaning it requires sodium ions to facilitate the transport of taurocholate into liver cells.
4. Mutations or dysfunction in NTCP can lead to impaired bile acid homeostasis and contribute to liver diseases, highlighting its clinical significance.
5. Research has shown that NTCP can be downregulated during viral infections, impacting the liver's ability to uptake bile acids and potentially leading to liver injury.

Review Questions

• How does sodium taurocholate cotransporting polypeptide facilitate viral entry into hepatocytes?
  • NTCP serves as a receptor for certain viruses, such as Hepatitis B and D viruses, enabling their entry into hepatocytes. The virus binds to NTCP on the surface of liver cells, exploiting this transport mechanism to gain access to the cellular interior. This interaction is crucial for the initial stages of viral infection and underscores the dual role of NTCP in both bile acid transport and viral pathogenesis.
• Discuss the physiological role of sodium taurocholate cotransporting polypeptide in bile acid metabolism.
  • NTCP plays a vital role in bile acid metabolism by mediating the uptake of sodium taurocholate from the bloodstream into hepatocytes. This uptake is essential for maintaining bile acid homeostasis and facilitating their recycling back into the intestinal tract. By ensuring an adequate supply of bile acids, NTCP supports digestion and absorption of dietary fats, highlighting its importance in overall metabolic health.
• Evaluate the implications of NTCP dysfunction in viral infections and liver diseases.
  • Dysfunction or downregulation of NTCP can significantly impact both viral infections and liver health. Impaired NTCP function may lead to decreased uptake of bile acids, resulting in cholestasis and liver damage. Additionally, if NTCP is altered during viral infections, it may limit viral entry or alter hepatic responses to infection. Thus, understanding NTCP's role offers insights into potential therapeutic targets for managing viral hepatitis and related liver disorders.

Related terms

Bile Acids: Bile acids are steroid acids found predominantly in the bile of mammals, aiding in the digestion and absorption of fats and fat-soluble vitamins.

Hepatocytes: Hepatocytes are the main functional cells of the liver, responsible for various metabolic processes, including detoxification, protein synthesis, and production of biochemicals necessary for digestion.

Viral Entry:

Viral entry is the process by which a virus penetrates the host cell membrane to initiate infection, often involving specific receptors on the host cell surface.