Lipoproteins and the hepatocyte

Lipoproteins and the hepatocyte

This slide summarizes the processes regarding lipoproteins in and around the hepatocyte.

  1. Binding of a lipoprotein (LDL, a remnant of chylomicron or IDL) to the LDL-receptor. After endocytosis, the ligand-receptor complex fuses with a lysosome. This results in digestion of the proteins and release of the cholesterol and triglycerides.
  2. Recycling of (excess) cholesterol
    • into bile acid. Cholesterol, which is released from the endosome is transported back to the gall bladder.
    • into newly synthesized lipoprotein (mainly LDL).
  3. Transport of cholesterol to the liver by HDL particles. At the hepatocyte this lipoprotein binds to the SR-B1 receptor and the cholesterol is released to the hepatocyte.
  4. New production of cholesterol. The hepatocyte also produces new cholesterol by an enzymatic process. HMG acetyl CoA converts acetyl CoA into cholesterol. The hepatocyte uses fatty acid oxidation for energy.
  5. Synthesis and assembly of new lipoproteins. The hepatocyte synthesizes new apoproteins. In the Golgi-apparatus these proteins and cholesterol and triglycerides are combined to form new lipoproteins.
1

The rate-limiting step in the conversion of cholesterol to bile acids is 

2

Fatty acids from adipose tissue are transported to sites of utilization in the form of