Rabbit small intestine does not contain an annexin II/caveolin 1 complex as a target for 2-azetidinone cholesterol absorption inhibitors.

Intestinal cholesterol absorption is specifically inhibited by the 2-azetidinone cholesterol absorption inhibitor ezetimibe. Photoreactive ezetimibe analogues specifically label a 145-kDa protein in the brush border membrane of enterocytes from rabbit small intestine identified as aminopeptidase N (CD13). In zebrafish and mouse small intestinal cytosol, a heterocomplex of M(r) 52 kDa between annexin II and caveolin 1 was suggested as a target of ezetimibe.

Aminopeptidase N (CD13) is a molecular target of the cholesterol absorption inhibitor ezetimibe in the enterocyte brush border membrane.

Intestinal cholesterol absorption is an important regulator of serum cholesterol levels. Ezetimibe is a specific inhibitor of intestinal cholesterol absorption recently introduced into medical practice; its mechanism of action, however, is still unknown. Ezetimibe neither influences the release of cholesterol from mixed micelles in the gut lumen nor the transfer of cholesterol to the enterocyte brush border membrane.

Intestinal cholesterol absorption: identification of different binding proteins for cholesterol and cholesterol absorption inhibitors in the enterocyte brush border membrane.

Absorption of cholesterol from the intestine is a central part of body cholesterol homeostasis. The molecular mechanisms of intestinal cholesterol absorption and the proteins mediating membrane transport are not known. We therefore aimed to identify the proteins involved in intestinal cholesterol absorption across the luminal brush border membrane of small intestinal enterocytes.

Synthesis of a biotin-tagged photoaffinity probe of 2-azetidinone cholesterol absorption inhibitors.

The design and synthesis of a biotin-tagged photoreactive analogue C-4 of the cholesterol absorption inhibitor Ezetimibe is described. Photoaffinity labeling of intestinal brush border membrane vesicles with C-4 and subsequent streptavidin-biotin chromatography leads to selective extraction of a 145 kDa integral membrane protein as the molecular target for cholesterol absorption inhibitors.

Identification of a ligand-binding site in the Na+/bile acid cotransporting protein from rabbit ileum.

Reabsorption of bile acids occurs in the terminal ileum by a Na(+)-dependent transport system composed of several subunits of the ileal bile acid transporter (IBAT) and the ileal lipid-binding protein. To identify the bile acid-binding site of the transporter protein IBAT, ileal brush border membrane vesicles from rabbit ileum were photoaffinity labeled with a radioactive 7-azi-derivative of cholyltaurine followed by enrichment of IBAT protein by preparative SDS gel electrophoresis. Enzymatic fragmentation with chymotrypsin yielded IBAT peptide fragments in the molecular range of 20.