Niemann-Pick C1-like 1 protein (NPC1L1)

Niemann-Pick C1-like 1 protein (NPC1L1) is a **membrane sterol transporter** that plays a critical role in the **absorption of dietary and biliary cholesterol** across the brush border membrane of enterocytes in the small intestine. It is also expressed on hepatocyte canalicular membranes in humans. Cholesterol present within bile salt-containing micelles is taken up by enterocytes primarily via this protein. Once inside the cell, free cholesterol must be transported to intracellular compartments such as the endoplasmic reticulum—recent research has identified members of the Aster family as key mediators linking plasma membrane uptake by NPC1L1 to further processing by ACAT2 enzyme for esterification and packaging into chylomicrons[5]. NPC1L1’s function is essential for maintaining whole-body lipid homeostasis; genetic variation or pharmacological inhibition can significantly alter serum LDL-cholesterol concentrations. The most clinically relevant inhibitor is **ezetimibe**, which specifically targets and blocks this transporter at its central tunnel domain, thereby reducing intestinal absorption efficiency and lowering circulating LDL-cholesterol levels—a mechanism distinct from statins that inhibit hepatic synthesis. Altered expression or function has been implicated not only in cardiovascular diseases but also potentially impacts cancer biology through effects on cellular lipid metabolism; notably, reduced expression has been observed in some hepatocellular carcinomas compared to adjacent tissues[2]. Safety concerns with long-term inhibition are generally mild but may include decreased absorption efficiency for fat-soluble nutrients. In summary, **NPC1L1** represents a well-characterized therapeutic target whose modulation directly affects systemic lipid profiles through control over intestinal sterol entry into circulation.[3][4][7]

Other names

NPC1L1Niemann–Pick C1-Like 1cholesterol absorption transporter

Inhibition of NPC1L1 blocks intestinal uptake of cholesterol from micelles into enterocytes, reducing plasma cholesterol levels. Ezetimibe binds to the central tunnel region of NPC1L1, occluding the path for cholesterol transport across the membrane.