NPC1L1 (Niemann-Pick C1-like 1) mediates sterol-specific unidirectional transport of non-esterified cholesterol in McArdle-RH7777 hepatoma cells

Biochem J. 2007 Sep 1;406(2):273-83. doi: 10.1042/BJ20070168.

Abstract

Recent evidence suggests that NPC1L1 (Niemann-Pick C1-like 1) is critical for intestinal sterol absorption in mice, yet mechanisms by which NPC1L1 regulates cellular sterol transport are lacking. In the study we used a McArdle-RH7777 rat hepatoma cell line stably expressing NPC1L1 to examine the sterol-specificity and directionality of NPC1L1-mediated sterol transport. As previously described, cholesterol-depletion-driven recycling of NPC1L1 to the cell surface facilitates cellular uptake of non-esterified (free) cholesterol. However, it has no impact on the uptake of esterified cholesterol, indicating free sterol specificity. Interestingly, the endocytic recycling of NPC1L1 was also without effect on beta-sitosterol uptake, indicating that NPC1L1 can differentiate between free sterols of animal and plant origin in hepatoma cells. Furthermore, NPC1L1-driven free cholesterol transport was unidirectional, since cellular cholesterol efflux to apolipoprotein A-I, high-density lipoprotein or serum was unaffected by NPC1L1 expression or localization. Additionally, NPC1L1 facilitates mass non-esterified-cholesterol uptake only when it is located on the cell surface and not when it resides intracellularly. Finally, NPC1L1-dependent cholesterol uptake required adequate intracellular K(+), yet did not rely on intracellular Ca(2+), the cytoskeleton or signalling downstream of protein kinase A, protein kinase C or pertussis-toxin-sensitive G-protein-coupled receptors. Collectively, these findings support the notion that NPC1L1 can selectively recognize non-esterified cholesterol and promote its unidirectional transport into hepatoma cells.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport
  • Calcium / metabolism
  • Carcinoma, Hepatocellular / metabolism*
  • Cell Line, Tumor
  • Cell Membrane / metabolism
  • Cholesterol / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Esters / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Mutation / genetics
  • Niemann-Pick Diseases / genetics
  • Niemann-Pick Diseases / metabolism
  • Oleic Acid / metabolism
  • Potassium / metabolism
  • Protein Kinase C / metabolism
  • Rats
  • Receptors, G-Protein-Coupled / metabolism
  • Signal Transduction
  • Sitosterols / metabolism

Substances

  • Esters
  • Membrane Proteins
  • Membrane Transport Proteins
  • NPC1L1 protein, rat
  • Receptors, G-Protein-Coupled
  • Sitosterols
  • Oleic Acid
  • gamma-sitosterol
  • Cholesterol
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Potassium
  • Calcium