Cholesterol transport pathways

Cholesterol transport pathways refer to the complex network of biological processes that regulate cholesterol movement within and between cells and tissues. These pathways are essential for maintaining cholesterol homeostasis throughout the body. The system includes multiple mechanisms: vesicular transport, diffusion through cytoplasm (either protein-bound or free), and transport across membrane contacts. Key components include ATP-binding cassette transporters (ABCA1, ABCG1, ABCG4, ABCG5/G8) that mediate active cholesterol efflux, scavenger receptor BI (SR-BI) that facilitates bidirectional cholesterol exchange, and high-density lipoproteins (HDL) that serve as cholesterol acceptors. The reverse cholesterol transport pathway specifically removes excess cholesterol from peripheral tissues, particularly macrophage foam cells, and delivers it to the liver for excretion via bile. ABCA1 initiates this process by lipidating apolipoprotein A-I to form nascent HDL, while ABCG1 and SR-BI preferentially transfer cholesterol to mature HDL particles. The liver then selectively absorbs lipids from HDL via SR-BI. In the liver and intestine, ABCG5/G8 heterodimers mediate cholesterol secretion into bile and the intestinal lumen. These pathways operate through both energy-dependent and passive mechanisms, with regulation occurring at multiple levels including transcriptional control, post-translational modifications, and substrate availability. Dysfunction in these pathways contributes to atherosclerosis, dyslipidemia, and other metabolic disorders.

Other names

Reverse cholesterol transport (RCT)cholesterol efflux pathwaysintracellular cholesterol transportcholesterol homeostasis pathways

Multiple mechanisms depending on specific targets: ATP-dependent cholesterol efflux (ABCA1, ABCG1), Selective lipid uptake (SR-BI), Cholesterol esterification (LCAT), Cholesterol ester transfer between lipoproteins (CETP), Receptor-mediated lipoprotein uptake (LDLR).