Cholesterol homeostasis machinery

The cholesterol homeostasis machinery is a sophisticated regulatory network responsible for maintaining cellular and systemic sterol balance through the coordinated action of sensors, transporters, enzymes, and transcription factors [Luo et al., 2020, Nat Rev Mol Cell Biol]. At the heart of this system is the SREBP-SCAP-Insig complex located in the endoplasmic reticulum, which senses membrane cholesterol levels and modulates the expression of genes involved in cholesterol uptake and biosynthesis [Brown & Goldstein, 1997, Cell]. When sterol levels are depleted, SREBPs are transported to the Golgi, cleaved into active forms, and translocated to the nucleus to upregulate the Low-Density Lipoprotein Receptor (LDLR) and HMG-CoA Reductase (HMGCR) [Horton et al., 2002, J Clin Invest]. This machinery also includes the PCSK9 protein, which regulates the lysosomal degradation of LDLR, thereby controlling the clearance of LDL from the blood [Seidah & Prat, 2012, Nat Rev Drug Discov]. Dysfunction in these regulatory loops is a major contributor to dyslipidemia, atherosclerosis, and coronary heart disease [Goldstein & Brown, 2015, Cell]. Therapeutic strategies targeting this machinery, most notably statins and PCSK9 inhibitors, are cornerstones of cardiovascular medicine, aimed at reducing circulating cholesterol to prevent major adverse cardiac events [Mach et al., 2020, Eur Heart J].

Other names

Cholesterol regulatory pathwaySREBP pathwaySterol-sensing machineryCholesterol metabolic pathway

Pharmacological modulation of the cholesterol homeostasis machinery involves the competitive inhibition of HMG-CoA reductase to decrease intracellular cholesterol synthesis, the inhibition of PCSK9 to prevent LDL receptor degradation and enhance LDL clearance, and the inhibition of NPC1L1 to block intestinal cholesterol absorption.