U 18666A

U-18666A is a cell-permeable, cationic amphiphilic steroid that primarily acts as a potent intracellular cholesterol transport inhibitor and cholesterol biosynthesis blocker . It is widely used in biochemical research as a pharmacological tool to manipulate lipid trafficking and composition.

• NPC1 Protein Targeting: U-18666A directly binds to the sterol-sensing domain of the Niemann-Pick type C1 (NPC1) protein. This binding blocks the exit of free, LDL-derived cholesterol from late endosomes and lysosomes.
• Lysosomal Accumulation: By arresting this transport mechanism, it induces massive accumulation of unesterified cholesterol inside lysosomal compartments.
• 2. Mimicking Niemann-Pick Type C (NPC) Disease .
  • Disease Modeling: Because it phenocopies the genetic mutations of the NPC1 protein, U-18666A is the standard chemical tool used to create in vitro and in vivo models of Niemann-Pick type C disease—a rare, fatal neurodegenerative lysosomal storage disorder.
  • 3. Disruption of Cholesterol Biosynthesis [ 1]
    • Enzyme Suppression: Beyond transport, it blocks multiple enzymes in the downstream cholesterol synthesis pathway. It acts as an inhibitor of oxidosqualene cyclase (OSC) and desmosterol reductase.
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