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. 2007 Oct 29;408(Pt 1):1–5. doi: 10.1042/BJ20071167

Scheme 1. Postulated pathways for intestinal sterol absorption.

Scheme 1

NPC1L1, a transporter located on the brush border of enterocytes, is required for uptake of cholesterol in the intestine. In the intestinal lumen, sterols might be presented to NPC1L1 in the form of mixed micelles (MM) (1) or NPC2, a lysosomal cholesterol-binding protein, might deliver the sterols to NPC1L1 (2). Once taken up in enterocytes via NPC1L1 (3), cholesterol is transported to the endoplasmic reticulum (ER) by pathways that might bypass (4) or involve (5) the endosomal (LE)/lysosomal (LYS) system. In the latter case, NPC1, a lysosomal cholesterol transporter, and NPC2 would be required for egress cholesterol from the endosomal/lysosomal system (6). Once in the endoplasmic reticulum (ER), cholesterol is esterified (CE) and packaged into chylomicron particles (CHY) that are exported in the lymph (7). TGN, trans-Golgi network.