TY - JOUR
T1 - Intestinal alkaline phosphatase: selective endocytosis from the enterocyte brush border during fat absorption.
AU - Hansen, Gert Helge
AU - Niels-Christiansen, Lise-Lotte
AU - Immerdal, Lissi
AU - Nystrøm, Birthe T
AU - Danielsen, E Michael
N1 - Keywords: Alkaline Phosphatase; Animals; Cells, Cultured; Dietary Fats; Endocytosis; Enterocytes; Intestine, Small; Mice; Microvilli
PY - 2007
Y1 - 2007
N2 - Absorption of dietary fat in the small intestine is accompanied by a rise of intestinal alkaline phosphatase (IAP) in the serum and of secretion of IAP-containing surfactant-like particles from the enterocytes. In the present work, fat absorption was studied in organ cultured mouse intestinal explants. By immunofluorescence microscopy, fat absorption caused a translocation of IAP from the enterocyte brush border to the interior of the cell, whereas other brush-border enzymes were unaffected. By electron microscopy, the translocation occurred by a rapid (5 min) induction of endocytosis via clathrin-coated pits. By 60 min, IAP was seen in subapical endosomes and along membranes surrounding fat droplets. IAP is a well-known lipid raft-associated protein, and fat absorption was accompanied by a marked change in the density and morphology of the detergent-resistant membranes harboring IAP. A lipid analysis revealed that fat absorption caused a marked increase in the microvillar membrane contents of free fatty acids. In conclusion, fat absorption rapidly induces a transient clathrin-dependent endocytosis via coated pits from the enterocyte brush border. The process selectively internalizes IAP and may contribute to the appearance of the enzyme in serum and surfactant-like particles.
AB - Absorption of dietary fat in the small intestine is accompanied by a rise of intestinal alkaline phosphatase (IAP) in the serum and of secretion of IAP-containing surfactant-like particles from the enterocytes. In the present work, fat absorption was studied in organ cultured mouse intestinal explants. By immunofluorescence microscopy, fat absorption caused a translocation of IAP from the enterocyte brush border to the interior of the cell, whereas other brush-border enzymes were unaffected. By electron microscopy, the translocation occurred by a rapid (5 min) induction of endocytosis via clathrin-coated pits. By 60 min, IAP was seen in subapical endosomes and along membranes surrounding fat droplets. IAP is a well-known lipid raft-associated protein, and fat absorption was accompanied by a marked change in the density and morphology of the detergent-resistant membranes harboring IAP. A lipid analysis revealed that fat absorption caused a marked increase in the microvillar membrane contents of free fatty acids. In conclusion, fat absorption rapidly induces a transient clathrin-dependent endocytosis via coated pits from the enterocyte brush border. The process selectively internalizes IAP and may contribute to the appearance of the enzyme in serum and surfactant-like particles.
U2 - 10.1152/ajpgi.00379.2007
DO - 10.1152/ajpgi.00379.2007
M3 - Journal article
C2 - 17947448
SN - 0193-1857
VL - 293
SP - G1325-32
JO - American Journal of Physiology: Gastrointestinal and Liver Physiology
JF - American Journal of Physiology: Gastrointestinal and Liver Physiology
IS - 6
ER -