|
Edward_B_Neufeld
, Adele M. Cooney , Josef Pitha,
Eliezar A. Dawidowicz
, Nancy K. Dwyer, Peter G. Pentchev, E.
Joan Blanchette-Mackie BJU International,
Volume 271, Number 35, Issue of August 30, 1996 pp.
21604-21613
Intracellular Trafficking of Cholesterol Monitored with
a Cyclodextrin
Lipid Cell Biology Section, Laboratory of Cell Biochemistry
and Biology, NIDDK, the ¶ Developmental and
Metabolic Neurology Branch, NINDS, National Institutes of
Health, Bethesda, Maryland 20892
The sterol binding agent 2-hydroxypropyl-b-cyclodextrin
is shown to be a convenient and useful experimental tool to
probe intracellular pathways of cholesterol transport.
Biochemical and cytochemical studies reveal that cyclodextrin
specifically removes plasma membrane cholesterol. Depletion of
plasma membrane sphingomyelin greatly accelerated cyclodextrin-mediated
cholesterol removal. Cholesterol arriving at the plasma membrane
from lysosomes and the endoplasmic reticulum was also removed by
cyclodextrin. Cellular cholesterol esterification linked to the
mobilization of cholesterol from lysosomes was strongly
attenuated by cyclodextrin, suggesting that the major portion of
endocytosed cholesterol is delivered from lysosomes to the
endoplasmic reticulum via the plasma membrane. Evidence for
translocation of lysosomal cholesterol to the endoplasmic
reticulum by a plasma membrane-independent pathway is provided
by the finding that cyclodextrin loses its ability to suppress
esterification when plasma membrane sphingomyelin is depleted.
The Golgi apparatus appears to play an active role in directing
the relocation of lysosomal cholesterol to the plasma membrane
since brefeldin A also abrogated cyclodextrin-mediated
suppression of cholesterol esterification. Using cyclodextrin we
further show that attenuated esterification of lysosomal
cholesterol in Niemann-Pick C cells reflects defective
translocation of cholesterol to the plasma membrane that may be
linked to abnormal Golgi trafficking. |
