Cholesterol modulates the membrane binding and intracellular distribution of annexin 6.
Annexins are Ca(2+)- and phospholipid-binding proteins that are widely expressed in mammalian tissues and that bind to different cellular membranes. In recent years its role in membrane traffic has emerged as one of its predominant functions, but the regulation of its intracellular distribution still remains unclear. We demonstrated that annexin 6 translocates to the late endocytic compartment in low density lipoprotein-loaded CHO cells. This prompted us to investigate whether cholesterol, one of the major constituents of low density lipoprotein, could influence the membrane binding affinity and intracellular distribution of annexin 6. Treatment of crude membranes or early and late endosomal fractions with digitonin, a cholesterol-sequestering agent, displayed a strong reduction in the binding affinity of a novel EDTA-resistant and cholesterol-sensitive pool of annexin 6 proteins. In addition, U18666A-induced accumulation of cholesterol in the late endosomal compartment resulted in a significant increase of annexin 6 in these vesicles in vivo. This translocation/recruitment correlates with an increased membrane binding affinity of GST-annexin 6 to late endosomes of U18666A-treated cells in vitro. In conclusion, the present study shows that changes in the intracellular distribution and concentration of cholesterol in different subcellular compartments participate in the reorganization of intracellular pools of Ca(2+)-dependent and -independent annexin 6.
de Diego
Iñaki
I
Departament de Biologia Cellular, Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Facultat de Medicina, Universitat de Barcelona, 0836 Barcelona, Spain.
Schwartz
Felix
F
Siegfried
Heide
H
Dauterstedt
Paul
P
Heeren
Joerg
J
Beisiegel
Ulrike
U
Enrich
Carlos
C
Grewal
Thomas
T
D000736:Androstenes / Q000494:pharmacology; D000818:Animals; D017317:Annexin A6 / Q000187:drug effects / Q000378:metabolism*; D000924:Anticholesteremic Agents / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D016466:CHO Cells; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002784:Cholesterol / Q000494:pharmacology*; D006224:Cricetinae; D004072:Digitonin / Q000494:pharmacology; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D007668:Kidney; D007700:Kinetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000187:drug effects / Q000378:metabolism
D000736:Androstenes; D017317:Annexin A6; D000924:Anticholesteremic Agents; D011993:Recombinant Fusion Proteins; C006261:3-beta-(2-(diethylamino)ethoxy)androst-5-en-17-one; D002784:Cholesterol; D004072:Digitonin; D002118:Calcium