Cholesterol efflux to apoA-I in ABCA1-expressing cells is regulated by Ca2+-dependent calcineurin signaling.
ATP-binding cassette transporter A1 (ABCA1) is required for the lipidation of apolipoprotein A-I (apoA-I), although molecular mechanisms supporting this process remain poorly defined. In this study, we focused on the role of cytosolic Ca(2+) and its signaling and found that cytosolic Ca(2+) was required for cholesterol efflux to apoA-I. Removing extracellular Ca(2+) or chelating cytosolic Ca(2+) were equally inhibitory for apoA-I lipidation. We provide evidence that apoA-I induced Ca(2+) influx from the medium. We further demonstrate that calcineurin activity, the downstream target of Ca(2+) influx, was essential; inhibition of calcineurin activity by cyclosporine A or FK506 completely abolished apoA-I lipidation. Furthermore, calcineurin inhibition abolished apoA-I binding and diminished JAK2 phosphorylation, an established signaling event for cholesterol efflux to apoA-I. Finally, we demonstrate that neither Ca(2+) manipulation nor calcineurin inhibition influenced ABCA1's capacity to release microparticles or to remodel the plasma membrane. We conclude that this Ca(2+)-dependent calcineurin/JAK2 pathway is specifically responsible for apoA-I lipidation without directly modifying ABCA1 activity.
Karwatsky
Joel
J
Ottawa Hospital Research Institute and Department of Biochemistry Microbiology and Immunology, University of Ottawa, Ottawa, ON K1H 8L6, Canada.
Ma
Loretta
L
Dong
Fumin
F
Zha
Xiaohui
X
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism*; D000818:Animals; D016632:Apolipoprotein A-I / Q000378:metabolism*; D019703:Calcineurin / Q000378:metabolism*; D065095:Calcineurin Inhibitors; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism*; D006224:Cricetinae; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D053614:Janus Kinase 2 / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D016632:Apolipoprotein A-I; D065095:Calcineurin Inhibitors; D004791:Enzyme Inhibitors; D002784:Cholesterol; D053614:Janus Kinase 2; D019703:Calcineurin; D002118:Calcium