Modulation of p-glycoprotein function by caveolin-1 phosphorylation.
p-glycoprotein (p-gp) is an ATP-binding cassette transporter and its overexpression is responsible for the acquisition of the multidrug resistance phenotype in human tumors. p-gp is localized at the blood-brain barrier and is involved in brain cytoprotection. Our previous work used immunoprecipitation to show that caveolin-1 can interact with p-gp. In this study, we provide evidence that caveolin-1 regulates p-gp transport activity in a rat brain endothelial cell line (RBE4). Down-regulation of caveolin-1 by siRNA reduced the interaction between p-gp and caveolin-1, followed by a decrease in [3H]-Taxol and [3H]-Vinblastine accumulation in RBE4 cells. The latter result showed that down-regulation of caveolin-1 enhanced p-gp transport activity. RBE4 cells were also transfected with Sarcoma in order to modulate caveolin-1 phosphorylation. Overexpression of Sarcoma, a protein tyrosine kinase, stimulated caveolin-1 phosphorylation and increased both [3H]-Taxol and [3H]-Vinblastine accumulation as well as Hoechst 33342 accumulation. Transfection of caveolin-1 inhibits p-gp transport activity. Conversely, transfection of the mutant cavY14F decreased the p-gp/caveolin-1 interaction and reduced accumulation of the two p-gp substrates. Thus, our data show that caveolin-1 regulates p-gp function through the phosphorylation state of caveolin-1 in endothelial cells from the blood-brain barrier.
Barakat
Stéphane
S
Laboratoire de médecine moléculaire, Hôpital Sainte-Justine, Université du Québec à Montréal, Montréal, Québec, Canada.
Demeule
Michel
M
Pilorget
Anthony
A
Régina
Anthony
A
Gingras
Denis
D
Baggetto
Loris G
LG
Béliveau
Richard
R
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D001812:Blood-Brain Barrier / Q000378:metabolism*; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D002461:Cell Line, Transformed; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D017239:Paclitaxel / Q000493:pharmacokinetics; D010766:Phosphorylation; D021381:Protein Transport / Q000502:physiology; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D051381:Rats; D014747:Vinblastine / Q000493:pharmacokinetics; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D051242:Caveolin 1; D034741:RNA, Small Interfering; D014747:Vinblastine; D019061:src-Family Kinases; D017239:Paclitaxel