Article

Modulation of p-glycoprotein function by caveolin-1 phosphorylation.

Laboratoire de médecine moléculaire, Hôpital Sainte-Justine, Université du Québec à Montréal, Montréal, Québec, Canada.
Journal of Neurochemistry (Impact Factor: 3.97). 05/2007; 101(1):1-8. DOI: 10.1111/j.1471-4159.2006.04410.x
Source: PubMed

ABSTRACT 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.

0 Bookmarks
 · 
145 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Lipid nanocapsules (LNCs) have been shown to improve paclitaxel (Ptx) bioavailability and transport across an intestinal barrier model. In the present study, the interaction between P-glycoprotein (P-gp) and LNC transport across Caco-2 cells are investigated. Transport experiments have been performed on Caco-2 cells displaying different P-gp activities (early and later cell passages). The permeability of Ptx encapsulated in LNCs has been studied in the presence of P-gp inhibitors (verapamil and vinblastin) or unloaded LNCs. The uptake of dye-labelled LNCs was also observed in the presence of the same inhibitors. It was found that the permeability of Ptx varied depending on the passages with later ones showing higher absolute values (5.74+/-1.21 cms(-1) vs 133.41+/-5.74 cms(-1)). P-gp inhibition obtained with verapamil or vinblastin improved Ptx transport up to 98%. LNCs have also demonstrated their capacity to increase their own transport. Experiments performed with dye-labelled LNCs demonstrated an enhancement of the uptake of dye (Nile red), only in the presence of verapamil. These results demonstrated an effect of P-gp on the transport of Ptx when loaded in LNCs and support a direct effect of P-gp on their endocytosis in Caco-2 cells. These finding may assist in the development of new nanomedicine for oral administration.
    European journal of pharmaceutical sciences: official journal of the European Federation for Pharmaceutical Sciences 05/2010; 40(5):422-9. · 2.61 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Increased brain expression of vascular endothelial growth factor (VEGF) is associated with neurological disease, brain injury, and blood-brain barrier (BBB) dysfunction. However, the specific effect of VEGF on the efflux transporter P-glycoprotein, a critical component of the BBB, is not known. Using isolated rat brain capillaries and in situ rat brain perfusion, we determined the effect of VEGF exposure on P-glycoprotein activity in vitro and in vivo. In isolated capillaries, VEGF acutely and reversibly decreased P-glycoprotein transport activity without decreasing transporter protein expression or opening tight junctions. This effect was blocked by inhibitors of the VEGF receptor flk-1 and Src kinase, but not by inhibitors of phosphatidylinositol-3-kinase or protein kinase C. VEGF also increased Tyr-14 phosphorylation of caveolin-1, and this was blocked by the Src inhibitor PP2. Pharmacological activation of Src kinase activity mimicked the effects of VEGF on P-glycoprotein activity and Tyr-14 phosphorylation of caveolin-1. In vivo, intracerebroventricular injection of VEGF increased brain distribution of P-glycoprotein substrates morphine and verapamil, but not the tight junction marker, sucrose; this effect was blocked by PP2. These findings indicate that VEGF decreases P-glycoprotein activity via activation of flk-1 and Src, and suggest Src-mediated phosphorylation of caveolin-1 may play a role in downregulation of P-glycoprotein activity. These findings also imply that P-glycoprotein activity is acutely diminished in pathological conditions associated with increased brain VEGF expression and that BBB VEGF/Src signaling could be targeted to acutely modulate P-glycoprotein activity and thus improve brain drug delivery.
    Journal of Neuroscience 01/2010; 30(4):1417-25. · 6.91 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Caveolin-1 (Cav-1) isoforms, including Cav-1α and Cav-1β, were identified as integral membrane proteins and the major components of caveolae. Cav-1 proteins are highly conserved during evolution from {itCaenorhabditis elegans} to human and are capable of interacting with many signaling molecules through their caveolin scaffolding domains to regulate the activities of multiple signaling pathways. Thus, Cav-1 plays crucial roles in the regulation of cellular proliferation, differentiation and apoptosis in a cell-specific and contextual manner. In addition, Cav-1 is essential for embryonic development of vertebrates owing to its regulation of BMP, Wnt, TGF-β and other key signaling molecules. Moreover, Cav-1 is mainly expressed in terminally differentiated cells and its abnormal expression is often associated with human diseases, such as tumor progression, cardiovascular diseases, fibrosis, lung regeneration, and diseases related to virus. In this review, we will further discuss the potential of Cav-1 as a target for disease therapy and multiple drug resistance. KeywordsCaveolin-1–signal transduction–embryonic development–human diseases
    01/2011; 6(5):367-376.

Full-text

View
3 Downloads
Available from