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
 · 
133 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: P-glycoprotein (ABCB1/MDR1, EC 3.6.3.44), the major efflux transporter at the blood-brain barrier (BBB), is a formidable obstacle to CNS pharmacotherapy. Understanding the mechanism(s) for increased P-glycoprotein activity at the BBB during peripheral inflammatory pain is critical in the development of novel strategies to overcome the significant decreases in CNS analgesic drug delivery. In this study, we employed the λ-carrageenan pain model (using female Sprague-Dawley rats), combined with confocal microscopy and subcellular fractionation of cerebral microvessels, to determine if increased P-glycoprotein function, following the onset of peripheral inflammatory pain, is associated with a change in P-glycoprotein trafficking which leads to pain-induced effects on analgesic drug delivery. Injection of λ-carrageenan into the rat hind paw induced a localized, inflammatory pain (hyperalgesia) and simultaneously, at the BBB, a rapid change in colocalization of P-glycoprotein with caveolin-1, a key scaffolding/trafficking protein. Subcellular fractionation of isolated cerebral microvessels revealed that the bulk of P-glycoprotein constitutively traffics to membrane domains containing high molecular weight, disulfide-bonded P-glycoprotein-containing structures that cofractionate with membrane domains enriched with monomeric and high molecular weight, disulfide-bonded, caveolin-1-containing structures. Peripheral inflammatory pain promoted a dynamic redistribution between membrane domains of P-glycoprotein and caveolin-1. Disassembly of high molecular weight P-glycoprotein-containing structures within microvascular endothelial luminal membrane domains was accompanied by an increase in ATPase activity, suggesting a potential for functionally active P-glycoprotein. These results are the first observation that peripheral inflammatory pain leads to specific structural changes in P-glycoprotein responsible for controlling analgesic drug delivery to the CNS.
    Journal of Neurochemistry 06/2012; 122(5):962-75. · 3.97 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aims of this work were (i) to evaluate the potential of nanostructured lipid carriers (NLCs) as a tool to enhance the oral bioavailability of poorly soluble compounds using saquinavir (SQV), a BCS class IV drug and P-gp substrate as a model drug, and (ii) to study NLC transport mechanisms across the intestinal barrier. Three different NLC formulations were evaluated. SQV transport across Caco-2 monolayers was enhanced up to 3.5-fold by NLCs compared to SQV suspension. M cells did not enhance the transport of NLCs loaded with SQV. The size and amount of surfactant in the NLCs influenced SQV permeability, the transcytosis pathway and the efflux of SQV by P-gp. An NLC of size 247nm and 1.5% (w/v) surfactant content circumvented P-gp efflux and used both caveolae- and clathrin-mediated transcytosis, in contrast to the other NLC formulations, which used only caveolae-mediated transcytosis. By modifying critical physicochemical parameters of the NLC formulation, we were thus able to overcome the P-gp drug efflux and alter the transcytosis mechanism of the nanoparticles. These findings support the use of NLCs approaches for oral delivery of poorly water-soluble P-gp substrates.
    Journal of Controlled Release 12/2012; · 7.63 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The blood-brain barrier (BBB) is a physical and metabolic barrier that separates the central nervous system from the peripheral circulation. Central nervous system drug delivery across the BBB is challenging, primarily because of the physical restriction of paracellular diffusion between the endothelial cells that comprise the microvessels of the BBB and the activity of efflux transporters that quickly expel back into the capillary lumen a wide variety of xenobiotics. Therapeutic manipulation of protein trafficking is emerging as a novel means of modulating protein function, and in this minireview, the targeting of the trafficking of 2 key BBB proteins, P-glycoprotein and occludin, is presented as a novel, reversible means of optimizing central nervous system drug delivery.
    Journal of Investigative Medicine 11/2012; · 1.75 Impact Factor

Full-text

View
3 Downloads
Available from