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: 4.24). 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.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Brain capillary endothelial cells express multiple ATP-binding cassette transport proteins on the luminal, blood-facing, plasma membrane. There these transporters function as ATP-driven efflux pumps for xenobiotics and endogenous metabolites, providing an important element of the barrier. When the transporters limit neurotoxicant entry into the central nervous system (CNS), they are neuroprotective; when they limit therapeutic drug entry, they are obstacles to drug delivery to treat CNS diseases. Certainly, changes in the transporter expression and transport activity can have a profound effect on CNS pharmacotherapy, with increased transport activity reducing drug access to the brain and vice versa. Here, I review the signals that alter transporter expression and transport function with an emphasis on P-glycoprotein, MRP2, and breast cancer resistance protein (ABCG2) (BCRP), the efflux transporters for which we have the most detailed picture of regulation. Recent work shows that transporter protein expression can be upregulated in response to inflammatory and oxidative stress, therapeutic drugs, diet, and persistent environmental pollutants; as a consequence, drug delivery to the brain is reduced. For many of these stimuli, the transcription factor, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), appears to be involved. However, NF-κB activation and nuclear translocation is often initiated by upstream signaling. In contrast, basal transport activity of P-glycoprotein and BCRP can be reduced through complex signaling pathways. Targeting such signals provides opportunities to rapidly and reversibly increase brain accumulation of drugs that are transporter substrates. The extent to which such signaling-based strategies can be utilized in the clinic remains to be seen.
    Advances in pharmacology (San Diego, Calif.) 01/2014; 71C:1-24. DOI:10.1016/bs.apha.2014.06.008
  • [Show abstract] [Hide abstract]
    ABSTRACT: The primary function of the blood-brain barrier (BBB)/neurovascular unit is to protect the central nervous system (CNS) from potentially harmful xenobiotic substances and maintain CNS homeostasis. Restricted access to the CNS is maintained via a combination of tight junction proteins as well as a variety of efflux and influx transporters that limits the transcellular and paracellular movement of solutes. Of the transporters identified at the BBB, P-glycoprotein (P-gp) has emerged as the transporter that is the greatest obstacle to effective CNS drug delivery. In this chapter, we provide data to support intracellular protein trafficking of P-gp within cerebral capillary microvessels as a potential target for improved drug delivery. We show that pain-induced changes in P-gp trafficking are associated with changes in P-gp's association with caveolin-1, a key scaffolding/trafficking protein that colocalizes with P-gp at the luminal membrane of brain microvessels. Changes in colocalization with the phosphorylated and nonphosphorylated forms of caveolin-1, by pain, are accompanied by dynamic changes in the distribution, relocalization, and activation of P-gp "pools" between microvascular endothelial cell subcellular compartments. Since redox-sensitive processes may be involved in signaling disassembly of higher-order structures of P-gp, we feel that manipulating redox signaling, via specific protein targeting at the BBB, may protect disulfide bond integrity of P-gp reservoirs and control trafficking to the membrane surface, providing improved CNS drug delivery. The advantage of therapeutic drug "relocalization" of a protein is that the physiological impact can be modified, temporarily or long term, despite pathology-induced changes in gene transcription.
    Advances in pharmacology (San Diego, Calif.) 01/2014; 71C:25-44. DOI:10.1016/bs.apha.2014.06.009
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Caveolin-1 is the principal marker of caveolae in endothelial cells. It plays an important role in physiological and pathological conditions of the blood-brain barrier and serves as a mediator in drug delivery through the blood-brain barrier. Caveolin-1 is related to the diminished expression of tight junction-associated proteins and metabolic pinocytosis vesicles when the blood-brain barrier is destroyed by outside invaders or malignant stimulus. The permeability of the blood-brain barrier, regulated by types of drugs or physical irradiation, is connected with drug transportation with the participation of caveolin-1. Caveolin-1, which serves as a platform or medium for signal transduction, cooperates with several signal molecules by forming a complex. Silencing of caveolin-1 and disruption of caveolae can attenuate or remove pathological damage and even engender the opposite effects in the blood-brain barrier. This review considers the role of caveolin-1 in the blood-brain barrier that may have profound implications for central nervous system disease and drug delivery through the blood-brain barrier.
    Reviews in the neurosciences 02/2014; 25(2). DOI:10.1515/revneuro-2013-0039 · 3.31 Impact Factor


Available from