Multidrug resistance-associated protein 4 regulates cAMP-dependent signaling pathways and controls human and rat SMC proliferation
Yassine Sassi, Larissa Lipskaia, Grégoire Vandecasteele, Viacheslav O. Nikolaev, Stéphane N. Hatem, Fleur Cohen Aubart, Frans G. Russel, Nathalie Mougenot, Cédric Vrignaud, Philippe Lechat, Anne-Marie Lompré, Jean-Sébastien Hulot
Yassine Sassi, Larissa Lipskaia, Grégoire Vandecasteele, Viacheslav O. Nikolaev, Stéphane N. Hatem, Fleur Cohen Aubart, Frans G. Russel, Nathalie Mougenot, Cédric Vrignaud, Philippe Lechat, Anne-Marie Lompré, Jean-Sébastien Hulot
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Research Article Vascular biology

Multidrug resistance-associated protein 4 regulates cAMP-dependent signaling pathways and controls human and rat SMC proliferation

Abstract

The second messengers cAMP and cGMP can be degraded by specific members of the phosphodiesterase superfamily or by active efflux transporters, namely the multidrug resistance-associated proteins (MRPs) MRP4 and MRP5. To determine the role of MRP4 and MRP5 in cell signaling, we studied arterial SMCs, in which the effects of cyclic nucleotide levels on SMC proliferation have been well established. We found that MRP4, but not MRP5, was upregulated during proliferation of isolated human coronary artery SMCs and following injury of rat carotid arteries in vivo. MRP4 inhibition significantly increased intracellular cAMP and cGMP levels and was sufficient to block proliferation and to prevent neointimal growth in injured rat carotid arteries. The antiproliferative effect of MRP4 inhibition was related to PKA/CREB pathway activation. Here we provide what we believe to be the first evidence that MRP4 acts as an independent endogenous regulator of intracellular cyclic nucleotide levels and as a mediator of cAMP-dependent signal transduction to the nucleus. We also identify MRP4 inhibition as a potentially new way of preventing abnormal VSMC proliferation.

Authors

Yassine Sassi, Larissa Lipskaia, Grégoire Vandecasteele, Viacheslav O. Nikolaev, Stéphane N. Hatem, Fleur Cohen Aubart, Frans G. Russel, Nathalie Mougenot, Cédric Vrignaud, Philippe Lechat, Anne-Marie Lompré, Jean-Sébastien Hulot

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Figure 5

Effect of MRP4 siRNA on cAMP and cGMP cellular levels.

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Effect of MRP4 siRNA on cAMP and cGMP cellular levels. Intracellular/ext...
Intracellular/extra­cellular ratios of (A) cAMP and (B) cGMP, measured with a specific competitive enzyme immunoassay, in hCASMCs transfected with scrambled, MRP5, or MRP4 siRNAs for 72 h and in hCASMCs treated with IBMX (100 μM, 24 h) in the presence or absence of MRP4 siRNA (for 72 h). n = 3. (C) Relative levels of MRP4 mRNA normalized to RPL32 mRNA (*P < 0.05) and (D) MRP4 protein normalized to PP2B in cells untreated or treated with IBMX (100 μM, 24 h). Western blot shows expression of MRP4 and PP2B in hCASMCs untreated or treated with IBMX. *P < 0.05, **P < 0.01, ***P < 0.001.