Multidrug resistance-associated protein 4 regulates cAMP-dependent signaling pathways and controls human and rat SMC proliferation
J. Clin. Invest. Yassine Sassi, et al. 118:2747 doi:10.1172/JCI35067 [Go to this article.]

Figure 1
Expression of MRP4 and MRP5 in hCASMCs. (A) Immuno­fluores­cence analysis of MRP4 and MRP5 expression (red) on a human coronary artery. eNOS (green) is used as a marker of the endothelium. MRP4 cDNA–transfected hCASMCs were labeled using a polyclonal affinity–purified antibody against MRP4. MRP5 was not detected in hCASMCs. Cells were labeled with DAPI (blue). Scale bars: 20 μm. (B) Representative RT-PCR showing detection of MRP4, MRP5, and RPL32 mRNA in cultured hCASMCs and hCAECs. (C) Western blot analysis of MRP4 and MRP5 in total (lane 1) and membrane (lane 2) lysates from hCASMCs and in membranes from wild-type HEK cells (lane 3) and HEK cells stably expressing MRP5 (lane 4) or MRP4 (lane 5). The plasma membrane Ca²⁺ ATPase, PMCA, was used as a loading control. (D) Western blot analysis of MRP4 and caveolin-1 expression in hCASMC membranes purified on a discontinuous sucrose gradient, showing that MRP4 is present in caveolin-1–enriched fractions. Lanes are numbered according to the position of fractions from the top to the bottom of the gradient. Lanes 8 and 9 were run on the same gel but were noncontiguous.