β-Arrestin1 mediates nicotinic acid–induced flushing, but not its antilipolytic effect, in mice
Robert W. Walters, … , Erin J. Whalen, Robert J. Lefkowitz
Robert W. Walters, … , Erin J. Whalen, Robert J. Lefkowitz
Published April 6, 2009
Citation Information: J Clin Invest. 2009;119(5):1312-1321. https://doi.org/10.1172/JCI36806.
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β-Arrestin1 mediates nicotinic acid–induced flushing, but not its antilipolytic effect, in mice

Abstract

Nicotinic acid is one of the most effective agents for both lowering triglycerides and raising HDL. However, the side effect of cutaneous flushing severely limits patient compliance. As nicotinic acid stimulates the GPCR GPR109A and Gi/Go proteins, here we dissected the roles of G proteins and the adaptor proteins, β-arrestins, in nicotinic acid–induced signaling and physiological responses. In a human cell line–based signaling assay, nicotinic acid stimulation led to pertussis toxin–sensitive lowering of cAMP, recruitment of β-arrestins to the cell membrane, an activating conformational change in β-arrestin, and β-arrestin–dependent signaling to ERK MAPK. In addition, we found that nicotinic acid promoted the binding of β-arrestin1 to activated cytosolic phospholipase A2 as well as β-arrestin1–dependent activation of cytosolic phospholipase A2 and release of arachidonate, the precursor of prostaglandin D2 and the vasodilator responsible for the flushing response. Moreover, β-arrestin1–null mice displayed reduced cutaneous flushing in response to nicotinic acid, although the improvement in serum free fatty acid levels was similar to that observed in wild-type mice. These data suggest that the adverse side effect of cutaneous flushing is mediated by β-arrestin1, but lowering of serum free fatty acid levels is not. Furthermore, G protein–biased ligands that activate GPR109A in a β-arrestin–independent fashion may represent an improved therapeutic option for the treatment of dyslipidemia.

Authors

Robert W. Walters, Arun K. Shukla, Jeffrey J. Kovacs, Jonathan D. Violin, Scott M. DeWire, Christopher M. Lam, J. Ruthie Chen, Michael J. Muehlbauer, Erin J. Whalen, Robert J. Lefkowitz

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Figure 6

Role of β-arrestin1 in binding and activation of cPLA2.

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Role of β-arrestin1 in binding and activation of cPLA2. (A) GPR109A-...
(A) GPR109A-expressing HEK-293 cells were transfected with FLAG–β-arrestin1 or FLAG–β-arrestin2. Nicotinic acid stimulation increased binding of cPLA2 to FLAG–β-arrestin1, but not FLAG–β-arrestin2. (B) Equivalent amounts of cPLA2 and FLAG–β-arrestins were present in each whole cell lysate. Equal amounts of FLAG–β-arrestin were immunoprecipitated in control and nicotinic acid–treated samples. GPR109A-expressing HEK-293 cells were stimulated with 200 μM nicotinic acid, and cell lysates were analyzed for phosphorylated cPLA2 at varying times. Agonist-stimulated activation of cPLA2 in the presence of control siRNA, β-arrestin1 siRNA, or control siRNA plus either pertussis toxin or PD98059 (PD). (C) Binding of FLAG–β-arrestin to cPLA2. *P = 0.0004 versus respective control. (D) Activation or phosphorylation of cPLA2 in siRNA-treated cells. **P = 0.0085 versus respective 10-minute value; ***P = 0.0047 versus respective 0-minute value. Data are mean ± SEM of 3 independent experiments.