Table 1. β-arrestin-dependent, G-protein-independent signalling by G-protein-coupled receptors.

GPCR	β-arrestin-dependent activity		G-protein-independent?	Sequestration	Response	Reference
B2AR	ERK1/2	↑	Yes	Membrane/nucleus	?? Transcription	Luttrell et al. (1999); Kobayashi et al. (2005); Shenoy et al. (2005)
	NF-kB	↓	??	Cytosol	Inhibition of inflammation	Chandrasekar et al. (2004); Gao et al. (2004); Parameswaran et al. (2006)
A2AR	Src	↑	Yes	??	??	Pierce et al. (2000)
	ERK1/2	↑	Yes			Wang et al. (2006)
AT1R	ERK1/2 (β2)	↑	Yes	Cytosol	Inhibition of transcription	Tohgo et al. (2002, 2003); Ahn et al. (2004); Szidonya et al. (2007)
	RhoA (β1)	↑	No	Cytosol	Stress fibre formation	Barnes et al. (2005)
	Jnk	↑	?	Cytosol	?	McDonald et al. (2000)
PAR-2	ERK1/2	↑	Yes	Cytosol/membrane	Chemotaxis, inhibits proliferation	DeFea et al. (2000a, 2000b); Ge et al. (2003, 2004); Kumar et al. (2007)
	Cofilin	↑	Yes	Leading edge	Filament severing, chemotaxis	Zoudilova et al. (2007)
	LIMK	↓	Yes	Membrane	Filament stability	Zoudilova et al. (2007)
	PI3K	↓	Yes	Membrane/leading edge	Chemotaxis, other functions?	Wang et al. (2006, 2007)
PTHR	ERK1/2	↑	Yes	??	Bone remodelling?	Ferrari et al. (2005); de Gortízar et al. (2006); Gesty-Palmer et al. (2006)
V2R	ERK1/2	↑	Yes	Cytosol	??	Charest and Bouvier (2003); Togho et al. (2003); Charest et al. (2007)
CXCR4	p38MAPK	↑	?	?	Chemotaxis	Sun et al. (2002)
D2R	AkT	↓	Yes?	Cytosol	Motor control/mood	Beaulieu et al. (2005)
MOR	ERK1/2 (β2)	↑	??	Cytosol	?	Clark et al. (2004); Macey et al. (2006); Rozenfeld and Devi (2007)
mGLUR1	ERK1/2	↑	Yes	?	↓Inward current	Tabata et al. (2007)
GHS-R1a	ERK1/2	↑	No	Nucleus	Proliferation	Camina et al. (2007)