Differential effects of β-arrestins on the internalization, desensitization and ERK1/2 activation downstream of protease activated receptor-2

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Abstract
β-Arrestins-1 and 2 are known to play important roles in desensitization of membrane receptors and facilitation of signal transduction pathways. It has been previously shown that β-arrestins are required for signal termination, internalization, and ERK1/2 activation downstream of protease-activated-receptor-2 (PAR-2), but it is unclear whether they are functionally redundant or mediate specific events. Here, we demonstrate that in mouse embryonic fibroblasts (MEFs) from β-arrestin-1/2 knockout mice, Gαq signaling by PAR-2, as measured by mobilization of intracellular Ca2+, is prolonged. Only expression of β-arrestin-1 shortened the signal duration, whereas either β-arrestin-1 or 2 was able to restore PKC-induced receptor desensitization. β-arrestin-1 also mediated early, while β-arrestin-2 mediated delayed, receptor internalization and membrane-associated ERK1/2 activation. While β-arrestin-1 colocalized with a lysosomal marker (LAMP-1), β-arrestin-2 did not, suggesting a specific role for β-arrestin-1 in lysosomal receptor degradation. Together, these data suggest distinct temporal and functional roles for β-arrestins in PAR-2 signaling, desensitization, and internalization.

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