Trafficking of proteinase-activated receptor-2 and β-arrestin-1 tagged with green fluorescent protein. β-Arrestin-dependent endocytosis of a proteinase receptor

Proteases cleave proteinase-activated receptors (PARs) to expose N- terminal tethered ligands that bind and activate the cleaved receptors. The tethered ligand, once exposed, is always available to interact with its binding site. Thus, efficient mechanisms must prevent continuous activation, including receptor phosphorylation and uncoupling from G-proteins, receptor endocytosis, and lysosomal degradation. β-Arrestins mediate uncoupling and endocytosis of certain neurotransmitter receptors, which are activated in a reversible manner. However, the role of β-arrestins in trafficking of PARs, which are irreversibly activated, and the effects of proteases on the subcellular distribution of β-arrestins have not been examined. We studied trafficking of PAR2 and β-arrestin-1 coupled to green fluorescent protein. Trypsin induced the following: (a) redistribution of β-arrestin-1 from the cytosol to the plasma membrane, where it co-localized with PAR2; (b) internalization of β-arrestin-1 and PAR2 into the same early endosomes; (c) redistribution of β-arrestin 1 to the cytosol concurrent with PAR2 translocation to lysosomes; and (d) mobilization of PAR2 from the Golgi apparatus to the plasma membrane. Overexpression of a C-terminal fragment of β-arrestin-^319-418, which interacts constitutively with clathrin but does not bind receptors, inhibited agonist-induced endocytosis of PAR2. Our results show that β-arrestins mediate endocytosis of PAR2 and support a role for β-arrestins in uncoupling of PARs.