P., S. from the Golgi to the plasma membrane of KNRK cells. After incubation of HEK293 cells and dorsal root ganglia neurons with CS, NE, or trypsin, PAR2 responsiveness initially declined, consistent with PAR2 cleavage and desensitization, and then gradually recovered. Inhibitors of PKD, G, and protein translation inhibited recovery of PAR2 responsiveness. PKD and G inhibitors also attenuated protease-evoked mechanical allodynia in mice. We conclude that proteases that activate PAR2 by canonical and biased mechanisms stimulate PKD in the Golgi; PAR2 mobilization and synthesis repopulate the cell surface with intact receptors and sustain nociceptive signaling by extracellular proteases. protein synthesis or translocation of intact receptor from a preexisting pool is required for replenishment of the plasma membrane with functioning receptors. PARs are a small family of GPCRs that are activated by proteolytic cleavage within the extracellular N-terminal region (8). Several serine and cysteine proteases can cleave and activate PAR2, including trypsins (9, 10), mast cell tryptase (11), kallikreins (12), NE (13, 14) and CS, a cysteine protease from antigen-presenting cells (15). Trypsin, tryptase, and kallikreins activate PAR2 by a canonical mechanism. Trypsin cleaves PAR2 at R36S37, which reveals the tethered ligand domain name (S37LIGKV for human PAR2). This cleavage results in PAR2 coupling to Gq, Gs, and -arrestins, FLJ12455 leading to mobilization of Ca2+, generation of cAMP, and activation of protein kinase C (PKC) and A (PKA) and of extracellular signal-regulated kinases (16, 17). -Arrestins mediate desensitization and endocytosis of PAR2, which then traffics to lysosomes and is degraded (17). Given the irreversible mechanism of proteolytic activation, Vaccarin cleaved PAR2 cannot be reactivated by proteolysis (16). Recovery of cell surface PAR2 signaling involves mobilization of intact receptors from a preexisting Golgi pool as well as synthesis of fresh receptors (16). NE and CS are activated and released from inflammatory cells at sites of injury and inflammation, retain activity in extracellular fluid, and can cause PAR2-dependent inflammation and pain (14, 15, 18). However, CS and NE activate biased pathways of PAR2 signaling and trafficking. CS cleaves human PAR2 at E56T57 to expose the tethered ligand (T57VFSVDEFSA), which promotes PAR2 coupling to Gs (15). NE cleaves at A66S67 and S67V68, adjacent to the first transmembrane domain name, which activates PAR2 by a nontethered ligand mechanism and induces coupling to Gs and G12/13 (13, 14). CS- and NE-activated PAR2 fails to couple Vaccarin to Gq and neither recruits -arrestins nor internalizes. We recently reported that trypsin cleavage of PAR2 at the plasma membrane induces translocation of G to the Golgi apparatus, where G activates PKD (19). PKD mediates the mobilization of PAR2 stores from the Golgi apparatus, which replenishes the plasma membrane with fresh receptors that are necessary for sustained trypsin signaling (19). In the present study, Vaccarin we investigated the mechanisms that underlie sustained signaling of proteases that activate PAR2 by biased mechanisms. Results Proteases that activate PAR2 by canonical and biased mechanisms induce PAR2-dependent PKD activation By using immunoblotting and immunofluorescence, we have previously reported that trypsin activation of PAR2 leads to PKD phosphorylation (activation) in the Golgi apparatus (19). To quantitatively assess PKD activation in live cells with high spatial and temporal fidelity, we expressed in human embryonic kidney (HEK293) cells genetically encoded FRET biosensors for PKD that are targeted to the cytosol (Cyto-DKAR) or Golgi apparatus (Golgi-DKAR) (20). We examined whether proteases that activate PAR2 by canonical or biased mechanisms can stimulate PKD activity in the cytosol or plasma membrane of HEK293 cells transiently expressing human PAR2 (hPAR2). To confirm that alterations in FRET were attributable to PKD activation, we expressed a T/A mutated PKD sensor (DKAR-T/A) in which the PKD phosphorylation site in the substrate domain is usually mutated. We first confirmed the expected subcellular localization of PKD FRET biosensors expressed in HEK293 cells by confocal microscopy. Cyto-DKAR was uniformly distributed throughout the cytosol, whereas Golgi-DKAR colocalized exclusively with immunoreactive TGN58K, a marker of the Golgi apparatus (Fig. 1= 3C5 experimental replicates, triplicate observations. *, 0.05; **, 0.01 to vehicle (one-way ANOVA, Bonferroni multiple comparisons). and and = 3C6 experimental replicates, triplicate observations. *, 0.05 (Student’s test)..