Novel Role for Proteinase-activated Receptor 2 (PAR2) in Membrane Trafficking of Proteinase-activated Receptor 4 (PAR4)

Abstract

Background: Bioinformatic analysis revealed that PAR 4 possesses an ER retention motif. Results: PAR 2 both abrogates and facilitates chaperone protein interaction with PAR 4 to allow PAR 4 to evade ER retention and be delivered to the plasma membrane. Conclusion: PAR 2 regulates PAR 4 localization and cell signaling through heterodimerization. Significance: Impact upon understanding PAR 2 and PAR 4 in inflammation where clear roles are defined.

Molecular Determinants of the Human α2C-Adrenergic Receptor Temperature-Sensitive Intracellular Traffic

“…The b-COP subunit of the COPI complex recognizes RXR motifs stimulating the retrograde traffic from Golgi to endoplasmic reticulum, whereas 14-3-3 proteins assist motif masking and promote export trafficking (Dong et al, 2007). Both these mechanisms were shown to modulate subcellular localization of different members of the GPCR family, such as PAR2 and GPR15 (Okamoto and Shikano, 2011;Cunningham et al, 2012). However, our results indicate that 14-3-3z is not involved in temperaturesensitive a 2C -AR transport.…”

“…Two major mechanisms were proposed to underlie the endoplasmic reticulum retention by the RXR motifs, namely, retrograde transport through COPI vesicles mediated by interactions with the b-COP subunit and binding to 14-3-3 proteins (Okamoto and Shikano, 2011;Cunningham et al, 2012). However, 14-3-3z overexpression did not change the human a 2C -AR plasma membrane levels at 37°C or at 30°C in transfected HEK293T cells (Fig.…”

Cofactoring and Dimerization of Proteinase-Activated Receptors

“…Disruption of a putative b2-AR dimerization motif GXXXGXXXL in TM VI also prevented wild-type b2-AR trafficking to the plasma membrane, suggesting that the mutants exert a dominant affect. PAR4 was also found to contain a functional arginine-based ER retention signal within the second intracellular loop (Cunningham et al, 2012). It is intriguing that PAR2 coexpression enhanced PAR4 trafficking to the cell surface in both a keratinocyte cell line NCTC-2544 and HEK293 cells, indicating that PAR2 drives PAR4 trafficking through the biosynthetic pathway.…”

“…BRET was also used to demonstrate that murine PAR3 and PAR4 form constitutive homodimers and heterodimers when expressed in HEK293 cells (Arachiche et al, 2013). Given the presence of an ER retention signal in PAR4 (Cunningham et al, 2012), it will be important to determine if PAR4 trafficking through the biosynthetic pathway is regulated by homodimerization and/or heterodimerization with either PAR1 or PAR3, which to our knowledge has not been investigated.…”

“…It is intriguing that PAR2 coexpression enhanced PAR4 trafficking to the cell surface in both a keratinocyte cell line NCTC-2544 and HEK293 cells, indicating that PAR2 drives PAR4 trafficking through the biosynthetic pathway. As a consequence, PAR2 enhanced N-linked glycosylation of PAR4 and signaling (Cunningham et al, 2012). To evaluate PAR4-PAR2 interaction, coimmunoprecipitation and intermolecular FRET were used together with full-length PAR4 fused to CFP and PAR2 fused to YFP in HEK293 cells.…”