Biology subjects

Birch, C. A.

Publications and source records attributed to Birch, C. A..

2 recordsLinked to original sources

bioRxiv2025

Signaling bias of the protease-activated receptor-1 is dictated by distinct GRK5 and β-arrestin-2 determinants

G protein-coupled receptors (GPCRs) exhibit signaling bias, or preferential activation of heterotrimeric G proteins versus GPCR receptor kinase (GRK)-mediated {beta}-arrestin signaling. The protease-activated receptor-1 (PAR1) GPCR activates both G protein and {beta}-arrestin in response to thrombin, but only {beta}-arrestin in response to activated protein C (APC). Thrombin-activated PAR1-G protein signaling is desensitized by {beta}-arrestin-1, whereas APC-activated PAR1 signaling is propagated by {beta}-arrestin-2. The mechanisms underlying PAR1 biased signaling are not known. Here, using computational modeling and cell biology studies, we reveal the molecular basis of signaling by thrombin- and APC-activated PAR1. Although both thrombin- and APC-induced PAR1 signaling are regulated by the same GRK isoform, GRK5, the two types of signaling are differentially dependent on GRK5 membrane anchoring, PAR1 C-terminal phosphorylation, and the binding mode of {beta}-arrestin-2. These differences translate into distinct {beta}-arrestin-2 conformations and define the cytoprotective signaling signature by APC which contrasts with thrombin inflammatory signaling.

cell biology↗

bioRxiv2021

aPC/PAR1 confers endothelial anti-apoptotic activity via a discrete β-arrestin-2 mediated SphK1-S1PR1-Akt signaling axis

Endothelial dysfunction is associated with multiple vascular diseases and lacks effective treatments. Activated Protein C (aPC) is a promising biotherapeutic that signals via protease-activated receptor-1 (PAR1) to promote diverse cytoprotective responses, including endothelial barrier stabilization, anti-inflammatory and anti-apoptotic activities, which is facilitated by co-receptors. We showed that aPC-activated PAR1 signals preferentially via {beta}-arrestin-2 ({beta}-arr2) and dishevelled-2 (Dvl2) scaffolds rather than G proteins to enhance barrier protection. However, the mechanisms by which aPC/PAR1 promotes other cytoprotective responses are poorly understood. Here we define a novel {beta}-arr2-mediated sphingosine kinase-1 (SphK1)-sphingosine-1-phosphate receptor-1 (S1PR1)-Akt signaling axis that confers aPC/PAR1-mediated protection against cell death. We show that PAR1 and S1PR1 co-exist in caveolin-1-rich microdomains basally and aPC markedly increases S1PR1-caveolin-1 co-association. Moreover, aPC stimulates {beta}-arr2-dependent SphK1 activation independent of Dvl2, which is critical for S1PR1 transactivation. These studies reveal that different aPC/PAR1 cytoprotective responses are mediated by discrete {beta}-arr2-driven signaling pathways in caveolae.

cell biology↗