Skip to main content
eScholarship
Open Access Publications from the University of California

Role of C-Terminal Tails of G Protein Coupled Receptors on Beta-Arrestin 1/2 Dependent Signaling

  • Author(s): Pal, Kasturi
  • Advisor(s): Defea, Kathryn A
  • et al.
Abstract

Protease activated receptor 2 (PAR2) and Neurokinin 1 receptor (NK1R) are 7 transmembrane receptors (7TMRs), which signal by G alpha q leading to Ca2+ release and protein kinase C (PKC) activation. Both receptors are desensitized by beta-arrestin binding to their C termini. They can also activate ERK1/2 through beta-arrestin scaffolding complexes. They differ in ERK1/2 mediated physiological outcomes: cell migration versus proliferation. Using beta-arrestins, PAR2 activates cofilin, to promote chemotaxis, which was not observed in NK1R. We hypothesized that the differences in beta-arrestin dependent signaling by these 7TMRs can be attributed to how the molecular scaffolds bind the C-tail of the receptors. Using wild type and C-tail chimeras, we showed that the rate of desensitization, internalization, subcellular localization post endocytosis as well as ERK1/2 dependent physiological responses depend on the nature of interaction of beta-arrestins with the C-termini. Bioluminescence resonance energy transfer (BRET) assays showed that PAR2 recruits both beta;-arrestin 1/2 faster and with greater affinity than NK1R. We further show that initial G alpha q signaling is necessary for beta-arrestin 1/2 recruitment to NK1R. PAR2 recruits beta-arrestin 1/2 even when G alpha q pathway is blocked. Assays with C terminal phosphorylation mutants of PAR2 indicated that, phosphorylation of certain residues are necessary for beta-arrestin 1/2 recruitment. Phosphorylation at putative PKC sites (S363 and T366) determine stability of PAR2-beta-arrestin 1/2 complex. This in turn ensures downstream cofilin activation and cell migration. BRET assays with PAR2 and G-protein coupled receptor kinase-2 (GRK-2), revealed that GRK2 is recruited to PAR2 in a dose dependent fashion. It is possible that GRK-2 maybe another kinase which regulates PAR2 signaling. Finally, using allergic proteases from Alternaria alternata and Blatella germanica we demonstrated that PAR2 activation by these proteases leads to beta-arrestin 1/2 recruitment and subsequent beta-arrestin 1 dependent cofilin activation and cell migration. Cell migration brought about by the beta-arrestin signaling arm of PAR2 might be an important molecular mechanism for migration of immune cells to the airways, which is an important symptom of allergic asthma.

Main Content
Current View