Characterization of beta-arrestin/PAR2 interactions: Role of receptor modification and specific beta-arrestin family members in downstream signaling events

In recent times, GPCR signaling has been a major hotbed of research activity on account of the increasing use of GPCR's as therapeutic targets. Traditionally, GPCR signaling has focused mainly on the signaling propagated by the G-protein components. However, the situation is now being seen as becoming increasingly complex. A multitude of factors are now realized as playing a role in modulating GPCR functioning & signaling. Some of them like the different conformations that the seven transmembrane receptors can adopt when bound by agonists have propagated the pharmacological design of newer and better agonist or inhibitors. Other factors like the identification of different post translationally modified forms of the receptor have also sparked a variety of research activity in the importance of structural features of the receptor in influencing the downstream signals. In addition to all these factors the implications of the interactions of the GPCR's with their non-G-protein downstream effectors that can form a plethora of scaffolding complexes and mediate an independent arm of signaling is also being appreciated.; In this study, we focus on two areas that can modulate the behavior of a GPCR PAR2, which has been shown to be important in a variety of physiological processes. In the first part, we show the importance of beta-arrestins in modulating PAR2 functioning and show that the two individual isoforms of beta-arrestins can have very different effects on the internalization, desensitization and downstream activation of PAR2. These effects are shown to be different in a spatial, temporal as well as a kinetic pattern using a variety of biochemical and cell based approaches. In the second half of this work, we highlight the importance of the different post-translational modifications like phosphorylation (on the carboxyl-tail of the receptor) and glycosylation on the functioning of the receptor. We show that these receptor modifications have the potential to completely alter the signaling profiles of the receptors and thereby change the overall cellular and physiological response.; On the whole this study tries to clarify some of the parameters important in signaling of PAR2 that can be used further in the research for the usage of PAR2 as a therapeutic target.