ß-arrestins are multifunctional proteins that modulate heptahelical 7 transmembrane receptors, also known as G protein-coupled receptors (GPCRs), a superfamily of receptors that regulate most physiological processes. ß-arrestin modulation of GPCR function includes termination of G protein-dependent signaling, initiation of ß-arrestin-dependent signaling, receptor trafficking to degradative or recycling pathways, receptor transactivation, transcriptional regulation, and localization of second messenger regulators. The pleiotropic influence ß-arrestins exert on these receptors regulates a breadth of physiological functions, and additionally, ß-arrestins are involved in the pathophysiology of numerous and wide-ranging diseases, making them prime therapeutic targets. In this review, we briefly describe the mechanisms by which ß-arrestins regulate GPCR signaling, including the functional cellular mechanisms modulated by ß-arrestins and relate this to observed pathophysiological responses associated with ß-arrestins. We focus on the role for ß-arrestins in transducing cell signaling; a pathway that is complementary to the classical G protein-coupling pathway. The existence of these GPCR dual signaling pathways offers an immense therapeutic opportunity through selective targeting of one signaling pathway over the other. Finally, we will consider several mechanisms by which the potential of dual signaling pathway regulation can be harnessed and the implications for improved disease treatments.

Internalization of membrane proteins plays a key role in many physiological functions; however, highly sensitive and versatile technologies are lacking to study such processes in real-time living systems. Here we describe an assay based on bioluminescence able to quantify membrane receptor trafficking for a wide variety of internalization mechanisms such as GPCR internalization/recycling, antibody-mediated internalization, and SARS-CoV2 viral infection. This study represents an alternative drug discovery tool to accelerate the drug development for a wide range of physiological processes, such as cancer, neurological, cardiopulmonary, metabolic, and infectious diseases including COVID-19.

Introduction: The adult heart lacks the regenerative capacity to self-repair. Serum response factor (SRF) is essential for heart organogenesis, sarcomerogenesis, and contractility. SRF interacts with co-factors, such as NKX2.5 and GATA4, required for cardiac specified gene activity. ETS factors such as ELK1 interact with SRF and drive cell replication. To weaken SRF interactions with NKX2.5 and GATA4, one mutant, SRF153(A3) named STEMIN, did not bind CArG boxes, yet induced stem cell factors such as NANOG and OCT4, cardiomyocyte dedifferentiation, and cell cycle reentry. The mutant YAP5SA of the Hippo pathway also promotes cardiomyocyte proliferation and growth. Aim: Infarcted adult mouse hearts were injected with translatable STEMIN and YAP5SA mmRNA to evaluate their clinical potential, Methods and Results: Mice were pulsed one day later with alpha-EDU and then heart sections were DAPI stained. Replicating cells were identified by immuno-staining against members of the DNA replisome pathway that mark entry to S phase of the cell cycle. Echocardiography was used to determine cardiac function following infarcts and mRNA treatment. To monitor cardiac wall repair, microscopic analysis was performed, and the extent of myocardial fibrosis was analyzed for immune cell infiltration. Injections of STEMIN and YAP5SA mmRNA into the left ventricles of infarcted adult mice promoted a greater than 17-fold increase in the DAPI stained and alpha-EDU marked cardiomyocyte nuclei, within a day. We observed de novo expression of phospho-histone H3, ORC2, MCM2, and CLASPIN. Cardiac function was significantly improved by four weeks post-infarct, and fibrosis and immune cell infiltration were diminished in hearts treated with STEMIN and YAP5SA mmRNA than each alone. Conclusion: STEMIN and YAP5SA mmRNA improved cardiac function and myocardial fibrosis in left ventricles of infarcted adult mice. The combinatorial use of mmRNA encoding STEMIN and YAP5SA has the potential to become a powerful clinical strategy to treat human heart disease.

The superfamily of G protein-coupled receptors (GPCRs) consists of biological microprocessors that can activate multiple signaling pathways. Most GPCRs have an orthosteric pocket where the endogenous ligand(s) typically binds. Conversely, allosteric ligands bind to GPCRs at sites that are distinct from the orthosteric binding region and they modulate the response elicited by the endogenous ligand. Allosteric ligands can also switch the response of a GPCR after ligand binding to a unique signaling pathway, these ligands are termed biased allosteric modulators. Thus, the development of allosteric ligands opens new and multiple ways in which the signaling pathways of GPCRs can be manipulated for potential therapeutic benefit. Furthermore, the mechanisms by which allosteric ligands modulate the effects of endogenous ligands have provided new insights into the interactions between allosteric ligands and GPCRs. These new findings have a high potential to improve drug discovery and development and, therefore, creating the need for better screening methods for allosteric drugs to increase the chances of success in the development of allosteric modulators as lead clinical compounds.