Structural Biology

Biography

Biography: Arfaxad Reyes Alcaraz

Abstract

Statement of the Problem: G protein coupled receptors (GPCRs) also known as seven-transmembrane receptors and are the largest family of cell-surface receptors that communicate extracellular stimuli to the cell interior (1). It is now accepted that chemically distinct ligands bind to the same GPCR and can stabilize the receptor in multiple active conformations, which results in differential activation of cell signaling pathways and, eventually, in different physiologic outcomes a phenomenon known as biased agonism (2). Biased agonism can be exploited to design drugs that selectively activate signaling pathways, leading to the desired physiologic effects while on target side effects elicited by activation of other signaling pathways via the same receptor subtype (3). Methodology & Theoretical Orientation: The aim of this study was to stablish a relationship between conformational changes in Galanin receptors and their signaling properties in living cells, for that purpose we develop a structural complementation assay based on NanoBit technology and a series of conformational fluorescein arsenical hairpin (FIASH) bioluminescence resonance energy transfer (BRET) biosensors to monitor structural changes β-arrestin 2 induced by the binding with each Galanin receptor. Findings: Here we show that Galanin receptors impose different conformational signatures in β-arrestin, moreover structurally different ligands activating the same receptor imposed different conformations in β-arrestin 2 producing biased signaling. Conclusion & Significance: Our data provide definite evidence that a receptor activated by structurally different ligands can adopt multiple active conformations. Moreover, this finding also demonstrates that functionally specific structural Galanin receptor conformations can indeed be translated to downstream effectors producing a different physiological response. 

References:

1. Reyes-Alcaraz A., Lee, Y. N., Son, G. H., Kim, N. H., Kim, D. K., and Yun, S., Kim D. H., Hwang, J. I. and Seong, J. Y. Development of Spexin-based Human Galanin Receptor Type IISpecific Agonists with Increased Stability in Serum and Anxiolytic Effect in Mice. Scientific Reports, 6:21453 (2016).
2. Reyes-Alcaraz A., Matinez-Archundia M., Ramon E. and Garriga P. Salt Effects on the Conformational Stability of the Visual G-Protein-Coupled Receptor Rhodopsin. Biophysical Journal, 101, 2798-2806 (2011).
3. Moon M. J., Lee Y.-N., Park S., Reyes-Alcaraz A., Hwang J. –I., Millar R. P., Choe H. and Seong J. Y. Ligand Binding Pocket Formed by Evolutionarily Conserved Residues in the Glucagon-like Peptide-1 (GLP-1) Receptor Core Domain. The Journal of Biological Chemistry, 290, 5696-5706, (2015).
4. Yun, S., Furlong M., Sim M., Cho M., Park, S., Cho E. B., Reyes-Alcaraz, A., Hwang, J. -I., Kim, J., and Seong J. Y. Prevertebrate Local Gene Duplication Facilitated Expansion of the Neuropeptide GPCR Superfamily. Molecular Biology and Evolution 1-15, (2015).
5. Reyes-Alcaraz A., Tzanov T. and Garriga P. Stabilization of Membrane Proteins: the Case of G-Protein-Coupled Receptors. Engineering in Life Sciences, 8, 207–217 (2008).