Structural Biology

Biography

Biography: Stanislav Engel

Abstract

Dissecting G protein-coupled receptors (GPCR) signaling in terms of the pathways being activated will boost our understanding of the molecular fundamentals of hormone action. The structural determinants governing the selectivity of GPCR/G protein coupling, however, remain obscure. The selectivity of GPCR/G protein recognition appears to be determined by both specific inter-residue interactions and features related to the overall 3D conformation of the ICD. It appears, therefore, that to elucidate the fundamentals of the selectivity of GPCR/G protein recognition, a comprehensive analysis of the structure-activity relationships of multiple GPCR complexes with different G protein isoforms is required. However, enormous technical difficulties associated with the isolation of functional receptors in quantities required for direct structural studies effectively impede progress in the field. Methodology: We constructed the functional mimetics of the intracellular domain (ICD) of a model GPCR - thyrotropin receptor (TSHR), based on a unique scaffold, 6-Helix, an artificial protein that was derived from the elements of the trimer-of-hairpins structure of HIV gp41 and represents a bundle of six a-helices. Findings: The 6-Helix scaffold, which endowed the substituted TSHR ICD elements with spatial constraints analogous to those, found in native receptors, enabled the reconstitution of a microdomain comprising the intracellular loops ICL-2 and ICL-3, which is capable of binding and activating Ga-(s). Conclusion & Significance: By using a soluble scaffold, which furnishes peptides derived from the GPCR ICD with spatial constraints similar to those, found in native receptors, the reconstitution of a native-like G protein-recognition epitope can be facilitated. The 6-Helix-based mimetics could be used as a platform to study the molecular basis of GPCR/G protein recognition. Such knowledge could lead to the development of novel therapeutic strategies for GPCR-related disorders by targeting the GPCR/G protein interfaces and help counteract cellular dysfunctions via focused tuning of GPCR signaling.

References:

1. Y. Y. Kuttner and S. Engel, Protein hot spots - the islands of stability, Journal of Molecular Biology, 415(2):419-28 (2012)
2. Y. Y. Kuttner, T. Nagar and S. Engel, Surface dynamics in allosteric regulation of protein-protein interactions: Modulation of calmodulin functions by Ca²⁺, PLOS Computational Biology, 9(4): e1003028 (2013)
3. B. Katzman, M. Vyazmensky, O. Press, M. Volokita and S. Engel, Tethered ribozyme ligation enables detection of molecular proximity in homogeneous solutions, Biotechnology Journal, 10 (3):379–385 (2015)
4. A. Kuzmina, K. Vaknin, G. Gdalevsky, M. Vyazmensky, R.S. Marks, R. Taube and S. Engel, Functional Mimetics of the HIV-1 CCR5 Co-Receptor Displayed on the Surface of Magnetic Liposomes, PLOS One, 10(12): e01440432015 (2015)
5. R. Osman, M. Mezei and S. Engel, The role of protein “Stability patches” in molecular recognition: A case study of the human growth hormone-receptor complex, Journal of Computational Chemistry, 37 (10):913-919 (2016)