Nature Of G Protein-coupled Receptors Research Articles

Biomimetic Transmembrane Signal Transducing DNA Nanosensor for Membrane Enclosed Nucleic Acid Biomarker Detection

Signal transduction across phospholipid bilayer is an important process in biology that allows cells to respond to changes in their external environment and communicate among cells. Trans-bilayer signal transduction by sophisticated membrane proteins such as G-protein coupled receptors (GPCR) play crucial role in regulating key physiological processes. Being able to mimic the signal transduction by GPCRs has enormous opportunity in synthetic biology for potential application in artificial tissue signaling, biosensing and controlled drug delivery. In a general sense, GPCRs consist of a dynamically reconfigurable, hydrophilic-hydrophobic-hydrophilic (Hi-Ho-Hi) molecular structure where the hydrophobic part is buried in the lipid bilayer while the two hydrophilic ends remain on the two sides of the bilayer. In this research, we mimic the Hi-Ho-Hi molecular design principle of GPCRs to create a DNA-based transmembrane Nano-Sensor (TraNS) that dynamically reconfigures upon sensing a membrane-enclosed nucleic acid target. Four interwoven DNA strands are self-assembled to form each TraNS device. Two hydrophobic cholesterol anchors are covalently conjugated to create a hydrophobic belt around each TraNS device to help it to span the lipid bilayer, similar to the Hi-Ho-Hi nature of GPCRs. We design the TraNS device such that after insertion to lipid bilayer, it selectively switches from a closed to an open state upon sensing a nucleic acid target encapsulated inside the membrane. Gel electrophoresis and fluorescence spectra confirms the formation and configurational switch of the TraNS device. Next, we demonstrate the use of the TraNS device for biosensing application by detecting presence of non-small cell lung cancer specific micro-RNA: miR-21-5p in exosomes. We believe this is the first demonstration of mimic of a transmembrane signal transducing protein using DNA nanostructures and use of the nanostructure towards diagnostic application.

Abstract 98: Profiling GPCR Expression in Cardiac Fibroblasts and Myofibroblasts

G-protein coupled receptors (GPCRs) are the largest class of cell surface receptors, serving as drug targets, at least in part, due to their diversity, selectivity in tissue expression and ability to regulate a wide variety of cellular functions. We hypothesized that cardiac fibroblasts (CFs) and pro-fibrotic myofibroblasts (myoFs) may express GPCRs that will regulate their activity and will identify previously unappreciated GPCRs as potential therapeutic targets for cardiac fibrosis. To test this hypothesis, we profiled non-chemosensory GPCR mRNA expression by using qPCR-based GPCR arrays in studies of CFs isolated from ventricular tissue of rats, mice and humans. Particular attention was paid to assessing cells at low passage (1-3) and grown on substrates that mimic the stiffness of cardiac tissue in-vivo. MyoFs were obtained by treating CFs ex-vivo with TGFβ, and from CFs that spontaneously transformed to MyoFs by growth on hard tissue culture substrates.We find that CFs from humans, rats and mice express ~120 GPCRs and that a majority of GPCRs (>75%), especially highly expressed GPCRs, are detected in human, rats and/or mice CFs; ~40% of highly expressed GPCRs are orphan receptors (without known physiologic agonists). Of GPCRs with known G-protein linkages, Gi-coupled receptors are most numerous, followed by Gq-, Gs- and G12/13-coupled GPCRs. GPCR expression profiles of rat atrial and ventricular CFs are highly similar in terms of both identity and level of expression. By contrast, GPCR expression in cardiac myocytes (CMs) differs significantly from CFs: most highly expressed receptors in CFs are undetected or much lower expressed in CMs. Several GPCRs detected in MyoFs have reduced expression vs CFs but a subset of GPCRs have higher expression in MyoFs. Validation of mRNA expression via protein detection as well as functional assays helps confirm the presence of a large number of the GPCRs. Conclusions: CFs and MyoFs from rodents and humans express ~120 GPCRs, including many orphan GPCRs. Atrial and ventricular CFs have similar GPCR profiles but ones that differ from that of CMs. CFs and MyoFs show differences in the number and nature of GPCRs expressed. We hypothesize that GPCRs higher expressed in MyoFs may contribute to their pro-fibrotic phenotype.