Engineering of Novel Analogues That Are More Receptor-Selective and Potent than the Native Hormone, Insulin-like Peptide 5 (INSL5).

Insulin-like peptide 5 (INSL5) targets the G protein-coupled receptor, relaxin family peptide receptor 4 (RXFP4), predominantly coexpressed in the colorectum. While INSL5 also binds to the related receptor RXFP3, it does not activate it. The INSL5/RXFP4 axis is a promising target for treating gastrointestinal disorders such as constipation.

Oxytocin Analogues for the Oral Treatment of Abdominal Pain.

Abdominal pain presents an onerous reality for millions of people affected by gastrointestinal disorders such as irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD). The oxytocin receptor (OTR) has emerged as a new analgesic drug target with OTR expression upregulated on colon-innervating nociceptors in chronic visceral hypersensitivity states, accessible via luminal delivery. However, the low gastrointestinal stability of OTR's endogenous peptide ligand oxytocin (OT) is a bottleneck for therapeutic development.

Long-Circulating Vasoactive 1,18-Octadecanedioic Acid-Terlipressin Conjugate.

Hepatorenal syndrome (HRS) is a life-threatening complication of end-stage liver disease first reported over a century ago, but its management still poses an unmet challenge. A therapeutic agent found to stabilize the condition is a short cyclic peptide, vasopressin analogue, terlipressin (TP). While TP is commonly prescribed for HRS patients in most parts of the world, it was only recently approved for use in the United States.

Developing insulin-like peptide 5-based antagonists for the G protein-coupled receptor, RXFP4.

Human insulin-like peptide 5 (INSL5) is a gut hormone produced by colonic L-cells, and its biological functions are mediated by Relaxin Family Peptide Receptor 4 (RXFP4). Our preliminary data indicated that RXFP4 agonists are potential drug leads for the treatment of constipation. More recently, we designed and developed a novel RXFP4 antagonist, A13-nR that was shown to block agonist-induced activity in cells and animal models.

Activation of Multiple G Protein Pathways to Characterize the Five Dopamine Receptor Subtypes Using Bioluminescence Technology.

G protein-coupled receptors show preference for G protein subtypes but can recruit multiple G proteins with various downstream signaling cascades. This functional selection can guide drug design. Dopamine receptors are both stimulatory (D-like) and inhibitory (D-like) with diffuse expression across the central nervous system.

ThermoBRET: A Ligand-Engagement Nanoscale Thermostability Assay Applied to GPCRs.

Measurements of membrane protein thermostability reflect ligand binding. Current thermostability assays often require protein purification or rely on pre-existing radiolabelled or fluorescent ligands, limiting their application to established targets. Alternative methods, such as fluorescence-detection size exclusion chromatography thermal shift, detect protein aggregation but are not amenable to high-throughput screening.

Bi-allelic variants in INSL3 and RXFP2 cause bilateral cryptorchidism and male infertility.

Study Question: What is the impact of variants in the genes INSL3 (Insulin Like 3) and RXFP2 (Relaxin Family Peptide Receptor 2), respectively, on cryptorchidism and male infertility?

Summary Answer: Bi-allelic loss-of-function (LoF) variants in INSL3 and RXFP2 result in bilateral cryptorchidism and male infertility, whereas heterozygous variant carriers are phenotypically unaffected.

What Is Known Already: The small heterodimeric peptide INSL3 and its G protein-coupled receptor RXFP2 play a major role in the first step of the biphasic descent of the testes, and variants in the INSL3 and RXFP2 genes have long been implicated in inherited cryptorchidism. However, only one single homozygous missense variant in RXFP2 has clearly been linked to familial bilateral cryptorchidism, so the effects of bi-allelic variants in INSL3 and heterozygous variants in both genes on cryptorchidism and male infertility remain unclear.

Functional solubilization of the β-adrenoceptor using diisobutylene maleic acid.

The β2-adrenoceptor (β2AR) is a well-established target in asthma and a prototypical G protein-coupled receptor for biophysical studies. Solubilization of membrane proteins has classically involved the use of detergents. However, the detergent environment differs from the native membrane environment and often destabilizes membrane proteins.

Using the novel HiBiT tag to label cell surface relaxin receptors for BRET proximity analysis.

Relaxin family peptide 1 (RXFP1) is the receptor for relaxin a peptide hormone with important therapeutic potential. Like many G protein-coupled receptors (GPCRs), RXFP1 has been reported to form homodimers. Given the complex activation mechanism of RXFP1 by relaxin, we wondered whether homodimerization may be explicitly required for receptor activation, and therefore sought to determine if there is any relaxin-dependent change in RXFP1 proximity at the cell surface.

Multi-Component Mechanism of H2 Relaxin Binding to RXFP1 through NanoBRET Kinetic Analysis.

The peptide hormone H2 relaxin has demonstrated promise as a therapeutic, but mimetic development has been hindered by the poorly understood relaxin receptor RXFP1 activation mechanism. H2 relaxin is hypothesized to bind to two distinct ECD sites, which reorientates the N-terminal LDLa module to activate the transmembrane domain. Here we provide evidence for this model in live cells by measuring bioluminescence resonance energy transfer (BRET) between nanoluciferase-tagged RXFP1 constructs and fluorescently labeled H2 relaxin (NanoBRET).