GPCRs - Pivotal Players in Metabolism

Scribble scrambles parathyroid hormone receptor interactions to regulate phosphate and vitamin D homeostasis

G protein-coupled receptors, including PTHR, are pivotal for controlling metabolic processes ranging from serum phosphate and vitamin D levels to glucose uptake, and cytoplasmic interactors may modulate their signaling, trafficking, and function. We now show that direct interaction with Scribble, a cell polarity-regulating adaptor protein, modulates PTHR activity. Scribble is a crucial regulator for establishing and developing tissue architecture, and its dysregulation is involved in various disease conditions, including tumor expansion and viral infections. Scribble co-localizes with PTHR at basal and lateral surfaces in polarized cells. Using X-ray crystallography, we show that colocalization is mediated by engaging a short sequence motif at the PTHR C-terminus using Scribble PDZ1 and PDZ3 domain, with binding affinities of 31.7 and 13.4 μM, respectively. Since PTHR controls metabolic functions by actions on renal proximal tubules, we engineered mice to selectively knockout Scribble in proximal tubules. The loss of Scribble impacted serum phosphate and vitamin D levels and caused significant plasma phosphate elevation and increased aggregate vitamin D3 levels, whereas blood glucose levels remained unchanged. Collectively these results identify Scribble as a vital regulator of PTHR-mediated signaling and function. Our findings reveal an unexpected link between renal metabolism and cell polarity signaling.

Genetically encoded tools for in vivo G-protein-coupled receptor agonist detection at cellular resolution

G-protein-coupled receptors (GPCRs) are the most abundant receptor type in the human body and are responsible for regulating many physiological processes, such as sensation, cognition, muscle contraction and metabolism. Further, GPCRs are widely expressed in the brain where their agonists make up a large number of neurotransmitters and neuromodulators. Due to the importance of GPCRs in human physiology, genetically encoded sensors have been engineered to detect GPCR agonists at cellular resolution in vivo. These sensors can be placed into two main categories: those that offer real-time information on the signalling dynamics of GPCR agonists and those that integrate the GPCR agonist signal into a permanent, quantifiable mark that can be used to detect GPCR agonist localisation in a large brain area. In this review, we discuss the various designs of real-time and integration sensors, their advantages and limitations, and some in vivo applications. We also discuss the potential of using real-time and integrator sensors together to identify neuronal circuits affected by endogenous GPCR agonists and perform detailed characterisations of the spatiotemporal dynamics of GPCR agonist release in those circuits. By using these sensors together, the overall knowledge of GPCR-mediated signalling can be expanded.

Human rs75776403 polymorphism links differential phenotypic and clinical outcomes to a CLEC18A p.T151M-driven multiomics

BACKGROUND

Human traits, diseases susceptibility, and clinical outcomes vary hugely among individuals. Despite a fundamental understanding of genetic (or environmental) contributions, the detailed mechanisms of how genetic variation impacts molecular or cellular behaviours of a gene, and subsequently leads to such variability remain poorly understood.

METHODS

Here, in addition to phenome-wide correlations, we leveraged multiomics to exploit mechanistic links, from genetic polymorphism to protein structural or functional changes and a cross-omics perturbation landscape of a germline variant.

RESULTS

We identified a missense cis-acting expression quantitative trait locus in CLEC18A (rs75776403) in which the altered residue (T₁₅₁→M₁₅₁) disrupts the lipid-binding ability of the protein domain. The altered allele carriage led to a metabolic and proliferative shift, as well as immune deactivation, therefore determines human anthropometrics (body height), kidney, and hematological traits.

CONCLUSIONS

Collectively, we uncovered genetic pleiotropy in human complex traits and diseases via CLEC18A rs75776403-regulated pathways.