Human induced pluripotent stem cells (hiPSC) are becoming a relevant model for the study of liver metabolic diseases once differentiated into hepatocyte-like cells (HLC), and it has been shown that they can faithfully recapitulate autosomal dominant hypercholesterolemia (ADH). PCSK9 is a critical modulator of cholesterol homeostasis, and quickly became a hot target for ADH pharmacological treatment strategies. However, current cellular models to further decipher the role of PCSK9 in ADH are limited, especially to study the PCSK9 gain of function mutation S127R, which seems to interfere with LDL cholesterol homeostasis intracellularly by still unknown mechanisms.

(From CHOPIN project)

G protein-coupled receptors (GPCRs) are essential for cellular responses to external stimuli, by triggering changes in cyclic AMP (cAMP) pathways and the phosphatidylinositol pathway. Near half of the current drugs target GPCRs signaling.

Anne Marie Quinn, founder of Montana Molecular, explains on SelectScience how it’s possible to measure, in real time, multiple signaling pathways inside a living cell.

“Our very first product was for detection of diacylglycerol (DAG) an important component of GPCR signaling through the Gq pathway. We specifically wanted to differentiate between Gs, Gi and Gq signaling,” notes Quinn. “This is an important goal for both drug discovery and basic research.”

“Upon ligand binding, the Gs-coupled GPCR receptor activates adenylyl cyclase that in turn produces cAMP, governing important cellular responses. Gi-coupled GPCR receptors, however, inhibit adenylyl cyclase and cAMP production. The phosphatidylinositol pathway, on the other hand, is triggered by the Gq-coupled receptors. In Gq-coupled signaling, DAG and intracellular calcium act as second messengers, ultimately influencing cell functions.”

The fluorescent bioscensors developped by Montana Molecular allow to follow both intracellular cAMP and DAG.

The use of two biosensors measuring different players in cell signaling can reveal more about the effects of a drug. Image courtesy of Montana Molecular for SelectScience

Complexify cell models to improve relevance of the phenotyic assay in order to find new drugs more efficient is that’s what everyone strives to do. To go further, Zebrafish is a whole organism more and more known and used during the process of drug discovery. As reported by MacRae & Peterson in “Zebrafish as tool for drug discovery” published in Nature Review Drus Discovery.

“It has become a prominent vertebrate model for disease and has already contributed to several examples of successful phenotype-based drug discovery.”

But to be usefool, the similarities and differences between human and zebrafish biology need to be understand to  know the limitation of this tool. In this review, an overview of those is made!