Molecular symmetry breaking in the Frizzled-dependent planar polarity pathway

Perspectives on polarity - exploring biological asymmetry across scales

In this Perspective, Journal of Cell Science invited researchers working on cell and tissue polarity to share their thoughts on unique, emerging or open questions relating to their field. The goal of this article is to feature 'voices' from scientists around the world and at various career stages, to bring attention to innovative and thought-provoking topics of interest to the cell biology community. These voices discuss intriguing questions that consider polarity across scales, evolution, development and disease. What can yeast and protists tell us about the evolution of cell and tissue polarity in animals? How are cell fate and development influenced by emerging dynamics in cell polarity? What can we learn from atypical and extreme polarity systems? How can we arrive at a more unified biophysical understanding of polarity? Taken together, these pieces demonstrate the broad relevance of the fascinating phenomenon of cell polarization to diverse fundamental biological questions.

Structure of the extracellular region of the adhesion GPCR CELSR1 reveals a compact module which regulates G protein-coupling

Cadherin EGF Laminin G seven-pass G-type receptors (CELSRs or ADGRCs) are conserved adhesion G protein-coupled receptors which are essential for animal development. CELSRs have extracellular regions (ECRs) containing 23 adhesion domains which couple adhesion to intracellular signaling. However, molecular-level insight into CELSR function is sparsely available. We report the 4.3 Å cryo-EM reconstruction of the mCELSR1 ECR with 13 domains resolved in the structure. These domains form a compact module mediated by interdomain interactions with contact between the N- and C-terminal domains. We show the mCELSR1 ECR forms an extended species in the presence of Ca 2+ , which we propose represents the antiparallel cadherin repeat dimer. Using assays for adhesion and G protein-coupling, we assign the N-terminal CADH1-8 module as necessary for cell adhesion and we show the C-terminal CAHD9-GAIN module regulates signaling. Our work provides important molecular context to the literature on CELSR function and opens the door towards further mechanistic studies.

The adhesion G-protein-coupled receptor mayo/CG11318 controls midgut development in Drosophila

Adhesion G-protein-coupled receptors (aGPCRs) form a large family of cell surface molecules with versatile tasks in organ development. Many aGPCRs still await their functional and pharmacological deorphanization. Here, we characterized the orphan aGPCR CG11318/mayo of Drosophila melanogaster and found it expressed in specific regions of the gastrointestinal canal and anal plates, epithelial specializations that control ion homeostasis. Genetic removal of mayo results in tachycardia, which is caused by hyperkalemia of the larval hemolymph. The hyperkalemic effect can be mimicked by a raise in ambient potassium concentration, while normal potassium levels in mayoKO mutants can be restored by pharmacological inhibition of potassium channels. Intriguingly, hyperkalemia and tachycardia are caused non-cell autonomously through mayo-dependent control of enterocyte proliferation in the larval midgut, which is the primary function of this aGPCR. These findings characterize the ancestral aGPCR Mayo as a homeostatic regulator of gut development.

Cell polarity: How to build an asymmetric bridge

A new study provides key insights into planar cell polarity (PCP) establishment through the discovery of molecular asymmetries in the homotypic adhesive interactions of the PCP cadherin, Flamingo, resulting in the formation of asymmetric, intercellular bridges.