Establishment of the PAR-1 cortical gradient by the aPKC-PRBH circuit

Cell polarity is the asymmetric compartmentalization of cellular components. An opposing gradient of partitioning-defective protein kinases, atypical protein kinase C (aPKC) and PAR-1, at the cell cortex guides diverse asymmetries in the structure of metazoan cells, but the mechanism underlying their spatial patterning remains poorly understood. Here, we show in Caenorhabditis elegans zygotes that the cortical PAR-1 gradient is patterned as a consequence of dual mechanisms: stabilization of cortical dynamics and protection from aPKC-mediated cortical exclusion. Dual control of cortical PAR-1 depends on a physical interaction with the PRBH-domain protein PAR-2. Using a reconstitution approach in heterologous cells, we demonstrate that PAR-1, PAR-2, and polarized Cdc42-PAR-6-aPKC comprise the minimal network sufficient for the establishment of an opposing cortical gradient. Our findings delineate the mechanism governing cortical polarity, in which a circuit consisting of aPKC and the PRBH-domain protein ensures the local recruitment of PAR-1 to a well-defined cortical compartment.

First person – Zhen Zhang and Yen Wei Lim

First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Zhen Zhang and Yen Wei Lim are joint first authors on ‘ImaEdge – a platform for quantitative analysis of the spatiotemporal dynamics of cortical proteins during cell polarization’, published in Journal of Cell Science. Zhen Zhang is a PhD student in the lab of Pakorn Kanchanawong at the National University of Singapore, developing novel and robust computational tools to analyse microscopic images and videos. Yen Wei Lim is a PhD student in the lab of Fumio Motegi at the National University of Singapore, investigating the intricacies behind cell fate determination by answering one fundamental question: how does an individual cell decide which fate it should adopt?