RT Journal Article
SR Electronic
T1 Rho-kinase planar polarisation at tissue boundaries depends on phospho-regulation of membrane residence time
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 615062
DO 10.1101/615062
A1 Clara Sidor
A1 Tim J. Stevens
A1 Li Jin
A1 Jérôme Boulanger
A1 Katja Röper
YR 2019
UL http://biorxiv.org/content/early/2019/04/21/615062.abstract
AB Rho-kinase (Rok) is a major myosin II activator during morphogenesis. In the Drosophila embryonic salivary gland placode Rok is planar polarised at the tissue boundary, through a negative regulation by the apical polarity protein Crumbs that is anisotropically localised at the boundary. However, in inner cells of the placode both Crumbs and Rok are isotropically enriched at junctions. We propose a model that reconciles both behaviours through modulation of Rok membrane residence time by Crumbs and downstream effectors. Using FRAP in embryos expressing endogenously-tagged Rok combined with in silico simulations, we find that the lower membrane dissociation rate (koff) of Rok at the tissue boundary, where Crumbs membrane levels are lower, explains this boundary-specific effect. The S/T-kinase Pak1 negatively affects Rok membrane association in vivo within the epidermis, and in vitro can phosphorylate Rok near the PH domain that mediates membrane association. Pak1 is recruited to the membrane by Cdc42 which, like its binding partner Crumbs, shows anisotropic localisation at the boundary. These data reveal an important mechanism of modulation of Rok membrane residence time via affecting the koff that may be widely employed during tissue morphogenesis.