Open AccessEffector-mediated ERM activation locally inhibits RhoA activity to shape the apical cell domain
Author(s) -
Riasat Zaman,
Andrew T. Lombardo,
Cécile Sauvanet,
Raghuvir Viswanatha,
Valerie Awad,
Locke Ezra-Ros Bonomo,
David J. McDermitt,
Anthony Bretscher
Publication year - 2021
Publication title -
the journal of cell biology/the journal of cell biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.414
H-Index - 380
eISSN - 1540-8140
pISSN - 0021-9525
DOI - 10.1083/jcb.202007146
Subject(s) - rhoa , moesin , microbiology and biotechnology , ezrin , radixin , biology , myosin , myosin light chain kinase , cdc42 , phosphorylation , guanine nucleotide exchange factor , actin , cytoskeleton , apical membrane , actin cytoskeleton , rac gtp binding proteins , effector , gtpase , rac1 , signal transduction , cell , biochemistry , membrane
Activated ezrin-radixin-moesin (ERM) proteins link the plasma membrane to the actin cytoskeleton to generate apical structures, including microvilli. Among many kinases implicated in ERM activation are the homologues LOK and SLK. CRISPR/Cas9 was used to knock out all ERM proteins or LOK/SLK in human cells. LOK/SLK knockout eliminates all ERM-activating phosphorylation. The apical domains of cells lacking LOK/SLK or ERMs are strikingly similar and selectively altered, with loss of microvilli and with junctional actin replaced by ectopic myosin-II–containing apical contractile structures. Constitutively active ezrin can reverse the phenotypes of either ERM or LOK/SLK knockouts, indicating that a central function of LOK/SLK is to activate ERMs. Both knockout lines have elevated active RhoA with concomitant enhanced myosin light chain phosphorylation, revealing that active ERMs are negative regulators of RhoA. As RhoA-GTP activates LOK/SLK to activate ERM proteins, the ability of active ERMs to negatively regulate RhoA-GTP represents a novel local feedback loop necessary for the proper apical morphology of epithelial cells.