title: Local phosphocycling mediated by LOK/SLK restricts ezrin function to the apical aspect of epithelial cells.
abstract: In this paper, we describe how a dynamic regulatory process is necessary to restrict microvilli to the apical aspect of polarized epithelial cells. We found that local phosphocycling regulation of ezrin, a critical plasma membrane-cytoskeletal linker of microvilli, was required to restrict its function to the apical membrane. Proteomic approaches and ribonucleic acid interference knockdown identified lymphocyte-oriented kinase (LOK) and SLK as the relevant kinases. Using drug-resistant LOK and SLK variants showed that these kinases were sufficient to restrict ezrin function to the apical domain. Both kinases were enriched in microvilli and locally activated there. Unregulated kinase activity caused ezrin mislocalization toward the basolateral domain, whereas expression of the kinase regulatory regions of LOK or SLK resulted in local inhibition of ezrin phosphorylation by the endogenous kinases. Thus, the domain-specific presence of microvilli is a dynamic process requiring a localized kinase driving the phosphocycling of ezrin to continually bias its function to the apical membrane.
authors.affiliation: Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Raghuvir
authors.initials: R
authors.lastname: Viswanatha
authors.forename: Patrice Y
authors.initials: PY
authors.lastname: Ohouo
authors.forename: Marcus B
authors.initials: MB
authors.lastname: Smolka
authors.forename: Anthony
authors.initials: A
authors.lastname: Bretscher
mesh_terms: D002460:Cell Line; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000378:metabolism*; D020868:Gene Silencing; D006801:Humans; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D040901:Proteomics; D000099149:Ezrin; D000099317:Hippo Kinases
chemical_list: D003598:Cytoskeletal Proteins; D004791:Enzyme Inhibitors; D017346:Protein Serine-Threonine Kinases; D000099149:Ezrin; C485733:SLK protein, human; D000099317:Hippo Kinases; C474806:STK10 protein, human