Local Phosphocycling Mediated by LOK/SLK Restricts Ezrin Function to the Apical Aspect of Epithelial Cells

J Cell Biol. 2012 Dec 10;199(6):969-84. doi: 10.1083/jcb.201207047. Epub 2012 Dec 3.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line
  • Cell Polarity / genetics
  • Cell Polarity / physiology
  • Cytoskeletal Proteins / metabolism*
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / metabolism*
  • Gene Silencing
  • Humans
  • Microvilli / drug effects
  • Microvilli / enzymology
  • Phosphorylation
  • Protein-Serine-Threonine Kinases / antagonists & inhibitors
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Proteomics

Substances

  • Cytoskeletal Proteins
  • Enzyme Inhibitors
  • ezrin
  • SLK protein, human
  • Protein-Serine-Threonine Kinases
  • STK10 protein, human