title: Antagonizing c-Cbl enhances EGFR-dependent corneal epithelial homeostasis.
abstract: OBJECTIVE
  In many cell types, the E3 ubiquitin ligase, c-Cbl, induces ligand-dependent ubiquitylation of the epidermal growth factor receptor (EGFR) and targets the receptor for lysosomal degradation. The goal of this study was to determine whether c-Cbl is a negative regulator of EGFR in the corneal epithelium and if it can be inhibited to promote corneal epithelial homeostasis.
  
  
  METHODS
  Expression and activity of c-Cbl were blocked in immortalized human corneal epithelial cells (hTCEpi) using RNAi and pharmacological agents ([4-amino-5-(4-methylphenyl)-7-(t-butyl)pyrazolo-d-3,4-pyrimidine] or PP1). Following c-Cbl inhibition, cells were assessed for ligand-dependent receptor ubiquitylation, receptor phosphorylation, and in vitro wound healing. Subsequent experiments used PP1 in hTCEpi cells and monitored in vivo murine corneal epithelial wound healing.
  
  
  RESULTS
  Knockdown and inhibition of c-Cbl decreased ligand-dependent ubiquitylation of the EGFR and prolonged receptor activity as measured by tyrosine phosphorylation. Further, these treatments also increased the extent of ligand-dependent corneal epithelial wound healing in vitro and in vivo.
  
  
  CONCLUSIONS
  Manipulating the duration of EGFR activity can enhance the rate of restoration of the corneal epithelial layer. Based on our findings, c-Cbl is a new therapeutic target to enhance EGFR-mediated corneal epithelial homeostasis that bypasses the limitations of previous approaches.
authors.affiliation: Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky, United States.
authors.forename: Jamie S
authors.initials: JS
authors.lastname: Rush
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, United States.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Boeving
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, United States.
authors.forename: William L
authors.initials: WL
authors.lastname: Berry
authors.affiliation: Department of Pharmacology and Toxicology, University of Louisville, Louisville, Kentucky, United States Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma, United States.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Ceresa
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors; D004797:Enzyme-Linked Immunosorbent Assay; D019573:Epithelium, Corneal / Q000293:injuries / Q000378:metabolism* / Q000473:pathology; D066246:ErbB Receptors / Q000378:metabolism*; D005131:Eye Injuries / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation; D050721:Proto-Oncogene Proteins c-cbl / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D015398:Signal Transduction; D054875:Ubiquitination; D014945:Wound Healing / Q000502:physiology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors
chemical_list: C108123:4-amino-5-(4-methylphenyl)-7-(tert-butyl)pyrazolo(3,4-d)pyrimidine; D004791:Enzyme Inhibitors; D011720:Pyrazoles; D011743:Pyrimidines; D050721:Proto-Oncogene Proteins c-cbl; D066246:ErbB Receptors; D019061:src-Family Kinases; C493849:Cbl protein, mouse
keywords: EGFR; corneal epithelium; corneal wound healing; endocytic trafficking