title: Cellular distribution of the IGF-1R in corneal epithelial cells.
abstract: This study characterized the expression and subcellular localization of the IGF-1R in human corneal epithelial cells. Using a human telomerase-immortalized corneal epithelial cell line, IGF-1R expression and localization was assayed by immunofluorescence and subcellular fractionation followed by western blot. IGF-1R expression was confirmed in primary cultured human corneal epithelial cells. Nuclear localization was assessed under basal and IGF-1 stimulated culture conditions; phosphorylation status of the receptor in response to IGF-1 was demonstrated by western blot. IGF-1R:E-cadherin interactions were detected by immunofluorescence and co-immunoprecipitation of whole cell lysates. The results of this study demonstrated that IGF-1R localized predominantly to the nucleus and in a perinuclear cap pattern which co-localized with the Golgi complex in proliferating corneal epithelial cells. There was no difference in nuclear localization between primary or telomerized cell lines. Subcellular fractionation confirmed IGF-1Rα- and β-subunit localization in soluble and chromatin-bound nuclear fractions. Neither growth factor withdrawal nor IGF-1 stimulation altered nuclear IGF-1R. At points of cell-cell contact, IGF-1R co-localized with E-cadherin; co- immunoprecipitation assays confirmed the presence of an IGF-1R:E-cadherin complex. Importantly, this is the first report to identify IGF-1R in the nucleus and complexed with E-cadherin at points of cell-cell contact in corneal epithelial cells. Nuclear trafficking appeared to be independent of ligand-mediated events at the plasma membrane. The identification of IGF-1R in the nucleus and complexed with E-cadherin suggests novel regulatory functions outside the canonical ligand-induced endocytosis signaling pathway.
authors.affiliation: Department of Ophthalmology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9057, USA. Danielle.Robertson@utsouthwestern.edu
authors.forename: Danielle M
authors.initials: DM
authors.lastname: Robertson
authors.forename: Meifang
authors.initials: M
authors.lastname: Zhu
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Wu
mesh_terms: D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells / Q000378:metabolism; D019573:Epithelium, Corneal / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D010766:Phosphorylation; D017526:Receptor, IGF Type 1 / Q000378:metabolism*
chemical_list: D015820:Cadherins; D017526:Receptor, IGF Type 1