Nuclear localization of the tight junction protein ZO-2 in epithelial cells.
The tight junction constitutes the major barrier to solute and water flow through the paracellular space of epithelia and endothelia. It is formed by transmembrane proteins and submembranous molecules such as the MAGUKs ZOs. We have previously found that several MAGUKs, including those of the tight (ZO-1, ZO-2, and ZO-3) and septate junction (tamou and Dlg), contain one or two nuclear sorting signals located at their first PDZ and GK domains. Now we show that these proteins also contain a nuclear export signal and focus our study on the nuclear membrane shuttling of ZO-2. In sparse cultures this molecule concentrates at the nucleus in clusters, where it partially colocalizes with splicing factor SC35. Nuclear staining diminishes as the monolayer acquires confluence through a process sensitive to the nuclear export inhibitor leptomycin B. Nuclear localization can be induced by impairing cell-cell contacts, by mechanical injury. ZO-2 that shuttles from the cell periphery into the nucleus is not newly synthesized but originates from a preexistent pool. The movement of this protein is mediated by the actin cytoskeleton.
Islas
Socorro
S
Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (CINVESTAV), D.F, 07000, México.
Vega
Jesús
J
Ponce
Lissette
L
González-Mariscal
Lorenza
L
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002450:Cell Communication; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D003599:Cytoskeleton / Q000502:physiology; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins / Q000378:metabolism; D021382:Protein Sorting Signals / Q000502:physiology*; D012261:Ribonucleoproteins; D015398:Signal Transduction; D019108:Tight Junctions / Q000737:chemistry; D062827:Zonula Occludens-2 Protein
D008565:Membrane Proteins; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D021382:Protein Sorting Signals; D012261:Ribonucleoproteins; D062827:Zonula Occludens-2 Protein