JRAB/MICAL-L2 is a junctional Rab13-binding protein mediating the endocytic recycling of occludin

Mol Biol Cell. 2006 May;17(5):2465-75. doi: 10.1091/mbc.e05-09-0826. Epub 2006 Mar 8.

Abstract

The dynamic turnover of tight junctions (TJs) is essential for epithelial-mesenchymal transitions and/or mesenchymal-epithelial transitions during epithelial morphogenesis. We previously demonstrated that Rab13 specifically mediates the endocytic recycling of occludin. Here, we identified MICAL-L2 (molecule interacting with CasL-like 2) as a novel Rab13-binding protein. Immunoprecipitation and immunofluorescence microscopy showed that MICAL-L2 specifically bound to the GTP-bound form of Rab13 via its C terminus, which contained a coiled-coil domain, and localized at TJs in epithelial MTD-1A cells. Recycling assay demonstrated that a MICAL-L2 mutant lacking the Rab13-binding domain (MICAL-L2-N) specifically inhibited the endocytic recycling of occludin but not transferrin receptor. Ca2+ switch assay further revealed that MICAL-L2-N as well as Rab13 Q67L inhibited the recruitment of occludin to the plasma membrane, the development of transepithelial electrical resistance, and the formation of a paracellular diffusion barrier. MICAL-L2 was displaced from TJs upon actin depolymerization and was distributed along radiating actin cables and stress fibers in Ca2+-depleted MTD-1A and fibroblastic NIH3T3 cells, respectively. These results suggest that MICAL-L2 mediates the endocytic recycling of occludin and the formation of functional TJs by linking Rab13 to actin cytoskeleton. We rename MICAL-L2 as JRAB (junctional Rab13-binding protein).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / metabolism
  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism
  • Cytoskeletal Proteins / analysis
  • Cytoskeletal Proteins / genetics
  • Cytoskeletal Proteins / metabolism*
  • Dogs
  • Endocytosis* / genetics
  • Epithelium / metabolism
  • Fibroblasts / metabolism
  • Membrane Proteins / metabolism*
  • Mice
  • Microfilament Proteins
  • Molecular Sequence Data
  • Mutation
  • NIH 3T3 Cells
  • Occludin
  • Protein Structure, Tertiary
  • Tight Junctions / chemistry
  • Tight Junctions / metabolism
  • rab GTP-Binding Proteins / metabolism*

Substances

  • Cytoskeletal Proteins
  • JRAB protein, mouse
  • Membrane Proteins
  • Microfilament Proteins
  • Occludin
  • Ocln protein, mouse
  • Rab13 protein, mouse
  • rab GTP-Binding Proteins
  • Calcium

Associated data

  • GENBANK/AB182579