Naked2 acts as a cargo recognition and targeting protein to ensure proper delivery and fusion of TGF-α-containing exocytic vesicles at the lower lateral membrane of polarized MDCK cells Academic Article uri icon


MeSH Major

  • Carrier Proteins
  • Cell Membrane
  • Cell Polarity
  • Exocytosis
  • Membrane Fusion
  • Transforming Growth Factor alpha
  • Transport Vesicles


  • Transforming growth factor-alpha (TGF-alpha) is the major autocrine EGF receptor ligand in vivo. In polarized epithelial cells, proTGF-alpha is synthesized and then delivered to the basolateral cell surface. We previously reported that Naked2 interacts with basolateral sorting determinants in the cytoplasmic tail of a Golgi-processed form of TGF-alpha and that TGF-alpha is not detected at the basolateral surface of Madin-Darby canine kidney (MDCK) cells expressing myristoylation-deficient (G2A) Naked2. By high-resolution microscopy, we now show that wild-type, but not G2A, Naked2-associated vesicles fuse at the plasma membrane. We further demonstrate that Naked2-associated vesicles are delivered to the lower lateral membrane of polarized MDCK cells independent of mu1B adaptin. We identify a basolateral targeting segment within Naked2; residues 1-173 redirect NHERF-1 from the apical cytoplasm to the basolateral membrane, and internal deletion of residues 37-104 results in apical mislocalization of Naked2 and TGF-alpha. Short hairpin RNA knockdown of Naked2 leads to a dramatic reduction in the 16-kDa cell surface isoform of TGF-alpha and increased cytosolic TGF-alpha immunoreactivity. We propose that Naked2 acts as a cargo recognition and targeting (CaRT) protein to ensure proper delivery, tethering, and fusion of TGF-alpha-containing vesicles to a distinct region at the basolateral surface of polarized epithelial cells.

publication date

  • August 2007



  • Academic Article



  • eng

PubMed Central ID

  • PMC1949375

Digital Object Identifier (DOI)

  • 10.1091/mbc.E07-02-0172

PubMed ID

  • 17553928

Additional Document Info

start page

  • 3081

end page

  • 93


  • 18


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