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

Cunxi Li, Mingming Hao, Zheng Cao, Wei Ding, Ramona Graves-Deal, Jianyong Hu, David W. Piston, Robert J. Coffey

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

Abstract

Transforming growth factor-α (TGF-α) is the major autocrine EGF receptor ligand in vivo. In polarized epithelial cells, proTGF-α 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-α and that TGF-α 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 μ1B 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-α. Short hairpin RNA knockdown of Naked2 leads to a dramatic reduction in the 16-kDa cell surface isoform of TGF-α and increased cytosolic TGF-α immunoreactivity. We propose that Naked2 acts as a cargo recognition and targeting (CaRT) protein to ensure proper delivery, tethering, and fusion of TGF-α-containing vesicles to a distinct region at the basolateral surface of polarized epithelial cells.

Original languageEnglish
Pages (from-to)3081-3093
Number of pages13
JournalMolecular biology of the cell
Volume18
Issue number8
DOIs
StatePublished - Aug 2007

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