Plakophilin 3 and Par3 facilitate desmosomes' association with the apical junctional complex

Mol Biol Cell. 2021 Sep 1;32(19):1824-1837. doi: 10.1091/mbc.E21-01-0001. Epub 2021 Jul 14.

Abstract

Desmosomes (DSMs), together with adherens junctions (AJs) and tight junctions (TJs), constitute the apical cell junctional complex (AJC). While the importance of the apical and basolateral polarity machinery in the organization of AJs and TJs is well established, how DSMs are positioned within the AJC is not understood. Here we use highly polarized DLD1 cells as a model to address how DSMs integrate into the AJC. We found that knockout (KO) of the desmosomal ARM protein Pkp3, but not other major DSM proteins, uncouples DSMs from the AJC without blocking DSM assembly. DLD1 cells also exhibit a prominent extraDSM pool of Pkp3, concentrated in tricellular (tC) contacts. Probing distinct apicobasal polarity pathways revealed that neither the DSM's association with AJC nor the extraDSM pool of Pkp3 are abolished in cells with defects in Scrib module proteins responsible for basolateral membrane development. However, a loss of the apical polarity protein, Par3, completely eliminates the extraDSM pool of Pkp3 and disrupts AJC localization of desmosomes, dispersing these junctions along the entire length of cell-cell contacts. Our data are consistent with a model whereby Par3 facilitates DSM assembly within the AJC, controlling the availability of an assembly competent pool of Pkp3 stored in tC contacts.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Adherens Junctions / genetics
  • Adherens Junctions / metabolism*
  • Animals
  • Caco-2 Cells
  • Cell Communication / genetics
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • Cell Polarity / genetics
  • Cells, Cultured
  • Desmosomes / genetics
  • Desmosomes / metabolism*
  • Dogs
  • Epithelial Cells / metabolism
  • Gene Knockout Techniques
  • Humans
  • Madin Darby Canine Kidney Cells
  • Microscopy, Fluorescence / methods
  • Plakophilins / genetics
  • Plakophilins / metabolism*
  • Tight Junctions / genetics
  • Tight Junctions / metabolism*

Substances

  • Adaptor Proteins, Signal Transducing
  • Cell Cycle Proteins
  • PARD3 protein, human
  • PKP3 protein, human
  • Plakophilins