Plakophilin 3 mediates Rap1-dependent desmosome assembly and adherens junction maturation.
Bottom Line: Moreover, Pkp3 forms a complex with Rap1 GTPase, promoting its activation and facilitating desmosome assembly.We show further that Pkp3 deficiency causes disruption of an E-cadherin/Rap1 complex required for adherens junction sealing.These findings reveal Pkp3 as a coordinator of desmosome and adherens junction assembly and maturation through its functional association with Rap1.
Affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.Show MeSH
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Mentions: To enhance the temporal resolution of DP trafficking to sites of newly forming cell–cell contacts, we next performed live-cell imaging on well-characterized doxycycline-inducible, green fluorescent protein (GFP)–tagged DP-expressing A431 cells (Godsel et al., 2005) coming into contact after scratch wounding (Figure 4 and Supplemental Videos S1 and S2). In control cells, the relative fluorescence intensity of DP increased both during initial phase 1 coalescence at the membrane and as precursors incorporated into the maturing border during phase 3 (Figure 4, A and B). In Pkp3 KD, the initial phase occurs, but the corresponding increase in DP accumulation during junction maturation appeared to be abolished (Figure 4A), resulting in a plateauing of the DP fluorescence intensity after phase 1 (Figure 4B). However, this leveling off belies the striking difference in DP particle dynamics at the borders of Pkp3 KD cells compared with control. Phase 3, during which particles assembled in the cytoplasm in phase 2 translocate and incorporate into the cell–cell border (Godsel et al., 2005), starts ∼40 min upon initial cell–cell contact. In contrast, in Pkp3 KD cells, this phase is missing. Instead of steady growth in both the numbers and fluorescence intensity of junctional DP particles observed in the control, Pkp3 KD cells exhibit extensive lateral DP particle coalescence and concomitant decrease in number (Figure 4, A–C, and Supplemental Video S2). Large structures formed in this manner may correspond to the clustered desmosomes observed by electron microscopy (Figure 1C).
Affiliation: Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611.