The desmoplakin tail domain position in the desmosomal plaque is isoform dependent

Desmoplakin (DP, also known as DSP) is a key protein in desmosomes, cell-cell junctions that provide mechanical integrity to the skin and heart. DP has three isoforms, DPI, DPIa and DPII, which differ only in the length of their central rod domain and arise from alternative splicing. Alterations of tissue-specific DP isoform expression underlie rare skin and heart diseases. Desmosomes are macromolecular complexes, and their protein architecture is essential for physiological function. Here, we used direct stochastic optical reconstruction microscopy (dSTORM) to define the architectural arrangement of DPI, DPIa and DPII with a C-terminal mEGFP expressed in DP-knockout (KO) HaCaT cells. We show the DP tail domain position is isoform dependent and correlates with rod length. DPI has the longest rod domain, and its tail is farthest from the plasma membrane, whereas DPII has the shortest rod and is closest. This variable tail location architecture was conserved in wild-type HaCaT cells expressing both DPI and DPII. We propose a novel aligned angle model, with each DP isoform co-aligned at an acute angle relative to the plasma membrane. These results provide insight into how DP architecture supports desmosome function.