Desmoplakins (DPs) I and II are two major related proteins located in the desmosomal plaque where they have been proposed to play a role in attaching intermediate filaments (IF) to the inner cell surface. The predicted amino acid sequence of DP was obtained by analysis of overlapping cDNA clones. Computer-aided analysis suggests that DPI will form a dumbbell-shaped homodimer, with a central α-helical coiled coil rod domain of 132 nm and two globular end domains. The DPII molecule is missing 599 residues from the central domain, resulting in a rod about one third the length of DPI. The carboxyl terminus comprises three subdomains each containing almost 5 repeats of a 38 residue repeating motif with a periodicity in acidic and basic residues similar to that found in the rod domain of IF proteins. This suggests a possible mechanism by which these proteins might interact. The amino terminus contains groups of heptad repeats that are predicted to form at least two major α-helical rich bundles. A series of c-myc-tagged mammalian expression vectors encoding specific predicted domains of DPI were transiently expressed in COS-7 cells. Light and electron microscopical observations revealed that DP polypeptides including the 90 kDa carboxyl terminal globular domain of DPI specifically colocalized with and ultimately resulted in the complete disruption of keratin and vimentin IF. This effect was specific for the carboxyl terminus, as the expression of the 95 kDa rod domain of DPI did not visibly alter IF networks. Immunogold localization of COS-7 cells transfected with constructs including the carboxyl terminus of DP demonstrated an accumulation of mutant protein within which IF subunits were sequestered. These results suggest a role for the DP carboxyl terminus in the attachment of IF to the desmosomal plaque in either a direct or indirect manner.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Dermatology|
|State||Published - 1992|
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