Abstract
Plakin proteins form critical connections between cell junctions and the cytoskeleton; their disruption within epithelial and cardiac muscle cells cause skin-blistering diseases and cardiomyopathies. Envoplakin has a single plakin repeat domain (PRD) which recognizes intermediate filaments through an unresolved mechanism. Herein we report the crystal structure of envoplakin's complete PRD fold, revealing binding determinants within its electropositive binding groove. Four of its five internal repeats recognize negatively charged patches within vimentin via five basic determinants that are identified by nuclear magnetic resonance spectroscopy. Mutations of the Lys1901 or Arg1914 binding determinants delocalize heterodimeric envoplakin from intracellular vimentin and keratin filaments in cultured cells. Recognition of vimentin is abolished when its residues Asp112 or Asp119 are mutated. The latter slot intermediate filament rods into basic PRD domain grooves through electrosteric complementarity in a widely applicable mechanism. Together this reveals how plakin family members form dynamic linkages with cytoskeletal frameworks.
Highlights
Plakin proteins form critical connections between cell junctions and the cytoskeleton; their disruption within epithelial and cardiac muscle cells cause skin-blistering diseases and cardiomyopathies
The cornified envelope presents vertebrate organisms with a remarkably durable yet adaptable layer of cross-linked protein that is formed in the outer epidermis and is vital for epidermal permeability barrier function
Envoplakin is not just expressed in the epidermis, but is found in a variety of other epithelial tissues including those of mammary gland, bladder and stomach[20], and this, together with its association with desmosomes at the cell periphery, strongly suggests that it has a role in intercellular adhesion with its plakin repeat domain (PRD) acting as a molecular linchpin connecting the membrane directly to the cytoskeleton
Summary
Plakin proteins form critical connections between cell junctions and the cytoskeleton; their disruption within epithelial and cardiac muscle cells cause skin-blistering diseases and cardiomyopathies. Recognition of vimentin is abolished when its residues Asp[112] or Asp[119] are mutated The latter slot intermediate filament rods into basic PRD domain grooves through electrosteric complementarity in a widely applicable mechanism. Together this reveals how plakin family members form dynamic linkages with cytoskeletal frameworks. The plakin protein envoplakin is upregulated during keratinocyte terminal differentiation, and interacts with the closely related protein periplakin to initiate cornified envelope formation[1] Both proteins associate with desmosomes, the interdesmosomal plasma membrane and intermediate filament cytoskeleton. The structure reveals a basic groove that can accommodate acidic patches on the cylindrical
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