Epiplakin, a member of the plakin
protein family, is exclusively expressed in epithelial tissues and was shown to bind to
keratins.
Epiplakin-deficient (EPPK-/-) mice showed no obvious spontaneous phenotype, however, EPPK-/- keratinocytes displayed faster
keratin network breakdown in response to stress. The role of
epiplakin in pancreas, a tissue with abundant
keratin expression, was not yet known. We analyzed
epiplakin's expression in healthy and inflamed pancreatic tissue and compared wild-type and EPPK-/- mice during
caerulein-induced
acute pancreatitis. We found that
epiplakin was expressed primarily in ductal cells of the pancreas and colocalized with apicolateral
keratin bundles in murine pancreatic acinar cells.
Epiplakin's diffuse subcellular localization in
keratin filament-free acini of K8-deficient mice indicated that its filament-associated localization in acinar cells completely depends on its binding partner
keratin. During
acute pancreatitis,
epiplakin was upregulated in acinar cells and its redistribution closely paralleled
keratin reorganization. EPPK-/- mice suffered from aggravated
pancreatitis but showed no obvious regeneration phenotype. At the most severe stage of the disease, EPPK-/- acinar cells displayed more
keratin aggregates than those of wild-type mice. Our data propose
epiplakin to be a protective
protein during
acute pancreatitis, and that its loss causes impaired disease-associated
keratin reorganization.