Calgranulin expression and association with the keratinocyte cytoskeleton

The molecules calgranulin A and B are two intracellular calcium-binding proteins which are expressed by the lesional keratinocytes of inflammatory dermatoses. We have investigated the induction of the calgranulin proteins in an in vitro system and characterized the epidermal form of calgranulin. Using calgranulin-specific monoclonal antibodies, we have shown that these proteins are expressed within the epidermis of skin explants after 12-24 h culture in vitro. The induction of calgranulin-specific staining on culture was prevented, however, by the inclusion of cycloheximide in the culture medium, in sufficient quantities to prevent de novo protein synthesis. Indirect immunofluorescence staining was used to analyse the subcellular localization of the calgranulin proteins. The specific staining pattern with antibodies which recognize the individual calgranulin proteins was retained in detergent insoluble cytoskeletal preparations of epidermis. In Western blotting experiments epidermal calgranulins could be solubilized only by using a urea-based protein extraction buffer. After sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis of the epidermal extracts a single antigen, with a molecular weight of 13.0 kD was detected with the calgranulin-specific antibody MAC 387. The expression of calgranulins, similar to other members of the same protein family, may regulate cytoskeletal changes in skin disease.