LEDGF/DFS70, a major autoantigen of atopic dermatitis, is a component of keratohyalin granules

Lens epithelium-derived growth factor/dense fine speckles 70 kDa protein (LEDGF/DFS70) is a transcriptional cofactor, a transcriptional activator, survival factor, and HIV-1 transporter. It is also a major autoantigen in patients with atopic dermatitis (AD), because autoantibodies to this protein are found in approximately 30% of AD patients. To better understand the role of autoantibodies and autoantigens in the pathogenesis of AD, we examined the distribution of LEDGF/DFS70 in the epidermis of normal human skin by light and electron microscopic immunocytochemistry. Increased amounts of LEDGF/DFS70 were located in the nuclei of cells in the basal layer, whereas the cytoplasm of cells in the granular layer stained for LEDGF/DFS70 by light microscopy. Using immunoelectron microscopy, we observed the accumulation of LEDGF/DFS70 in keratohyalin granules (KGs) in the cytoplasm of cells in the granular layer. In addition, Ig heavy chain-binding protein/glucose-regulated protein, 78-kDa (Bip/GRP78), a stress sensing protein in the endoplasmic reticulum, colocalized with LEDGF/DFS70 in the KGs. These results suggest that LEDGF/DFS70 is predominantly located in the nucleus of the basal epidermal cells and translocates into the cytoplasm during differentiation. Once in the cytoplasm, LEDGF/DFS70 accumulates in the KGs in the granular layer. Finally, LEDGF/DFS70, a "nuclear" autoantigen in AD, may play a functional role in the KGs.