β-Amyloid precursor protein in human digital skin

Abstract

The occurrence and distribution of β-amyloid precursor protein (βAPP) and of β-amyloid peptide (β/A4) was investigated using immunoblotting and immunohistochemical techniques in the digital skin of healthy adult subjects. βAPP-like proteic bands with apparent molecular masses between 55–60 kDa, 100–125 kDa (corresponding to the full-length βAPP isoforms), 145–150 kDa, and 200 kDa were found in pellets and supernatants of whole skin and dermis. The same proteins, except that of ∼200 kDa, were also found in pellets from the epidermis, whereas epidermic supernatants were unreactive. β/A4 was not found by immunoblotting. Light microscope immunohistochemistry showed βAPP immunoreactivity (IR) in: (a) dermal nerves; (b) lamellar cells of Meissner, as well as inner-core, outer-core and capsule of Pacinian corpuscles; and (c) dermal blood vessels, sweat glands and, occasionally, epidermis. The distribution of β/A4 IR matched that of βAPP, and no evidence of extracellular β/A4 IR was encountered. Present results demonstrate that PAPP, but not β/A4, is normally present in human glabrous (digital) skin. The potential clinical relevance of these findings is discussed.