title: Cytoprotective function of sAppalpha in human keratinocytes.
abstract: sAPPalpha, the soluble form of the beta-amyloid precursor protein, has been shown to act as a potent epidermal growth factor by stimulating keratinocyte proliferation and migration. In this report we provide evidence for a cytoprotective role of sAPPalpha. As a model we used HaCaT cells and normal human keratinocytes (NHK) cultured in the absence of fetal calf serum and bovine pituitary extract. Under these conditions keratinocytes began to undergo apoptosis at increasing rates after 96 h of culture. Surprisingly, keratinocytes were protected from apoptosis by the addition of 50 nM recombinant sAPPalpha. Subsequent experiments were performed to elucidate the regulatory basis of the cytoprotective role of sAPPalpha. We found that recombinant sAPPalpha facilitated the substrate adhesion of keratinocytes in the first 30 minutes after seeding. The basis for this adhesion-promoting function was shown by the ability of recombinant sAPPalpha to continuously coat the culture dish thereby promoting the ability to bind keratinocytes. A second mechanism explaining the cytoprotective role was found in the significant inhibition of apoptosis by recombinant sAPPalpha. In HaCaT cells moderate UV-B irradiation was sufficient to induce apoptosis. In contrast, induction of apoptosis in NHK required additionally the depletion of endogenous sAPPalpha suggesting that sAPPalpha mediates protection against UV-B irradiation. Staurosporine-induced apoptosis rates were significantly reduced by about 59% after addition of recombinant sAPPalpha. These results show that sAPPalpha exerts a pronounced cytoprotective effect and that this effect is mediated by facilitated cell adhesion and by the antiapoptotic function of sAPPalpha.
authors.affiliation: Institute of Cell Biology and Bonner Forum Biomedizin, University of Bonn, Bonn, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Wehner
authors.forename: Christina
authors.initials: C
authors.lastname: Siemes
authors.forename: Gregor
authors.initials: G
authors.lastname: Kirfel
authors.forename: Volker
authors.initials: V
authors.lastname: Herzog
mesh_terms: D016564:Amyloid beta-Protein Precursor / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D019610:Cytoprotection; D004789:Enzyme Activation / Q000187:drug effects; D000078404:Epidermal Cells; D004815:Epidermal Growth Factor / Q000494:pharmacology; D004817:Epidermis / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000528:radiation effects; D010446:Peptide Fragments / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000494:pharmacology; D019311:Staurosporine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D013473:Sunscreening Agents / Q000494:pharmacology; D014466:Ultraviolet Rays
chemical_list: C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D013473:Sunscreening Agents; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019311:Staurosporine