During the final steps of epidermal differentiation, extracellular calcium ions enter keratinocytes and induce transglutaminase activity and comified envelope formation. In other cell types, entry of calcium mediated by ionophores has been reported to induce exocytosis of lysosomes. In this study, we investigated whether lysosomes of keratinocytes might exhibit a similar behaviour. Ionomycin treatment induced comified envelope formation in keratinocytes, but also morphological changes including plasma membrane blebbing, although no immediate alteration in cell viability could be detected. The activity of the soluble lysosomal enzymes cathepsin C and β-galactosidase in the culture medium was increased upon ionomycin treatment. Cell leakage did not seem to be responsible for this phenomenon, as suggested by measurements of the cytosolic enzymes adenylate kinase and dipeptidylpeptidase III in the culture medium. Metabolic labelling followed by immunoprecipitation showed that ionomycin induced release of cathepsin D into the culture medium. Simultaneously, lysosome-associated membrane proteins (Lamps) 1 and 2 were detected at the cell surface of ionomycin-treated keratinocytes by biochemical and morphological approaches. These results suggest that upon ionomycin treatment, calcium entry stimulates exocytosis of lysosomes in keratinocytes.
|Number of pages||12|
|Journal||Archives of Dermatological Research|
|Publication status||Published - 1 Jun 2004|
Etude du rôle des lysosomes et du cholestérol au cours de la différenciation des kératinocytes épidermiquesAuthor: Jans, R., 22 Apr 2004
Supervisor: Poumay, Y. (Supervisor), Jadot, M. (Co-Supervisor), Mainferme, F. (External person) (Jury), Michiels, C. (Jury), Piront, A. (Jury), GARMYN, M. (External person) (Jury) & Van den Brule, F. (External person) (Jury)
Student thesis: Doc types › Doctor of SciencesFile