title: Expression of lysosome-associated membrane protein 1 (Lamp-1) and galectins in human keratinocytes is regulated by differentiation.
abstract: Lysosomes and their components are suspected to be involved in epidermal differentiation. In this study, lysosomal enzyme activities, expression of the lysosome-associated membrane protein 1 (Lamp-1) and expression of the epidermal galectins-1, -3 and -7 were investigated in human keratinocytes cultured at different cell densities (subconfluence, confluence and postconfluence) in order to induce differentiation. Detected by Western blot and immunofluorescence, Lamp-1 expression is transiently upregulated at culture confluence, but reduced at postconfluence. Northern blot analyses performed on subconfluent, confluent and post-confluent cultures of keratinocytes show that Lamp-1 mRNA expression is also upregulated at culture confluence, but downregulated at postconfluence. Measurements of lysosomal enzyme activities indicate a transient upregulation at culture confluence, whereas cathepsins B, C and L are particularly downregulated at postconfluence. Cell density and differentiation of epidermal cells also differentially regulates galectin expression in autocrine cultures. As the expression of galectin-1 mRNA is high in subconfluent cells, it is assumed to be associated with their proliferative state. On the other hand, as the mRNA levels for galectins-3 and -7 are notably upregulated at culture confluence (galectin-7) or at postconfluence (galectin-3), their expression is thought to be related to the differentiated state of keratinocytes. However, we collected evidence by confocal microscopy that galectin-3 and Lamp-1 do not colocalize in vitro in keratinocytes. Altogether, our results suggest that the upregulated Lamp-1 expression at confluence could be involved in keratinocyte differentiation, but apparently not through interaction with galectin-3.
authors.affiliation: Department of Histologie-Embryologie, Facultés Universitaires Notre-Dame de la Paix, 61, Rue de Bruxelles, 5000, Namur, Belgium.
authors.forename: Victoria
authors.initials: V
authors.lastname: Sarafian
authors.forename: Ralph
authors.initials: R
authors.lastname: Jans
authors.forename: Yves
authors.initials: Y
authors.lastname: Poumay
mesh_terms: D001483:Base Sequence; D002452:Cell Count; D002454:Cell Differentiation; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D037161:Galectins / Q000235:genetics* / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D015603:Keratinocytes / Q000166:cytology* / Q000378:metabolism*; D051907:Lysosomal Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D017931:DNA Primers; D037161:Galectins; D051907:Lysosomal Membrane Proteins; D012333:RNA, Messenger; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1