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Differentiation-related changes in glycoprotein synthesis by human keratinocytes.

ABSTRACT: Human keratinocytes were cultured in media in which the Ca2+ concentration controlled the stage of differentiation. In media containing less than 0.1 mM-Ca2+ keratinocytes grew as a monolayer, but in the presence of 2mM-Ca2+ the cells differentiated and formed stratified colonies. Glycoproteins of both stratified and unstratified cells were radiolabelled by metabolic incorporation of radioactive precursors and by cell-surface labelling using galactose oxidase/NaB3H4. The radiolabelled keratinocytes were extracted with 0.5% Triton X-100, and the glycoproteins in both the Triton X-100-soluble and Triton X-100-insoluble fractions were analysed by polyacrylamide-gel electrophoresis in the presence of SDS. Two Triton X-100-soluble glycoproteins with high Mr values (greater than 200,000) were major glycoproteins in stratified keratinocytes, but were present in only trace amounts in unstratified keratinocytes. Characterization of these glycoproteins by examination of the effect of tunicamycin on their synthesis and the effect of neuraminidase on their migration characteristics showed that they were cell-surface sialoglycoproteins containing O-glycosidically linked oligosaccharides. Analysis of the adherent cytoskeletons left after Triton X-100 extraction of stratified and unstratified keratinocytes revealed that a glycoprotein of Mr 184,000 was decreased in stratified keratinocytes. Incubation of unstratified keratinocytes in high-Ca2+ medium resulted in a rapid modification of the glycoprotein of Mr 184,000, and it is suggested that this event may be related to desmosome formation and stratification.

SUBMITTER: Roberts GP

PROVIDER: S-EPMC1147015 | biostudies-other | 1986 Jul

REPOSITORIES: biostudies-other

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Project description:BACKGROUND: Nodular melanoma is one of the most life threatening tumors with still poor therapeutic outcome. Similarly to other tumors, permissive microenvironment is essential for melanoma progression. Features of this microenvironment are arising from molecular crosstalk between the melanoma cells (MC) and the surrounding cell populations in the context of skin tissue. Here, we study the effect of melanoma cells on human primary keratinocytes (HPK). Presence of MC is as an important modulator of the tumor microenvironment and we compare it to the effect of nonmalignant lowly differentiated cells also originating from neural crest (NCSC). METHODS: Comparative morphometrical and immunohistochemical analysis of epidermis surrounding nodular melanoma (n?=?100) was performed. Data were compared to results of transcriptome profiling of in vitro models, in which HPK were co-cultured with MC, normal human melanocytes, and NCSC, respectively. Differentially expressed candidate genes were verified by RT-qPCR. Biological activity of candidate proteins was assessed on cultured HPK. RESULTS: Epidermis surrounding nodular melanoma exhibits hyperplastic features in 90% of cases. This hyperplastic region exhibits aberrant suprabasal expression of keratin 14 accompanied by loss of keratin 10. We observe that MC and NCSC are able to increase expression of keratins 8, 14, 19, and vimentin in the co-cultured HPK. This in vitro finding partially correlates with pseudoepitheliomatous hyperplasia observed in melanoma biopsies. We provide evidence of FGF-2, CXCL-1, IL-8, and VEGF-A participation in the activity of melanoma cells on keratinocytes. CONCLUSION: We conclude that the MC are able to influence locally the differentiation pattern of keratinocytes in vivo as well as in vitro. This interaction further highlights the role of intercellular interactions in melanoma. The reciprocal role of activated keratinocytes on biology of melanoma cells shall be verified in the future.

Project description:Objective: It has been demonstrated that the transcription factors TAZ (transcriptional coactivator with PDZ-binding motif), paired box gene 8 (PAX8), and NK2 homeobox 1 (NKX2-1) are coexpressed in the nucleus of thyroid cells. Furthermore, TAZ is known to enhance the transcriptional activity of PAX8 and NKX2-1 as well as the key thyroid-specific gene, thyroglobulin (TG), suggesting a critical role for TAZ in the control of thyroid cell speciation. We previously reported that the small molecule ethacridine, identified as a TAZ activator, was able to induce thyroid-specific transcription in endodermal cells differentiated from human embryonic stem (hES) cells using activin A. Since transcription factors are epigenetically regulated in cell differentiation, we investigated the epigenetic changes in the promoter regions of these key transcription factors during in vitro differentiation of hES cells into thyrocytes. Methods: We initially profiled chromatin accessibility using the technique of Assay for Transposase Accessible Chromatin sequencing (ATAC-seq), and then examined DNA methylation and histone acetylation in the promoter regions of the three selected thyroid transcription factors and the thyroid-specific genes during hES cell differentiation. Results: ATAC-seq analysis showed enriched chromatin accessibility of TAZ, NKX2-1, and PAX8 after exposure to activin A and ethacridine. There were no methylation changes found in the NKX2-1, PAX8, and TAZ promoters by bisulfite sequencing. In contrast, acetylation of histone H4, specifically acetylation of lysine 16, was observed in each of the promoters when measured by chromatin immunoprecipitation polymerase chain reaction assays, which correlated with the activity and expression of NKX2-1 and PAX8 as well as sodium/iodide symporter, thyroid stimulating hormone receptor, and TG genes. Conclusions: These results indicate that ethacridine treatment of activin A-derived endodermal hES cells leads to enhanced chromatin accessibility, which, in turn, allows histone H4 acetylation in the regulation of active genes for speciation of thyroid follicular cells from hES cells.

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Differentiation-related changes in glycoprotein synthesis by human keratinocytes.

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