UVB radiation affects the mobility of epidermal growth factor receptors in human keratinocytes and fibroblasts |
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Authors: | Margareta Lirvall Pia Ljungqvist-Höddelius Åke Wasteson Karl-Eric Magnùsson |
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Institution: | (1) Department of Cell Biology, Faculty of Health Sciences, University of Linköping, Linköping, Sweden;(2) Department of Medical Microbiology, Faculty of Health Sciences, University of Linköping, Linköping, Sweden |
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Abstract: | Growth factor receptors transmit biological signals for the stimulation of cell growth in vitro and in vivo and their autocrine stimulation may be involved in tumorigenesis. It is therefore, of great value to understand receptor reactions in response to ultraviolet (UV) light which certain normal human cells are invaribly exposed to during their growth cycle. UV irradiation has recently been shown to deplete antioxidant enzymes in human skin. The aims of the present study were a) to compare the lateral mobility of epidermal growth factor receptors (EGF-R) in cultured human keratinocytes and human foreskin fibroblasts, b) to investigate effects of ultraviolet B radiation on the mobility of EGF-R in these cells, and c) study the response of EGF-R on addition of antioxidant enzymes. The epidermal growth factor receptors were labeled with rhodaminated EGF, the lateral diffusion was determined and the fraction of mobile EGF-R assessed with the fluorescence recovery after photobleaching (FRAP). We found that human keratinocytes display a higher basal level of EGF-R mobility than human skin fibroblasts, viz. with diffusion coefficients (D ± standard error of the mean, SEM) of 4.2±0.2 × 10–10 cm2/s, and 1.8±0.2 × 10–10 cm2/s, respectively. UVB-irradiated fibroblasts showed an almost four-fold increase in the diffusion coefficient; D was 6.3±0.3 × 10–10 cm2/s. The keratinocytes, however, displayed no significant increase in receptor diffusion after irradiation; D was 5.1±0.8 × 10–10 cm2/s. In both cell types the percentage of EGF-R fluorescence recovery after photobleaching, i.e. the fraction of mobile receptors, was significantly increased after irradiation. In keratinocytes it increased from 69% before irradiation to 78% after irradiation. Analogous figures for fibroblasts were 61% and 73%. The effect of UVB on fibroblast receptors was abolished by prior addition of superoxide dismutase (SOD) and catalase (CAT). It is concluded that UVB radiation of fibroblasts and keratinocytes can affect their biophysical properties of EGF-R. The finding that addition of antioxidant enzymes prevented the UVB effect in fibroblasts may indicate the involvement of reactive oxygen metabolites.Abbreviations CAT
Catalase
- D
Lateral diffusion coefficient
- EDTA
Ethylenediaminetetraacetic acid
- EGF
Epidermal growth factor
- E-MEM
Eagle's minimum essential medium
- FCS
Fetal calf serum
- FRAP
Fluorescence recovery after photobleaching
- KRG
Krebs-Ringer phosphate buffer
- PBS
Phosphate-buffered saline
- R
Mobile fraction
- ROS
Reactive oxygen species
- SEM
Standard error of the mean
- SOD
Superoxide dismutase
- UVA
Ultraviolet light-A (315-400 nm)
- UVB
Ultraviolet light-B (280-315 nm) |
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Keywords: | Ultraviolet light B reactive oxygen species EGF receptors keratinocytes fibroblasts |
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