Insulin-like growth factor-I and epidermal growth factor regulate insulin-like growth factor binding protein-3 (IGFBP-3) in the human keratinocyte cell line HaCaT.
The human keratinocyte cell line HaCaT has a basal phenotype and secretes an insulin-like growth factor (IGF) binding protein, IGFBP-3, which modulates its IGF-I response. Keratinocytes are highly responsive to mitogenic stimulation by IGF-I and epidermal growth factor (EGF), but the effect of these growth factors on IGFBP secretion by keratinocytes is not known. We investigated the effects of IGF-I and EGF, as well as three other skin-growth regulators, retinoic acid, basic fibroblast growth factor, and dexamethasone, on mitogenic stimulation and IGFBP-3 production in HaCaT cells. IGF-I and EGF were strongly mitogenic, whereas retinoic acid, basic fibroblast growth factor, and dexamethasone were not significantly mitogenic. IGF-I increased the level of IGFBP-3 in cell-conditioned medium by up to twofold, whereas EGF caused a twentyfold reduction in IGFBP-3. Retinoic acid and basic fibroblast growth factor had only minor effects on IGFBP-3 and dexamethasone had no effect. IGF-I stimulation of IGFBP-3 did not involve increases in IGFBP-3 mRNA; however, EGF, consistent with its effect on IGFBP-3 protein, caused a fivefold reduction in IGFBP-3 mRNA. In summary, EGF profoundly inhibited IGFBP-3 synthesis in basal keratinocytes, whereas IGF-I increased IGFBP-3 levels by a posttranscriptional mechanism. We hypothesize that by inhibiting IGFBP-3 production in basal keratinocytes, epidermal mitogens such as EGF might stimulate epidermal growth indirectly by increasing local IGF-I availability.
Wraight
C J
CJ
Centre for Hormone Research, Royal Children's Hospital, Parkville, Victoria, Australia.
Werther
G A
GA
D002455:Cell Division / Q000187:drug effects; D002461:Cell Line, Transformed; D017077:Culture Media, Conditioned / Q000737:chemistry; D004261:DNA Replication / Q000187:drug effects; D003907:Dexamethasone / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000096:biosynthesis* / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology
D017077:Culture Media, Conditioned; D018972:Insulin-Like Growth Factor Binding Protein 3; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D014212:Tretinoin; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone