Human keratinocytes express transcripts for three isoforms of parathyroid hormone-related protein (PTHrP), but not for the parathyroid hormone/PTHrP receptor: effects of 1,25(OH)2 vitamin D3

Autor: G R, Sharpe, J P, Dillon, B, Durham, J A, Gallagher, W D, Fraser
Rok vydání: 1998
Předmět:
Zdroj: British Journal of Dermatology. 138:944-951
ISSN: 1365-2133
0007-0963
DOI: 10.1046/j.1365-2133.1998.02259.x
Popis: Parathyroid hormone-related protein (PTHrP) is strongly expressed in the epidermis and has been implicated in the regulation of growth and differentiation of keratinocytes. PTHrP has N-terminal sequence homology with parathyroid hormone (PTH) and binds to the type I PTH/PTHrP receptor, but earlier reports suggest that keratinocytes do not possess this cell surface receptor. In order to determine which PTHrP mRNA isoforms are expressed by keratinocytes and whether the type I receptor mRNA is present, we designed specific primers for reverse transcriptase-polymerase chain reaction. The interaction of PTHrP with other promoters of keratinocyte differentiation is unclear. In particular. 1,25(OH) 2 D 3 is also fundamental in calcium homeostasis and induces changes in intracellular calcium. We therefore investigated the effect of 1,25(OH) 2 D 3 on PTHrP mRNA expression and protein production in cultured human keratinocytes. Cells were incubated for 3 days at concentrations of 1.25(OH) 2 D 3 of 10 -10 -10 -6 mol/L. PTHrP in culture supernatant, measured by two site immunoradiometric assay, was 915 ± 98 PTHrP fmol/mg of cell layer protein in untreated cultures decreasing to 57() ± 113 with 10 -8 mol/L and 402 ± 24 with 10 -6 mol/L 1.25OH) 2 D 3 (mean ± SEM, P < 0.01, n = 6). Transcripts for all three PTHrP isoforms (139. 141 and 173 amino acids) were detectable in keratinocyte mRNA. Corresponding to the decrease in PTHrP protein we demonstrated a reduction in all three PTHrP mRNA transcripts after 3 days' incubation with 1.25(OH) 2 D 3 over a concentration range 10 -10 -10 -6 mol/L. Repeated studies failed to detect type I PTH/PTHrP receptor mRNA in human keratinocytes. either in control cultures or in the presence of 1.25(OH) 2 D 3 . We have shown that keratinocytes produce abundant PTHrP and that this is modulated by 1,25(OH) 2 D 3 , suggesting a physiological role. Further studies are required to investigate the relative expression of PTHrP isoforms, their role in keratinocyte signalling and the receptors involved.
Databáze: OpenAIRE
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