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  • Author: P L Hanson x
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A Scarlett Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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M P Parsons Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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P L Hanson Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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K K Sidhu Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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T P Milligan Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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J M Burrin Bart's and the London School of Medicine and Dentistry, William Harvey Research Institute, Queen Mary, Centre for Endocrinology, University of London, Charterhouse Square, London EC1M 6BQ, UK

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The aim of the present study was to examine whether triiodo-l-thyronine (T3) or l-thyroxine (T4) rapidly activated the mitogen-activated protein kinase (MAPK) intracellular signalling cascade in osteoblast-like cells and investigate whether this activation was initiated at the integrin αVβ3 cell surface receptor. Using PCR and western blotting, the expression of integrin αVβ3 mRNA and protein was demonstrated in the human osteoblast-like cell lines MG-63 and SaOS-2. The treatment of MG-63 cells with T3 (10 nM) or T4 (100 nM) for 10 min stimulated extracellular signal-regulated kinase activity (ERK, a component of the MAPK pathway) as determined by fluorescent immunocytochemistry and an immunocomplex activity assay (T3 by 10.7-fold, P<0.01 and T4 by 10.4-fold, P<0.01 compared with control). T3 (10 nM) and T4 (100 nM) also significantly stimulated thymidine incorporation into MG-63 cells by 2.3±0.7-fold (P<0.01) and 2.1±0.1-fold (P<0.05) respectively. To establish whether transient ERK activation via the integrin αVβ3 cell surface receptor mediated these effects, MG-63 cells were pretreated for 30 min with the specific MAPK kinase inhibitor, U0126 (1 μM), or an anti-integrin αVβ3-blocking antibody. Both pretreatments significantly inhibited T3- and T4-stimulated ERK activation and abolished T3-stimulated thymidine incorporation (P<0.01). T4-stimulated incorporation was significantly inhibited from 2.1- to 1.3-fold above control (P<0.05). Thus, our results suggest that T3 and T4 rapidly stimulate ERK activation in MG-63 cells via integrin αVβ3 and that one functional effect of this ERK activation is increased DNA synthesis.

Article Type:
Research Article
DOI:
https://doi.org/10.1677/JOE-07-0344
Volume/Issue:
Volume 196: Issue 3
Free access