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Transforming growth factor-beta-mediated mast cell migration depends on mitogen-activated protein kinase activity
N Olsson1, E Piek, M Sundström
1Department of Genetics and Pathology, Rudbeck Laboratory, Uppsala University, S-751 85, Uppsala, Sweden
Abstract:
Transforming growth factor-beta (TGF-beta) isoforms regulate numerous cellular functions through binding to receptors with intrinsic serine/threonine kinase activity that transduce the intracellular signals via activation of Smad proteins. In this study, we examined the signalling pathways involved in TGF-beta1-mediated growth inhibition and migration in a human mast cell line, HMC-1. TGF-beta1 evoked optimal migration at 40 fM, whereas maximal growth inhibition was obtained at 400 pM. Protein tyrosine kinase inhibitors completely inhibited TGF-beta1-mediated migration, without affecting the antimitogenic response. Smad2 was phosphorylated upon TGF-beta1 treatment, both in the absence and presence of genistein. The mitogen-induced extracellular kinase (MEK) inhibitor, PD98059, blocked the migratory response without affecting growth inhibition. In contrast, the p38 MAP kinase inhibitor, SB203580, had no significant effect on either migration or growth inhibition. These results indicate that different signalling pathways mediate TGF-beta1-induced migration and growth inhibition in HMC-1 cells, where the migration involves MEK activity.
Insights
Transforming growth factor-beta1 (TGF-beta1) differentially regulates human mast cell migration and growth inhibition via distinct signaling pathways. Migration involves MEK signaling, while growth inhibition is independent of MEK and p38 MAP kinase.
Area of Science:
- Cellular Biology
- Molecular Signaling
- Immunology
Background:
- Transforming growth factor-beta (TGF-beta) isoforms are crucial regulators of cellular functions.
- TGF-beta signaling involves receptor binding, serine/threonine kinase activity, and Smad protein activation.
- Understanding TGF-beta1's role in human mast cells is vital for immunology and cell biology.
Purpose of the Study:
- To investigate the specific signaling pathways mediating TGF-beta1-induced growth inhibition and migration in the HMC-1 human mast cell line.
- To differentiate the molecular mechanisms underlying TGF-beta1's opposing effects on cell proliferation and motility.
Main Methods:
- Utilized a human mast cell line (HMC-1) for experimental studies.
- Administered TGF-beta1 at varying concentrations to determine optimal effects on migration and growth inhibition.
- Employed specific inhibitors: protein tyrosine kinase inhibitors, PD98059 (MEK inhibitor), and SB203580 (p38 MAP kinase inhibitor).
- Assessed Smad2 phosphorylation as a key downstream signaling event.
Main Results:
- TGF-beta1 induced optimal migration at 40 fM and maximal growth inhibition at 400 pM.
- Protein tyrosine kinase inhibitors completely blocked TGF-beta1-mediated migration but not growth inhibition.
- Smad2 phosphorylation occurred irrespective of genistein presence.
- MEK inhibition (PD98059) abolished migration without affecting growth inhibition.
- p38 MAP kinase inhibition (SB203580) showed no significant impact on migration or growth inhibition.
Conclusions:
- TGF-beta1 utilizes distinct signaling pathways to mediate cellular migration and growth inhibition in HMC-1 cells.
- Cell migration is dependent on protein tyrosine kinases and MEK activity.
- Growth inhibition is regulated independently of MEK and p38 MAP kinase pathways.