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Signaling by the Mpl receptor involves IKK and NF-kappaB
Ying Zhang1, Shishinn Sun, Zhengyu Wang
1Department of Biochemistry, Whitaker Cardiovascular Institute, Cancer Research Center, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Journal of Cellular Biochemistry
|April 23, 2002
Summary
Mpl ligand signaling, also known as thrombopoietin, influences NF-kappaB activity in megakaryocytes. This study reveals a link between Mpl ligand, IKK, and NF-kappaB, impacting megakaryocyte proliferation and apoptosis.
Area of Science:
- Molecular Biology
- Cell Signaling
- Hematopoiesis
Background:
- Tumor necrosis factor-alpha (TNF-alpha) receptor binding activates IKK complex, inducing NF-kappaB activity.
- Mpl ligand (thrombopoietin/TPO) signaling is crucial for megakaryocyte differentiation, proliferation inhibition, polyploidization, and platelet formation.
- Megakaryocyte apoptosis is associated with polyploidization and fragmentation into platelets.
Purpose of the Study:
- To investigate the relationship between Mpl ligand activation and IKK/NF-kappaB activity.
- To identify the role of NF-kappaB in megakaryocyte proliferation and apoptosis during late megakaryopoiesis.
Main Methods:
- Treatment of a Mpl ligand-responding megakaryocytic cell line with Mpl ligand.
- Assessing IKK activity over time.
- Analyzing DNA-binding activity of NF-kappaB p50 homodimers and p50-p65 heterodimers.
- Evaluating NF-kappaB-dependent promoter activity.
Main Results:
- Mpl ligand treatment caused a transient increase followed by a sustained decrease in IKK activity.
- This decrease in IKK activity was independent of IKKalpha and IKKbeta levels.
- Proliferating megakaryocytes exhibited constitutive NF-kappaB p50 homodimer and p50-p65 heterodimer DNA-binding activity.
- Reduced IKK activity correlated with decreased NF-kappaB DNA binding and NF-kappaB-dependent promoter activity.
Conclusions:
- This study establishes the first link between Mpl receptor signaling and IKK/NF-kappaB activities.
- Mpl ligand signaling modulates IKK and NF-kappaB activity in megakaryocytes.
- Downregulation of NF-kappaB activity, mediated by Mpl signaling, may contribute to the inhibition of mitotic proliferation and promotion of apoptosis in late megakaryopoiesis.