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The role of MAP kinase kinase in interleukin-3 stimulation of proliferation
G R Perkins1, C J Marshall, M K Collins
1CRC Centre for Cell and Molecular Biology, Chester Beatty Laboratories, London, UK.
Abstract:
Expression of a dominant interfering mutant of MAP kinase kinase (MAPKK) inhibits interleukin-3 (IL-3) activation of MAP kinase in the murine bone marrow-derived cell line BAF3. This results in an increase in the level of IL-3 required to stimulate cell proliferation and suppress apoptosis. When apoptosis is constitutively inhibited by coexpression of bcl-2, the dominant interfering MAPKK inhibits IL-3 driven cell cycle progression. Thus, MAPKK function is necessary for optimal IL-3 inhibition of apoptosis and optimal IL-3 stimulation of entry into S phase. Expression of a constitutively activated mutant of MAPKK does not replace IL-3, but renders cells able to proliferate in a density-dependent manner. Cell contact is required to allow cell proliferation; such contact can be supplied by cells without activated MAPKK.
Insights
MAP kinase kinase (MAPKK) is crucial for interleukin-3 (IL-3) signaling in cell proliferation and apoptosis. Inhibiting MAPKK function increases IL-3 levels needed for cell growth and survival.
Area of Science:
- Cell Biology
- Molecular Signaling
- Hematopoiesis
Background:
- Interleukin-3 (IL-3) is a key cytokine regulating hematopoietic cell proliferation and survival.
- MAP kinase kinase (MAPKK) is a central component of intracellular signaling pathways.
Purpose of the Study:
- To investigate the role of MAPKK in IL-3-mediated signaling.
- To determine MAPKK's necessity for IL-3's effects on cell cycle progression and apoptosis.
Main Methods:
- Utilized a dominant interfering mutant of MAPKK in the BAF3 murine cell line.
- Coexpressed bcl-2 to constitutively inhibit apoptosis.
- Assessed IL-3-dependent cell proliferation, apoptosis suppression, and cell cycle entry.
Main Results:
- Dominant interfering MAPKK inhibited IL-3-induced MAP kinase activation.
- Increased IL-3 concentrations were required to stimulate proliferation and suppress apoptosis.
- MAPKK inhibition blocked IL-3-driven cell cycle progression, even when apoptosis was inhibited by bcl-2.
- Activated MAPKK did not substitute for IL-3 but enabled density-dependent proliferation.
Conclusions:
- MAPKK is essential for optimal IL-3-mediated inhibition of apoptosis.
- MAPKK function is necessary for IL-3-stimulated entry into the S phase of the cell cycle.
- Cell-cell contact is required for proliferation, which can be provided by cells lacking activated MAPKK.