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Interleukin-3-induced phosphorylation of BAD through the protein kinase Akt
L del Peso1, M González-García, C Page
1Department of Pathology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, MI 48109, USA.
Abstract:
BAD is a distant member of the Bcl-2 family that promotes cell death. Phosphorylation of BAD prevents this. BAD phosphorylation induced by interleukin-3 (IL-3) was inhibited by specific inhibitors of phosphoinositide 3-kinase (PI 3-kinase). Akt, a survival-promoting serine-threonine protein kinase, was activated by IL-3 in a PI 3-kinase-dependent manner. Active, but not inactive, forms of Akt were found to phosphorylate BAD in vivo and in vitro at the same residues that are phosphorylated in response to IL-3. Thus, the proapoptotic function of BAD is regulated by the PI 3-kinase-Akt pathway.
Insights
Interleukin-3 (IL-3) signaling activates the phosphoinositide 3-kinase (PI 3-kinase)-Akt pathway, which phosphorylates BAD and inhibits its cell death-promoting function. This pathway thus regulates BAD
Area of Science:
- Molecular Biology
- Cell Signaling
- Cancer Research
Background:
- BAD is a pro-apoptotic protein belonging to the Bcl-2 family.
- Phosphorylation of BAD inhibits its pro-apoptotic activity.
- Interleukin-3 (IL-3) is known to promote cell survival.
Purpose of the Study:
- To investigate the mechanism by which IL-3 inhibits BAD-mediated apoptosis.
- To identify the signaling pathway responsible for BAD phosphorylation induced by IL-3.
Main Methods:
- Utilized specific inhibitors of phosphoinositide 3-kinase (PI 3-kinase).
- Assessed the activation of Akt, a serine-threonine protein kinase.
- Performed in vivo and in vitro phosphorylation assays of BAD by Akt.
Main Results:
- IL-3-induced BAD phosphorylation was blocked by PI 3-kinase inhibitors.
- IL-3 activated Akt in a PI 3-kinase-dependent manner.
- Active Akt phosphorylated BAD at the same residues as IL-3 treatment.
Conclusions:
- The PI 3-kinase-Akt pathway is crucial for IL-3-mediated inhibition of BAD.
- Akt directly phosphorylates BAD, thereby regulating its pro-apoptotic function.
- This signaling cascade represents a key mechanism for cell survival signaling.