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Inhibition of the anti-apoptotic PI(3)K/Akt/Bad pathway by stress
1Cancer Biology Program, Mayer Cancer Biology Research Laboratory, Department of Radiation Oncology, Stanford University School of Medicine, Stanford, California 94305-5468 USA.
Abstract:
The initiation of apoptosis often transpires in the presence of agents that regulate cell survival. This study evaluated the effects of stress-induced ceramide on the anti-apoptotic activity of the phosphoinositide-3 kinase [PI(3)K] pathway. PI(3)K activity is directly down-regulated by stress-induced ceramide in a dose-dependent manner with rapid kinetics and high specificity. Ceramide inhibition of PI(3)K is dependent on acid-sphingomyelinase. Down-regulation of PI(3)K by ceramide results in inhibition of the kinase Akt and decreased phosphorylation of the death effector Bad. Thus, ceramide levels could act as a general apoptotic rheostat controlling cell survival by regulating PI(3)K anti-apoptotic effector mechanisms.
Insights
Stress-induced ceramide inhibits the phosphoinositide-3 kinase (PI(3)K) pathway, a key regulator of cell survival. This ceramide-mediated down-regulation of PI(3)K impacts Akt and Bad, influencing apoptosis.
Area of Science:
- Cellular biology
- Biochemistry
- Molecular mechanisms of apoptosis
Background:
- Apoptosis (programmed cell death) is crucial for multicellular organisms.
- Cell survival pathways, like the phosphoinositide-3 kinase (PI(3)K) pathway, counteract apoptosis.
- Stress-induced ceramide is implicated in regulating cell fate.
Purpose of the Study:
- To investigate the impact of stress-induced ceramide on the anti-apoptotic PI(3)K pathway.
- To elucidate the specific molecular mechanisms by which ceramide affects PI(3)K signaling.
Main Methods:
- Enzymatic assays to measure PI(3)K activity.
- Biochemical analyses to assess protein phosphorylation and interactions.
- Pharmacological inhibition of acid-sphingomyelinase.
Main Results:
- Stress-induced ceramide directly down-regulates PI(3)K activity in a dose-dependent and time-specific manner.
- Ceramide's inhibitory effect on PI(3)K is dependent on acid-sphingomyelinase activity.
- Ceramide-induced PI(3)K inhibition leads to reduced Akt kinase activity and decreased phosphorylation of the pro-apoptotic protein Bad.
Conclusions:
- Ceramide acts as a critical regulator of the PI(3)K pathway, influencing cell survival decisions.
- Ceramide levels may function as an 'apoptotic rheostat,' controlling cell fate by modulating PI(3)K effectors.
- Targeting ceramide metabolism or its interaction with the PI(3)K pathway could offer therapeutic strategies for diseases involving aberrant apoptosis.