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Tsc2 is not a critical target of Akt during normal Drosophila development
1Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040, USA.
Abstract:
Signaling by insulin and target of rapamycin are both required for cell growth, but their interrelationships remain poorly defined. It was reported that Akt, an essential component of the insulin pathway, stimulates growth by phosphorylating and inhibiting tuberous sclerosis complex 2 (TSC2). Here we evaluate this model genetically in Drosophila by engineering Tsc2 mutants in which the Akt phosphorylation sites are changed to nonphosphorylatable or phospho-mimicking residues. Strikingly, such mutants completely rescue the lethality and cell growth defects of Tsc2-null mutants. Taken together, our data suggest that Tsc2 is not a critical substrate of Akt in normal Drosophila development.
Insights
Insulin signaling and the target of rapamycin pathway regulate cell growth. Data suggest tuberous sclerosis complex 2 (TSC2) is not a critical substrate of Akt in normal Drosophila development, challenging previous models.
Area of Science:
- Cellular biology
- Molecular biology
- Genetics
Background:
- Insulin and target of rapamycin (TOR) signaling pathways are crucial for cell growth regulation.
- The precise interplay between these pathways is not fully understood.
- Akt, a key component of the insulin pathway, is proposed to promote growth by phosphorylating and inhibiting tuberous sclerosis complex 2 (TSC2).
Purpose of the Study:
- To genetically investigate the role of Akt phosphorylation sites on TSC2 in Drosophila.
- To determine if TSC2 is a critical substrate of Akt in vivo.
Main Methods:
- Genetic engineering of Drosophila Tsc2 mutants.
- Introduction of nonphosphorylatable or phospho-mimicking residues at Akt phosphorylation sites in Tsc2.
- Assessment of mutant Tsc2 in rescuing Tsc2-null mutant phenotypes.
Main Results:
- Tsc2 mutants with altered Akt phosphorylation sites fully rescued lethality and cell growth defects in Tsc2-null mutants.
- These findings challenge the established model of Akt-mediated TSC2 inhibition.
Conclusions:
- Tuberous sclerosis complex 2 (TSC2) is not a critical substrate of Akt in normal Drosophila development.
- The current model of Akt-TSC2 interaction in growth regulation requires re-evaluation in the context of Drosophila development.
