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Updated: May 4, 2026
Assessment of Selective mRNA Translation in Mammalian Cells by Polysome Profiling
Published on: October 28, 2014
Differential effects of PDCD4 depletion on protein synthesis in myoblast and myotubes
Dhanshri Kakade, Nushaba Islam, Naomi Maeda
1School of Kinesiology & Health Science and Muscle Health Research Centre, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada. oadegoke@yorku.ca.
Background:
Reduced muscle mass is a hallmark of metabolic diseases like diabetes and cancer. The mammalian (mechanistic) target of rapamycin complex 1/S6 kinase 1 (mTORC1/S6K1) pathway is critical to the regulation of muscle protein synthesis and mass but its mechanism of action is not completely understood.
Results:
Using L6 myotubes, we characterized the regulation of programmed cell death 4 (PDCD4), a recently described substrate of S6K1. The abundance, but not Ser67 phosphorylation, of PDCD4 was sensitive to amino acid and serum deprivation: values in starved cells were 4.5X of control (P < 0.001). Refeeding had opposite effects. Growth factors, compared to amino acids, appeared more critical in regulating PDCD4 abundance. Furthermore, inhibition of mTORC1 or the proteasome prevented the refeeding-associated decrease in PDCD4 abundance. Amino acid and serum deprivation significantly increased PDCD4 binding to eIF4A (P < 0.05); this was reversed during refeeding. PDCD4 depletion by RNA interference had no significant effect on phenylalanine incorporation into myotube mixed proteins in control cells but further suppressed (30%) this measure in nutrient-deprived cells (P < 0.0005). This was not observed in myoblasts. In starved myotubes, PDCD4 depletion further reduced the association of eIF4G with eIF4E.
Conclusion:
Our data suggest that in myotubes, PDCD4 abundance is sensitive to nutritional manipulation in an mTORC1 and proteasome depended manner. Furthermore, the role of PDCD4 in regulating protein synthesis appears dependent on the developmental state of the cell.
Insights
Nutrient deprivation increases programmed cell death 4 (PDCD4) in muscle cells, impacting protein synthesis. This regulation is controlled by the mTORC1 pathway and proteasome, and varies with cell development.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Reduced muscle mass is a key feature of metabolic diseases.
- The mTORC1/S6K1 pathway is crucial for muscle protein synthesis and mass.
- The precise mechanisms of mTORC1/S6K1 in muscle regulation are not fully understood.
Purpose of the Study:
- To investigate the regulation of programmed cell death 4 (PDCD4) by the mTORC1/S6K1 pathway in muscle cells.
- To understand the role of PDCD4 in muscle protein synthesis under varying nutrient conditions.
Main Methods:
- Utilized L6 myotubes to study PDCD4 regulation.
- Manipulated nutrient availability (amino acid and serum deprivation/refeeding).
- Employed mTORC1 inhibition, proteasome inhibition, and RNA interference for PDCD4 depletion.
Main Results:
- PDCD4 abundance, not phosphorylation, was sensitive to nutrient changes, increasing with deprivation and decreasing with refeeding.
- mTORC1 and proteasome inhibition blocked the decrease in PDCD4 during refeeding.
- PDCD4 depletion suppressed protein synthesis in nutrient-deprived myotubes and affected translation initiation factor complex formation.
Conclusions:
- PDCD4 abundance in myotubes is regulated by nutrient availability via mTORC1 and proteasome.
- The function of PDCD4 in protein synthesis is context-dependent on cellular differentiation state.
