Differing effects of rapamycin and mTOR kinase inhibitors on protein synthesis

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• The mammalian target of rapamycin (mTOR) pathway regulates cell growth and protein synthesis.
• mTOR forms two complexes: mTORC1 and mTORC2, with distinct functions.
• Rapamycin inhibits mTORC1, while mTOR kinase inhibitors affect both complexes.

Purpose of the Study:

• To investigate the differential effects of rapamycin and mTOR kinase inhibitors on protein synthesis.
• To analyze the impact on both general and specific protein synthesis using a novel stable isotope-labeling method.

Main Methods:

• Treatment of HeLa cells with rapamycin and mTOR kinase inhibitors.
• Measurement of total protein synthesis.
• Stable isotope-labeling to quantify synthesis of specific proteins.
• Analysis of eukaryotic initiation factor (eIF) binding.

Main Results:

• mTOR kinase inhibitors reduced total protein synthesis by approximately 30%, while rapamycin had a modest effect.
• Inhibition of 5 acronym{'-'}TOP mRNA translation was observed with both agents, more strongly with kinase inhibitors.
• Differential effects on specific protein synthesis were noted, with some non-TOP mRNA-encoded proteins also affected.

Conclusions:

• mTOR kinase inhibitors have a more profound impact on overall protein synthesis than rapamycin.
• The differential inhibition suggests complex regulation of protein synthesis by mTOR pathway components.
• Findings provide insights into the distinct roles of mTORC1 and mTORC2 in controlling protein production.