Loss of 4E-BPs prevents the hindlimb immobilization-induced decrease in protein synthesis in skeletal muscle.

Area of Science:

• Muscle physiology
• Molecular biology
• Translational control

Background:

• Disuse atrophy leads to significant muscle mass loss.
• Protein synthesis regulation is crucial for maintaining muscle mass.
• The roles of translational repressors 4E-BP1 and 4E-BP2 in muscle atrophy are not fully understood.

Purpose of the Study:

• To test if upregulating protein synthesis can attenuate disuse-induced muscle atrophy.
• To investigate the impact of lacking 4E-BP1 and 4E-BP2 on muscle protein synthesis and atrophy during immobilization.
• To explore compensatory mechanisms that might counteract elevated protein synthesis.

Main Methods:

• Comparison of wild-type (WT) and double-knockout (DKO) mice lacking 4E-BP1 and 4E-BP2.
• Unilateral hindlimb immobilization model to induce disuse atrophy.
• Measurement of protein synthesis rates, expression of atrophy markers (MAFbx, MuRF-1), and proteomic analysis of newly synthesized proteins.

Main Results:

• Immobilization downregulated protein synthesis in both WT and DKO mice, but synthesis was higher in DKO mice.
• Despite elevated protein synthesis in DKO mice, muscle atrophy occurred to the same extent as in WT mice.
• Downregulation of eukaryotic initiation factor eIF4E expression and altered translation of glycolytic enzymes were observed in DKO mice.

Conclusions:

• Elevated protein synthesis in DKO mice is insufficient to prevent disuse-induced muscle atrophy.
• Compensatory mechanisms, including reduced eIF4E expression, likely counteract increased protein synthesis.
• Differential translation of glycolytic enzymes may contribute to metabolic changes during atrophy.