A patient with prolonged immobilization shows significant skeletal muscle atrophy. The reduction in muscle fiber size is primarily mediated by increased protein degradation through which pathway?

• A Caspase-mediated proteolysis
• B Complement-mediated lysis
• C Necroptosis signaling
• D Ubiquitin-proteasome pathway ✓

Explanation

Atrophy involves increased protein degradation via the ubiquitin-proteasome pathway, where ubiquitin-tagged proteins are degraded by proteasomes. Caspases mediate apoptosis, not atrophy. Complement mediates immune cell lysis. Necroptosis is a form of programmed necrosis. The ubiquitin-proteasome pathway is the key mechanism in disuse and cachectic atrophy.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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