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Questions and Answers
What are the major proteolytic systems involved in muscle protein degradation?
What are the major proteolytic systems involved in muscle protein degradation?
The autophagy-lysosomal system is conserved from yeast to mammals.
The autophagy-lysosomal system is conserved from yeast to mammals.
True
What plays an essential role in the initiation of autophagy?
What plays an essential role in the initiation of autophagy?
Atg7
The ______ system is responsible for poly-ubiquitinated proteins.
The ______ system is responsible for poly-ubiquitinated proteins.
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Which muscle fiber types have higher rates of protein synthesis?
Which muscle fiber types have higher rates of protein synthesis?
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Match the following protein degradation pathways with their characteristics:
Match the following protein degradation pathways with their characteristics:
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What effect does fasting/starvation have on muscle atrophy?
What effect does fasting/starvation have on muscle atrophy?
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Study Notes
Muscle Protein Degradation
- Two major proteolytic systems play a role in muscle protein degradation: the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal system.
- The UPS is responsible for degrading short-lived and misfolded proteins.
- The autophagy-lysosomal system is responsible for degrading long-lived proteins, aggregates and organelles, like mitochondria and the endoplasmic reticulum.
- The ubiquitin-proteasome pathway (UPP) requires the attachment of ubiquitin molecules to target proteins, which then get degraded by the proteasome.
- Atrogin-1 and Murf-1 are key E3 ubiquitin ligases involved in muscle atrophy.
- MG132 is a known inhibitor of the proteasome.
- Autophagy is an important cellular process that involves the formation of autophagosomes, which engulf cellular components and deliver them to lysosomes for degradation.
- The autophagy-lysosomal system plays a role in the degradation of long-lived proteins, protein aggregates, and damaged organelles.
- Atg7 is a crucial protein in the autophagy pathway, and its deletion leads to a major disruption in the process.
- Autophagy disruption leads to the accumulation of ubiquitinated proteins in skeletal muscle.
- Autophagy is essential for muscular health and tissue repair.
Skeletal Muscle Fibers: Protein Synthesis & Degradation
- Muscle fiber types exhibit differences in protein synthesis and degradation rates.
- Slow-twitch (Type 1) and Type IIa fibers have higher rates of both protein synthesis and degradation compared to Type IIx and Iib fibers.
- Soleus (SO) muscle is comprised primarily of slow-twitch fibers and has high protein synthesis and degradation rates.
- Plantaris (PL) muscle contains a mix of fiber types (SO, FOG, FG).
- White Vastus Lateralis (WV) muscle has a higher percentage of fast-twitch fibers, which have lower protein synthesis and degradation rates.
Mitochondrial Content & Basal Autophagy
- Mitochondrial content is directly related to the levels of basal autophagy in muscles.
Protein Synthesis Assessment
- Two methods for assessing protein synthesis are heavy amino acid labeling and puromycin labeling.
Exercise Training & Detraining Effects
- Exercise training increases protein synthesis rates.
- Disuse or detraining leads to a decrease in protein synthesis rates.
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Description
Test your knowledge on the mechanisms of muscle protein degradation, focusing on the ubiquitin-proteasome system and autophagy-lysosomal system. This quiz will cover key concepts such as E3 ubiquitin ligases, proteasome inhibitors, and the roles of autophagosomes in cellular degradation processes.
