Aberrant Protein Turn-Over Associated With Myofibrillar Disorganization in FHL1 Knockout Mice
Jingjing Ding1, Yan Fei Cong1, Bo Liu1
1Medical Research Center of Shengjing Hospital, China Medical University, Shenyang, China.
Abstract:
Mutations in the FHL1 gene, and FHL1 protein deletion, are associated with rare hereditary myopathies and cardiomyopathies. FHL1-null mice develop age-dependent myopathy and increased autophagic activity. However, the molecular pathway involved in contractile function and increased autophagic activity in the FHL1-null mouse has not yet been fully elucidated. In this study, FHL1 protein was knocked out in mice using Transcription Activator-like Effector Nucleases (TALENs) and the IRS1-FOXO1/mTOR signaling pathway was investigated in skeletal muscles and heart. TALEN constructs caused targeted mutations in 30% of newborn mice; these mutations caused a deletion of 1-13 base pairs which blocked synthesis of the full-length FHL1 protein. Furthermore, 2.5-month old FHL1-null male mice were not prone to global muscular fatigue when compared with WT littermates, but histological analysis and ultrastructural analysis by transmission electron microscopy confirmed the presence of myofibrillar disorganization and the accumulation of autophagosome or autolysosome-like structures in FHL1-null mice. Moreover, autophagy and mitophagy were both activated in FHL1 KO mice and the degradation of autophagic lysosomes was impeded. Enhanced autophagic activity in FHL1 KO mice was induced by FOXO1 up-regulation and protein synthesis was increased via mTOR. The cytoskeletal proteins, MYBPC2 and LDB3, were involved in the formation of pathological changes in FHL1 KO mice. Markers of early differentiation (MEF2C and MYOD1) and terminal differentiation (total MYH) were both up-regulated in tibialis anterior (TA) muscles in FHL1 KO mice. The number of type I and type II fibers increased in FHL1-null TA muscles, but the number of type| | b, and type | | d fibers were both reduced in FHL1-null TA muscles. The results obtained from the heart were consistent with those from the skeletal muscle and indicated autophagic activation by FOXO1 and an increase in protein synthesis via mTOR also occurred in the heart tissue of FHL1 knockout mice. In conclusion, aberrant protein turn-over associated with myofibrillar disorganization in FHL1 knockout mice. the up-regulation of FOXO1 was associated with enhanced autophagic activity and pathological changes in the muscle fibers of FHL1 KO mice. These results indicated that autophagy activated by FOXO1 is a promising therapeutic target for hereditary myopathies and cardiomyopathies induced by FHL1.
Insights
FHL1 gene mutations cause hereditary myopathies. FHL1 knockout mice show muscle disorganization and increased autophagy via FOXO1, suggesting autophagy as a therapeutic target for FHL1-related muscle diseases.
Area of Science:
- Muscle Biology
- Cellular Biology
- Genetics
Background:
- Mutations in the Four-and-a-Half LIM domains 1 (FHL1) gene are linked to rare hereditary myopathies and cardiomyopathies.
- FHL1-null mice exhibit age-dependent myopathy and heightened autophagic activity, but the underlying molecular mechanisms remain unclear.
Purpose of the Study:
- To investigate the molecular pathway regulating contractile function and autophagy in FHL1-null mice.
- To elucidate the role of the IRS1-FOXO1/mTOR signaling pathway in skeletal and cardiac muscle of FHL1 knockout mice.
Main Methods:
- FHL1 protein was knocked out in mice using Transcription Activator-like Effector Nucleases (TALENs).
- Skeletal muscles and heart tissues were analyzed for histological, ultrastructural, and molecular changes, including autophagy and signaling pathway activation.
Main Results:
- FHL1 knockout mice displayed myofibrillar disorganization and accumulation of autophagosomes/autolysosomes.
- Autophagy and mitophagy were activated, with impaired lysosomal degradation, driven by FOXO1 up-regulation and increased protein synthesis via mTOR.
- Cytoskeletal proteins MYBPC2 and LDB3 were implicated in pathological changes, and muscle fiber type distribution was altered.
Conclusions:
- Aberrant protein turnover and myofibrillar disorganization characterize FHL1 knockout mice.
- FOXO1-mediated autophagy activation contributes to muscle pathology in FHL1 deficiency.
- Targeting FOXO1-activated autophagy presents a potential therapeutic strategy for FHL1-related myopathies and cardiomyopathies.
More Related Videos
Related Concept Videos
02:04Protein-protein Interfaces
02:15Protein and Protein Structure
A protein's shape is critical to its function. For example, an enzyme...
02:26Conservation of Protein Domains Over Different Proteins
A limited set of protein domains often duplicate and recombine during evolution. These domains can be organized in different combinations to...
01:55What are Proteins?
02:26Protein Networks
These interactions can be represented through maps depicting protein-protein interaction networks, represented as nodes and edges. Nodes are circles that are representative of a protein,...
02:47Protein Families