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Mitophagy is required for mitochondrial biogenesis and myogenic differentiation of C2C12 myoblasts.

Sin J, Andres AM, Taylor DJ, Weston T, Hiraumi Y, Stotland A, Kim BJ, Huang C, Doran KS, Gottlieb RA - Autophagy (2016)

Bottom Line: We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis.Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks.Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation.

View Article: PubMed Central - PubMed

Affiliation: a The Cedars-Sinai Heart Institute and the Barbra Streisand Women's Heart Center Cedars-Sinai Medical Center , Los Angeles , CA , USA.

ABSTRACT
Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Differentiation of primitive myoblasts into mature myotubes requires a metabolic switch to support the increased energetic demand of contractile muscle. Skeletal myoblasts specifically shift from a highly glycolytic state to relying predominantly on oxidative phosphorylation (OXPHOS) upon differentiation. We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis. During early myogenic differentiation, autophagy is robustly upregulated and this coincides with DNM1L/DRP1 (dynamin 1-like)-mediated fragmentation and subsequent removal of mitochondria via SQSTM1 (sequestosome 1)-mediated mitophagy. Mitochondria are then repopulated via PPARGC1A/PGC-1α (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha)-mediated biogenesis. Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks. The final product is a myotube replete with new mitochondria. Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts. Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation. Together these data highlight the integral role of autophagy and mitophagy in myogenic differentiation.

No MeSH data available.


Related in: MedlinePlus

Schematic of mitochondrial remodeling during differentiation. (A) Myoblasts rely primarily on glycolysis and to a lesser extent glucose oxidation and contain sparsely-populated networks of mitochondria. (B) With a differentiation stimulus, mitochondrial fission protein DNM1L and mitophagy receptor protein SQSTM1 are upregulated, leading to mitochondrial fragmentation and mitophagy. (C) Following clearance of the myoblast mitochondria, new mitochondria are synthesized via PPARGC1A-mediated biogenesis. These new mitochondria which rely primarily on fatty acid oxidation, are more tightly-coupled and better equipped to perform OXPHOS. Dense mitochondrial networks are established via OPA1-mediated fusion.
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f0010: Schematic of mitochondrial remodeling during differentiation. (A) Myoblasts rely primarily on glycolysis and to a lesser extent glucose oxidation and contain sparsely-populated networks of mitochondria. (B) With a differentiation stimulus, mitochondrial fission protein DNM1L and mitophagy receptor protein SQSTM1 are upregulated, leading to mitochondrial fragmentation and mitophagy. (C) Following clearance of the myoblast mitochondria, new mitochondria are synthesized via PPARGC1A-mediated biogenesis. These new mitochondria which rely primarily on fatty acid oxidation, are more tightly-coupled and better equipped to perform OXPHOS. Dense mitochondrial networks are established via OPA1-mediated fusion.

Mentions: The myogenic precursor cell population residing within skeletal muscle is a crucial component of repair and homeostasis. Once activated, these cells must undergo a substantial transformation from a mostly glycolytic myoblast7 with mildly uncoupled mitochondria to a metabolically active OXPHOS-dependent myotube (Fig. 10). To meet this increased energetic demand, mitochondrial biogenesis is induced to expand the mitochondrial mass. Indeed we have observed that during the later phase of myogenic differentiation, mitochondrial biogenesis leads to the formation of a dense mitochondrial network. However, our data indicate that this expansion is preceded by a wave of mitochondrial clearance, eliminating most of the pre-existing mitochondria that were adapted to serve the needs of a stem cell in order to make way for functionally different mitochondria capable of robust ATP production via fatty acid oxidation. The dramatic break-down and reassembly of the mitochondrial networks is interesting as it highlights several key players involved in the “mitochondrial differentiation” process. During the early phase of differentiation, DNM1L is upregulated but cleared soon after. Recent work has shown that mice with a cardiac-specific Dnm1l knockout have inhibited cardiac mitophagy resulting in cardiac dysfunction.15 Therefore DNM1L-mediated fission appears to be a crucial prerequisite for mitophagy. Following the mitochondrial clearance stage, mitochondrial constituents are replenished and densely populated networks are built via OPA1-mediated fusion. Interestingly, this rebuilding phase does not occur until mitochondrial clearance has subsided. This was illustrated when we pretreated myoblasts with BAF and placed them in differentiation media. Mitochondrial fission and autophagosomes were prominent; however because lysosomal fusion was blocked and degradation was prevented, the progression to biogenesis and further differentiation was impeded. Our findings show that mitochondrial autophagy dependent upon intact autophagic flux and SQSTM1 translocation is essential for mitochondrial clearance during early myogenic differentiation.


Mitophagy is required for mitochondrial biogenesis and myogenic differentiation of C2C12 myoblasts.

Sin J, Andres AM, Taylor DJ, Weston T, Hiraumi Y, Stotland A, Kim BJ, Huang C, Doran KS, Gottlieb RA - Autophagy (2016)

Schematic of mitochondrial remodeling during differentiation. (A) Myoblasts rely primarily on glycolysis and to a lesser extent glucose oxidation and contain sparsely-populated networks of mitochondria. (B) With a differentiation stimulus, mitochondrial fission protein DNM1L and mitophagy receptor protein SQSTM1 are upregulated, leading to mitochondrial fragmentation and mitophagy. (C) Following clearance of the myoblast mitochondria, new mitochondria are synthesized via PPARGC1A-mediated biogenesis. These new mitochondria which rely primarily on fatty acid oxidation, are more tightly-coupled and better equipped to perform OXPHOS. Dense mitochondrial networks are established via OPA1-mediated fusion.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4836019&req=5

f0010: Schematic of mitochondrial remodeling during differentiation. (A) Myoblasts rely primarily on glycolysis and to a lesser extent glucose oxidation and contain sparsely-populated networks of mitochondria. (B) With a differentiation stimulus, mitochondrial fission protein DNM1L and mitophagy receptor protein SQSTM1 are upregulated, leading to mitochondrial fragmentation and mitophagy. (C) Following clearance of the myoblast mitochondria, new mitochondria are synthesized via PPARGC1A-mediated biogenesis. These new mitochondria which rely primarily on fatty acid oxidation, are more tightly-coupled and better equipped to perform OXPHOS. Dense mitochondrial networks are established via OPA1-mediated fusion.
Mentions: The myogenic precursor cell population residing within skeletal muscle is a crucial component of repair and homeostasis. Once activated, these cells must undergo a substantial transformation from a mostly glycolytic myoblast7 with mildly uncoupled mitochondria to a metabolically active OXPHOS-dependent myotube (Fig. 10). To meet this increased energetic demand, mitochondrial biogenesis is induced to expand the mitochondrial mass. Indeed we have observed that during the later phase of myogenic differentiation, mitochondrial biogenesis leads to the formation of a dense mitochondrial network. However, our data indicate that this expansion is preceded by a wave of mitochondrial clearance, eliminating most of the pre-existing mitochondria that were adapted to serve the needs of a stem cell in order to make way for functionally different mitochondria capable of robust ATP production via fatty acid oxidation. The dramatic break-down and reassembly of the mitochondrial networks is interesting as it highlights several key players involved in the “mitochondrial differentiation” process. During the early phase of differentiation, DNM1L is upregulated but cleared soon after. Recent work has shown that mice with a cardiac-specific Dnm1l knockout have inhibited cardiac mitophagy resulting in cardiac dysfunction.15 Therefore DNM1L-mediated fission appears to be a crucial prerequisite for mitophagy. Following the mitochondrial clearance stage, mitochondrial constituents are replenished and densely populated networks are built via OPA1-mediated fusion. Interestingly, this rebuilding phase does not occur until mitochondrial clearance has subsided. This was illustrated when we pretreated myoblasts with BAF and placed them in differentiation media. Mitochondrial fission and autophagosomes were prominent; however because lysosomal fusion was blocked and degradation was prevented, the progression to biogenesis and further differentiation was impeded. Our findings show that mitochondrial autophagy dependent upon intact autophagic flux and SQSTM1 translocation is essential for mitochondrial clearance during early myogenic differentiation.

Bottom Line: We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis.Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks.Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation.

View Article: PubMed Central - PubMed

Affiliation: a The Cedars-Sinai Heart Institute and the Barbra Streisand Women's Heart Center Cedars-Sinai Medical Center , Los Angeles , CA , USA.

ABSTRACT
Myogenesis is a crucial process governing skeletal muscle development and homeostasis. Differentiation of primitive myoblasts into mature myotubes requires a metabolic switch to support the increased energetic demand of contractile muscle. Skeletal myoblasts specifically shift from a highly glycolytic state to relying predominantly on oxidative phosphorylation (OXPHOS) upon differentiation. We have found that this phenomenon requires dramatic remodeling of the mitochondrial network involving both mitochondrial clearance and biogenesis. During early myogenic differentiation, autophagy is robustly upregulated and this coincides with DNM1L/DRP1 (dynamin 1-like)-mediated fragmentation and subsequent removal of mitochondria via SQSTM1 (sequestosome 1)-mediated mitophagy. Mitochondria are then repopulated via PPARGC1A/PGC-1α (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha)-mediated biogenesis. Mitochondrial fusion protein OPA1 (optic atrophy 1 [autosomal dominant]) is then briskly upregulated, resulting in the reformation of mitochondrial networks. The final product is a myotube replete with new mitochondria. Respirometry reveals that the constituents of these newly established mitochondrial networks are better primed for OXPHOS and are more tightly coupled than those in myoblasts. Additionally, we have found that suppressing autophagy with various inhibitors during differentiation interferes with myogenic differentiation. Together these data highlight the integral role of autophagy and mitophagy in myogenic differentiation.

No MeSH data available.


Related in: MedlinePlus