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Pannexin 1 and pannexin 3 channels regulate skeletal muscle myoblast proliferation and differentiation.

Langlois S, Xiang X, Young K, Cowan BJ, Penuela S, Cowan KN - J. Biol. Chem. (2014)

Bottom Line: Using HSMM, we found that Panx1 expression promotes this process, whereas it was impaired in the presence of probenecid or carbenoxolone.Reduction of its endogenous expression using two Panx3 shRNAs significantly inhibited HSMM proliferation without triggering their differentiation.In summary, our results demonstrate that Panx1 and Panx3 are co-expressed in human skeletal muscle myoblasts and play a pivotal role in dictating the proliferation and differentiation status of these cells.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Surgery, Division of Paediatric Surgery, University of Ottawa, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada, Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada.

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Panx1 and Panx3 levels are modulated during skeletal muscle myoblast differentiation and regulate this process as well as myoblast proliferation. Proliferative undifferentiated skeletal muscle myoblasts express high levels of the ∼70-kDa immunoreactive species of Panx3, whereas its lower Mr species or Panx1 were very low. Its levels were drastically diminished during differentiation, suggesting that the ∼70-kDa immunoreactive species of Panx3 may play a role in keeping undifferentiated skeletal muscle myoblasts in a proliferative state. On the other hand, the levels of the low Mr form of Panx3 are very low in skeletal muscle myoblasts in culture, slightly detected in fetal skeletal muscle tissue, and further increased in the adult. Its expression promotes human skeletal muscle myoblast differentiation and inhibits their proliferation. Altogether, our data suggest that the lower Mr species of Panx3 play a role in maintaining differentiated myoblasts in a differentiated and non-proliferative state. As for Panx1, its protein levels were drastically augmented during skeletal muscle myoblast differentiation and promote this process independently of cell proliferation.
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Figure 10: Panx1 and Panx3 levels are modulated during skeletal muscle myoblast differentiation and regulate this process as well as myoblast proliferation. Proliferative undifferentiated skeletal muscle myoblasts express high levels of the ∼70-kDa immunoreactive species of Panx3, whereas its lower Mr species or Panx1 were very low. Its levels were drastically diminished during differentiation, suggesting that the ∼70-kDa immunoreactive species of Panx3 may play a role in keeping undifferentiated skeletal muscle myoblasts in a proliferative state. On the other hand, the levels of the low Mr form of Panx3 are very low in skeletal muscle myoblasts in culture, slightly detected in fetal skeletal muscle tissue, and further increased in the adult. Its expression promotes human skeletal muscle myoblast differentiation and inhibits their proliferation. Altogether, our data suggest that the lower Mr species of Panx3 play a role in maintaining differentiated myoblasts in a differentiated and non-proliferative state. As for Panx1, its protein levels were drastically augmented during skeletal muscle myoblast differentiation and promote this process independently of cell proliferation.

Mentions: In addition to their differential expression in fetal versus adult skeletal muscle tissue, we also show here that Panx levels are regulated during skeletal muscle myoblast differentiation in vitro. During development, embryonic muscle mass increases predominantly by proliferative growth of myoblasts that differentiate to eventually generate fully differentiated myofibers in adults. Skeletal muscle terminal differentiation is a temporally ordered process that follows an organized sequence of events including commitment, cell cycle withdrawal, expression of muscle-specific proteins, and myoblast fusion to form multinucleated myotubes (34). Our results clearly demonstrated that both Panx1 and Panx3 regulate skeletal muscle myoblast differentiation and proliferation, which are summarized in our proposed model in Fig. 10. Indeed, we have found that the levels of Panx1 are very low in undifferentiated and proliferative skeletal muscle myoblasts but increased drastically during their differentiation. Accordingly, its overexpression accelerated skeletal muscle myoblast differentiation through a process that likely involves its channel functions but did not regulate myoblast proliferation. As for Panx3, its lower molecular weight form was not detected or was below detectable levels in both undifferentiated and differentiated HSMM but was expressed in human skeletal muscle tissue, which may suggest that it is expressed further along the differentiation process. This form was also more abundant in adult versus fetal skeletal muscle tissue. When overexpressed in HSMM, it promoted their differentiation and inhibited their proliferation, suggesting that it may play a role in maintaining the skeletal muscle myoblasts in a differentiated and non-proliferative state. On the other hand, the ∼70-kDa immunoreactive species of Panx3 was found highly expressed in undifferentiated HSMM. Its levels were drastically down-regulated during differentiation, and its knockdown significantly inhibited HSMM proliferation, which may thus suggest a role in keeping the undifferentiated skeletal muscle myoblasts in a proliferative state. Altogether, our results thus indicate that various species of Panx1 and Panx3 are expressed in skeletal muscle tissue and that they differentially regulate skeletal muscle myoblast differentiation and proliferation.


Pannexin 1 and pannexin 3 channels regulate skeletal muscle myoblast proliferation and differentiation.

Langlois S, Xiang X, Young K, Cowan BJ, Penuela S, Cowan KN - J. Biol. Chem. (2014)

Panx1 and Panx3 levels are modulated during skeletal muscle myoblast differentiation and regulate this process as well as myoblast proliferation. Proliferative undifferentiated skeletal muscle myoblasts express high levels of the ∼70-kDa immunoreactive species of Panx3, whereas its lower Mr species or Panx1 were very low. Its levels were drastically diminished during differentiation, suggesting that the ∼70-kDa immunoreactive species of Panx3 may play a role in keeping undifferentiated skeletal muscle myoblasts in a proliferative state. On the other hand, the levels of the low Mr form of Panx3 are very low in skeletal muscle myoblasts in culture, slightly detected in fetal skeletal muscle tissue, and further increased in the adult. Its expression promotes human skeletal muscle myoblast differentiation and inhibits their proliferation. Altogether, our data suggest that the lower Mr species of Panx3 play a role in maintaining differentiated myoblasts in a differentiated and non-proliferative state. As for Panx1, its protein levels were drastically augmented during skeletal muscle myoblast differentiation and promote this process independently of cell proliferation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4215249&req=5

Figure 10: Panx1 and Panx3 levels are modulated during skeletal muscle myoblast differentiation and regulate this process as well as myoblast proliferation. Proliferative undifferentiated skeletal muscle myoblasts express high levels of the ∼70-kDa immunoreactive species of Panx3, whereas its lower Mr species or Panx1 were very low. Its levels were drastically diminished during differentiation, suggesting that the ∼70-kDa immunoreactive species of Panx3 may play a role in keeping undifferentiated skeletal muscle myoblasts in a proliferative state. On the other hand, the levels of the low Mr form of Panx3 are very low in skeletal muscle myoblasts in culture, slightly detected in fetal skeletal muscle tissue, and further increased in the adult. Its expression promotes human skeletal muscle myoblast differentiation and inhibits their proliferation. Altogether, our data suggest that the lower Mr species of Panx3 play a role in maintaining differentiated myoblasts in a differentiated and non-proliferative state. As for Panx1, its protein levels were drastically augmented during skeletal muscle myoblast differentiation and promote this process independently of cell proliferation.
Mentions: In addition to their differential expression in fetal versus adult skeletal muscle tissue, we also show here that Panx levels are regulated during skeletal muscle myoblast differentiation in vitro. During development, embryonic muscle mass increases predominantly by proliferative growth of myoblasts that differentiate to eventually generate fully differentiated myofibers in adults. Skeletal muscle terminal differentiation is a temporally ordered process that follows an organized sequence of events including commitment, cell cycle withdrawal, expression of muscle-specific proteins, and myoblast fusion to form multinucleated myotubes (34). Our results clearly demonstrated that both Panx1 and Panx3 regulate skeletal muscle myoblast differentiation and proliferation, which are summarized in our proposed model in Fig. 10. Indeed, we have found that the levels of Panx1 are very low in undifferentiated and proliferative skeletal muscle myoblasts but increased drastically during their differentiation. Accordingly, its overexpression accelerated skeletal muscle myoblast differentiation through a process that likely involves its channel functions but did not regulate myoblast proliferation. As for Panx3, its lower molecular weight form was not detected or was below detectable levels in both undifferentiated and differentiated HSMM but was expressed in human skeletal muscle tissue, which may suggest that it is expressed further along the differentiation process. This form was also more abundant in adult versus fetal skeletal muscle tissue. When overexpressed in HSMM, it promoted their differentiation and inhibited their proliferation, suggesting that it may play a role in maintaining the skeletal muscle myoblasts in a differentiated and non-proliferative state. On the other hand, the ∼70-kDa immunoreactive species of Panx3 was found highly expressed in undifferentiated HSMM. Its levels were drastically down-regulated during differentiation, and its knockdown significantly inhibited HSMM proliferation, which may thus suggest a role in keeping the undifferentiated skeletal muscle myoblasts in a proliferative state. Altogether, our results thus indicate that various species of Panx1 and Panx3 are expressed in skeletal muscle tissue and that they differentially regulate skeletal muscle myoblast differentiation and proliferation.

Bottom Line: Using HSMM, we found that Panx1 expression promotes this process, whereas it was impaired in the presence of probenecid or carbenoxolone.Reduction of its endogenous expression using two Panx3 shRNAs significantly inhibited HSMM proliferation without triggering their differentiation.In summary, our results demonstrate that Panx1 and Panx3 are co-expressed in human skeletal muscle myoblasts and play a pivotal role in dictating the proliferation and differentiation status of these cells.

View Article: PubMed Central - PubMed

Affiliation: From the Department of Surgery, Division of Paediatric Surgery, University of Ottawa, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada, Apoptosis Research Center, Children's Hospital of Eastern Ontario, Ottawa, Ontario K1H 8L1, Canada.

Show MeSH
Related in: MedlinePlus