Pannexin 1 and pannexin 3 channels regulate skeletal muscle myoblast proliferation and differentiation.
Bottom Line: Using HSMM, we found that Panx1 expression promotes this process, whereas it was impaired in the presence of probenecid or carbenoxolone.As for Panx3, its lower molecular weight species were prominent in adult skeletal muscle but very low in the fetal tissue and in undifferentiated skeletal muscle cells and myoblasts.On the other hand, a ∼70-kDa immunoreactive species of Panx3, likely glycosylated, sialylated, and phosphorylated, was highly expressed in proliferative myoblasts but strikingly down-regulated during their differentiation.
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
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Mentions: As the lower molecular weight forms of Panxs were faint or below detectable levels in human primary skeletal muscle myoblasts in culture, we wanted to confirm that the higher molecular weight bands detected correspond to Panx1 and Panx3. To this end, HSMM and adult skeletal muscle tissue lysates were treated with a mixture of deglycosylation enzymes (N-glycosidase F, O-glycanase, neuraminidase (Sialidase), β(1,4)-galactosidase, and β-N-acetylglucosaminidase) and submitted to Western blotting. After deglycosylation, the endogenous ∼50-kDa protein species detected by anti-Panx1 in HSMM migrated further at ∼38 kDa (Fig. 3A). As a positive control, we show that the more classical Panx1 species also migrated further after treatment of Panx1-expressing HEK293T cell lysate with deglycosylation enzymes (Fig. 3A) (4). As for Panx3, the ∼70-kDa immunoreactive species detected by anti-Panx3 in HSMM and human fetal skeletal muscle lysates also migrated further into a predominant band at ∼50–51 kDa after treatment with deglycosylation enzymes (Fig. 3B). As a positive control, we show that this band was also present after submitting HEK293T over-expressing Panx3 to deglycosylation in addition to bands ranging from ∼35–40 kDa (Fig. 3B) (7). Because these results suggest that the ∼70-kDa immunoreactive species of Panx3 may have post-translational modifications that are different from the classical ∼43 kDa form, we wanted to better understand and characterize the glycosylation status of this higher Mr species. To this end, HSMM lysates were treated with the same enzymes but individually. As shown in Fig. 3C, the ∼70-kDa species of Panx3 migrated further after treatment with N-glycosidase F and sialidase A but not with O-glycanase, β(1,4)-galactosidase, or β-N-acetylglucosaminidase. However, O-glycosylation cannot be completely ruled out as the presence of sialic acids can block the action of O-glycanase. These results thus indicate that the ∼70-kDa immunoreactive species of Panx3 is modified by N-glycosylation and sialylation. Taken together these data suggest that the higher molecular weight species detected in HSMM and human skeletal muscle correspond to highly glycosylated species of endogenous human Panx1 and Panx3.
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.