Fig. 3
From: The p75NTR-mediated effect of nerve growth factor in L6C5 myogenic cells
Effects of NGF supplementation on NFκB, αB-crystallin and Hsp27 during L6C5 in vitro differentiation. a NFκB activity measurement in myoblasts and differentiating L6C5 cells (2, 5 and 9 days) grown with or without NGF supplementation. Nuclear protein extract from Jurkat cells stimulated by TPA and calcium ionophore was used as positive control (2 days: − NGF vs + NGF, 2.2 vs 3.0, p < 0.05). b, c Quantitative analysis of αB-Cry and Hsp27 expression during differentiation process (2, 5 and 9 days) of myogenic cells supplemented with or without NGF (αB-Cry: NGF 1.3 ± 0.08 vs Ctrl 2.0 ± 0.11, p < 0.05; Hsp27: NGF 1.0 ± 0.03 vs Ctrl 0.53 ± 0.04, p < 0.05). The histograms represent the mean ± SD of experiments repeated at least three times. *p < 0.05. d Representative western blot of αB-crystallin and Hsp27 expression. The β-actin was used as housekeeping for both markers. e Proposed mechanism for NGF-p75NTR signaling pathways in L6C5 myogenic cells: during myoblast proliferation and serum-deprivation condition, the supplementation with NGF can sustain the activity of key enzymes in carbohydrate metabolism, such as citrate synthase and glyceraldehyde-phosphate-dehydrogenase, through the activation of the JNK pathway. During the early stage of myoblast fusion, NGF transiently up-regulates NFκB activity and, directly or indirectly trough a NFκB-mediated mechanism, anticipates the myogenic progression by modulating αBcry and Hsp27 expression and promoting, at a late differentiation stage, myonuclear fusion and the accumulation and stabilization of the MyHC myofibrillar component. CS citrate synthase, GAPDH Glyceraldehyde-phosphate-dehydrogenase, NGF nerve growth factor, αBcry αB-crystallin, JNK c-Jun N-terminal kinases, NFκB nuclear factor kappa-light-chain-enhancer of activated B cells, p75 NTR neurotrophin receptor p75