Fig. 4

Mediators and signaling pathways involved in the control of myotube degradation and repairing via satellite cell activation. a Schematic representation of muscle growth and muscle wasting pathways generated in the studies of gene expression patterns in skeletal muscle from cancer cachexia mice models. Genes with growth-promoting activity in skeletal muscle are shown in orange and genes involved muscle wasting in green and genes involved in satellite cell activation in blue. This set of genes is significantly up-regulated during food deprivation, diabetes, uremia, and cancer cachexia and target genes under the control of FoxO transcription factors in skeletal muscle wasting. b Quiescent satellite cells (white) activated by myokines and injury initiate symmetric and asymmetric divisions to produce activated satellite cells (green) and self-renewing satellite cell and myogenic stem cells (blue). After many rounds of division their progeny differentiate into myocytes and then myotubes. A different set of the transcription factors and membrane protein are expressed along each differentiation state of satellite cells. Some specific biomarkers are indicated in the panels inside the figure. Adapted from Bonetto et al. (2014) and Yin et al. (2013). IGF insulin-like growth factor; INSR, insulin receptor substrate 1; IGFR, insulin-like growth factor receptor; PI3K, phosphoinositide 3-kinase; GSK3, Glycogen synthase kinase 3; 4E-BP1, Eukaryotic translation initiation factor 4E binding protein 1; mTOR, mammalian target of rapamycin; p70S6K, serine/threonine kinase; Akt, Protein kinase B; FoxO, Forkhead box O transcription factors; IL-6, interleukin-6; LIF, leukemia inhibitory factor, TNF, tumor necrosis factor, IL-1, interleukin-1, TRAF, TNF receptor associated factor; NF-κB, factor nuclear kappa B; IKK, inhibitor of nuclear factor kappa-B kinase; MAPK, mitogen-activated protein kinase; JAK, janus kinase; STAT, Signal Transducer and Activator of Transcription; ERK, extracellular signal regulated kinase; ALK, activin receptor-like kinase, ACVR2B, activin receptor, SMAD, transcription factor; Atrogin, E3 ubiquitin ligases Muscle Atrophy Fbox (MAFbx); MURF1, Muscle Ring Finger 1, MHC, myosin heavy chain; MCK, muscle creatine kinase; SOCS, Suppressor of cytokine signaling; BCL2/adenovirus E1B 19 kDa protein-interacting protein 3