Sam68 and ERKs regulate leptin-induced expression of OB-Rb mRNA in C2C12 myotubes

Leptin Rapidly Induces the Expression of Metabolic and Myokine Genes in C2C12 Muscle Cells to Regulate Nutrient Partition and Oxidation

“…Contrarily, in terms of the expression of the long form of the leptin receptor (OB-Rb) it seems that the effect of the hormone would be to induce its expression (more markedly with the treatment of 10ng/ml, see results section), without effects on SOCS3 expression, thus suggesting a possible slight effect of leptin inducing a greater sensitivity to its own effects, at least with not really prolonged treatments (the longest treatment here lasts 24h). A similar effect on OB-Rb expression was observed by Maroni et al [37] with short leptin treatment (30'), involving the signaling proteins Sam68 and ERKs. Although we do not observe significant changes of leptin treatment on SOCS3 expression, other authors [38] have described the induction of SOCS3 expression by leptin in vitro; nevertheless, this discrepancy can be due to various factors such as a different cell line (L6 myocites), different medium conditions and especially significantly higher concentration of leptin.…”

Leptin impairs myogenesis in C2C12 cells through JAK/STAT and MEK signaling pathways

“…STAT protein (STAT3 in particular) activated by leptin is frequently essential for both mitogenicity and decreased cell viability [37,52]. Anyway, besides JAK/STAT the other signaling pathways as PKCf, MAPK (ERK1/2), NF-jB and PI3-K seem to participate in certain leptin effects [9,10,47,49]. We conclude, that some of the leptin effects were apparently specific (through cognate OB-Rb-JAK-STAT signaling pathway) whereas other was mediated by alternative routes.…”

“…Leptin expression was detected in placenta [4], stomach [5], colon [6], mammary gland [7] and skeletal muscle [8]. Experimental evidence suggests that leptin evokes intracellular signaling cascades in muscle and cultured muscle cells [9,10]. Interestingly, its expression is markedly reduced during differentiation of primary skeletal muscle cells [11].…”

Leptin receptor activation increases Sam68 tyrosine phosphorylation and expression in human trophoblastic cells

“…However there is limited information regarding expression of Sam68 in placenta and whether it may be recruited by the activated leptin receptor. The aim of this study was to investigate whether acute leptin administration affects phosphorylation (function) and expression of Sam68 in JEG-3 trophoblastic cell and, in addition, whether downregulation of Sam68 may affect the expression of LEPR, as it has been previously reported in C2C12 muscle cells, in which, the positive M a n u s c r i p t regulation of LEPR mRNA by leptin is one of the early events triggered by the hormone, which depends on both Sam68 and ERK activity (Maroni et al 2009).…”