Sphingosine kinase/sphingosine 1-phosphate axis: a new player for insulin-like growth factor-1-induced myoblast differentiation

Abstract

BackgroundInsulin-like growth factor-1 (IGF-1) is the most important physiological regulator of skeletal muscle progenitor cells, which are responsible for adult skeletal muscle regeneration. The ability of IGF-1 to affect multiple aspects of skeletal muscle cell biology such as proliferation, differentiation, survival and motility is well recognized, although the molecular mechanisms implicated in its complex biological action are not fully defined. Since sphingosine 1-phosphate (S1P) has recently emerged as a key player in skeletal muscle regeneration, we investigated the possible involvement of the sphingosine kinase (SK)/S1P receptor axis on the biological effects of IGF-1 in murine myoblasts.MethodsRNA interference, chemical inhibition and immunofluorescence approaches were used to assess the role of the SK/S1P axis on the myogenic and mitogenic effects of IGF-1 in C2C12 myoblasts.ResultsWe show that IGF-1 increases SK activity in mouse myoblasts. The effect of the growth factor does not involve transcriptional regulation of SK1 or SK2, since the protein content of both isoforms is not affected; rather, IGF-1 enhances the fraction of the active form of SK. Moreover, transactivation of the S1P2 receptor induced by IGF-1 via SK activation appears to be involved in the myogenic effect of the growth factor. Indeed, the pro-differentiating effect of IGF-1 in myoblasts is impaired when SK activity is pharmacologically inhibited, or SK1 or SK2 are specifically silenced, or the S1P2 receptor is downregulated. Furthermore, in this study we show that IGF-1 transactivates S1P1/S1P3 receptors via SK activation and that this molecular event negatively regulates the mitogenic effect elicited by the growth factor, since the specific silencing of S1P1 or S1P3 receptors increases cell proliferation induced by IGF-1.ConclusionsWe demonstrate a dual role of the SK/S1P axis in response to myoblast challenge with IGF-1, that likely is important to regulate the biological effect of this growth factor. These findings add new information to the understanding of the mechanism by which IGF-1 regulates skeletal muscle regeneration.

Endothelial sphingosine kinase/SPNS2 axis is critical for vessel-like formation by human mesoangioblasts

“…It has to be considered that while the single knock-out mice have no phenotype, the SK1/SK2 double knock-out ones are lethal with abnormal angiogenesis and neural tube defects, supporting the concept that the two isoenzymes might have overlapping and/or complementary functions [4]. Moreover, the involvement of SK1 as well as SK2 is in agreement with what was previously demonstrated for the IGF-1 promyogenic action in C2C12 myoblasts [36], for Cell organization was examined microscopically (related magnification ×100) taking random photomicrographs at 6 h. The multi-cellular structures were quantified as described in Fig. 1a.…”

Lysophosphatidic acid stimulates cell migration of satellite cells. A role for the sphingosine kinase/sphingosine 1‐phosphate axis

“…Next, taking into account the key role of the S1P signaling axis in cultured myoblasts [12][13][14][15][16] and the robust migratory response elicited by S1P in the cell type investigated here [6], we examined whether SK activity is required for the migratory response exerted by LPA. To address this issue, satellite cell migration was measured under experimental conditions in which satellite cells were previously incubated with 1 lM VPC96047, a selective inhibitor of SK that is capable of blocking both the SK1 and SK2 isoforms, or 1 lM VPC96091, an inhibitor of the SK1 isoform only.…”

“…In cultured myoblasts, the SK/S1P signaling axis was previously implicated in transmission of important biological effects evoked by growth factors and cytokines, such as the pro-myogenic effect of insulin growth factor-1 [15] and tumor necrosis factor-a at low dose [12], the pro-fibrotic [13] and proapoptotic [16] effects of transforming growth factor-b, and, more pertinent to this study, the pro-migratory Effect of down-regulation of LPA receptors on the migratory action of LPA. Cells treated with control SCR-siRNA or with specific siRNA for individual LPA receptors were used to measure cell migration toward 1 lM LPA for 6 h in a Boyden chamber apparatus.…”

“…Interestingly, recent studies performed in mice in which S1P 2 was genetically ablated or pharmacologically blocked have provided experimental evidence that this receptor subtype promotes skeletal muscle regeneration [8], while altered cell-cycle progression has been observed in satellite cells of S1P 3 knockout mice [9]. Furthermore, comprehensive studies performed in the C2C12 myoblast cell line, which is largely used to investigate the biological properties of skeletal muscle precursor cells, have clearly demonstrated that S1P and its metabolism play a critical role in myogenic differentiation, and that the S1P signaling pathway is used by various growth factors and cytokines to elicit specific biological effects [10][11][12][13][14][15][16].…”

Ameliorating Effects of Sphingomyelin-Based Liposomes on Sarcopenia in Senescence-Accelerated Mice

“…51) Sphingosine-1-phosphate might stimulate the secretion of insulin-like growth factor-1 (IGF-1), a growth factor which activates the transcription of MHC IIB and X in satellite cells. 52,53) Because the expression of MHC IIB and X was shown to be higher in quadriceps femoris muscle than in soleus or gastrocnemius muscle, 51) it is possible that the SM-lipo treatment resulted in significant mass gain of quadriceps femoris muscle via IGF-1 signaling activation. Although the reason for increase in the weight of quadriceps femoris muscle in the PC-lipo group (Fig.…”