Proto-oncogenic H-Ras, K-Ras, and N-Ras are involved in muscle differentiation via phosphatidylinositol 3-kinase

Oncogenic H-Ras G12V and its variants have been shown to inhibit muscle differentiation. However, the role of proto-oncogenic Ras （c-Ras） in muscle differentiation remains unclear. The active GTP-bound form of Ras has been known to associate with diverse effectors including Raf, phosphatidylinositol 3-kinase （PI3K）, RaI-GDS, and other molecules to transmit downstream signals. We hypothesize that c-Ras may stimulate muscle differentiation by selectively activating PI3K, an important mediator for muscle differentiation. In our experiments, inhibition of c-Ras by farnesyltransferase inhibitors and a dominant negative form of H-Ras （Ras S17N） suppressed muscle differentiation. Consistently, individual knockdown of H-Ras, K-Ras, and N-Ras by siRNAs all blocked muscle differentiation. Interestingly, we found that c-Ras preferentially interacts with PI3K rather than its major binding partner c-Raf, during myogenic differentiation, with total c-Ras activity remaining unchanged. PI3K and its downstream myogenic pathway, the Nox2/NF-kB/inducible nitric oxide synthase （iNOS） pathway, were found to be suppressed by inhibition of c-Ras activity during differentiation. Furthermore, expression of a constitutively active form of PI3K completely rescued the differentiation block and reactivated the Nox2/NF-kB/iNOS pathway in c-Ras-inhibited cells. On the ba- sis of our results, we conclude that contrary to oncogenic Ras, proto-oncogenic H-Ras, K-Ras, and N-Ras are directly involved in the promotion of muscle differentiation via PI3K and its downstream signaling pathways. In addition, PI3K pathway activation is associated with a concurrent suppression of the otherwise predominantly activated Raf/ Mek/Erk pathway.

Vascular smooth muscle cell differentiation－2010

Vascular smooth muscle cells have attracted considerable interest as a model for a flexible program of gene expression.This cell type arises throughout the embryo body plan via poorly understood signaling cascades that direct the expression of transcription factors and microRNAs which,in turn,orchestrate the activation of contractile genes collectively defining this cell lineage.The discovery of myocardin and its close association with serum response factor has represented a major break-through for the molecular understanding of vascular smooth muscle cell differentiation.Retinoids have been shown to improve the outcome of vessel wall remodeling following injury and have provided further insights into the molecular circuitry that defines the vascular smooth muscle cell phenotype.This review summarizes the progress to date in each of these areas of vascular smooth muscle cell biology.

Linc-RAM promotes muscle cell differentiation via regulating glycogen phosphorylase activity

Long non-coding RNAs(lncRNAs)are important regulators of diverse biological processes,especially skeletal muscle cell differentiation.Most of the lncRNAs identified to date are localized in the nucleus and play regulatory roles in gene expression.The cytoplasmic lncRNAs are less well understood.We previously identified a long intergenic non-coding RNA(linc-RNA)activator of myogenesis(Linc-RAM)that directly binds MyoD in the nucleus to enhance muscle cell differentiation.Here,we report that a substantial fraction of Linc-RAM is localized in the cytoplasm of muscle cells.To explore the molecular functions of cytoplasmic Linc-RAM,we sought to identify Linc-RAM-binding proteins.We report here that Linc-RAM physically interacts with glycogen phosphorylase(PYGM)in the cytoplasm.Knockdown of PYGM significantly attenuates the function of Linc-RAM in promoting muscle cell differentiation.Loss-of-function and gain-of function assays demonstrated that PYGM enhances muscle cell differentiation in an enzymatic activity-dependent manner.Finally,we show that the interaction between Linc-RAM and PYGM positively regulates the enzymatic activity of PYGM in muscle cells.Collectively,our findings unveil a molecular mechanism through which cytoplasmic Linc-RAM contributes to muscle cell differentiation by regulating PYGM activity.Our findings establish that there is crosstalk between lncRNAs and cellular metabolism during myogenic cell differentiation.

The functional analysis of transiently upregulated miR-101 suggests a “braking” regulatory mechanism during myogenesis

Skeletal muscle differentiation is a highly coordinated process that involves many cellular signaling pathways and microRNAs(miRNAs).A group of muscle-specific miRNAs has been reported to promote myogenesis by suppressing key signaling pathways for cell growth.However,the functional role and regulatory mechanism of most non-muscle-specific miRNAs with stage-specific changes during differentiation are largely unclear.Here,we describe the functional characterization of miR-101a/b,a pair of non-muscle-specific miRNAs that show the largest change among a group of transiently upregulated miRNAs during myogenesis in C2C12 cells.The overexpression of miR-101a/b inhibits myoblast differentiation by suppressing the p38/MAPK,Interferon Gamma,and Wnt pathways and enhancing the C/EBP pathway.Mef2a,a key protein in the p38/MAPK pathway,was identified as a direct target of miR-101a/b.Interestingly,we found that the long non-coding RNA(lncRNA)Malat1,which promotes muscle differentiation,interacts with miR-101a/b,and this interaction competes with Mef2a mRNA to relieve the inhibition of the p38/MAPK pathway during myogenesis.These results uncovered a“braking”role in differentiation of transiently upregulated miRNAs and provided new insights into the competing endogenous RNA(ceRNA)regulatory mechanism in myoblast differentiation and myogenesis.

Long round-sharp needle release technique for 34 cases of superior cluneal nerve entrapment syndrome

Objective:To observe the clinical effect on superior cluneal nerve(SCN)entrapment syndrome treated with the release technique of long round-sharp needle.Methods:The syndrome differentiation based on meridian muscle region was adopted.The release technique of the long round-sharp needle was used at the lesions of meridian tendon region,Yāoyícì(Beside Yaoyi)and the transverse process of the third lumbar vertebra in 34 patients with SCN entrapment syndrome.The treatment was given once a week,4 treatments made one course.After one course treatment,the therapeutic effect was observed.The results of pain rating index(PRI),the visual analogy scores(VAS)and the present pain intensity(PPI)were compared before and after treatment.Results:Of 34 patients,28 cases(82%)were cured,6 cases(18%)effective and 0 case(0%)failed.The total effective rate was 100%.The scores of PRI,VAS and PPI were(10.78±1.98),(5.98±1.19)and(3.91±1.68)successively in 34 cases before treatment and they were(1.98±1.79),(0.89±1.12)and(0.82±0.79)after treatment.The score of every evaluation scale after treatment was lower significantly than that before treatment(all P<0.01).Conclusion:The release technique of long round-sharp needle achieves the satisfactory clinical effect on SCN entrapment syndrome.Hence,this therapeutic method deserves to be promoted.

Myogenesis controlled by a long non-coding RNA 1700113A16RIK and post-transcriptional regulation

Long non-coding(lnc)RNA plays important roles in many cellular processes.The function of the vast majority of lncRNAs remains unknown.Here we identified that lncRNA-1700113A16RIK existed in skeletal muscle stem cells(MuSCs)and was significantly elevated during MuSC differentiation.Knockdown of 1700113A16RIK inhibits the differentiation of muscle stem cells.In contrast,overexpression of 1700113A16RIK promotes the differentiation of muscle stem cells.Further study shows the muscle specific transcription factor Myogenin(MyoG)positively regulates the expression of 1700113A16RIK by binding to the promoter region of 1700113A16RIK.Mechanistically,1700113A16RIK may regulate the expression of myogenic genes by directly binding to 3’UTR of an important myogenic transcription factor MEF2D,which in turn promotes the translation of MEF2D.Taken together,our results defined 1700113A16RIK as a positive regulator of MuSC differentiation and elucidated a mechanism as to how 1700113A16RIK regulated MuSC differentiation.