• BMB Reports
• /
• 제49권6호
• /
• pp.303-304
• /
• 2016

Myoblast fusion is important for skeletal muscle formation. Even though the knowledge of myoblast fusion mechanism has accumulated over the years, the initial signal of fusion is yet to be elucidated. Our study reveals the novel function of a phosphatidylserine (PS) receptor, stabilin-2 (Stab2), in the modulation of myoblast fusion, through the recognition of PS exposed on myoblasts. During differentiation of myoblasts, Stab2 expression is higher than other PS receptors and is controlled by calcineurin/NFAT signaling on myoblasts. The forced expression of Stab2 results in an increase in myoblast fusion; genetic ablation of Stab2 in mice causes a reduction in muscle size, as a result of impaired myoblast fusion. After muscle injury, muscle regeneration is impaired in Stab2-deficient mice, resulting in small myofibers with fewer nuclei, which is due to reduction of fusion rather than defection of myoblast differentiation. The fusion-promoting role of Stab2 is dependent on its PS-binding motif, and the blocking of PS-Stab2 binding impairs cell-cell fusion on myoblasts. Given our previous finding that Stab2 recognizes PS exposed on apoptotic cells for sensing as an "eat-me" signal, we propose that PS-Stab2 binding is required for sensing of a "fuse-me" signal as the initial signal of myoblast fusion.

• BMB Reports
• /
• 제28권3호
• /
• pp.191-196
• /
• 1995

The role of polyamines in skeletal myoblast differentiation was investigated using the polyamine metabolic inhibitor methylglyoxal bis(guanylhydrazone)(MGBG). Concentrations of intracellular free spermidine and spermine increased 2 to 2.5-fold at the onset of myoblast fusion. The systhesis of actin, and creatine kinase activity both dramatically increased during myotube formation. However, MGBG at a concentration of 0.5 mM not only abolished the increase of intracellular free polyamines, but also reduced cell fusion to almost half the level of untreated cells, without noticeable morphological alteration. The production of actin, and creatine kinase activity were almost completely abolished by MGBG. The inhibition of myoblast fusion by MGBG was partially recovered with 0.1 mM of spermidine or spermine added externally. Results indicate that polyamines are necessary for normal myoblast differentiation. Since the first indication of myoblast differentiation is alignment of muscle cells and membrane fusion of adjacent cells, and since polyamine depletion completely inhibited the synthesis of actin, which might be associted with membranes, polyamine might be involved in myoblast differentiation through membrane reorganization events.

• 생명과학회지
• /
• 제12권1호
• /
• pp.55-60
• /
• 2002

골격근 세포의 분화는 근육특이 유전자들의 전사적 활성과 근육아세포에서 근육소관으로의 형태적 분화로 특징지어진다. 본 연구에서는 TSA가 근육형성의 일련의 과정에서 NF-kB DNA 결합 활성과 융합에 미치는 영향을 조사하였다. 대조군과 비교해서 TSA가 처리된 C2C12 myoblast는 융합하여 근육소관을 형성할 수 없었으며 NF-kB DNA 결합 활성은 억제되었다. 이런 현상들이 TSA에 의한 직접적인 것인지 알아보기 위해서 TSA가 처리되지 않고 분화를 유도하기 위해서 사용된 배지를 농축하여 C2C12 myoblast에 TSA와 함께 동시에 처리하였다. 그 결과 세포는 융합하여 근육소관을 형성하였으며 NF-kB DNA 결합 활성이 회복되었다. 이러한 결과는 TSA가 아마도 여러 관련 인자들을 통해 myoblast의 융합과 NF-kB DNA 결합 활성을 억제함으로 근육형성과정에 영향을 미침을 시사한다.

• The Korean Journal of Physiology and Pharmacology
• /
• 제7권6호
• /
• pp.375-379
• /
• 2003

$Ca^{2+}$ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how $Ca^{2+}$ influx rises prior to myoblast fusion. Recently, several studies suggested that NMDA receptors may be involved in $Ca^{2+}$ mobilization of muscle, and that $Ca^{2+}$ influx is mediated by NMDA receptors in C2C12 myoblasts. Here, we report that other types of ionotropic glutamate receptors, non-NMDA receptors (AMPA and KA receptors), are also involved in $Ca^{2+}$ influx in myoblasts. To explore which subtypes of non-NMDA receptors are expressed in C2C12 myogenic cells, RT-PCR was performed, and the results revealed that KA receptor subunits were expressed in both myoblasts and myotubes. However, AMPA receptor was not detected in myoblasts but expressed in myotubes. Using a $Ca^{2+}$ imaging system, $Ca^{2+}$ influx mediated by these receptors was directly measured in a single myoblast cell. Intracellular $Ca^{2+}$ level was increased by KA, but not by AMPA. These results were consistent with RT-PCR data. In addition, KA-induced intracellular $Ca^{2+}$ increase was completely suppressed by treatment of nifedifine, a L-type $Ca^{2+}$ channel blocker. Furthermore, KA stimulated myoblast fusion in a dose-dependent manner. CNQX inhibited not only KA-induced myoblast fusion but also spontaneous myoblast fusion. Therefore, these results suggest that KA receptors are involved in intracellular $Ca^{2+}$ increase in myoblasts and then may play an important role in myoblast fusion.

• 한국동물학회지
• /
• 제32권2호
• /
• pp.163-175
• /
• 1989

철 운반 단백질인 Transferrin (Tf)은 계배 근원세포의 분화에 필요한 요소임이 이미 알려져 있다. 따라서 Tf이 작용하는데 필요한 Tf 수용체의 양적 증감은 근원세포의 분화와 깊은 관계가 있을 것으로 생각된다. 본 연구에서는 배양 근원세포의 분화 과정에서 Tf 수용체가 어떠한 변화를 겪는지 알아 보았다. Tf 수용체의 양을 알아보기 위해 세포 표면에 결합되는 125I-Tf의 양을 측정한 결과, Tf 수용체는 근원세포의 분화과정의 하나인 세포융합이 일어나기 약 12시간 전까지 그 양이 증가하다가, 그 이후 근원세포의 분화가 더욱 진행됨에 따라 급격히 감소함을 알 수 있었다. 한편, 근원세포의 융합을 억제하는 여러가지 융합억제제들에 의해서도 그 양이 조절되는 것을 알 수 있었다. 이와 같은 결과들은 통해 근원세포의 분화는 근원세포 표면의 Tf 수용체의 양과 조절되는 것으로 미루어 보아, 생체내에서도 근원세포의 분화에 따라 Tf 수용체의 변화가 있는 것으로 추정되었다.

• 한국동물학회지
• /
• 제27권2호
• /
• pp.73-84
• /
• 1984

근원세포가 분화하는 과정에서 신경전달물질의 영향을 연구하기 위하여 배양한 근세포에 dopamine과 epinephrine을 처리하여 근원세포의 융합과 세포내 cAMP의 농도에 미치는 효과를 조사하였다. Dopamine $(3\\times10^{-5}M)$과 epinephrine $(3\\times10^{-5}M)$을 세포배양후 34시간에 처리했을 때 근원세포의 융합이 크게 억제되었으며, 특히 dopamine의 효과가 epinephrine보다 현저하게 나타났다. 한편, 세포내 cAMP농도는 dopamine과 epinephrine을 처리해도 거의 변화가 없었다. 근원세포의 분화에 cAMP가 관계하는지를 조사하기 위해 dbcAMP, $PGE_1$ 및 aspirin을 처리하였는데, dbcAMP $(1\\times10^{-4}M)$는 근원세포의 융합을 억제한 반면, $PGE_1 (3\\times10^{-6}M)$은 오히려 융합을 촉진하였고, PG 합성효소의 억제물질인 aspirin은 융합 억제효과를 보였다. Dopamine과 epinephrine이 근원세포의 융합과정에 작용하는 가능성있는 기작에 대해서 고찰하였다.

• Molecules and Cells
• /
• 제38권4호
• /
• pp.362-372
• /
• 2015

Setdb1, an H3-K9 specific histone methyltransferase, is associated with transcriptional silencing of euchromatic genes through chromatin modification. Functions of Setdb1 during development have been extensively studied in embryonic and mesenchymal stem cells as well as neurogenic progenitor cells. But the role of Sedtdb1 in myogenic differentiation remains unknown. In this study, we report that Setdb1 is required for myogenic potential of C2C12 myoblast cells through maintaining the expressions of MyoD and muscle-specific genes. We find that reduced Setdb1 expression in C2C12 myoblast cells severely delayed differentiation of C2C12 myoblast cells, whereas exogenous Setdb1 expression had little effect on. Gene expression profiling analysis using oligonucleotide microarray and RNA-Seq technologies demonstrated that depletion of Setdb1 results in downregulation of MyoD as well as the components of muscle fiber in proliferating C2C12 cells. In addition, exogenous expression of MyoD reversed transcriptional repression of MyoD promoter-driven luciferase reporter by Setdb1 shRNA and rescued myogenic differentiation of C2C12 myoblast cells depleted of endogenous Setdb1. Taken together, these results provide new insights into how levels of key myogenic regulators are maintained prior to induction of differentiation.

• 대한본초학회지
• /
• 제34권2호
• /
• pp.59-66
• /
• 2019

Objectives : Decrease in muscle mass and loss of muscle function due to aging are associated with various diseases. As interest in healthy aging increases, efforts to prevent and treat muscle hypoxia as an illness are increasing. Considering the physical limitations, a pharmacologic approach to the treatment of myopenia is needed. Methods : Terminalia chebula Rets has a wide range of pharmacological effects and is used as a medicinal product in traditional medicine. However, the drug effect on the treatment of muscle disorders has not been revealed. The purpose of this study was to evaluate the value of water extract of Terminalia chebula (WETC) as a therapeutic agent to relieve symptoms of muscle hypoxia. Results : WETC showed strong radical scavenging ability. In addition, WETC increased cell activity of myoblast, and we observed that WETC induces myoblast differentiation by immunoblot analysis using differentiation protein markers as well as cell morphology of myoblast. Based on these results, we examined the effect of chebulic acid, chebulagic acid, gallic acid, geraniin, and punicalagin on cell activity and differentiation of myoblasts. Gallic acid significantly increased cell activity of myoblast, and it was found to be an effective substance which not only induces myoblast differentiation but also promotes proliferation. Conclusions : We suggest that the WETC with antioxidant effect and its indicator gallic acid on cell activity, proliferation and differentiation of myoblast can be studied and developed as a food and medicine for prevention and treatment of various muscle diseases.

• 한국동물학회지
• /
• 제27권3호
• /
• pp.151-164
• /
• 1984

근원세포의 융합에 관여하는 융합유도물질의 존재를 구명하기 위하여 계배의 근세포를 배양하면서, muscle-conditioned medium (MCM) 이 근원세포의 융합에 미치는 영향을 조사하고, 근원세포로부터 배양액 내로 방출되는 단백질을 분석하여 다음과 같은 결과를 얻었다. (1) MCM은 뚜렷한 융합촉진 효과를 나타냈으며, 이러한 효과는 첨가된 MCM의 농도가 층가함에 따라 증가하였다. (2) MCM의 융합촉진 효과는 주로 근원세포로부터 방출되는 융합유도물질에 의하여 일어나는 것으로 판단된다. (3) 배양근원세포로부터 분비되는 45,000달톤과 65,000달톤의 단백질이 융합 유도물질일 가능성이 높다.

• Molecules and Cells
• /
• 제21권2호
• /
• pp.294-301
• /
• 2006

We have previously reported that phosphorylation of eukaryotic elongation factor 2 (eEF2) is related to the differentiation of chick embryonic muscle cells in culture. In the present study, we found that eEF2 phosphorylation declined shortly after induction of differentiation of L6 myoblasts, when the cells prepare for terminal differentiation by withdrawing from the cell cycle. This decrease in phosphorylation was prevented by inhibitors of phosphoinositide 3-kinase (PI3-kinase) that strongly inhibit myoblast differentiation. We hypothesized that PI3-kinase plays an important role in myoblast differentiation by regulating eEF2 phosphorylation in the early stages of differentiation. To test this hypothesis, myoblasts were synchronized at in $G_2/M$ and cultured in fresh differentiation medium (DM) or growth medium (GM). In DM the released cells accumulated in $G_0$/$G_1$ while in GM they progressed to S phase. In addition, cyclin D1 was more rapidly degraded in DM than in GM, and eEF2 phosphorylation decreased more. Inhibitors of PI3-kinase increased eEF2 phosphorylation, but PI3-kinase became more activated when eEF2 phosphorylation declined. These results suggest that the regulation of L6 myoblast differentiation by PI3-kinase is related to eEF2 phosphorylation.