scholarly journals Coordinate Control of Muscle Cell Survival by Distinct Insulin-like Growth Factor Activated Signaling Pathways

2000 ◽  
Vol 151 (6) ◽  
pp. 1131-1140 ◽  
Author(s):  
Margaret A. Lawlor ◽  
Peter Rotwein
Keyword(s):  
Growth Factors ◽  
Muscle Cell ◽  
Kinase Inhibitor ◽  
Ectopic Expression ◽  
Pi3 Kinase ◽  
Cellular Functions ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Rapid Induction ◽  
Peptide Growth Factors ◽  
Igf I

Peptide growth factors control diverse cellular functions by regulating distinct signal transduction pathways. In cultured myoblasts, insulin-like growth factors (IGFs) stimulate differentiation and promote hypertrophy. IGFs also maintain muscle cell viability. We previously described C2 skeletal muscle lines lacking expression of IGF-II. These cells did not differentiate, but underwent progressive apoptotic death when incubated in differentiation medium. Viability could be sustained and differentiation enabled by IGF analogues that activated the IGF-I receptor; survival was dependent on stimulation of phosphatidylinositol 3-kinase (PI3-kinase). We now find that IGF action promotes myoblast survival through two distinguishable PI3-kinase–regulated pathways that culminate in expression of the cyclin-dependent kinase inhibitor, p21. Incubation with IGF-I or transfection with active PI3-kinase led to rapid induction of MyoD and p21, and forced expression of either protein maintained viability in the absence of growth factors. Ectopic expression of MyoD induced p21, and inhibition of p21 blocked MyoD-mediated survival, thus defining one PI3-kinase–dependent pathway as leading first to MyoD, and then to p21 and survival. Unexpectedly, loss of MyoD expression did not impede IGF-mediated survival, revealing a second pathway involving activation by PI3-kinase of Akt, and subsequent induction of p21. Since inhibition of p21 caused death even in the presence of IGF-I, these results establish a central role for p21 as a survival factor for muscle cells. Our observations also define a MyoD-independent pathway for regulating p21 in muscle, and demonstrate that distinct mechanisms help ensure appropriate expression of this key protein during differentiation.

scholarly journals Insulin-Like Growth Factor-Mediated Muscle Cell Survival: Central Roles for Akt and Cyclin-Dependent Kinase Inhibitor p21

2000 ◽  
Vol 20 (23) ◽  
pp. 8983-8995 ◽  
Author(s):  
Margaret A. Lawlor ◽  
Peter Rotwein
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Viability ◽  
Cell Survival ◽  
Muscle Cell ◽  
Kinase Inhibitor ◽  
Insulin Like Growth Factor ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Igf I

ABSTRACT Polypeptide growth factors activate specific transmembrane receptors, leading to the induction of multiple intracellular signal transduction pathways which control cell function and fate. Recent studies have shown that growth factors promote cell survival by stimulating the serine-threonine protein kinase Akt, which appears to function primarily as an antiapoptotic agent by inactivating death-promoting molecules. We previously established C2 muscle cell lines lacking endogenous expression of insulin-like growth factor II (IGF-II). These cells underwent apoptotic death in low-serum differentiation medium but could be maintained as viable myoblasts by IGF analogues that activated the IGF-I receptor or by unrelated growth factors such as platelet-derived growth factor BB (PDGF-BB). Here we show that IGF-I promotes muscle cell survival through Akt-mediated induction of the cyclin-dependent kinase inhibitor p21. Treatment of myoblasts with IGF-I or transfection with an inducible Akt maintained muscle cell survival and enhanced production of p21, and ectopic expression of p21 was able to sustain viability in the absence of growth factors. Blocking of p21 protein accumulation through a specific p21 antisense cDNA prevented survival regulated by IGF-I or Akt but did not block muscle cell viability mediated by PDGF-BB. Our results define Akt as an intermediate and p21 as a critical effector of an IGF-controlled myoblast survival pathway that is active during early myogenic differentiation and show that growth factors are able to maintain cell viability by inducing expression of pro-survival molecules.

scholarly journals Dual Control of Muscle Cell Survival by Distinct Growth Factor-Regulated Signaling Pathways

2000 ◽  
Vol 20 (9) ◽  
pp. 3256-3265 ◽  
Author(s):  
Margaret A. Lawlor ◽  
Xiuhong Feng ◽  
Daniel R. Everding ◽  
Kerry Sieger ◽  
Claire E. H. Stewart ◽  
...  
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Cell Survival ◽  
Signaling Pathways ◽  
Muscle Cell ◽  
Transient Transfection ◽  
Pi3 Kinase ◽  
Signal Transduction Pathways ◽  
Apoptotic Death ◽  
Igf I

ABSTRACT In addition to their ability to stimulate cell proliferation, polypeptide growth factors are able to maintain cell survival under conditions that otherwise lead to apoptotic death. Growth factors control cell viability through regulation of critical intracellular signal transduction pathways. We previously characterized C2 muscle cell lines that lacked endogenous expression of insulin-like growth factor II (IGF-II). These cells did not differentiate but underwent apoptotic death in low-serum differentiation medium. Death could be prevented by IGF analogues that activated the IGF-I receptor or by unrelated growth factors such as platelet-derived growth factor BB (PDGF-BB). Here we analyze the signaling pathways involved in growth factor-mediated myoblast survival. PDGF treatment caused sustained activation of extracellular-regulated kinases 1 and 2 (ERK1 and -2), while IGF-I only transiently induced these enzymes. Transient transfection of a constitutively active Mek1, a specific upstream activator of ERKs, maintained myoblast viability in the absence of growth factors, while inhibition of Mek1 by the drug UO126 blocked PDGF-mediated but not IGF-stimulated survival. Although both growth factors activated phosphatidylinositol 3-kinase (PI3-kinase) to similar extents, only IGF-I treatment led to sustained stimulation of its downstream kinase, Akt. Transient transfection of a constitutively active PI3-kinase or an inducible Akt promoted myoblast viability in the absence of growth factors, while inhibition of PI3-kinase activity by the drug LY294002 selectively blocked IGF- but not PDGF-mediated muscle cell survival. In aggregate, these observations demonstrate that distinct growth factor-regulated signaling pathways independently control myoblast survival. Since IGF action also stimulates muscle differentiation, these results suggest a means to regulate myogenesis through selective manipulation of different signal transduction pathways.

scholarly journals Subcellular Targeting of p33ING1b by Phosphorylation-Dependent 14-3-3 Binding Regulates p21WAF1 Expression

2006 ◽  
Vol 26 (8) ◽  
pp. 2947-2954 ◽  
Author(s):  
Wei Gong ◽  
Michael Russell ◽  
Keiko Suzuki ◽  
Karl Riabowol
Keyword(s):  
Kinase Inhibitor ◽  
Biological Activities ◽  
Ectopic Expression ◽  
Growth Stress ◽  
Nuclear Localization Sequence ◽  
Binding Motif ◽  
Subcellular Targeting ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Cargo Proteins ◽  
Localization Sequence

ABSTRACT ING1 is a type II tumor suppressor that affects cell growth, stress signaling, apoptosis, and DNA repair by altering chromatin structure and regulating transcription. Decreased ING1 expression is seen in several human cancers, and mislocalization has been noted in diverse types of cancer cells. Aberrant targeting may, therefore, functionally inactivate ING1. Bioinformatics analysis identified a sequence between the nuclear localization sequence and plant homeodomain domains of ING1 that closely matched the binding motif of 14-3-3 proteins that target cargo proteins to specific subcellular locales. We find that the widely expressed p33ING1b splicing isoform of ING1 interacts with members of the 14-3-3 family of proteins and that this interaction is regulated by the phosphorylation status of ING1. 14-3-3 binding resulted in significant amounts of p33ING1b protein being tethered in the cytoplasm. As shown previously, ectopic expression of p33ING1b increased levels of the p21Waf1 cyclin-dependent kinase inhibitor upon UV-induced DNA damage. Overexpression of 14-3-3 inhibited the up-regulation of p21Waf1 by p33ING1b, consistent with the idea that mislocalization blocks at least one of ING1's biological activities. These data support the idea that the 14-3-3 proteins play a crucial role in regulating the activity of p33ING1b by directing its subcellular localization.

scholarly journals IGFs stimulate zebrafish cell proliferation by activating MAP kinase and PI3-kinase-signaling pathways

2001 ◽  
Vol 280 (4) ◽  
pp. R1230-R1239 ◽  
Author(s):  
Kasiani C. Pozios ◽  
Jun Ding ◽  
Brian Degger ◽  
Zee Upton ◽  
Cunming Duan
Keyword(s):  
Cell Proliferation ◽  
Protein Kinase ◽  
Dna Synthesis ◽  
Signaling Pathways ◽  
Kinase Inhibitor ◽  
Pi3 Kinase ◽  
Dependent Manner ◽  
Embryonic Cells ◽  
Kinase Signaling ◽  
Igf I

Insulin-like growth factor (IGF)-I and -II have been cloned from a number of teleost species, but their cellular actions in fish are poorly defined. In this study, we show that both IGF-I and -II stimulated zebrafish embryonic cell proliferation and DNA synthesis in a concentration-dependent manner, whereas insulin had little mitogenic activity. Affinity cross-linking and immunoblotting studies revealed the presence of IGF receptors with the characteristics of the mammalian type I IGF receptor. Competitive binding assay results indicated that the binding affinities of the zebrafish IGF-I receptors to IGF-I, IGF-II, and insulin are 1.9, 2.6, and >190 nM, indicating that IGF-I and -II bind to the IGF-I receptor(s) with approximately equal high affinity. To further investigate the cellular mechanism of IGF actions, we have studied the effects of IGFs on two major signal transduction pathways: mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3-kinase (PI3 kinase). IGFs activated MAPK in zebrafish embryonic cells in a dose-dependent manner. This activation occurred within 5 min of IGF-I stimulation and disappeared after 1 h. IGF-I also caused a concentration-dependent activation of protein kinase B, a downstream target of PI3 kinase, this activation being sustained for several hours. Inhibition of MAPK activation by the MAPK kinase inhibitor PD-98059 inhibited the IGF-I-stimulated DNA synthesis. Similarly, use of the PI3 kinase inhibitor LY-294002 also inhibited IGF-I-stimulated DNA synthesis. When both the MAPK and PI3 kinase pathways were inhibited using a combination of these compounds, the IGF-I-stimulated DNA synthesis was completely negated. These results indicate that both IGF-I and -II are potent mitogens for zebrafish embryonic cells and that activation of both the MAPK and PI3 kinase-signaling pathways is required for the mitogenic action of IGFs in zebrafish embryonic cells.

scholarly journals Negative Regulation of ASK1 by p21Cip1 Involves a Small Domain That Includes Serine 98 That Is Phosphorylated by ASK1 In Vivo

2007 ◽  
Vol 27 (9) ◽  
pp. 3530-3541 ◽  
Author(s):  
Jun Zhan ◽  
John B. Easton ◽  
Shile Huang ◽  
Ashutosh Mishra ◽  
Limin Xiao ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Cellular Functions ◽  
Terminal Protein ◽  
Jnk Pathway ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Small Domain ◽  
Cellular Stresses

ABSTRACT The cyclin-dependent kinase inhibitor p21Cip1 regulates multiple cellular functions and protects cells from genotoxic and other cellular stresses. Activation of apoptosis signal-regulating kinase 1 (ASK1) induced by inhibition of mTOR signaling leads to sustained phospho-c-Jun that is suppressed in cells with functional p53 or by forced expression of p21Cip1. Here we show that small deletions of p21Cip1 around S98 abrogate its association with ASK1 but do not affect binding to Cdk1, hence distinguishing between the cell cycle-regulating functions of p21Cip1 and its ability to suppress activation of the ASK1/Jun N-terminal protein kinase (JNK) pathway. p21Cip1 is phosphorylated in vitro by both ASK1 and JNK1 at S98. In vivo phosphorylation of p21Cip1, predominantly carried out by ASK1, is associated with binding to ASK1 and inactivation of ASK1 kinase function. Binding of p21Cip1 to ASK1 requires ASK1 kinase function and may involve phosphorylation of S98.

Inhibition of smooth muscle cell migration by the p21 cyclin-dependent kinase inhibitor (Cip1)

1997 ◽  
Vol 132 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Ryousuke Fukui ◽  
Nobuhiko Shibata ◽  
Eiko Kohbayashi ◽  
Masahiro Amakawa ◽  
Daisuke Furutama ◽  
...  
Keyword(s):  
Smooth Muscle ◽  
Cell Migration ◽  
Smooth Muscle Cell ◽  
Muscle Cell ◽  
Kinase Inhibitor ◽  
Cyclin Dependent Kinase ◽  
Cyclin Dependent Kinase Inhibitor ◽  
Smooth Muscle Cell Migration

scholarly journals Separating myoblast differentiation from muscle cell fusion using IGF-I and the p38 MAP kinase inhibitor SB202190

2015 ◽  
Vol 309 (7) ◽  
pp. C491-C500 ◽  
Author(s):  
Samantha Gardner ◽  
Sean M. Gross ◽  
Larry L. David ◽  
John E. Klimek ◽  
Peter Rotwein
Keyword(s):  
Growth Factor ◽  
Map Kinase ◽  
Cell Fusion ◽  
Muscle Cell ◽  
Map Kinases ◽  
Kinase Inhibitor ◽  
P38 Map Kinase ◽  
Myoblast Differentiation ◽  
Igf I ◽  
Muscle Biology

The p38 MAP kinases play critical roles in skeletal muscle biology, but the specific processes regulated by these kinases remain poorly defined. Here we find that activity of p38α/β is important not only in early phases of myoblast differentiation, but also in later stages of myocyte fusion and myofibrillogenesis. By treatment of C2 myoblasts with the promyogenic growth factor insulin-like growth factor (IGF)-I, the early block in differentiation imposed by the p38 chemical inhibitor SB202190 could be overcome. Yet, under these conditions, IGF-I could not prevent the later impairment of muscle cell fusion, as marked by the nearly complete absence of multinucleated myofibers. Removal of SB202190 from the medium of differentiating myoblasts reversed the fusion block, as multinucleated myofibers were detected several hours later and reached ∼90% of the culture within 30 h. Analysis by quantitative mass spectroscopy of proteins that changed in abundance following removal of the inhibitor revealed a cohort of upregulated muscle-enriched molecules that may be important for both myofibrillogenesis and fusion. We have thus developed a model system that allows separation of myoblast differentiation from muscle cell fusion and should be useful in identifying specific steps regulated by p38 MAP kinase-mediated signaling in myogenesis.

scholarly journals Roles of the Tumor Suppressor p53 and the Cyclin-dependent Kinase Inhibitor p21WAF1/CIP1 in Receptor-mediated Apoptosis of WEHI 231 B Lymphoma Cells

1998 ◽  
Vol 187 (10) ◽  
pp. 1671-1679 ◽  
Author(s):  
Min Wu ◽  
Robert E. Bellas ◽  
Jian Shen ◽  
Gail E. Sonenshein
Keyword(s):  
Tumor Suppressor ◽  
B Cell ◽  
Kinase Inhibitor ◽  
Ectopic Expression ◽  
Cyclin Dependent Kinase ◽  
Lymphoma Cells ◽  
B Lymphoma ◽  
Cyclin Dependent Kinase Inhibitor ◽  
B Lymphoma Cells ◽  
Wehi 231

Treatment of WEHI 231 immature B lymphoma cells with an antibody against their surface immunoglobulin M (anti-IgM) induces apoptosis and has been studied extensively as a model of self-induced B cell tolerance. Since the tumor suppressor protein p53 has been implicated in apoptosis in a large number of cell types and has been found to be mutated in a variety of B cell tumors, here we sought to determine whether p53 and the p53 target gene cyclin-dependent kinase inhibitor p21WAF1/CIP1 were involved in anti-IgM–induced cell death. Anti-IgM treatment of WEHI 231 cells increased expression of p53 and p21 protein levels. Ectopic expression of wild-type p53 in WEHI 231 cells induced both p21 expression and apoptosis. Ectopic expression of p21 similarly induced apoptosis. Rescue of WEHI 231 cells from apoptosis by costimulation with CD40 ligand ablated the increase in p21 expression. Lastly, a significant decrease in anti-IgM–mediated apoptosis was seen upon downregulation of endogenous p53 activity by expression of a dominant-negative p53 protein or upon microinjection of an antisense p21 expression vector or antibody. Taken together, the above data demonstrate important roles for p53 and p21 proteins in receptor-mediated apoptosis of WEHI 231 B cells.

scholarly journals Permissive Roles of Phosphatidyl Inositol 3-Kinase and Akt in Skeletal Myocyte Maturation

2004 ◽  
Vol 15 (2) ◽  
pp. 497-505 ◽  
Author(s):  
Elizabeth M. Wilson ◽  
Jolana Tureckova ◽  
Peter Rotwein
Keyword(s):  
Growth Factors ◽  
Signaling Pathways ◽  
Transcriptional Activation ◽  
Muscle Development ◽  
Kinase Inhibitor ◽  
Troponin T ◽  
Phosphatidyl Inositol ◽  
Muscle Differentiation ◽  
Pi3 Kinase ◽  
Dominant Negative

Skeletal muscle differentiation, maturation, and regeneration are regulated by interactions between signaling pathways activated by hormones and growth factors, and intrinsic genetic programs controlled by myogenic transcription factors, including members of the MyoD and myocyte enhancer factor 2 (MEF2) families. Insulin-like growth factors (IGFs) play key roles in muscle development in the embryo, and in the maintenance and hypertrophy of mature muscle in the adult, but the precise signaling pathways responsible for these effects remain incompletely defined. To study mechanisms of IGF action in muscle, we have developed a mouse myoblast cell line termed C2BP5 that is dependent on activation of the IGF-I receptor and the phosphatidyl inositol 3-kinase (PI3-kinase)-Akt pathway for initiation of differentiation. Here, we show that differentiation of C2BP5 myoblasts could be induced in the absence of IGF action by recombinant adenoviruses expressing MyoD or myogenin, but it was reversibly impaired by the PI3-kinase inhibitor LY294002. Similar results were observed using a dominant-negative version of Akt, a key downstream component of PI3-kinase signaling, and also were seen in C3H 10T1/2 fibroblasts. Inhibition of PI3-kinase did not prevent accumulation of muscle differentiation-specific proteins (myogenin, troponin T, or myosin heavy chain), did not block transcriptional activation of E-box containing muscle reporter genes by MyoD or myogenin, and did not inhibit the expression or function of endogenous MEF2C or MEF2D. An adenovirus encoding active Akt could partially restore terminal differentiation of MyoD-expressing and LY294002-treated myoblasts, but the resultant myofibers contained fewer nuclei and were smaller and thinner than normal, indicating that another PI3-kinase-stimulated pathway in addition to Akt is required for full myocyte maturation. Our results support the idea that an IGF-regulated PI3-kinase pathway functions downstream of or in parallel with MyoD, myogenin, and MEF2 in muscle development to govern the late steps of differentiation that lead to multinucleated myotubes.

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