scholarly journals IGF-I and insulin induce different intracellular calcium signals in skeletal muscle cells

2004 ◽  
Vol 182 (2) ◽  
pp. 339-352 ◽  
Author(s):  
A Espinosa ◽  
M Estrada ◽  
E Jaimovich
Keyword(s):  
Skeletal Muscle ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Normal Muscle ◽  
Action Mechanisms ◽  
Early Action ◽  
Igf I ◽  
Intracellular Ca ◽  
Cultured Myotubes

We studied the effect of IGF-I and insulin on intracellular Ca(2+) in primary cultured myotubes. IGF-I induced a fast and transient Ca(2+) increase, measured as fluo-3 fluorescence. This response was blocked by both genistein and AG538. IGF-I induced a fast inositol-1,4,5-trisphosphate (IP(3)) increase, kinetically similar to the Ca(2+) rise. The Ca(2+) signal was blocked by inhibitors of the IP(3) pathway. On the other hand, insulin produced a fast (<1 s) and transient Ca(2+) increase. Insulin-induced Ca(2+) increase was blocked in Ca(2+)-free medium and by either nifedipine or ryanodine. In the normal muscle NLT cell line, the Ca(2+ )signals induced by both hormones resemble those of primary myotubes. GLT cells, lacking the alpha1-subunit of dihydropyridine receptor (DHPR), responded to IGF-I but not to insulin, while GLT cells transfected with the alpha1-subunit of DHPR reacted to both hormones. Moreover, dyspedic muscle cells, lacking ryanodine receptors, responded to IGF-I as NLT cells, however they show no insulin-induced calcium increase. Moreover, G-protein inhibitors, pertussis toxin (PTX) and GDPbetaS, blocked the insulin-induced Ca(2+) increase without major modification of the response to IGF-I. The different intracellular Ca(2+) patterns produced by IGF-I and insulin may improve our understanding of the early action mechanisms for these hormones in skeletal muscle cells.

NF-κB activation by depolarization of skeletal muscle cells depends on ryanodine and IP3 receptor-mediated calcium signals

2007 ◽  
Vol 292 (5) ◽  
pp. C1960-C1970 ◽  
Author(s):  
Juan Antonio Valdés ◽  
Jorge Hidalgo ◽  
José Luis Galaz ◽  
Natalia Puentes ◽  
Mónica Silva ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Calcium Release ◽  
Ryanodine Receptors ◽  
Field Potential ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Ip3 Receptor ◽  
Pharmacological Agents ◽  
Calcium Dependent ◽  
Element Binding Protein

Depolarization of skeletal muscle cells by either high external K+ or repetitive extracellular field potential pulses induces calcium release from internal stores. The two components of this release are mediated by either ryanodine receptors or inositol 1,4,5-trisphosphate (IP3) receptors and show differences in kinetics, amplitude, and subcellular localization. We have reported that the transcriptional regulators including ERKs, cAMP/Ca2+-response element binding protein, c- fos, c- jun, and egr-1 are activated by K+-induced depolarization and that their activation requires IP3-dependent calcium release. We presently describe the activation of the nuclear transcription factor NF-κB in response to depolarization by either high K+ (chronic) or electrical pulses (fluctuating). Calcium transients of relative short duration activate an NF-κB reporter gene to an intermediate level, whereas long-lasting calcium increases obtained by prolonged electrical stimulation protocols of various frequencies induce maximal activation of NF-κB. This activation is independent of extracellular calcium, whereas calcium release mediated by either ryanodine or IP3 receptors contribute in all conditions tested. NF-κB activation is mediated by IκBα degradation and p65 translocation to the nucleus. Partial blockade by N-acetyl-l-cysteine, a general antioxidant, suggests the participation of reactive oxygen species. Calcium-dependent signaling pathways such as those linked to calcineurin and PKC also contribute to NF-κB activation by depolarization, as assessed by blockade through pharmacological agents. These results suggest that NF-κB activation in skeletal muscle cells is linked to membrane depolarization and depends on the duration of elevated intracellular calcium. It can be regulated by sequential activation of calcium release mediated by the ryanodine and by IP3 receptors.

scholarly journals Isolation and validation of human prepubertal skeletal muscle cells: maturation and metabolic effects of IGF-I, IGFBP-3 and TNFα

2005 ◽  
Vol 568 (1) ◽  
pp. 229-242 ◽  
Author(s):  
Malcolm Grohmann ◽  
Emily Foulstone ◽  
Gavin Welsh ◽  
Jeff Holly ◽  
Julian Shield ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Metabolic Effects ◽  
Igf I ◽  
Igfbp 3

scholarly journals Focal adhesion kinase is required for IGF-I-mediated growth of skeletal muscle cells via a TSC2/mTOR/S6K1-associated pathway

2013 ◽  
Vol 305 (2) ◽  
pp. E183-E193 ◽  
Author(s):  
Hannah Crossland ◽  
Abid A. Kazi ◽  
Charles H. Lang ◽  
James A. Timmons ◽  
Philippe Pierre ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cell Growth ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Muscle Hypertrophy ◽  
Kinase Activity ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Cell Phenotype ◽  
Igf I

Focal adhesion kinase (FAK) is an attachment complex protein associated with the regulation of muscle mass through as-of-yet unclear mechanisms. We tested whether FAK is functionally important for muscle hypertrophy, with the hypothesis that FAK knockdown (FAK-KD) would impede cell growth associated with a trophic stimulus. C2C12 skeletal muscle cells harboring FAK-targeted (FAK-KD) or scrambled (SCR) shRNA were created using lentiviral transfection techniques. Both FAK-KD and SCR myotubes were incubated for 24 h with IGF-I (10 ng/ml), and additional SCR cells (±IGF-1) were incubated with a FAK kinase inhibitor before assay of cell growth. Muscle protein synthesis (MPS) and putative FAK signaling mechanisms (immunoblotting and coimmunoprecipitation) were assessed. IGF-I-induced increases in myotube width (+41 ± 7% vs. non-IGF-I-treated) and total protein (+44 ± 6%) were, after 24 h, attenuated in FAK-KD cells, whereas MPS was suppressed in FAK-KD vs. SCR after 4 h. These blunted responses were associated with attenuated IGF-I-induced FAK Tyr397 phosphorylation and markedly suppressed phosphorylation of tuberous sclerosis complex 2 (TSC2) and critical downstream mTOR signaling (ribosomal S6 kinase, eIF4F assembly) in FAK shRNA cells (all P < 0.05 vs. IGF-I-treated SCR cells). However, binding of FAK to TSC2 or its phosphatase Shp-2 was not affected by IGF-I or cell phenotype. Finally, FAK-KD-mediated suppression of cell growth was recapitulated by direct inhibition of FAK kinase activity in SCR cells. We conclude that FAK is required for IGF-I-induced muscle hypertrophy, signaling through a TSC2/mTOR/S6K1-dependent pathway via means requiring the kinase activity of FAK but not altered FAK-TSC2 or FAK-Shp-2 binding.

scholarly journals Binding of an ankyrin-1 isoform to obscurin suggests a molecular link between the sarcoplasmic reticulum and myofibrils in striated muscles

2003 ◽  
Vol 160 (2) ◽  
pp. 245-253 ◽  
Author(s):  
Paola Bagnato ◽  
Virigina Barone ◽  
Emiliana Giacomello ◽  
Daniela Rossi ◽  
Vincenzo Sorrentino
Keyword(s):  
Skeletal Muscle ◽  
Sarcoplasmic Reticulum ◽  
Binding Site ◽  
Physiological Activity ◽  
Ryanodine Receptors ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Structural Function ◽  
Striated Muscles

Assembly of specialized membrane domains, both of the plasma membrane and of the ER, is necessary for the physiological activity of striated muscle cells. The mechanisms that mediate the structural organization of the sarcoplasmic reticulum with respect to the myofibrils are, however, not known. We report here that ank1.5, a small splice variant of the ank1 gene localized on the sarcoplasmic reticulum membrane, is capable of interacting with a sequence of 25 aa located at the COOH terminus of obscurin. Obscurin is a giant sarcomeric protein of ∼800 kD that binds to titin and has been proposed to mediate interactions between myofibrils and other cellular structures. The binding sites and the critical aa required in the interaction between ank1.5 and obscurin were characterized using the yeast two-hybrid system, in in vitro pull-down assays and in experiments in heterologous cells. In differentiated skeletal muscle cells, a transfected myc-tagged ank1.5 was found to be selectively restricted near the M line region where it colocalized with endogenous obscurin. The M line localization of ank1.5 required a functional obscurin-binding site, because mutations of this domain resulted in a diffused distribution of the mutant ank1.5 protein in skeletal muscle cells. The interaction between ank1.5 and obscurin represents the first direct evidence of two proteins that may provide a direct link between the sarcoplasmic reticulum and myofibrils. In keeping with the proposed role of obscurin in mediating an interaction with ankyrins and sarcoplasmic reticulum, we have also found that a sequence with homology to the obscurin-binding site of ank1.5 is present in the ank2.2 isoform, which in striated muscles has been also shown to associate with the sarcoplasmic reticulum. Accordingly, a peptide containing the COOH terminus of ank2.2 fused with GST was found to bind to obscurin. Based on reported evidence showing that the COOH terminus of ank2.2 is necessary for the localization of ryanodine receptors and InsP3 receptors in the sarcoplasmic reticulum, we propose that obscurin, through multiple interactions with ank1.5 and ank2.2 isoforms, may assemble a large protein complex that, in addition to a structural function, may play a role in the organization of specific subdomains in the sarcoplasmic reticulum.

IGF-I and vitamin C promote myogenic differentiation of mouse and human skeletal muscle cells at low temperatures

2011 ◽  
Vol 317 (3) ◽  
pp. 356-366 ◽  
Author(s):  
Ai Shima ◽  
Jennifer Pham ◽  
Erica Blanco ◽  
Elisabeth R. Barton ◽  
H. Lee Sweeney ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Vitamin C ◽  
Low Temperatures ◽  
Human Skeletal Muscle ◽  
Myogenic Differentiation ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Human Skeletal Muscle Cells ◽  
Igf I

Developmental regulation of the mouse IGF-I exon 1 promoter region by calcineurin activation of NFAT in skeletal muscle

2007 ◽  
Vol 292 (5) ◽  
pp. C1887-C1894 ◽  
Author(s):  
Christina M. Alfieri ◽  
Heather J. Evans-Anderson ◽  
Katherine E. Yutzey
Keyword(s):  
Skeletal Muscle ◽  
Signaling Pathways ◽  
Muscle Development ◽  
Developmental Regulation ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Conserved Regions ◽  
Igf I ◽  
Exon 1 ◽  
I Gene

Skeletal muscle development and growth are regulated through multiple signaling pathways that include insulin-like growth factor I (IGF-I) and calcineurin activation of nuclear factor of activated T cell (NFAT) transcription factors. The developmental regulation and molecular mechanisms that control IGF-I gene expression in murine embryos and in differentiating C2C12 skeletal myocytes were examined. IGF-I is expressed in developing skeletal muscle, and its embryonic expression is significantly reduced in embryos lacking both NFATc3 and NFATc4. During development, the IGF-I exon 1 promoter is active in multiple organ systems, including skeletal muscle, whereas the alternative exon 2 promoter is expressed predominantly in the liver. The IGF-I exon 1 promoter flanking sequence includes two highly conserved regions that contain NFAT consensus binding sequences. One of these conserved regions contains a calcineurin/NFAT-responsive regulatory region that is preferentially activated by NFATc3 in C2C12 skeletal muscle cells and NIH3T3 fibroblasts. This NFAT-responsive region contains three clustered NFAT consensus binding sequences, and mutagenesis experiments demonstrated the requirement for two of these in calcineurin or NFATc3 responsiveness. Chromatin immunoprecipitation analyses demonstrated that endogenous IGF-I genomic sequences containing these conserved NFAT binding sequences interact preferentially with NFATc3 in C2C12 cells. Together, these experiments demonstrated that a NFAT-rich regulatory element in the IGF-I exon 1 promoter flanking region is responsive to calcineurin signaling and NFAT activation in skeletal muscle cells. The identification of a calcineurin/NFAT-responsive element in the IGF-I gene represents a potential mechanism of intersection of these signaling pathways in the control of muscle development and homeostasis.

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