scholarly journals Angiotensin II Induces Skeletal Muscle Wasting through Enhanced Protein Degradation and Down-Regulates Autocrine Insulin-Like Growth Factor I*

Endocrinology ◽  
2001 ◽  
Vol 142 (4) ◽  
pp. 1489-1496 ◽  
Author(s):  
Marijke Brink ◽  
S. Russ Price ◽  
Jacqueline Chrast ◽  
James L. Bailey ◽  
Asif Anwar ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Angiotensin Ii ◽  
Growth Factor ◽  
Protein Degradation ◽  
Muscle Wasting ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Skeletal Muscle Wasting ◽  
Growth Factor I

Insulin-like growth factor I slows the rate of denervation induced skeletal muscle atrophy

2005 ◽  
Vol 15 (2) ◽  
pp. 139-146 ◽  
Author(s):  
Thea Shavlakadze ◽  
Jason D. White ◽  
Marilyn Davies ◽  
Joseph F.Y. Hoh ◽  
Miranda D. Grounds
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Muscle Atrophy ◽  
Skeletal Muscle Atrophy ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Growth Factor I

scholarly journals Intact Insulin and Insulin-Like Growth Factor-I Receptor Signaling Is Required for Growth Hormone Effects on Skeletal Muscle Growth and Functionin Vivo

Endocrinology ◽  
2005 ◽  
Vol 146 (4) ◽  
pp. 1772-1779 ◽  
Author(s):  
Hyunsook Kim ◽  
Elisabeth Barton ◽  
Naser Muja ◽  
Shoshana Yakar ◽  
Patricia Pennisi ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Growth Hormone ◽  
Growth Factor ◽  
Muscle Growth ◽  
Insulin Like Growth Factor ◽  
Receptor Signaling ◽  
Skeletal Muscle Growth ◽  
Factor I ◽  
Hormone Effects ◽  
Growth Factor I

Effects of insulin-like growth factor-I, insulin, and leucine on protein turnover and ubiquitin ligase expression in rainbow trout primary myocytes

2010 ◽  
Vol 298 (2) ◽  
pp. R341-R350 ◽  
Author(s):  
Beth M. Cleveland ◽  
Gregory M. Weber
Keyword(s):  
Protein Synthesis ◽  
Rainbow Trout ◽  
Growth Factor ◽  
Protein Degradation ◽  
Ubiquitin Ligase ◽  
Protein Turnover ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

The effects of insulin-like growth factor-I (IGF-I), insulin, and leucine on protein turnover and pathways that regulate proteolytic gene expression and protein polyubiquitination were investigated in primary cultures of 4-day-old rainbow trout myocytes. Supplementing media with 100 nM IGF-I increased protein synthesis by 13% ( P < 0.05) and decreased protein degradation by 14% ( P < 0.05). Treatment with 1 μM insulin increased protein synthesis by 13% ( P < 0.05) and decreased protein degradation by 17% ( P < 0.05). Supplementing media containing 0.6 mM leucine with an additional 2.5 mM leucine did not increase protein synthesis rates but reduced rates of protein degradation by 8% ( P < 0.05). IGF-I (1 nM–100 nM) and insulin (1 nM-1 μM) independently reduced the abundance of ubiquitin ligase mRNA in a dose-dependent manner, with maximal reductions of ∼70% for muscle atrophy F-box (Fbx) 32, 40% for Fbx25, and 25% for muscle RING finger-1 (MuRF1, P < 0.05). IGF-I and insulin stimulated phosphorylation of FOXO1 and FOXO4 ( P < 0.05), which was inhibited by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin, and decreased the abundance of polyubiquitinated proteins by 10–20% ( P < 0.05). Supplementing media with leucine reduced Fbx32 expression by 25% ( P < 0.05) but did not affect Fbx25 nor MuRF1 transcript abundance. Serum deprivation decreased rates of protein synthesis by 60% ( P < 0.05), increased protein degradation by 40% ( P < 0.05), and increased expression of all ubiquitin ligases. These data suggest that, similar to mammals, the inhibitory effects of IGF-I and insulin on proteolysis occur via P I3-kinase/protein kinase B signaling and are partially responsible for the ability of these compounds to promote protein accretion.

scholarly journals Insulin-like growth factor I stimulates degradation of an mRNA transcript encoding the 14 kDa ubiquitin-conjugating enzyme

1996 ◽  
Vol 319 (2) ◽  
pp. 455-461 ◽  
Author(s):  
Simon S WING ◽  
Nathalie BEDARD
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Binding Proteins ◽  
Mrna Levels ◽  
Insulin Like Growth Factor ◽  
Mrna Transcript ◽  
Factor I ◽  
Igf I ◽  
Ubiquitin Conjugating Enzyme ◽  
Growth Factor I

Upon fasting, the ubiquitin-dependent proteolytic system is activated in skeletal muscle in parallel with the increases in rates of proteolysis. Levels of mRNA encoding the 14 kDa ubiquitin-conjugating enzyme (E214k), which can catalyse the first irreversible reaction in this pathway, rise and fall in parallel with the rates of proteolysis [Wing and Banville (1994) Am. J. Physiol. 267, E39-E48], indicating that the conjugation of ubiquitin to proteins is a regulated step. To characterize the mechanisms of this regulation, we have examined the effects of insulin, insulin-like growth factor I (IGF-I) and des(1–3) insulin-like growth factor I (DES-IGF-I), which does not bind IGF-binding proteins, on E214k mRNA levels in L6 myotubes. Insulin suppressed levels of E214k mRNA with an IC50 of 4×10-9 M, but had no effects on mRNAs encoding polyubiquitin and proteasome subunits C2 and C8, which, like E214k, also increase in skeletal muscle upon fasting. Reduction of E214k mRNA levels was more sensitive to IGF-I with an IC50 of approx. 5×10-10 M. During the incubation of these cells for 12 h there was significant secretion of IGF-I-binding proteins into the medium. DES-IGF-I, which has markedly reduced affinity for these binding proteins, was found to potently reduce E214k mRNA levels with an IC50 of 3×10-11 M. DES-IGF-I did not alter rates of transcription of the E214k gene, but enhanced the rate of degradation of the 1.2 kb mRNA transcript. The half-life of the 1.2 kb transcript was approximately one-third that of the 1.8 kb transcript and can explain the more marked regulation of this transcript observed previously. This indicates that the additional 3´ non-coding sequence in the 1.8 kb transcript confers stability. These observations suggest that IGF-I is an important regulator of E214k expression and demonstrate, for the first time, stimulation of degradation of a specific mRNA transcript by this hormone, while overall RNA accumulates.

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