Activating cAMP/PKA signaling in skeletal muscle suppresses the ubiquitin-proteasome-dependent proteolysis: implications for sympathetic regulation.
Although we have recently demonstrated that plasma catecholamines induce antiproteolytic effects on skeletal muscle (Graça FA, Gonçalves DAP, Silveira WA, Lira EC, Chaves VE, Zanon NM, Garófalo MAR, Kettelhut IC, Navegantes LCC. Am J Physiol Endocrinol Metab. 305: E1483-E1494, 2013), the role of the muscle sympathetic innervation and, more specifically, norepinephrine (NE) in regulating the ubiquitin (Ub)-proteasome system (UPS) remains unknown. Based on previous findings that chemical sympathectomy acutely reduces UPS activity, we hypothesized that muscle NE depletion induces adrenergic supersensitivity in rat skeletal muscles. We report that surgical sympathetic denervation (SDEN), a condition in which only muscle NE from both hindlimbs is depleted, transiently reduced the overall proteolysis and the UPS activity (∼25%) in both soleus and extensor digitorum longus muscles. This antiproteolytic response was accompanied by increased activity of adenylyl cyclase (112%), levels of cyclic adenosine monophosphate (cAMP; 191%), and the serine phosphorylation of cAMP response element-binding protein (32%). In extensor digitorum longus from normal rats, NE (10(-4) M) in vitro increased the levels of cAMP (115%) and the serine phosphorylation of both cAMP response element-binding protein (2.7-fold) and forkhead box class O1 transcription factor. Similar effects were observed in C2C12 cells incubated with forskolin (10 μM). In parallel, NE significantly reduced the basal UPS (21%) activity and the mRNA levels of atrophy-related Ub-ligases. Similar responses were observed in isolated muscles exposed to 6-BNZ-cAMP (500 μM), a specific PKA activator. The phosphorylation levels of Akt were not altered by SDEN, NE, forskolin or 6-BNZ-cAMP. Our results demonstrate that SDEN induces muscle adrenergic supersensitivity for cAMP leading to the suppression of UPS, and that the suppressive effects of NE on UPS activity and expression of Ub-ligases can be mediated by the activation of cAMP/PKA signaling, with the inhibition of forkhead box class O1 transcription factor.
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil;
W A
WA
Silveira
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil;
D A
DA
Gonçalves
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil;
F A
FA
Graça
Division of Cellular Pharmacology, Department of Pharmacology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil.
A L
AL
Andrade-Lopes
Division of Cellular Pharmacology, Department of Pharmacology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil.
L B
LB
Bergantin
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil;
N M
NM
Zanon
Division of Cellular Pharmacology, Department of Pharmacology, Universidade Federal de São Paulo (UNIFESP), São Paulo, Brazil.
R O
RO
Godinho
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil; Department of Biochemistry/Immunology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil; and.
I C
IC
Kettelhut
Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil; navegantes@fmrp.usp.br.
L C C
LC
Navegantes
D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000378:metabolism; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D059748:Proteolysis; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology*; D013564:Sympathetic Nervous System / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
D017362:Cyclic AMP Response Element-Binding Protein; D051858:Forkhead Transcription Factors; D009124:Muscle Proteins; D012333:RNA, Messenger; D025801:Ubiquitin; D000242:Cyclic AMP; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D046988:Proteasome Endopeptidase Complex; D009638:Norepinephrine
MuRF1; atrogin-1; catecholamines; proteolysis; sympathectomy