title: Calcitonin gene-related peptide inhibits autophagic-lysosomal proteolysis through cAMP/PKA signaling in rat skeletal muscles.
abstract: Calcitonin gene-related peptide (CGRP) is a neuropeptide released by motor neuron in skeletal muscle and modulates the neuromuscular transmission by induction of synthesis and insertion of acetylcholine receptor on postsynaptic muscle membrane; however, its role in skeletal muscle protein metabolism remains unclear. We examined the in vitro and in vivo effects of CGRP on protein breakdown and signaling pathways in control skeletal muscles and muscles following denervation (DEN) in rats. In isolated muscles, CGRP (10(-10) to 10(-6)M) reduced basal and DEN-induced activation of overall proteolysis in a concentration-dependent manner. The in vitro anti-proteolytic effect of CGRP was completely abolished by CGRP8-37, a CGRP receptor antagonist. CGRP down-regulated the lysosomal proteolysis, the mRNA levels of LC3b, Gabarapl1 and cathepsin L and the protein content of LC3-II in control and denervated muscles. In parallel, CGRP elevated cAMP levels, stimulated PKA/CREB signaling and increased Foxo1 phosphorylation in both conditions. In denervated muscles and starved C2C12 cells, Rp-8-Br-cAMPs or PKI, two PKA inhibitors, completely abolished the inhibitory effect of CGRP on Foxo1, 3 and 4 and LC3 lipidation. A single injection of CGRP (100 μg kg(-1)) in denervated rats increased the phosphorylation levels of CREB and Akt, inhibited Foxo transcriptional activity, the LC3 lipidation as well as the mRNA levels of LC3b and cathepsin L, two bona fide targets of Foxo. This study shows for the first time that CGRP exerts a direct inhibitory action on autophagic-lysosomal proteolysis in control and denervated skeletal muscle by recruiting cAMP/PKA signaling, effects that are related to inhibition of Foxo activity and LC3 lipidation.
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Juliano
authors.initials: J
authors.lastname: Machado
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Leandro H
authors.initials: LH
authors.lastname: Manfredi
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Wilian A
authors.initials: WA
authors.lastname: Silveira
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Dawit A P
authors.initials: DAP
authors.lastname: Gonçalves
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Danilo
authors.initials: D
authors.lastname: Lustrino
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Neusa M
authors.initials: NM
authors.lastname: Zanon
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; Department of Biochemistry/Immunology, Ribeirão Preto Medical School, University of São Paulo, Brazil.
authors.forename: Isis C
authors.initials: IC
authors.lastname: Kettelhut
authors.affiliation: Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil. Electronic address: navegantes@fmrp.com.br.
authors.forename: Luiz C
authors.initials: LC
authors.lastname: Navegantes
mesh_terms: D000818:Animals; D001343:Autophagy / Q000187:drug effects*; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D003714:Denervation; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology* / Q000187:drug effects* / Q000294:innervation; D009419:Nerve Tissue Proteins / Q000378:metabolism; D059748:Proteolysis / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects*; D000071161:Forkhead Box Protein O1
chemical_list: D015740:Calcitonin Gene-Related Peptide; D000242:Cyclic AMP; D017362:Cyclic AMP Response Element-Binding Protein; D017868:Cyclic AMP-Dependent Protein Kinases; D008869:Microtubule-Associated Proteins; D009419:Nerve Tissue Proteins; D051057:Proto-Oncogene Proteins c-akt; C526109:Anxa3 protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1
keywords: Autophagy; CGRP; Proteolysis; Skeletal muscle; cAMP/PKA signaling