The TORC1/P70S6K and TORC1/4EBP1 signaling pathways have a stronger contribution on skeletal muscle growth than MAPK/ERK in an early vertebrate: Differential involvement of the IGF system and atrogenes

Eduardo N. Fuentes, Ingibjörg Eir Einarsdottir, Rodolfo Paredes, Christian Hidalgo, Juan Antonio Valdes, Björn Thrandur Björnsson, Alfredo Molina

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Knowledge about the underlying mechanisms, particularly the signaling pathways that account for muscle growth in vivo in early vertebrates is still scarce. Fish ( Paralichthys adspersus) were fasted for 3. weeks to induce a catabolic period of strong muscle atrophy. Subsequently, fish were refed for 2. weeks to induce compensatory muscle hypertrophy. During refeeding, the fish were treated daily with either rapamycin (TORC blocker), PD98059 (MEK blocker), or PBS (V; vehicle), or were untreated (C; control). Rapamycin and PD98059 differentially impaired muscle cellularity in vivo, growth performance, and the expression of growth-related genes, and the inhibition of TORC1 had a greater impact on fish muscle growth than the inhibition of MAPK. Blocking TORC1 inhibited the phosphorylation of P70S6K and 4EBP1, two downstream components activated by TORC1, thus affecting protein contents in muscle. Concomitantly, the gene expression in muscle of igf-1, 2 and igfbp-4, 5 was down-regulated while the expression of atrogin-1, murf-1, and igfbp-2, 3 was up-regulated. Muscle hypertrophy was abolished and muscle atrophy was promoted, which finally affected body weight. TORC2 complex was not affected by rapamycin. On the other hand, the PD98059 treatment triggered ERK inactivation, a downstream component activated by MEK. mRNA contents of igf-1 in muscle were down-regulated, and muscle hypertrophy was partially impaired. The present study provides the first direct data on the in vivo contribution of TORC1/P70S6K, TORC1/4EBP1, and MAPK/ERK signaling pathways in the skeletal muscle of an earlier vertebrate, and highlights the transcendental role of TORC1 in growth from the cellular to organism level.

Original languageEnglish
Pages (from-to)96-106
Number of pages11
JournalGeneral and Comparative Endocrinology
Volume210
DOIs
Publication statusPublished - 1 Jan 2015

Keywords

  • Atrophy
  • ERK
  • Hypertrophy
  • IGF system
  • Teleost fish
  • TORC

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Endocrinology

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