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Activation of anabolic signal transduction pathways in L6 muscle cells in response to Amino Acids (AA) and Insulin
Author(s) -
Patel Rekha,
Smith Ken,
Rennie Michael,
Atherton Philip
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.306.6
Subject(s) - insulin , signal transduction , phosphorylation , chemistry , pi3k/akt/mtor pathway , medicine , anabolism , protein kinase b , insulin receptor , endocrinology , p70 s6 kinase 1 , microbiology and biotechnology , biochemistry , biology , insulin resistance
Muscle protein synthesis (MPS) in vivo is stimulated by feeding‐associated increases in AA and insulin. However, there is limited knowledge of their separate and common effects on signal transduction pathways regulating MPS. We aimed to measure the activation and temporal responses of signalling proteins to insulin, AA or their combination in vitro. After withdrawal of serum for 6h and of AA for 3h L6 cells were treated with either, AA (1× plasma concentration) or insulin (5 μIU/ml) alone, or a combination thereof. Proteins were extracted at intervals between 15–105 min. Activation of most proteins studied occurred by 15 min. Insulin stimulated PKB, mTOR, 4EBP1, eIF4G, eIF4B and eIF2Bε by >300% at all time‐points. AA alone only stimulated eIF2Bε phosphorylation by ~50%. Addition of AA with insulin potentiated peak insulin‐stimulated phosphorylation of PKB, p70 and 4EBP1 >200%. eEF2 was activated from 45 min onward. Insulin with or without AA induced rapid activation of growth pathways and their co‐provision augmented insulin‐induced phosphorylation events. Conversely, AA provision alone was insufficient, to induce anabolic signalling, except for eIF2Bε. Delayed activation of eEF2 may be indicative of its role in elongation and not initiation. To conclude, insulin is required for AA‐induced stimulation of MPS, and their co‐provision potentiates activation of signalling proteins regulating MPS.