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Contractions Activate Hormone‐Sensitive Lipase in Rat Muscle by Protein Kinase C and Mitogen‐Activated Protein Kinase
Author(s) -
Donsmark Morten,
Langfort Jozef,
Holm Cecilia,
Ploug Thorkil,
Galbo Henrik
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2003.042333
Subject(s) - protein kinase c , protein kinase a , medicine , endocrinology , calphostin c , mapk/erk pathway , calphostin , chemistry , bisindolylmaleimide , kinase , phorbol , mitogen activated protein kinase kinase , hormone sensitive lipase , biology , microbiology and biotechnology , biochemistry , lipolysis , adipose tissue
Intramuscular triacylglycerol is an important energy store and is also related to insulin resistance. The mobilization of fatty acids from this pool is probably regulated by hormone‐sensitive lipase (HSL), which has recently been shown to exist in muscle and to be activated by both adrenaline and contractions. Adrenaline acts via cAMP‐dependent protein kinase (PKA). The signalling mediating the effect of contractions is unknown and was explored in this study. Incubated soleus muscles from 70 g male rats were electrically stimulated to perform repeated tetanic contractions for 5 min. The contraction‐induced activation of HSL was abolished by the protein kinase C (PKC) inhibitors bisindolylmaleimide I and calphostin C and reduced 50 % by the mitogen‐activated protein kinase kinase (MEK) inhibitor U0126, which also completely blocked extracellular signal‐regulated kinase (ERK) 1 and 2 phosphorylation. None of the inhibitors reduced adrenaline‐induced HSL activation in soleus muscle. Both phorbol‐12‐myristate‐13‐acetate (PMA), which activates PKC and, in turn, ERK, and caffeine, which increases intracellular Ca 2+ without eliciting contraction, increased HSL activity. Activated ERK increased HSL activity in supernatant from basal but not from electrically stimulated muscle. In conclusion, in muscle, PKC can stimulate HSL through ERK. Contractions and adrenaline enhance muscle HSL activity by different signalling mechanisms. The effect of contractions is mediated by PKC, at least partly via the ERK pathway.