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Suppression of insulin signalling by a synthetic peptide KIFMK suggests the cytoplasmic linker between DIII‐S6 and DIV‐S1 as a local anaesthetic binding site on the sodium channel
Author(s) -
Hirose Munetaka,
Kuroda Yoshihiro,
Sawa Shinichi,
Nakagawa Terumichi,
Hirata Masashi,
Sakaguchi Masahiro,
Tanaka Yoshifumi
Publication year - 2004
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0705575
Subject(s) - autophosphorylation , phosphorylation , dephosphorylation , linker , tyrosine , peptide , biochemistry , allosteric regulation , western blot , insulin , biology , insulin receptor , tyrosine phosphorylation , chemistry , receptor , protein kinase a , endocrinology , phosphatase , computer science , gene , operating system , insulin resistance
Acetyl‐KIFMK‐amide (KIFMK) restores fast inactivation to mutant sodium channels having a defective inactivation gate. Its binding site with sodium channels could be considered to be the cytoplasmic linker (III–IV linker) connecting domains III and IV of the sodium channel α subunit. There is a close resemblance of the amino‐acid sequences between the III–IV linker and the activation loop of the insulin receptor (IR). This resemblance of the amino‐acid sequences suggests that KIFMK may also modulate insulin signalling. In order to test this assumption, we studied the effects of KIFMK and its related (KIYEK, KIQMK, and DIYET) and unrelated (LPFFD) peptides on tyrosine phosphorylation or dephosphorylation of IR in vitro . Purified IR was phosphorylated in vitro with insulin in the presence of various synthetic peptides and lignocaine. The phosphorylation level of IR was then evaluated after SDS–PAGE separation, followed by Western blot analysis with antiphosphotyrosine antibody. KIFMK and KIYEK inhibited insulin‐stimulated autophosphorylation of IR. Lignocaine showed similar effects, but at a higher order of concentration. KIYEK and DIYET, but not KIFMK, dephosphorylated the phosphorylated tyrosine residues. The structurally unrelated peptide LPFFD had no effect either on phosphorylation or dephosphorylation of IR. These results indicate that KIFMK, KIYEK, and lignocaine bind with the autophosphorylation sites of IR. The present findings also suggest that KIFMK and lignocaine bind with the III–IV linker of sodium channel α subunit.British Journal of Pharmacology (2004) 142 , 222–228. doi: 10.1038/sj.bjp.0705575