Proinsulin C-peptide rapidly stimulates mitogen-activated protein kinases in swiss 3T3 fibroblasts: Requirement of protein kinase C, phosphoinositide 3-kinase and pertussis toxin-sensitive G-protein

T. Kitamura, K. Kimura*, B. D. Jung, K. Makondo, S. Okamoto, X. Cañas, N. Sakane, T. Yoshida, M. Saito

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

It has been demonstrated that proinsulin C-peptide possesses several biological activities and that its specific binding sites are present on the surface of cell membranes. However, the molecular and cellular mechanisms of C-peptide actions are poorly known. In the present study we examined the possible involvement of the mitogen-activated protein kinase (MAPK) pathway in C-peptide effects. C-peptide induced the phosphorylation of MAPK [p44 extracellular signal-regulated kinase 1 (ERK1) and p42 ERK2] in Swiss 3T3 and 3T3-F442A fibroblasts but not in 3T3-L1 fibroblasts and some other cell lines such as L6E9 muscle cells. In Swiss 3T3 cells, C-peptide-induced phosphorylation of MAPK was dependent on time and concentration, being maximal at 1 min and at 1 nM C-peptide and was accompanied by an increase in MAPK activity and MAPK kinase (MEK) phosphorylation. The MAPK phosphorylation by C-peptide was abolished by treatment with pertussis toxin (PTX) and also with a MEK inhibitor, PD 98059. In addition, MAPK phosphorylation was attenuated by treatment with a phosphoinositide 3-kinase (PI-3K) inhibitor, wortmannin, and with a protein kinase C (PKC) inhibitor, GF109203X, and by down-regulation of PKC by prolonged treatment with PMA. Similar effects of the inhibitors and PTX were found on the MAPK phosphorylation induced by neuropeptide Y. These results suggest that C-peptide activates MAPK through a putative Gi/Go-linked receptor for C-peptide and through PI-3K-dependent and PKC-dependent pathways.

Original languageEnglish
Pages (from-to)123-129
Number of pages7
JournalBiochemical Journal
Volume355
Issue number1
DOIs
Publication statusPublished - 1 Apr 2001

Keywords

  • 3T3-F442A
  • Insulin
  • MAP kinase kinase
  • Neuropeptide Y
  • Wortmannin

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