Figure 1

Tpl2 is expressed in β-cells and rodent pancreatic islets and activated by proinflammatory cytokines. Tpl2 protein expression in (a) INS-1E cell line, mouse, rat and human islets and macrophage RAW264.7 cell line; or in (c) INS-1E treated for the indicated period of time with a cytokine mix (CK); or in (d) INS-1E treated for 20 min with glucose (Glc, 10 mM). (b) Tpl2 phosphorylation (Ser400) in INS-1E stimulated for 10 min with the CK. (e and f) Western blot analysis of phosphorylated and total proteins for ERK1/2 and p90RSK in INS-1E cells, pretreated without (black bars) or with (white bars) a Tpl2 inhibitor (Tpl2-I, 3 μM) for 2 h and then unstimulated (Basal) or stimulated with CK (e) or Glc 10 mM (f). (g and h) Western blot analysis of phosphorylated and total proteins for ERK1/2 in mouse islets (g) or human islets (h) treated with a Tpl2 inhibitor as in (e), and stimulated with CK. Representative immunoblots and quantification of three to six independent experiments are shown and expressed as a percentage of the ratio of p-Tpl2 to total Tpl2 (b), of Tpl2 to β-actin protein amount in untreated cells (c and d) or as ratio of phosphorylated to total protein amount and fold of phosphorylation over basal in cells without treatment (e–h). Data are presented as mean±S.E.M. *P<0.05, **P<0.01, and ***P<0.001 versus corresponded indicated controls (t-test (b, d) or one-way analysis of variance (c, e–h))