Insulin has many different effects on Tetrahymena, as e.g. on the glucose uptake, cell division, survival, phosholipase D activity and insulin production. PI 3-kinase is one of the key enzymes in the action of insulin. Thus it was supposed that similarly to the higher eukaryotes, PI 3-kinase activity plays fundamental role in the insulin action also in Tetrahymena. Here we report that PI 3-kinase-like activity is immunoprecipitated from Tetrahymena cell lysate with anti-IRS 1 and anti-p85 antibodies. Both immunoprecipitates contain higher PI 3-kinase activity from lysate of insulin treated cells than the lysate of untreated ones. In vivo treatments with PI 3-kinase inhibitors wortmannin (100-500 nM) and LY 294002 (10-20 μM) elevated the PI 3-kinase activity in the IRS 1-antibody precipitable material, while in anti-p85 antibody precipitate this activity was lower than in the controls. In vitro, wortmannin proved to be an effective PI 3-kinase inhibitor. Immunostaining revealed that p85 immunoreactivity localized to the cortex of cells, while IRS 1 localized cytoplasmically. In vivo treatments with both PI 3-kinase inhibitors elevated the amount of IRS 1, while p85 immunoreactivity was increased only after wortmannin treatments. Both PI 3-kinase inhibitors reduced the F-actin content of cells. Wortmannin caused a forward cytoplasmic stream, which translocate the nucleus towards cytopharynx. These treatments inhibited the phagocytotic activity significantly. On the basis of the results, we propose that in Tetrahymena a PI 3-kinase like activity is functioning; the ability of both PI 3-kinase inhibitors and insulin to influence the synthesis or association of subunits of PI 3-kinase, and to influence F-actin remodelling and F-actin dependent processes (e.g. phagocytosis) indicate the supposed activity of PI 3-kinase in Tetrahymena.
|Number of pages||9|
|Publication status||Published - Nov 1 2003|
- IRS 1
- LY 294002
- PI 3-kinase
ASJC Scopus subject areas
- Agricultural and Biological Sciences(all)