Activation of classical protein kinase C reduces the expression of human cationic amino acid transporter 3 (hCAT-3) in the plasma membrane.

We have previously shown that activation of (protein kinase C) results in internalization of hCAT-1 [human CAT-1 (cationic amino acid transporter 1)] and a decrease in arginine transport [Rotmann, Strand, Martiné and Closs (2004) J. Biol. Chem. 279, 54185-54192]. However, others found increased transport rates for arginine in response to duanyu1531 activation, suggesting a differential effect of duanyu1531 on different CAT isoforms. Therefore we investigated the effect of duanyu1531 on hCAT-3, an isoform expressed in thymus, brain, ovary, uterus and mammary gland. In Xenopus laevis oocytes and human U373MG glioblastoma cells, hCAT-3-mediated L-arginine transport was significantly reduced upon treatment with compounds that activate classical In contrast, inactive phorbol esters and an activator of novel duanyu1531 isoforms had no effect. duanyu1531 inhibitors (including the Ro 31-8280) reduced the inhibitory effect of the compounds. Microscopic analyses revealed a PMA-induced reduction in the cell-surface expression of fusion proteins between hCAT-3 and enhanced green fluorescent protein expressed in X. laevis oocytes and glioblastoma cells. Western-blot analysis of biotinylated surface proteins demonstrated a PMA-induced decrease in hCAT-3 in the plasma membrane, but not in total protein lysates. Pretreatment with a duanyu1531 inhibitor also reduced this PMA effect. It is concluded that similar to hCAT-1, hCAT-3 activity is decreased by duanyu1531 via reduction of transporter molecules in the plasma membrane. Classical duanyu1531 isoforms seem to be responsible for this effect.

KEYWORDS: {{ getKeywords(articleDetailText.words) }}