Oncogenic activity of Ect2 is regulated through protein kinase C iota-mediated phosphorylation.
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Justilien V, Jameison L, Der CJ, Rossman KL, Fields AP
Oncogenic activity of Ect2 is regulated through protein kinase C iota-mediated phosphorylation.
J Biol Chem. 2011 Mar 11;286(10):8149-57. doi: 10.1074/jbc.M110.196113. Epub 2010 Dec 28.
- PubMed ID
- 21189248 [ View in PubMed]
- Abstract
The Rho GTPase guanine nucleotide exchange factor Ect2 is genetically and biochemically linked to the PKCiota oncogene in non-small cell lung cancer (NSCLC). Ect2 is overexpressed and mislocalized to the cytoplasm of NSCLC cells where it binds the oncogenic PKCiota-Par6 complex, leading to activation of the Rac1 small GTPase. Here, we identify a previously uncharacterized phosphorylation site on Ect2, threonine 328, that serves to regulate the oncogenic activity of Ect2 in NSCLC cells. PKCiota directly phosphorylates Ect2 at Thr-328 in vitro, and RNAi-mediated knockdown of either PKCiota or Par6 leads to a decrease in phospho-Thr-328 Ect2, indicating that PKCiota regulates Thr-328 Ect2 phosphorylation in NSCLC cells. Both wild-type Ect2 and a phosphomimetic T328D Ect2 mutant bind the PKCiota-Par6 complex, activate Rac1, and restore transformed growth and invasion when expressed in NSCLC cells made deficient in endogenous Ect2 by RNAi-mediated knockdown. In contrast, a phosphorylation-deficient T328A Ect2 mutant fails to bind the PKCiota-Par6 complex, activate Rac1, or restore transformation. Our data support a model in which PKCiota-mediated phosphorylation regulates Ect2 binding to the oncogenic PKCiota-Par6 complex thereby activating Rac1 activity and driving transformed growth and invasion.