Regulation of EGFR Degradation by Ankyrin105
Growth factors can regulate a variety of cellular processes by activating receptors on the cell surface. Many of the receptors belong to the receptor tyrosine kinase family, including the platelet-derived growth factor receptor and the epidermal growth factor receptor and its related family members, such as ErbB2. Constitutively activated receptor tyrosine kinases and their downstream signaling pathways (such as the Ras-mitogen activated protein kinase pathway and the phosphatidylinositol 3 kinase-Akt pathway) are frequently observed in cancer cells. Therefore, understanding the degradation mechanism of receptors is important and may facilitate the development of new prognostic or treatment strategies for cancer. Ankyrin105 is the smaller isoform of ankyrin3 and is localized to late endosomes and lysosomes. Our laboratory has previously shown that ankyrin105 can bind to the phosphatidylinositol 3 kinase regulatory subunit p85, stimulate lysosomal-mediated degradation of the platelet-derived growth factor receptor and differentially affect its signaling pathways in NIH 3T3 cells. To determine whether ankyrin105 can induce degradation of multiple receptor tyrosine kinases in a similar manner, we extended these studies to include the epidermal growth factor receptor and its downstream signaling in this project. Hemagglutinin-tagged ankyrin105 was introduced into COS-1, HEK293T, MCF10A, MDA-MB-231 and AU565 cells, respectively. We demonstrated that overexpression of ankyrin105 did not enhance the epidermal growth factor receptor degradation or downregulation of its signaling pathways in these selected cell lines. AU565 cells, which expressed relatively high levels of both epidermal growth factor receptor and ErbB2, were susceptible to geldanamycin or herceptin facilitated ErbB2 internalization and degradation, which subsequently promoted the epidermal growth factor receptor degradation. However, ankyrin105 did not further improve geldanamycin-induced epidermal growth factor receptor degradation or impact its downstream signaling pathways. These studies suggest that the influence of ankyrin105 may be receptor-specific (platelet-derived growth factor receptor, but not epidermal growth factor receptor) and/or cell type specific (NIH 3T3 cells, but not COS-1, HEK293T, MCF10A, MDA-MB-231 or AU565 cells).
EGFR, ankyrin105, downregulation
Master of Science (M.Sc.)