Downregulation of ErbB2 by Perturbing Its Endocytic Recycling; Annual rept. 22 Jun 2005-21 Jun 2006

摘要

About 25% of breast cancers arise from the overexpression of ErbB2 that increases its cell surface level on mammary cells to result in enhanced mitogenic signaling. This high surface level of ErbB2 is maintained by efficient endocytic recycling rather than slowed internalization. Although transport efficiency involves the recognition of specific sequences in the cytoplasmic domain of cargo proteins (known as sorting signals) by the cellular sorting machinery, this mechanism is thought not to be applicable for the endocytic recycling pathways. However, this long-held paradigm has been reversed by the recent discovery of sorting signals that function in the endocytic recycling of transferrin receptor. As transferrin receptor has been the model system for studying recycling, a key prediction is that other recycling proteins will also possess sorting signals for their efficient recycling. Thus, we propose to identify the predicted recycling sorting signal(s) in ErbB2 by first mutagenizing its cytoplasmic domain, and then stably expressing these mutants as epitope-tagged forms in the ErbB2-driven SKBR3 breast cancer cell line to assess effect on recycling. We anticipate that residues critical for the efficient recycling of ErbB2 will be identified, with the implication that mechanisms of ErbB2 recycling will be an attractive target in the future therapeutic effort to downregulate ErbB2-driven mitogenic signaling.