Mutant huntingtin regulates EGF receptor fate in non-neuronal cells lacking wild-type protein

Huntingtin (htt) is a scaffold protein localized at the subcellular level and is involved in coordinating the activity of several protein for signaling and intracellular transport. The emerging properties of hit in intracellular trafficking prompted us to study the role of mutant hit (polyQ-htt) in the intracellular fate of epidermal growth factor receptor (EGFR), whose activity seems to be strictly regulated by htt. In particular, to evaluate whether protein trafficking dysfunction occurs in non-neuronal cells in the absence of functional htt, we monitored the EGFR protein in fibroblasts from homozygotic HD patients and their healthy counterpart We found that polyQ-htt controls EGFR degradation and recycling. Lack of wild-type hit caused alteration of the ubiquitination cycle, formation of EGFR-incorporating high-molecular weight protein aggregates and abnormal EGFR distribution in endosomes of the degradation and recycling pathways after EGF stimulation. PolyQ-htt-induced alteration of EGFR trafficking affected cell migration and proliferation, at least in part, through inhibition of ERK signaling. To our knowledge the data here reported represent the first signaling and phenotypic characterization of polyQ-htt involvement in the modulation of growth factor stimulation in non-neuronal cells. (C) 2012 Elsevier B.V. All rights reserved.