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J. Biol. Chem., Vol. 282, Issue 43, 31504-31516, October 26, 2007

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Presenilin 1 Regulates Epidermal Growth Factor Receptor Turnover and Signaling in the Endosomal-Lysosomal Pathway^*

Emanuela Repetto, Il-Sang Yoon, Hui Zheng, and David E. Kang¹

From the Department of Neurosciences, University of California, San Diego, La Jolla, California 92093 and the Huffington Center on Aging, Baylor College of Medicine, Houston, Texas 77030

Mutations in the gene encoding presenilin 1 (PS1) cause the most aggressive form of early-onset familial Alzheimer disease. In addition to its well established role in A production and Notch proteolysis, PS1 has been shown to mediate other physiological activities, such as regulation of the Wnt/-catenin signaling pathway, modulation of phosphatidylinositol 3-kinase/Akt and MEK/ERK signaling, and trafficking of select membrane proteins and/or intracellular vesicles. In this study, we present evidence that PS1 is a critical regulator of a key signaling receptor tyrosine kinase, epidermal growth factor receptor (EGFR). Specifically, EGFR levels were robustly increased in fibroblasts deficient in both PS1 and PS2 (PS^-/-) due to delayed turnover of EGFR protein. Stable transfection of wild-type PS1 but not PS2 corrected EGFR to levels comparable to PS^+/+ cells, while FAD PS1 mutations showed partial loss of activity. The C-terminal fragment of PS1 was sufficient to fully reduce EGFR levels. In addition, the rapid ligand-induced degradation of EGFR was markedly delayed in PS^-/- cells, resulting in prolonged signal activation. Despite the defective turnover of EGFR, ligand-induced autophosphorylation, ubiquitination, and endocytosis of EGFR were not affected by the lack of PS1. Instead, the trafficking of EGFR from early endosomes to lysosomes was severely delayed by PS1 deficiency. Elevation of EGFR was also seen in brains of adult mice conditionally ablated in PS1 and in skin tumors associated with the loss of PS1. These findings demonstrate a critical role of PS1 in the trafficking and turnover of EGFR and suggest potential pathogenic effects of elevated EGFR as well as perturbed endosomal-lysosomal trafficking in cell cycle control and Alzheimer disease.

Received for publication, May 24, 2007 , and in revised form, August 23, 2007.

^* This work was supported in part by Alzheimer's Association Grant IIRG-05-14752 (to D. E. K.) and by American Health Assistance Foundation Grant A2005-039 (to D. E. K.). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. S1-S3.

¹ To whom correspondence should be addressed: Dept. of Neurosciences, University of California at San Diego, Leichtag Biomedical Research 380, 9500 Gilman Drive, La Jolla, CA 92093. Tel.: 858-822-6484; Fax: 858-822-1021; E-mail: dekang{at}ucsd.edu.

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