The β-Amyloid Precursor Protein Functions as a Cytosolic Anchoring Site That Prevents Fe65 Nuclear Translocation

• Published in: The Journal of biological chemistry Vol. 276; no. 9; pp. 6545 - 6550
• Main Authors: Minopoli, Giuseppina, de Candia, Paola, Bonetti, Alessandro, Faraonio, Raffaella, Zambrano, Nicola, Russo, Tommaso
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 02-03-2001
• Subjects: Active Transport, Cell Nucleus; Amyloid beta-Protein Precursor - physiology; Animals; Biological Transport; Cell Membrane - metabolism; COS Cells; CP2/LSF/LBP1 protein; Cytosol - metabolism; Endoplasmic Reticulum - metabolism; Fe65 protein; Golgi Apparatus - metabolism; Medicin och hälsovetenskap; Nerve Tissue Proteins - metabolism; Nuclear Proteins - metabolism; PC12 Cells; Rats; Recombinant Fusion Proteins - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M007340200

In this study we addressed the question of the intracellular localization of Fe65, an adaptor protein interacting with the β-amyloid precursor protein (APP) and with the transcription factor CP2/LSF/LBP1. By using tagged Fe65 expression vectors, we observed that a significant fraction of Fe65 is localized in the nucleus of transfected COS7 cells. Furthermore, the isolation of nuclei from untransfected PC12 cells allowed us to observe that a part of the endogenous Fe65 is present in the nuclear extract. The analysis of Fe65 mutant constructs demonstrated that the region of the protein required for its nuclear translocation includes the WW domain, and that, on the other hand, a small fragment of 100 residues, including this WW domain, contains enough structural information to target a reporter protein (green fluorescent protein (GFP)-GFP) to the nucleus. To evaluate whether the Fe65-APP interaction could affect Fe65 intracellular trafficking, COS7 cells were cotransfected with APP695 or APP751 and with GFP-Fe65 expression vectors. These experiments demonstrated that Fe65 is no longer translocated to the nucleus when the cells overexpress APP, whereas the nuclear targeting of GFP-Fe65 mutants, unable to interact with APP, is unaffected by the coexpression of APP, thus suggesting that the interaction with APP anchors Fe65 in the cytosol.