Pivotal role of RanBP9 in integrin-dependent focal adhesion signaling and assembly

• Published in: The FASEB journal Vol. 26; no. 4; p. 1672
• Main Authors: Woo, Jung A, Roh, Seung-Eon, Lakshmana, Madepalli K, Kang, David E
• Format: Journal Article
• Language: English
• Published: United States 01.04.2012
• Subjects: Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Amyloid beta-Protein Precursor - metabolism; Animals; Cell Adhesion - physiology; Cells, Cultured; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Endocytosis - physiology; Focal Adhesions - metabolism; Hippocampus - cytology; Humans; Integrin beta1 - metabolism; LDL-Receptor Related Proteins - genetics; LDL-Receptor Related Proteins - metabolism; Mice; Mice, Transgenic; Neurons - cytology; Neurons - physiology; Nuclear Proteins - genetics; Nuclear Proteins - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Signal Transduction - physiology; Talin - genetics; Talin - metabolism; Vinculin - genetics; Vinculin - metabolism
• ISSN: 1530-6860
• DOI: 10.1096/fj.11-194423

Accumulation of the amyloid β (Aβ) peptide derived from the amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimer's disease (AD). We previously reported that the scaffolding protein RanBP9 is markedly increased in AD brains and promotes Aβ generation by scaffolding APP/BACE1/LRP complexes together and accelerating APP endocytosis. Because APP, LRP, and RanBP9 all physically interact with β-integrins, we investigated whether RanBP9 alters integrin-dependent cell adhesion and focal adhesion signaling. Here, we show that RanBP9 overexpression dramatically disrupts integrin-dependent cell attachment and spreading in NIH3T3 and hippocampus-derived HT22 cells, concomitant with strongly decreased Pyk2/paxillin signaling and talin/vinculin localization in focal adhesion complexes. Conversely, RanBP9 knockdown robustly promotes cell attachment, spreading, and focal adhesion signaling and assembly. Cell surface biotinylation and endocytosis assays reveal that RanBP9 overexpression and RanBP9 siRNA potently reduces and increases surface β1-integrin and LRP by accelerating and inhibiting their endocytosis, respectively. Primary hippocampal neurons derived from RanBP9-transgenic mice also demonstrate severely reduced levels of surface β1-integrin, LRP, and APP, as well as neurite arborization. Therefore, these data indicate that RanBP9 simultaneously inhibits cell-adhesive processes and enhances Aβ generation by accelerating APP, LRP, and β1-integrin endocytosis.