Amyloid beta protein‐related death‐inducing protein induces G2/M arrest: Implications for neurodegeneration in Alzheimer's disease

Abstract

Amyloid beta protein (Abeta)-related death-inducing protein (AB-DIP) is a novel Abeta binding protein expressed ubiquitously. Here we demonstrate that overexpression of AB-DIP in SH-SY5Y neuroblastoma cells causes G2/M arrest. By deletion mutant analysis, we have identified the minimal region within AB-DIP required for G2/M arrest. We have also shown that microtubule-interfering agents (MIAs) such as nocodazole, vinblastine, paclitaxel, and vincristine, known to arrest cells at G2/M, also phosphorylate AB-DIP. However, etoposide, which causes genotoxic stress; tunicamycin, an ER stress inducer; and rotenone, which causes mitochondrial damage, fail to phosphorylate AB-DIP, implying that phosphorylation of AB-DIP is specific to microtubule-disruption-induced G2/M arrest. By using different classes of kinase inhibitors, we also demonstrate that a putative tyrosine kinase phosphorylates AB-DIP. Mono- or multisite mutations of tyrosine or serine/threonine residues confirmed that mutation of tyrosine residues but not serine/threonine residues greatly reduces nocodazole-induced phosphorylation of AB-DIP. Furthermore, phosphorylation of AB-DIP can be induced in MCF-7 cells that lack functional p53, suggesting that AB-DIP phosphorylation is independent of p53. Mounting experimental evidence continues to support the role of cell cycle abnormalities in the pathogenesis of Alzheimer's disease, and our results suggest that AB-DIP might provide a mechanistic link between microtubule disruption, mitotic abnormalities, neuronal dysfunction, and death. Therefore, interfering with AB-DIP may have therapeutic applications in conditions such as Alzheimer's disease, in which microtubule disruption and mitotic abnormalities have been suggested to play a pathological role.