Nuclear Factor-κB Activated by Capacitative Ca2+ Entry Enhances Muscarinic Receptor-mediated Soluble Amyloid Precursor Protein (sAPPα) Release in SH-SY5Y Cells

Abstract

G q / 11 protein-coupled muscarinic receptors are known to regulate the release of soluble amyloid precursor protein (sAPP␣) produced by ␣-secretase processing; however, their signaling mechanisms remain to be elucidated. It has been reported that a muscarinic agonist activates nuclear factor (NF)-B, a transcription factor that has been shown to play an important role in the Alzheimer disease brain, and that NF-B activation is regulated by intracellular Ca 2؉ level. In the present study, we investigated whether NF-B activation plays a role in muscarinic receptor-mediated sAPP␣ release enhancement and contributes to a changed capacitative Ca 2؉ entry (CCE), which was suggested to be involved in the muscarinic receptor-mediated stimulation of sAPP␣ release. Muscarinic receptor-mediated NF-B activation was confirmed by observing the translocation of the active subunit The amyloid precursor protein (APP)4 is a transmembrane protein that produces ␤ amyloid (A␤) by proteolytic cleavage in brains of individuals with Alzheimer disease. APP normally undergoes proteolytic cleavage within the A␤ sequence liberating the ␣-secretase-cleaved APP (sAPP␣). Although evidence indicates that sAPP␣ plays important roles in regulating neuronal survival and plasticity, the mechanisms that mediate these biological activities and the regulation of sAPP␣ secretion have not been established. The transcriptional nuclear factor-B (NF-B) responds to a large number of environmental cues, and in the nervous system, it is modulated under physiological and pathological conditions, which include developmental cell death and acute of chronic neurodegenerative disorders (1, 2). It was proposed that NF-B or other B-binding proteins may be involved in a neuroprotective change in gene expression evoked by various cytokines and by secreted APP in neuronal cells, and therefore, may have a positive effect on Alzheimer disease (3-6).The NF-B/Rel family of dimeric transcriptional factors is involved in the immediate early transcription of a large array of genes induced by mitogenic and antiapoptotic pathogen-associated stimuli (7,8). The eukaryotic NF-B/Rel family of eukaryotic transcription factors, which includes p50, p65, c-Rel, RelB, and p52, bind DNA with high specificity and affinity as homo-or heterodimers to mediate a diverse range of biological processes (9 -11). The most common form of NF-B consists of a heterodimer of p50 (NF-B1) and p65 (Rel A) (12-15). In most resting cells, NF-B is retained in the cytoplasm by its association with inhibitor molecules of the IB family (16). The formation of NF-B-IB complex masks the nuclear localization signal sequence in NF-B and thus prevents its nuclear translocation. In response to various stimuli, NF-B dimers are released from cytoplasmic IB proteins by a process involving site-specific phosphorylation of IB by IB kinase, ubiquitination, and subsequent proteolytic degradation via the 26 S proteasome pathway (6,17,18).The induction of NF-B activity is known to be regulated by the intracellular Ca 2ϩ leve...

Differential involvement of TNFα in hypoxic suppression of astrocyte glutamate transporters

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The antidiuretic neurohormone RhoprCAPA-2 downregulates fluid transport across the anterior midgut in the blood-feeding insect Rhodnius prolixus

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Calcium influx blocked by SK&F 96365 modulates the LPS plus IFN-γ-induced inflammatory response in murine peritoneal macrophages

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