The Intracellular Domain of Amyloid Precursor Protein is a Potential Therapeutic Target in Alzheimer's Disease.

Amyloid-β (Aβ) is widely believed to cause Alzheimer's disease (AD), as it is the major constituent of the amyloid plaques observed in the brains of people with AD (the so-called amyloid hypothesis). Based on this hypothesis, therapies utilizing immune responses against Aβ have been performed and have succeeded in effectively removing amyloid plaques, but have shown no evidence of improvements in survival and/or cognitive function. Thus, it may be necessary to think about this problem from a different viewpoint.

γ-Secretase-regulated signaling typified by Notch signaling in the immune system.

Notch signaling mediates the fates of numerous cells not only in the nervous system but also in the immune system. Notch signaling contributes to the generation and maintenance of hematopoietic stem cells, lymphocyte development, and several immune responses. The molecular mechanism of Notch signaling is unique: ligands bind to the extracellular domain of Notch and trigger sequential proteolytic cleavages.

γ-Secretase-regulated mechanisms similar to notch signaling may play a role in signaling events, including APP signaling, which leads to Alzheimer's disease.

Although γ-secretase was first identified as a protease that cleaves amyloid precursor protein (APP) within the transmembrane domain, thus producing Aβ peptides that are thought to be pathogenic in Alzheimer's disease (AD), its physiological functions have not been fully elucidated. In the canonical Notch signaling pathway, intramembrane cleavage by γ-secretase serves to release an intracellular domain of Notch that shows activity in the nucleus through binding to transcription factors. Many type 1 transmembrane proteins, including Notch, Delta, and APP, have recently been shown to be substrates for γ-secretase, and their intracellular domains are released from the cell membrane following cleavage by γ-secretase.

γ-Secretase-regulated signaling pathways, such as notch signaling, mediate the differentiation of hematopoietic stem cells, development of the immune system, and peripheral immune responses.

Notch signaling mediates the fates of numerous cells in both invertebrates and vertebrates. In the immune system, Notch signalling contributes to the generation of hematopoietic stem cells (HSCs), the promotion of HSC self-renewal, T lineage commitment, intrathymic T cell development, and peripheral lymphocyte differentiation/activation. The intracellular domain (ICD) of Notch is released from the cell membrane by γ-secretase and translocates to the nucleus to modulate gene expression.

The amyloid precursor protein intracellular domain alters gene expression and induces neuron-specific apoptosis.

Although amyloid precursor protein (APP) plays a central role in Alzheimer's disease, the physiological functions of this protein have yet to be fully elucidated. As previously reported, we established an embryonic carcinoma P19 cell line expressing the intracellular domain of APP (AICD). While neurons were differentiated from these cell lines with retinoic acid treatment, expression of AICD induced neuron-specific apoptosis.

Similar mechanisms regulated by gamma-secretase are involved in both directions of the bi-directional Notch-Delta signaling pathway as well as play a potential role in signaling events involving type 1 transmembrane proteins.

In the canonical Notch signaling pathway, intramembrane cleavage by gamma-secretase serves to release an intracellular domain of Notch that has activity in the nucleus through binding to transcription factors. In addition, we showed that Notch also supplies signals to Delta, a major Notch ligand, to release the intracellular domain of Delta by gamma-secretase from the cell membrane, which then translocates to the nucleus, where it mediates the transcription of specific genes. Therefore, the Notch-Delta signaling pathway is bi-directional and similar mechanisms regulated by gamma-secretase are involved in both directions.

The intracellular domain of amyloid precursor protein induces neuron-specific apoptosis.

Although amyloid precursor protein (APP) has central roles in Alzheimer's disease, the physiological functions of this protein have yet to be fully elucidated. APP homologues show significant sequence conservation in the intracellular domain through evolution, which may reflect the functional importance of the intracellular domain of APP (AICD). To examine this possibility, we established embryonic carcinoma P19 cell lines overexpressing AICD.

The Delta intracellular domain mediates TGF-beta/Activin signaling through binding to Smads and has an important bi-directional function in the Notch-Delta signaling pathway.

Delta is a major transmembrane ligand for Notch receptor that mediates numerous cell fate decisions. The Notch signaling pathway has long been thought to be mono-directional, because ligands for Notch were generally believed to be unable to transmit signals into the cells expressing them. However, we showed here that Notch also supplies signals to neighboring mouse neural stem cells (NSCs).

Interaction of LDL receptor-related protein 4 (LRP4) with postsynaptic scaffold proteins via its C-terminal PDZ domain-binding motif, and its regulation by Ca/calmodulin-dependent protein kinase II.

We cloned here a full-length cDNA of Dem26[Tian et al. (1999)Mol. Brain Res.

Multiple POU-binding motifs, recognized by tissue-specific nuclear factors, are important for Dll1 gene expression in neural stem cells.

We cloned the 5'-flanking region of the mouse homolog of the Delta gene (Dll1) and demonstrated that the sequence between nucleotide position -514 and -484 in the 5'-flanking region of Dll1 played a critical role in the regulation of its tissue-specific expression in neural stem cells (NSCs). Further, we showed that multiple POU-binding motifs, located within this short sequence of 30bp, were essential for transcriptional activation of Dll1 and also that multiple tissue-specific nuclear factors recognized these POU-binding motifs in various combinations through differentiation of NSCs. Thus, POU-binding factors may play an important role in Dll1 expression in developing NSCs.

Estrogen-induced proliferation of normal endometrial glandular cells is initiated by transcriptional activation of cyclin D1 via binding of c-Jun to an AP-1 sequence.

To explore the mechanism of estrogen-induced growth of normal endometrium, the transactivation system of the cyclin D1 gene was analysed using cultured normal endometrial glandular cells. Estradiol (E2) treatment of cultured normal endometrial glandular cells induced upregulation of c-Jun, and then cyclin D1 proteins, followed by serial expressions of cyclins E, A and B1 proteins. Increase in the mRNA expression of cyclin D1 preceded the protein expression of cyclin D1 under E2 treatment.

Receptor gene expression of glucagon-like peptide-1, but not glucose-dependent insulinotropic polypeptide, in rat nodose ganglion cells.

We previously reported that afferent signals of the rat hepatic vagus increased upon intraportal appearance of insulinotropic hormone glucagon-like peptide-1(7-36) amide (GLP-1), but not glucose-dependent insulinotropic polypeptide (GIP). To obtain molecular evidence for the vagal chemoreception of GLP-1, the concept derived from those electrophysiological observations, receptor gene expressions of GLP-1 and GIP in the rat nodose ganglion were examined by means of reverse transcriptase-mediated polymerase chain reaction (RT-PCR) and Northern blot analysis. Gene expression of the GLP-1 receptor was clearly detected by both RT-PCR and Northern blot analysis.

A novel ubiquitin-specific protease, synUSP, is localized at the post-synaptic density and post-synaptic lipid raft.

Recent reports suggest an important role for protein ubiquitination in synaptic plasticity. We cloned, from the rat brain, a novel gene that encoded an ubiquitin-specific protease (USP), and termed this protein synaptic ubiquitin-specific protease (synUSP, GenBankTM Accession no. AB073880).

Mechanism for the action of bone morphogenetic proteins and regulation of their activity.

Although the bone morphogenetic proteins (BMPs) are multifunctional proteins, implantation of osteogenic BMPs such as BMP-2 and BMP-7 at an osseous or extraosseous site results in bone and cartilage formation. These molecules are soluble, local-acting signaling proteins, which bind to specific receptors on the surface of the cell. The receptors then transduce the signal via a group of proteins called Smads, which in turn activate particular genes.

HLA DRB10405-DQB10401 haplotype is associated with autoimmune pancreatitis in the Japanese population.

Background & Aims: Autoimmune pancreatitis is a distinctive disease entity characterized by high serum immunoglobulin G4 concentrations. Because of the close association between some autoimmune diseases and particular alleles of major histocompatibility complex genes, we investigated the association between HLA alleles and autoimmune pancreatitis.

Methods: HLA-A, -B, -C, -DR, and -DQ gene typing and HLA-DRB1, -DQB1, and -DPB1 allele typing were performed by the polymerase chain reaction sequence-specific primers method and the restriction fragment length polymorphism method, respectively, in 40 patients with autoimmune pancreatitis, 43 patients with chronic calcifying pancreatitis, and 201 healthy subjects.

Inhibitory effects of pyrrolidine dithiocarbamate on endotoxin-induced uveitis in Lewis rats.

Purpose: To determine the effect of pyrrolidine dithiocarbamate (PDTC), an antioxidant nuclear factor (NF)-kappaB inhibitor, on the ocular inflammation induced by lipopolysaccharide (LPS).

Methods: Endotoxin-induced uveitis (EIU) was produced by a footpad injection of 200 microg LPS in male Lewis rats. PDTC (200 mg/kg) was injected intraperitoneally 30 minutes before the LPS administration.

Growth inhibition and differentiation of pancreatic cancer cell lines by PPAR gamma ligand troglitazone.

Introduction: Ligand activation of peroxisome proliferator-activated receptor gamma (PPAR gamma) results in growth inhibition and differentiation of various cancer cells.

Aims: We determined whether the PPAR gamma ligand, troglitazone, inhibits the growth of pancreatic cancer cells and clarified the underlying mechanisms with a special focus on restriction point control of the late G1 phase of the cell cycle.

Methodology: Nine pancreatic cancer cell lines were used to study a variety of troglitazone effects on cell growth by MTT assay, on cell cycle by flow cytometry, on cell cycle regulating factors of late G1 phase by Western and Northern blotting and CDK2 kinase assay, and on morphology by collagen gel culture and electron-microscopy.