humanin and pyrazolanthrone

Amyloid precursor protein (APP), the precursor of Abeta, has been shown to function as a cell surface receptor that mediates neuronal cell death by anti-APP antibody. The c-Jun N-terminal kinase (JNK) can mediate various neurotoxic signals, including Abeta neurotoxicity. However, the relationship of APP-mediated neurotoxicity to JNK is not clear, partly because APP cytotoxicity is Abeta independent. Here we examined whether JNK is involved in APP-mediated neuronal cell death and found that: (i) neuronal cell death by antibody-bound APP was inhibited by dominant-negative JNK, JIP-1b and SP600125, the specific inhibitor of JNK, but not by SB203580 or PD98059; (ii) constitutively active (ca) JNK caused neuronal cell death and (iii) the pharmacological profile of caJNK-mediated cell death closely coincided with that of APP-mediated cell death. Pertussis toxin (PTX) suppressed APP-mediated cell death but not caJNK-induced cell death, which was suppressed by Humanin, a newly identified neuroprotective factor which inhibits APP-mediated cytotoxicity. In the presence of PTX, the PTX-resistant mutant of Galphao, but not that of Galphai, recovered the cytotoxic action of APP. These findings demonstrate that JNK is involved in APP-mediated neuronal cell death as a downstream signal transducer of Go.

Topics: Adaptor Proteins, Signal Transducing; Amyloid beta-Protein Precursor; Animals; Anthracenes; Antibodies; Carrier Proteins; Cell Death; Cells, Cultured; Enzyme Inhibitors; Genes, Dominant; GTP-Binding Protein alpha Subunits, Gi-Go; Heterotrimeric GTP-Binding Proteins; Hybrid Cells; Intracellular Signaling Peptides and Proteins; JNK Mitogen-Activated Protein Kinases; Mice; Mitogen-Activated Protein Kinases; Neurons; Neuroprotective Agents; Pertussis Toxin; Proteins

The biological function of full-length amyloid-beta protein precursor (AbetaPP), the precursor of Abeta, is not fully understood. Multiple laboratories have reported that antibody binding to cell surface AbetaPP causes neuronal cell death. Here we examined whether induced dimerization of the cytoplasmic domain of AbetaPP (AbetaPPCD) triggers neuronal cell death. In neurohybrid cells expressing fusion constructs of the epidermal growth factor (EGF) receptor with AbetaPPCD (EGFR/AbetaPP hybrids), EGF drastically enhanced neuronal cell death in a manner sensitive to acetyl-l-aspartyl-l-glutamyl-l-valyl-l-aspartyl-aldehyde (Ac-DEVD-CHO; DEVD), GSH-ethyl ester (GEE), and pertussis toxin (PTX). Dominant-negative apoptosis signal-regulating kinase 1 (ASK1) blocked this neuronal cell death, but not alpha-synuclein-induced cell death. Constitutively active ASK1 (caASK1) caused DEVD/GEE-sensitive cell death in a manner resistant to PTX and sensitive to Humanin, which also suppressed neuronal cell death by EGFR/AbetaPP hybrid. ASK1 formed a complex with AbetaPPCD via JIP-1b, the c-Jun N-terminal kinase (JNK)-interacting protein. EGFR/AbetaPP hybrid-induced and caASK1-induced neuronal cell deaths were specifically blocked by SP600125 (anthra[1,9-cd]pyrazol-6(2H)-one), a specific JNK inhibitor. Combined with our earlier study, these data indicate that dimerization of AbetaPPCD triggers ASK1/JNK-mediated neuronal cell death. We also noticed a potential role of ASK1/JNK in sustaining the activity of this mechanism after initial activation by AbetaPP, which allows for the achievement of cell death by short-term anti-AbetaPP antibody treatment. Understanding the function of AbetaPPCD and its downstream pathway should lead to effective anti-Alzheimer's disease therapeutics.

Topics: Adaptor Proteins, Signal Transducing; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Anthracenes; Carrier Proteins; Dimerization; Epidermal Growth Factor; ErbB Receptors; Flavonoids; Humans; Hybrid Cells; Imidazoles; Intracellular Signaling Peptides and Proteins; JNK Mitogen-Activated Protein Kinases; MAP Kinase Kinase Kinase 5; MAP Kinase Kinase Kinases; Mice; Mitogen-Activated Protein Kinases; Neurons; Oligopeptides; p38 Mitogen-Activated Protein Kinases; Protein Structure, Tertiary; Proteins; Pyridines; Rats; Signal Transduction