M1 muscarinic receptor activation protects neurons from B-amyloid toxicity. A role for Wnt signaling pathway Ginny G. Farı ´as, a Juan A. Godoy, a Fe ´lix Herna ´ndez, b Jesu ´s Avila, b Abraham Fisher, c and Nibaldo C. Inestrosa a, * a Centro FONDAP de Regulacio ´n Celular y Patologı ´a bJoaquin V. LucoQ, MIFAB, Facultad de Ciencias Biolo ´ gicas, Pontificia Universidad Cato ´lica de Chile, Santiago Chile b Centro de Biologı ´a Molecular bSevero OchoaQ, CSIC/Universidad Auto ´noma de Madrid, Cantoblanco, 28049 Madrid, Spain c Department of Medicinal and Organic Chemistry, Israel Institute of Biological Research (IIBR), Ness Ziona 74100, Israel Received 15 March 2004; revised 4 June 2004; accepted 9 July 2004 Amyloid-h-peptide (Ah) deposits are one of the hallmark features of Alzheimer’s disease. Signal transduction alterations are implicate in the neuronal responses to Ah, which include neurotransmitter systems and pathways involved in the maintenance of the nervous system. In this context, we have recently found that Ah-neurotoxicity triggers a loss of Wnt signaling. We report here that M1-acetylcholine-muscarinic- receptor (mAChR) activation protects neurons from Ah-toxicity. Concomitant with this effect, a modulation of the Wnt signaling was observed. M1 mAChR activation inhibits glycogen-synthase-kinase-3h (GSK-3h) activity, stabilizes cytoplasmic and nuclear h-catenin, and induces the expression of the Wnt target genes engrailed and cyclin-D1, reverting the switch off of the Wnt pathway caused by Ah-toxicity. Neurons from mice that overexpress GSK-3h allow us to establish that M1 mAChR stimulation leads to GSK-3h inactivation. We conclude that the cross-talk between the muscarinic signaling and Wnt components underlie the neuroprotective effect of the M1 mAChR activation. D 2004 Elsevier Inc. All rights reserved. Keywords: M1 mAChR; Ah neurotoxicity; GSK-3h transgenic mice; Wnt Signaling; Alzheimer’s disease Introduction Alzheimer’s disease (AD) is the most common neurodegener- ative disease that involves a gradual and progressive memory loss and dementia (Selkoe, 2001). Neuropathologically, the disease is characterized by the presence of extracellular deposits of amyloid h-peptide (Ah) as fibril aggregates that form senile plaques, intracellular neurofibrillary tangles, and degeneration of presynap- tic cholinergic neurons that ascend from the basal forebrain to cortical and hippocampal areas (Coyle et al., 1983; Palmer, 2002). The M1 acetylcholine muscarinic receptor (mAChR) is expressed in the cerebral cortex and hippocampus and its major role is in cognitive processing including short-term memory (Anagnostaras et al., 2003; Levey, 1996); however, muscarinic agonists were not effective in AD treatment, inter alia, due to the lack of selectivity for the M1 mAChR, narrow safety margin, very low bioavailability and poor tolerability (Eglen et al., 2001; Fisher, 2000). M1 mAChR activation modulates learning and memory (Anagnostaras et al., 2003; Lin et al., 1999); protects cells from apoptotic effects induced by H 2 O 2 including DNA damage, oxidative stress, and mitochondrial impairment in cortical neurons (De Sarno et al., 2003). M1 agonists also block caspase activation in neurons deprived of serum (Leloup et al., 2000); increase the non- amyloidogenic processing of the amyloid precursor protein (APP), reducing the Ah-peptide production (Buxbaum et al., 1992; Haring et al., 1998; Nitsch et al., 1992); reduce H phosphorylation (Genis et al., 1999; Sadot et al., 1996); increase inhibitory postsynaptic currents (Gu et al., 2003; Ma et al., 2003). However, the mechanism by which mAChR activation protects neurons from insults is not well understood. It has been reported that treatment of primary cortical and hippocampal neuronal cultures with Ah increases glycogen- synthase-kinase-3h (GSK-3h) activity inducing apoptosis (Taka- shima et al., 1996), which is inhibited by GSK-3h antisense oligonucleotides and treatments with lithium (Alvarez et al., 1999; Takashima et al., 1993). GSK-3h participates in several signaling pathways including the Wnt pathway that regulates h-catenin sta- bility. When h-catenin accumulates and is stabilized in the cytoplasm, it is translocated into the nucleus where it interacts with the Tcf/LEF transcription factors, inducing the expression of Wnt target genes important in neural development and main- tenance (Patapoutian and Reichardt, 2000). It has been reported that a loss of signaling through the h-catenin-Tcf pathway in- 0969-9961/$ - see front matter D 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.nbd.2004.07.016 * Corresponding author. Centro FONDAP de Regulacio ´n Celular y Patologı ´a bJoaquin V. LucoQ, MIFAB, Facultad de Ciencias Biolo ´ gicas, Pontificia Universidad Cato ´lica de Chile, PO Box 114-D, Santiago Chile. Fax: +56 2 6862959. E-mail address: ninestr@genes.bio.puc.cl (N.C. Inestrosa). Available online on ScienceDirect (www.sciencedirect.com.) www.elsevier.com/locate/ynbdi Neurobiology of Disease 17 (2004) 337 – 348