Regulation of gene expression by muscarinic ...

Biochemical Society Transactions (2000) Volume 28, part I F13

Regulation of gene expression by muscarinic acetylcholine receptors C. Albrccht, M.Mayhaus, B. Hoffmann, C. Dcmiralay, H.von dcr lCImmcr Center for Molecular Ncurobrology, Untversity of Hamburg. Germany and Dept. of Psychiatry Research, Untversiry of Zurich, August Fore1 Strasse I , 8008 Zunch, Switzerland

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Muscarhic acetylcholine receptors (mAChRs) are involved in synaptic plasticity. In a screen designed to identify genes involved in mAChR signaling. w e found I 1 genes that were readily activated by mAChR These included the transcription factors Egr-I. Egr-2, Egr-3, c-jun, jun-D, and GOS3, the growth regulator hCyr61, the signaling factors NGFi-B, ETRIOl, and Gig-2 as well as the acetylcholine cstcrasc gene (AChE). hCyr61 encodes a secretory protein with groarrh-promoting functions mediated by interactions with inregrins and heparin-containing components of the extracellular matrix. Gig-2 is a novel gene with similarities to serine-threonine kinases, and with potential targeting to the secretory pathway. Both mAChR over-expressing 293 lines and primary cortical neurons responded to receptor stimulation with increased expression of both genes within 15 minutes, attained a maximum after 1 hour with sustained high expression for 4 hours. Receptor stimulation also triggered gene expression in the presence of cycloheximide, indicating that hCyr61 and gig-2 arc immediate urly genes. I n vivo experiments with pilocarpine strongly induced gig-2 expression in neurons of several layers of the brain cortex, the hippoumpal CAI region, and the puumcn. Increased expression of both hCyr61 and gig-2 was coupled to mAChRs by PKC. whereas CAMPfailed to affect expression. We also observed that mAChR rudily increased both Egr-l transcription and nuclear concentrations of Egr-l protein; with subsequent strong activation of transcription from the human AChE promoter, and expression of the AChE gene.

Our data show that multiple immediate-urly genes arc under the control of mAChRs, and they suggest that both hCyr61 and gig-2 play important roles in coupling receptor stimulation to long-term neuronal responses. The results also suggest a feedback mechanism by which increases in cholinergic transmission are limited by upregulated AChE expression, and accelerated breakdown of ACh at the cholincrgic synapses.

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ALTERED NEURONAL SIGNALING ASSOCIATED WITH APP A N D PRESENILIN MUTATIONS PROMOTES APOPTOSIS A N D EXClTOTOXICiTY. Mark I? Mattson Sanders-Brown Research Crnter on Agmg, Uniwnsity of Kentucky, Lexington, K Y 40136 USA.

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Oxidative signalling and inflammatory pathways in Alzheimer’s disease -‘, C. Adinolfi+, I. Anderson”, S. Doctrow+, K. Huffman+, K.Joy‘, P. Soden‘, B. Malfroy+, H.T.Rupniak,. ‘GlaxoWellcome Medicines Research Centre. Gunnel3 Wood Road, Stevenage, H e m , UK, SGI 2NY; +Eukarion Inc., 6F Alfred Circle, Bedford, MA 01730; “Cambridge Antibody Technology, The Science Park, Melbourn, Cambs, UK, SG8 6JJ Evidence that aberrations in oxidative signalling and glial inflammatory pathways are features of the pathology of Alzheimer’s disease (AD) remains undisputed. Data generated over the past 15 yCars have consistently reported the presence of a variety of inflammatory proteins in the brain of A D patients taken post-mortem (see McGccr & McGecr, 1995). There is also considerable evidence for damage caused by free radicals that arc produced by alterations in the homeostatic mechanisms controlling oxygen utilisation (see Smith et al, 1999). However. one of the key hurdles for research continues to be able to address whether oxidative stress andlor inflammation are early aetiological factors that contribute to the devclopment of the progressive pathology of the disease and thus provide specific targets for drug intervention. This talk will describe the utility of pharmacological tools to probe mechanisms of oxidative stress and inflammation, both in vitro and in vivo. The data to be presented support the premise that specific mediators of inflammation and oxidative stress are involved in the processes leading to neurodcgeneration and that their involvement is early enough to make them attractive molecular targets for therapeutic intervention McGeer and McGeer (1995) Brain Res. Rev. 21, 195-281 Smith et aL(1999) Drug Dev. Rcs. 46,26-33.

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Receptor - G-protein signalling in Alzheimer’s disease R.F. Cowburn, C. O’Neill, W.L. Bonkale, T. G. O h m , J Fastbom. Karolinska Instituter, NEUROTEC, Section for Geriatric Medione, N O V U M . KFC, S-141 86, Huddinge. Sweden., Dcpartmrnt of Biochemistry, Universrty College, Lee Maltings, Cork, Ireland.. Institute fur Anatomie, Univ. Klinikum Charite. 0-100098 Berlin, Germany Based on radioligand binding studies, it has long been assumed that the ncurochemical pathology of Alzheimer’s disease (AD) does not involve widespread changes in post-synaptic receptor function. However, more recent studies suggest that receptor function in A D may be compromised due to disrupted post-receptor signal transduction, in particular that mediated by the G-protein regulated phosphoinositide (PI) hydrolysis and adenylyl cyclase (AC) pathways. The PI hydrolysis pathway has been shown to be altered at a number of levels in A D post-mortem brain, including impaired agonist and G-protein regulation of phospholipasc C, decreased PKC levels and activity, and a reduced number of receptor sites for the second messenger, inositol 1.4.5-trisphosphate (lns(I,4,5)P3). Of these, loss of Ins(1,4,5)P3 receptors and PKC in the entorhinal cortex and hippocampus correlates with AD-related neurofibrillary changes, as staged according to Braak’s protocol. Disregulation of the PI hydrolysis pathway may therefore have consequences for the progression of A D pathology. In contrast to the extensive pattern of disruption seen with the PI hydrolysis pathway, changes to A C signalling in A D appear more circumscribed. Disruptions include a lesion at the level of Gs-protein stimulation of A C and, at least in the hippocampus, reduced enzyme activities in response to forskolin stimulation. Of these, the later change has been shown to precede A D neurofibrillary changes. Apart from a loss of calcium I calmodulin sensitive A C isoforms, other components of this signalling pathway, including G-protein levels, Gi-protein mediated inhibition and PKA levels and activity remain relatively preserved in the disorder.

0 2000 Biochemical Society