Altered glycosylation of acetylcholinesterase in APP (SW) Tg2576 transgenic mice occurs prior to amyloid plaque deposition Lisa R. Fodero,* Javier Sa ´ez-Valero, Catriona A. McLean,* Ralph N. Martins,à Konrad Beyreuther,§ Colin L. Masters,* Terry A. Robertson¶ and David H. Small* *Laboratory of Molecular Neurobiology, Department of Pathology, The University of Melbourne, Melbourne, Australia  Instituto de Neurociencias, Universidad Miguel Herna ´ndez-CSIC, San Juan de Alicante, Spain àUniversity Department of Surgery, Hollywood Private Hospital, University of Western Australia, Perth, Australia §Centre of Molecular Biology (ZMBH), University of Heidelberg, Heidelberg, Germany ¶Department of Pathology, University of Western Australia, Perth, Australia Abstract Previous studies have shown that a minor glycoform of ace- tylcholinesterase (AChE) is increased in Alzheimer’s disease brain and cerebrospinal fluid. This glycoform can be distin- guished from other AChE species by its lack of binding to concanavalin A (Con A). In this study, the temporal relation- ship between AChE glycosylation and Ab deposition was examined in Tg2576 mice. There was a significant (p < 0.05) difference in AChE glycosylation in Tg2576 mice compared with age-matched background strain control mice at 4 months of age. This difference in glycosylation was also observed in 8- and 12-month-old Tg2576 mice. In contrast, Ab plaques were only seen in the Tg2576 mice at 12 months of age, and were not detected at 4 and 8 months of age. Soluble human- sequence Ab was detected as early as 4 months of age in the transgenic mice. The altered AChE glycosylation was due to an increase in a minor AChE isoform, which did not bind Con A, similar to that previously observed to be increased in Alzheimer’s disease brain and cerebrospinal fluid. The results demonstrate that in transgenic mice altered AChE glycosyla- tion is associated with very early events in the development of AD-like pathology. The study supports the possibility that glycosylation may also be a useful biomarker of AD. Keywords: AChE, amyloid, glycosylation, Tg2576. J. Neurochem. (2002) 81, 441–448. Alzheimer’s disease (AD) is one of the most common forms of dementia among the elderly. As clinical diagnosis is problematic, biochemical markers of AD are potentially of great value, especially if they detect cases of AD early in the course of the disease. Several promising candidates have been identified in cerebrospinal fluid (CSF). Several studies have shown that the levels of tau (Arai et al. 1995; Galasko et al. 1998;Trojanowski et al. 1999)andAb (Nakamura et al. 1994; Motter et al. 1995; Galasko et al. 1998; Kanai et al. 1998) are altered in AD CSF. However, these biomarkers are not of sufficient sensitivity or specificity for routine clinical diagnosis. Therefore, other CSF biomarkers may be needed. Many studies have examined the possibility that acetyl- cholinesterase (AChE) may be a useful diagnostic marker of AD (see review by Small et al. 1996). Indeed, the levels of cholinesterases are altered in the AD brain (Friede 1965; Mesulam and Moran 1987; Small et al. 1996). AChE exists in multiple isoforms that can be distinguished by their different molecular weights and hydrodynamic properties (Massoulie ´ and Bon 1982). Our previous studies have shown that a minor glycoform ofAChE,whichdoesnotbindtoconcanavalinA(ConA),is increased in AD brain and CSF (Sa ´ez-Valero et al. 1997). This minor glycoform has been proposed as a diagnostic marker for AD (Sa ´ez-Valero et al. 1997; Sa ´ez-Valero et al. Received November 11, 2001; revised manuscript received December 13, 2001; accepted December 14, 2001. Address correspondence and reprint requests to Dr David H. Small, Department of Pathology, The University of Melbourne, Parkville, Victoria 3010, Australia. E-mail: davidhs@unimelb.edu.au. Abbreviations used: AChE, acetylcholinesterase; AD, Alzheimer’s disease; AP, ammonium persulfate; CSF, cerebrospinal fluid; Con, A, concanavalin A; DAB, diaminobenzidine; ECL, enhanced chemilumi- nescence;GFAP,glialfibrillaryacidicprotein;Ig,immunoglobulin;PBS, phosphate-buffered saline; SDS–PAGE, sodium dodecyl sulfate–poly- acrylamide gel electrophoresis; WGA, wheat-germ agglutinin. Journal of Neurochemistry , 2002, 81, 441–448 Ó 2002 International Society for Neurochemistry, Journal of Neurochemistry , 81, 441–448 441