Aβ reduction in BACE1 heterozygous null 5XFAD mice is associated with transgenic APP level

Molecular Neurodegeneration

Robert Vassar³  Sarah L Cole¹  William A Eimer²  Katherine R Sadleir³ 

[1] Takeda Cambridge, Neurodegeneration Group, Cambridge, UK;Department of Neurology, Massachusetts General Hospital, Charlestown, MA 02129, USA;Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60605, USA

关键词: Estrogen response element;    Dot blot;    Aβ;    Amyloid;    BACE1 heterozygous;    5XFAD;    APP transgenic mouse models;    Alzheimer’s disease;    Amyloid precursor protein;    β-secretase;   

Others  :  1138546
DOI  :  10.1186/1750-1326-10-1

 received in 2014-08-13, accepted in 2014-12-21,  发布年份 2015

【 摘 要 】

Background

The β-secretase, BACE1, cleaves APP to initiate generation of the β-amyloid peptide, Aβ, that comprises amyloid plaques in Alzheimer’s disease (AD). Reducing BACE1 activity is an attractive therapeutic approach to AD, but complete inhibition of BACE1 could have mechanism-based side-effects as BACE1^−/− mice show deficits in axon guidance, myelination, memory, and other neurological processes. Since BACE1^+/− mice appear normal there is interest in determining whether 50% reduction in BACE1 is potentially effective in preventing or treating AD. APP transgenic mice heterozygous for BACE1 have decreased Aβ but the extent of reduction varies greatly from study to study. Here we assess the effects of 50% BACE1 reduction on the widely used 5XFAD mouse model of AD.

Results

50% BACE1 reduction reduces Aβ42, plaques, and BACE1-cleaved APP fragments in female, but not in male, 5XFAD/BACE1^+/− mice. 5XFAD/BACE1^+/+ females have higher levels of Aβ42 and steady-state transgenic APP than males, likely caused by an estrogen response element in the transgene Thy-1 promoter. We hypothesize that higher transgenic APP level in female 5XFAD mice causes BACE1 to no longer be in excess over APP so that 50% BACE1 reduction has a significant Aβ42 lowering effect. In contrast, the lower APP level in 5XFAD males allows BACE1 to be in excess over APP even at 50% BACE1 reduction, preventing lowering of Aβ42 in 5XFAD/BACE1^+/− males. We also developed and validated a dot blot assay with an Aβ42-selective antibody as an accurate and cost-effective alternative to ELISA for measuring cerebral Aβ42 levels.

Conclusions

50% BACE1 reduction lowers Aβ42 in female 5XFAD mice only, potentially because BACE1 is not in excess over APP in 5XFAD females with higher transgene expression, while BACE1 is in excess over APP in 5XFAD males with lower transgene expression. Our results suggest that greater than 50% BACE1 inhibition might be necessary to significantly lower Aβ, given that BACE1 is likely to be in excess over APP in the human brain. Additionally, in experiments using the 5XFAD mouse model, or other Thy-1 promoter transgenic mice, equal numbers of male and female mice should be used, in order to avoid artifactual gender-related differences.

【 授权许可】

   
2015 Sadleir et al.; licensee BioMed Central.

【 图 表 】

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【 参考文献 】

• [1]Haass C, Kaether C, Thinakaran G, Sisodia S: Trafficking and proteolytic processing of APP. Cold Spring Harb Perspect Med 2012, 2(5):a006270.
• [2]Tanzi RE: The genetics of Alzheimer disease. Cold Spring Harb Perspect Med 2012, 2(10):a006296.
• [3]Cai H, Wang Y, McCarthy D, Wen H, Borchelt DR, Price DL, et al.: BACE1 is the major beta-secretase for generation of Abeta peptides by neurons. Nat Neurosci 2001, 4(3):233-234.
• [4]Luo Y, Bolon B, Damore MA, Fitzpatrick D, Liu H, Zhang J, et al.: BACE1 (beta-secretase) knockout mice do not acquire compensatory gene expression changes or develop neural lesions over time. Neurobiol Dis 2003, 14(1):81-88.
• [5]Luo Y, Bolon B, Kahn S, Bennett BD, Babu-Khan S, Denis P, et al.: Mice deficient in BACE1, the Alzheimer’s beta-secretase, have normal phenotype and abolished beta-amyloid generation. Nat Neurosci 2001, 4(3):231-232.
• [6]Ohno M, Cole SL, Yasvoina M, Zhao J, Citron M, Berry R, et al.: BACE1 gene deletion prevents neuron loss and memory deficits in 5XFAD APP/PS1 transgenic mice. Neurobiol Dis 2007, 26(1):134-145.
• [7]Ohno M, Sametsky EA, Younkin LH, Oakley H, Younkin SG, Citron M, et al.: BACE1 deficiency rescues memory deficits and cholinergic dysfunction in a mouse model of Alzheimer’s disease. Neuron 2004, 41(1):27-33.
• [8]Vassar R, Kuhn PH, Haass C, Kennedy ME, Rajendran L, Wong PC, et al.: Function, therapeutic potential and cell biology of BACE proteases: current status and future prospects. J Neurochem 2014, 130(1):4-28.
• [9]Yan R, Vassar R: Targeting the beta secretase BACE1 for Alzheimer’s disease therapy. Lancet Neurol 2014, 13(3):319-329.
• [10]Roberds SL, Anderson J, Basi G, Bienkowski MJ, Branstetter DG, Chen KS, et al.: BACE knockout mice are healthy despite lacking the primary beta-secretase activity in brain: implications for Alzheimer’s disease therapeutics. Hum Mol Genet 2001, 10(12):1317-1324.
• [11]Dominguez D, Tournoy J, Hartmann D, Huth T, Cryns K, Deforce S, et al.: Phenotypic and biochemical analyses of BACE1- and BACE2-deficient mice. J Biol Chem 2005, 280(35):30797-30806.
• [12]Hitt BD, Jaramillo TC, Chetkovich DM, Vassar R: BACE1−/− mice exhibit seizure activity that does not correlate with sodium channel level or axonal localization. Mol Neurodegener 2010, 5:31. BioMed Central Full Text
• [13]Hu X, Hicks CW, He W, Wong P, Macklin WB, Trapp BD, et al.: Bace1 modulates myelination in the central and peripheral nervous system. Nat Neurosci 2006, 9(12):1520-1525.
• [14]Laird FM, Cai H, Savonenko AV, Farah MH, He K, Melnikova T, et al.: BACE1, a major determinant of selective vulnerability of the brain to amyloid-beta amyloidogenesis, is essential for cognitive, emotional, and synaptic functions. J Neurosci Off J Soc Neurosci 2005, 25(50):11693-11709.
• [15]Rajapaksha TW, Eimer WA, Bozza TC, Vassar R: The Alzheimer’s beta-secretase enzyme BACE1 is required for accurate axon guidance of olfactory sensory neurons and normal glomerulus formation in the olfactory bulb. Mol Neurodegener 2011, 6:88. BioMed Central Full Text
• [16]Savonenko AV, Melnikova T, Laird FM, Stewart KA, Price DL, Wong PC: Alteration of BACE1-dependent NRG1/ErbB4 signaling and schizophrenia-like phenotypes in BACE1-null mice. Proc Natl Acad Sci U S A 2008, 105(14):5585-5590.
• [17]Willem M, Garratt AN, Novak B, Citron M, Kaufmann S, Rittger A, et al.: Control of peripheral nerve myelination by the beta-secretase BACE1. Science 2006, 314(5799):664-666.
• [18]Hitt B, Riordan SM, Kukreja L, Eimer WA, Rajapaksha TW, Vassar R: Beta-Site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1)-deficient mice exhibit a close homolog of L1 (CHL1) loss-of-function phenotype involving axon guidance defects. J Biol Chem 2012, 287(46):38408-38425.
• [19]Kuhn PH, Koroniak K, Hogl S, Colombo A, Zeitschel U, Willem M, et al.: Secretome protein enrichment identifies physiological BACE1 protease substrates in neurons. EMBO J 2012, 31(14):3157-3168.
• [20]Zhou L, Barao S, Laga M, Bockstael K, Borgers M, Gijsen H, et al.: The neural cell adhesion molecules L1 and CHL1 are cleaved by BACE1 protease in vivo. J Biol Chem 2012, 287(31):25927-25940.
• [21]Devi L, Ohno M: Genetic reductions of beta-site amyloid precursor protein-cleaving enzyme 1 and amyloid-beta ameliorate impairment of conditioned taste aversion memory in 5XFAD Alzheimer’s disease model mice. Eur J Neurosci 2010, 31(1):110-118.
• [22]Devi L, Ohno M: Phospho-eIF2alpha level is important for determining abilities of BACE1 reduction to rescue cholinergic neurodegeneration and memory defects in 5XFAD mice. PLoS One 2010, 5(9):e12974.
• [23]Kimura R, Devi L, Ohno M: Partial reduction of BACE1 improves synaptic plasticity, recent and remote memories in Alzheimer’s disease transgenic mice. J Neurochem 2010, 113(1):248-261.
• [24]McConlogue L, Buttini M, Anderson JP, Brigham EF, Chen KS, Freedman SB, et al.: Partial reduction of BACE1 has dramatic effects on Alzheimer plaque and synaptic pathology in APP Transgenic Mice. J Biol Chem 2007, 282(36):26326-26334.
• [25]Pastorino L, Ikin AF, Lamprianou S, Vacaresse N, Revelli JP, Platt K, et al.: BACE (beta-secretase) modulates the processing of APLP2 in vivo. Mol Cell Neurosci 2004, 25(4):642-649.
• [26]Rabe S, Reichwald J, Ammaturo D, de Strooper B, Saftig P, Neumann U, et al.: The Swedish APP mutation alters the effect of genetically reduced BACE1 expression on the APP processing. J Neurochem 2011, 119(1):231-239.
• [27]Oakley H, Cole SL, Logan S, Maus E, Shao P, Craft J, et al.: Intraneuronal beta-amyloid aggregates, neurodegeneration, and neuron loss in transgenic mice with five familial Alzheimer’s disease mutations: potential factors in amyloid plaque formation. J Neurosci Off J Soc Neurosci 2006, 26(40):10129-10140.
• [28]Zhao J, Fu Y, Yasvoina M, Shao P, Hitt B, O’Connor T, et al.: Beta-site amyloid precursor protein cleaving enzyme 1 levels become elevated in neurons around amyloid plaques: implications for Alzheimer’s disease pathogenesis. J Neurosci Off J Soc Neurosci 2007, 27(14):3639-3649.
• [29]Sadleir KR, Bennett DA, Schneider JA, Vassar R: Elevated Abeta42 in aged, non-demented individuals with cerebral atherosclerosis. Curr Alzheimer Res 2013, 10(8):785-789.
• [30]Kandalepas PC, Sadleir KR, Eimer WA, Zhao J, Nicholson DA, Vassar R: The Alzheimer’s beta-secretase BACE1 localizes to normal presynaptic terminals and to dystrophic presynaptic terminals surrounding amyloid plaques. Acta Neuropathol 2013, 126(3):329-352.
• [31]Moechars D, Lorent K, De Strooper B, Dewachter I, Van Leuven F: Expression in brain of amyloid precursor protein mutated in the alpha-secretase site causes disturbed behavior, neuronal degeneration and premature death in transgenic mice. EMBO J 1996, 15(6):1265-1274.
• [32]Ingraham HA, Evans GA: Characterization of two atypical promoters and alternate mRNA processing in the mouse Thy-1.2 glycoprotein gene. Mol Cell Biol 1986, 6(8):2923-2931.
• [33]Gruber CJ, Gruber DM, Gruber IM, Wieser F, Huber JC: Anatomy of the estrogen response element. Trends Endocrinol Metab: TEM 2004, 15(2):73-78.
• [34]Games D, Adams D, Alessandrini R, Barbour R, Berthelette P, Blackwell C, et al.: Alzheimer-type neuropathology in transgenic mice overexpressing V717F beta-amyloid precursor protein. Nature 1995, 373(6514):523-527.
• [35]Fukumoto H, Cheung BS, Hyman BT, Irizarry MC: Beta-secretase protein and activity are increased in the neocortex in Alzheimer disease. Arch Neurol 2002, 59(9):1381-1389.
• [36]Holsinger RMD, McLean CA, Beyreuther K, Masters CL, Evin G: Increased expression of the amyloid precursor beta-secretase in Alzheimer’s disease. Ann Neurol 2002, 51:783-786.
• [37]Citron M, Oltersdorf T, Haass C, McConlogue L, Hung AY, Seubert P, et al.: Mutation of the beta-amyloid precursor protein in familial Alzheimer's disease increases beta-protein production. Nature 1992, 360(6405):672-674.
• [38]Callahan MJ, Lipinski WJ, Bian F, Durham RA, Pack A, Walker LC: Augmented senile plaque load in aged female beta-amyloid precursor protein-transgenic mice. Am J Pathol 2001, 158(3):1173-1177.
• [39]Hirata-Fukae C, Li HF, Hoe HS, Gray AJ, Minami SS, Hamada K, et al.: Females exhibit more extensive amyloid, but not tau, pathology in an Alzheimer transgenic model. Brain Res 2008, 1216:92-103.
• [40]Sierksma AS, Prickaerts J, Chouliaras L, Rostamian S, Delbroek L, Rutten BP, et al.: Behavioral and neurobiological effects of prenatal stress exposure in male and female APPswe/PS1dE9 mice. Neurobiol Aging 2013, 34(1):319-337.
• [41]Overk CR, Lu PY, Wang YT, Choi J, Shaw JW, Thatcher GR, et al.: Effects of aromatase inhibition versus gonadectomy on hippocampal complex amyloid pathology in triple transgenic mice. Neurobiol Dis 2012, 45(1):479-487.
• [42]Hy LX, Keller DM: Prevalence of AD among whites: a summary by levels of severity. Neurology 2000, 55(2):198-204.