title: Maturation and processing of the amyloid precursor protein is regulated by the potassium/sodium hyperpolarization-activated cyclic nucleotide-gated ion channel 2 (HCN2).
abstract: The toxic amyloid β-peptide (Aβ) is a key player in Alzheimer Disease (AD) pathogenesis and selective inhibition of the production of this peptide is sought for. Aβ is produced by the sequential cleavage of the Aβ precursor protein (APP) by β-secretase (to yield APP-C-terminal fragment β (APP-CTFβ) and soluble APPβ (sAPPβ)) and γ-secretase (to yield Aβ). We reasoned that proteins that associate with γ-secretase are likely to regulate Aβ production and to be targets of pharmaceutical interventions and therefore performed a pull-down assay to screen for such proteins in rat brain. Interestingly, one of the purified proteins was potassium/sodium hyperpolarization-activated cyclic nucleotide-gated ion channel 2 (HCN2), which has been shown to be involved in epilepsy. We found that silencing of HCN2 resulted in decreased secreted Aβ levels. To further investigate the mechanism behind this reduction, we also determined the levels of full-length APP, sAPP and APP-CTF species after silencing of HCN2. A marked reduction in sAPP and APP-CTF, as well as glycosylated APP levels was detected. Decreased Aβ, sAPP and APP-CTF levels were also detected after treatment with the HCN2 inhibitor ZD7288. These results indicate that the effect on Aβ levels after HCN2 silencing or inhibition is due to altered APP maturation or processing by β-secretase rather than a direct effect on γ-secretase. However, HCN2 and γ-secretase were found to be in close proximity, as evident by proximity ligation assay and immunoprecipitation. In summary, our results indicate that silencing or inhibition of HCN2 affects APP processing and thereby could serve as a potential treatment strategy.
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden. Electronic address: susanne.frykman@ki.se.
authors.forename: Susanne
authors.initials: S
authors.lastname: Frykman
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden; Sumitomo Dainippon Pharma Co., Ltd., Drug Research Division, Osaka, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Inoue
authors.affiliation: Sumitomo Dainippon Pharma Co., Ltd., Drug Research Division, Osaka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Ikeda
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden; Sumitomo Dainippon Pharma Co., Ltd., Drug Research Division, Osaka, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Teranishi
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden; Sumitomo Dainippon Pharma Co., Ltd., Drug Research Division, Osaka, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Kihara
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden.
authors.forename: Jolanta L
authors.initials: JL
authors.lastname: Lundgren
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden; Sumitomo Dainippon Pharma Co., Ltd., Drug Research Division, Osaka, Japan.
authors.forename: Natsuko G
authors.initials: NG
authors.lastname: Yamamoto
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden.
authors.forename: Nenad
authors.initials: N
authors.lastname: Bogdanovic
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden.
authors.forename: Bengt
authors.initials: B
authors.lastname: Winblad
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden.
authors.forename: Sophia
authors.initials: S
authors.lastname: Schedin-Weiss
authors.affiliation: Karolinska Institutet, Dept. of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Division of Neurogeriatrics, Novum, Blickagången 6, 141 57, Huddinge, Sweden.
authors.forename: Lars O
authors.initials: LO
authors.lastname: Tjernberg
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D004827:Epilepsy / Q000378:metabolism; D005260:Female; D020868:Gene Silencing; D006031:Glycosylation; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism*; D011743:Pyrimidines / Q000737:chemistry; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C545487:APP protein, human; D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C578710:HCN2 protein, human; C578711:Hcn2 protein, mouse; C578712:Hcn2 protein, rat; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015221:Potassium Channels; D011743:Pyrimidines; C082246:ICI D2788
keywords: Alzheimer disease; Amyloid beta-peptide; Amyloid precursor protein; Glycosylation; Potassium/sodium hyperpolarization-activated cyclic nucleotide-gated ion channel 2