Hiroshi Hasegawa

Human CRB2 Inhibits γ-Secretase Cleavage of Amyloid Precursor Protein by Binding to the Presenilin Complex

Drosophila Crumbs has been reported to attenuate Notch signaling by inhibition of γ-secretase cleavage at the wing margins. γ-Secretase is an intramembrane protease that is responsible for the generation of amyloid-β (Aβ) peptides from the β-amyloid precursor protein (APP). Here, we re-examined γ-secretase inhibition by human CRB2, which is the most abundant Crumbs ortholog in the brain. Transfected CRB2 inhibited proteolytic production of Aβ and APP intracellular domains from APP C-terminal fragments in HEK293 and SH-SY5Y cells. Conversely, knockdown of endogenous CRB2 increased γ-secretase cleavage products in SH-SY5Y cells. CRB2 inhibition of γ-cleavage was also detected in cell-free assays. CRB2 interacted with the γ-secretase complex, but was not a competitive substrate for γ-cleavage. The transmembrane domain of CRB2 was indispensable for inhibition of Aβ generation and mediated CRB2 binding with the γ-secretase complex. In addition, the cytoplasmic domain appeared to play a supportive role in γ-secretase inhibition, whereas mutational disruption of the two protein-binding motifs involved in the formation of cell adhesion complexes did not affect γ-secretase inhibition. Co-overexpression of presenilin-1 or APH-1 abrogated γ-secretase inhibition probably through prevention of the incorporation of CRB2 into the γ-secretase complex. Our results suggest that CRB2 functions as an inhibitory binding protein that is involved in the formation of a mature but inactive pool of the γ-secretase complex.

Dilysine retrieval signal-containing p24 proteins collaborate in inhibiting γ-cleavage of amyloid precursor protein

J. Neurochem. (2010) 115, 771–781.

Destruxin E Decreases Beta-Amyloid Generation by Reducing Colocalization of Beta-Amyloid-Cleaving Enzyme 1 and Beta-Amyloid Protein Precursor

Alzheimer-disease-associated β-amyloid (Aβ) is produced by sequential endoproteolysis of β-amyloid protein precursor (βAPP): the extracellular portion is shed by cleavage in the juxtamembrane region by β-amyloid-cleaving enzyme (BACE)/β-secretase, after which it is cleaved by presenilin (PS)/γ-secretase near the middle of the transmembrane domain. Thus, inhibition of either of the secretases reduces Aβ generation and is a fundamental strategy for the development of drugs to prevent Alzheimer disease. However, it is not clear how small compounds reduce Aβ production without inhibition of the secretases. Such compounds are expected to avoid some of the side effects of secretase inhibitors. Here, we report that destruxin E (Dx-E), a natural cyclic hexadepsipeptide, reduces Aβ generation without affecting BACE or PS/γ-secretase activity. In agreement with this, Dx-E did not inhibit Notch signaling. We found that Dx-E decreases colocalization of BACE1 and βAPP, which reduces β-cleavage of βAPP. Therefore, the data demonstrate that Dx-E represents a novel Aβ-reducing process which could have fewer side effects than secretase inhibitors.

Letter: a potassium-competitive acid blocker vs a proton pump inhibitor for healing endoscopic submucosal dissection-induced artificial ulcers after treatment of gastric neoplasms

1. Hyun MH, Lee YS, Kim JH, et al. Systematic review with meta-analysis: the efficacy and safety of tenofovir to prevent mother-to-child transmission of hepatitis B virus. Aliment Pharmacol Ther. 2017;45:1493-1505. 2. Zanng C-Y, Ahri B-K, Wu G-B, Zhong J-H, Li L-Q. Letter: role of tenofovir to prevent mother-to-child transmission of hepatitis B virus. Aliment Pharmacol Ther. 2017;46:562-563. 3. Sun W, Zhao S, Ma L, et al. Telbivudine treatment started in early and middle pregnancy completely blocks HBV vertical transmission. BMC Gastroenterol. 2017;17:51. 4. Marcellin P, Heathcote EJ, Buti M, et al. Tenofovir disoproxil fumarate versus adefovir dipivoxil for chronic hepatitis B. N Engl J Med. 2008;359:2442-2455. 5. Zou H, Chen Y, Duan Z, Zhang H, Pan C. Virologic factors associated with failure to passive-active immunoprophylaxis in infants born to HBsAg-positive mothers. J Viral Hepat. 2012;19:e18-e25. 6. Wen WH, Chang MH, Zhao LL, et al. Mother-to-infant transmission of hepatitis B virus infection: significance of maternal viral load and strategies for intervention. J Hepatol. 2013;59:24-30. 7. European Association for the Study of the Liver. EASL 2017 Clinical Practice Guidelines on the management of hepatitis B virus infection. J Hepatol 2017; https://doi.org/10.1016/j.jhep.2017.03.021 8. Korean Association for the Study of the L. KASL clinical practice guidelines: management of chronic hepatitis B. Clin Mol Hepatol 2016;22:18-75. 9. Chang MH, You SL, Chen CJ, et al. Long-term effects of hepatitis B immunization of infants in preventing liver cancer. Gastroenterology. 2016;151:472-480.e1. 10. Eke AC, Eleje GU, Eke UA, Xia Y, Liu J. Hepatitis B immunoglobulin during pregnancy for prevention of mother-to-child transmission of hepatitis B virus. Cochrane Database Syst Rev 2017;2:CD008545.

Factors affecting pancreatic hyperamylasemia in patients undergoing peroral single-balloon enteroscopy

Acute pancreatitis following balloon‐assisted enteroscopy is a rare but serious complication. The causative mechanism is uncertain and prevention strategies are not established. We conducted a retrospective study to clarify the risk factors for pancreatic hyperamylasemia.

Usefulness of the clip-flap method of endoscopic submucosal dissection: A randomized controlled trial

AIM To prospectively investigate the efficacy and safety of clip-flap assisted endoscopic submucosal dissection (ESD) for gastric tumors. METHODS From May 2015 to October 2016, we enrolled 104 patients with gastric cancer or adenoma scheduled for ESD at Shiga University of Medical Science Hospital. We randomized patients into two subgroups using the minimization method based on location of the tumor (upper, middle or lower third of the stomach), tumor size (< 20 mm or > 20 mm) and ulcer status: ESD using an endoclip (the clip-flap group) and ESD without an endoclip (the conventional group). Therapeutic efficacy (procedure time) and safety (complication: Gastrointestinal bleeding and perforation) were assessed. RESULTS En bloc resection was performed in all patients. Four patients had delayed bleeding (3.8%) and two had perforation (1.9%). No significant differences in en bloc resection rate (conventional group: 100%, clip flap group: 100%), curative endoscopic resection rate (conventional group: 90.9%, clip flap group: 89.8%, P = 0.85), procedure time (conventional group: 70.8 ± 46.2 min, clip flap group: 74.7 ± 53.3 min, P = 0.69), area of resected specimen (conventional group: 884.6 ± 792.1 mm2, clip flap group: 1006.4 ± 1004.8 mm2, P = 0.49), delayed bleeding rate (conventional group: 5.5%, clip flap group: 2.0%, P = 0.49), or perforation rate (conventional group: 1.8%, clip flap group: 2.0%, P = 0.93) were found between the two groups. Less-experienced endoscopists did not show any differences in procedure time between the two groups. CONCLUSION For patients with early-stage gastric tumors, the clip-flap method has no advantage in efficacy or safety compared with the conventional method.

Interaction of p24alpha2 with gamma-secretase complex attenuates gamma-cleavage of APP

impairments, suggesting that deficits in neurogenesis may play a role in the disease or contribute to neuropathology. To address this, in this study we examined possible molecular link(s) between neurogenic signaling and FAD proteins.Methods:To determine the significance of APP cleavage by a-secretase and the role of sAPPa in adult neurogenesis we inhibited a-secretase activity in neural progenitor cells using metalloproteinase inhibitor. To determine the role of PS1 in adult neurogenesis we developed a siRNA-expressing lentiviral vector system for the silencing of PS1 in the neurogenic microenvironments in the adult mouse brain. Results: We show that inhibition of a-secretase decreases neural progenitor cell proliferation without affecting their differentiation, and that this decrease can be rescued by sAPPa. In addition, sAPPa can rescue proliferation deficits of neural progenitor cells derived from APP knockout mice. We further show that knocking down PS1 expression in the neurogenic niches of the adult brain enhances cell cycle exit of neural progenitor cell and induces their differentiation. Neural progenitor cells expressing reduced levels of PS1 could differentiate into neurons and glia. Conclusions: This study suggests that sAPPa and PS1 regulate neural progenitor cell maintenance in the adult brain. The results of these studies imply that FAD-linked mutations may alter neurogenic processes in Alzheimer’s disease.