Lysosomal TPCN (two pore segment channel) inhibition ameliorates beta-amyloid pathology and mitigates memory impairment in Alzheimer disease
Creators: name: Tong, Benjamin Chun-Kit
name: Wu, Aston Jiaxi
name: Huang, Alexis Shiying
name: Dong, Rui
name: Malampati, Sandeep
name: Iyaswamy, Ashok
name: Krishnamoorthi, Senthilkumar
name: Sreenivasmurthy, Sravan Gopalkrishnashetty
name: Zhu, Zhou
name: Su, Chengfu
name: Liu, Jia
name: Song, Juxian
name: Lu, Jia-Hong
name: Tan, Jieqiong
name: Pan, Weidong
name: Li, Min
name: Cheung, King-Ho
Publisher: name: Taylor & Francis
Year: 2021
Subjects: subject: Biochemistry
subject: Cell Biology
subject: Molecular Biology
subject: Neuroscience
subject: Chemical Sciences not elsewhere classified
subject: Immunology
subject: FOS: Clinical medicine
subject: Cancer

description: Impairment of the macroautophagy/autophagy-lysosomal pathway (ALP) can lead to amyloid plaque accumulation in Alzheimer disease (AD); however, the underlying mechanism remains unresolved. This study revealed a mechanism of ALP impairment mediated by gain-of-function of lysosomal TPCN2/TPC2 (two pore segment channel 2) and suggests a molecular target for AD intervention. Using mutant PSEN1/PS1 (presenilin 1)-expressing human neuroblastoma SH-SY5Y and familial AD fibroblasts collected from human patients, we showed lysosomal pH was increased in AD cells due to exaggerated TPCN2-mediated calcium (Ca<sup>2+</sup>) release which increases lysosomal pH and compromises ALP degradation. Genetic knockdown or pharmacological inhibition of the TPCN2 channel restored lysosomal Ca<sup>2+</sup> homeostasis, acidity of the lysosome and ALP function. Furthermore, AD mice (5xFAD) that had received treatment with the TPCN2 inhibitor tetrandrine for 6 months or injection of AAV-sh<i>Tpcn2</i> to knock down <i>Tpcn2</i> showed reduction in amyloid plaques in cortical and hippocampal regions. These treatments also improved spine morphology and density and corrected cognitive deficits in 5xFAD mice assayed by immunohistochemistry, behavioral tests, and electrophysiological measurements, respectively. Taken together, these findings reveal a previously under-appreciated role of lysosomal TPCN2 in ALP impairment of AD. They also suggest targeting the lysosomal TPCN2 can serve as a therapeutic strategy for AD treatment in future drug development. Aβ: β-amyloid; AD: Alzheimer disease; AIF1/IBA1: allograft inflammatory factor 1; ALP: autophagy-lysosomal pathway; APP: amyloid beta precursor protein; ATP6V1B1/V-ATPase V1b1: ATPase H+ transporting V1 subunit B1; AVs: autophagy vacuoles; BAF: bafilomycin A<sub>1</sub>; CFC: contextual/cued fear conditioning assay; CHX: Ca<sup>2+</sup>/H<sup>+</sup> exchanger; CTF-β: carboxy-terminal fragment derived from β-secretase; CTSD: cathepsin D; fAD: familial Alzheimer disease; GFAP: glial fibrillary acidic protein; LAMP1: lysosomal associated membrane protein 1; LTP: long‐term potentiation; MCOLN1/TRPML1: mucolipin 1; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAPT: microtubule associated protein tau; MWM: Morris water maze; NFT: neurofibrillary tangles; PFC: prefrontal cortex; PSEN1: presenilin 1; SQSTM1/p62: sequestosome 1; TBS: theta burst stimulation; TEM: transmission electronic microscopy; TPCN2/TPC2: two pore segment channel 2; WT: wild-type; V-ATPase: vacuolar type H<sup>+</sup>-ATPase