title: Inhibition of store-operated calcium entry by sub-lethal levels of proteasome inhibition is associated with STIM1/STIM2 degradation.
abstract: Dysfunction of the ubiquitin-proteasome system (UPS) and calcium homeostasis has been implicated in the neurodegeneration of Alzheimer's and Parkinson's diseases. The cytosolic calcium concentration is maintained by store-operated calcium entry (SOCE), which is repressed by Alzheimer's disease-associated mutants, such as mutant presenilins. We hypothesized that inhibition of UPS impacts SOCE. This study showed that pretreatment with sub-lethal levels of proteasome inhibitors, including MG-132 and clasto-lactacystin-β-lactone (LA), reduced SOCE after depletion of endoplasmic reticulum calcium in rat neurons. With the same treatment, MG-132 and LA reduced the protein levels of stromal interaction molecule 1and 2 (STIM1/2), but not the levels of Orai1 and canonical transient receptor potential channel 1 (TRPC1). STIM1 or STIM2 protein was mobilized to lysosome by MG-132/LA treatment as observed under an immunofluorescence confocal laser microscope. In the neurons, MG-132 and LA degraded p62/SQSTM1, promoted autophagy, converted LC3I to LC3II, and promoted co-localization of LC3 and lysosomes. Rapamycin, which enhances autophagy, reduced STIM1/2 protein levels, whereas bafilomycin, which inhibits autophagy, increased their protein levels. The protein levels of STIM1/2 and the amplitude of SOCE were decreased in SH-SY5Y with decreased protein level of proteasome subunit beta type-5 induced by shRNA. We conclude that sub-lethal levels of proteasome inhibition reduce SOCE and promote autophagy-mediated degradation of STIM1/2. UPS inhibition, a common finding in neurodegenerative diseases, interferes with calcium homeostasis via repression of SOCE.
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: Xiu-Li
authors.initials: XL
authors.lastname: Kuang
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Liu
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Chang
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: He
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, PR China.
authors.forename: Yiping
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China.
authors.forename: Jia
authors.initials: J
authors.lastname: Qu
authors.affiliation: School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China; Cultivation Base and Key Laboratory of Vision Science, Ministry of Health and Zhejiang Provincial Key Laboratory of Ophthalmology and Optometry, Wenzhou Medical University, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, PR China. Electronic address: wszlab@mail.eye.ac.cn.
authors.forename: Shengzhou
authors.initials: S
authors.lastname: Wu
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017136:Ion Transport / Q000502:physiology; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000009:adverse effects* / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D000071737:Stromal Interaction Molecule 1 / Q000378:metabolism*; D000071738:Stromal Interaction Molecule 2 / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C560435:STIM2 protein, rat; C518857:Stim1 protein, rat; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D046988:Proteasome Endopeptidase Complex; D002118:Calcium
keywords: ER stress; Low calcium; Neurodegeneration; Orai1; PSMB5; Presenilin; Store-operated calcium channel; Stromal interaction molecule; Ubiquitin-proteasome system