title: Dynamic presenilin 1 and synaptotagmin 1 interaction modulates exocytosis and amyloid β production.
abstract: Alzheimer's disease (AD)-linked protein, presenilin 1 (PS1), is present at the synapse, and the knock-out of presenilin in mice leads to synaptic dysfunction. On the other hand, synaptic activity was shown to influence PS1-dependent generation of distinct amyloid β (Aβ) species. However, the precise nature of these regulations remains unclear. The current study reveals novel role of PS1 at the synapse, and deciphers how PS1 and synaptic vesicle-associated protein, synaptotagmin 1 (Syt1) modulate each other functions in neurons via direct activity-triggered interaction. Additionally, the therapeutic potential of fostering PS1-Syt1 binding is investigated as a synapse-specific strategy for AD prevention.
  
  
  
  PS1-based cell-permeable peptide targeting PS1-Syt1 binding site was designed to inhibit PS1-Syt1 interaction in neurons. PS1 conformation, synaptic vesicle exocytosis and trafficking were assayed by fluorescence lifetime imaging microscopy (FLIM), glutamate release/synaptopHluorin assay, and fluorescence recovery after photobleaching, respectively. Syt1 level and interaction with PS1 in control and sporadic AD brains were determined by immunohistochemistry and FLIM. AAV-mediated delivery of Syt1 into mouse hippocampi was used to investigate the therapeutic potential of strengthening PS1-Syt1 binding in vivo. Statistical significance was determined using two-tailed unpaired Student's t-test, Mann-Whitney's U-test or two-way ANOVA followed by a Bonferroni's post-test.
  
  
  
  We demonstrate that targeted inhibition of the PS1-Syt1 binding in neurons, without changing the proteins' expression level, triggers "pathogenic" conformational shift of PS1, and consequent increase in the Aβ42/40 ratio. Moreover, our data indicate that PS1, by binding directly to Syt1, regulates synaptic vesicle trafficking and facilitates exocytosis and neurotransmitter release. Analysis of human brain tissue revealed that not only Syt1 levels but also interactions between remaining Syt1 and PS1 are diminished in sporadic AD. On the other hand, overexpression of Syt1 in mouse hippocampi was found to potentiate PS1-Syt1 binding and promote "protective" PS1 conformation.
  
  
  
  The study reports novel functions of PS1 and Syt1 at the synapse, and demonstrates the importance of PS1-Syt1 binding for exocytosis and safeguarding PS1 conformation. It suggests that reduction in the Syt1 level and PS1-Syt1 interactions in AD brain may present molecular underpinning of the pathogenic PS1 conformation, increased Aβ42/40 ratio, and impaired exocytosis.
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
authors.forename: Katarzyna Marta
authors.initials: KM
authors.lastname: Zoltowska
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
authors.forename: Masato
authors.initials: M
authors.lastname: Maesako
authors.affiliation: Department of Cytology, Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Street, 01024, Kyiv, Ukraine.
authors.forename: Iryna
authors.initials: I
authors.lastname: Lushnikova
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
authors.forename: Shuko
authors.initials: S
authors.lastname: Takeda
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
authors.forename: Laura J
authors.initials: LJ
authors.lastname: Keller
authors.affiliation: Department of Cytology, Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Street, 01024, Kyiv, Ukraine.
authors.forename: Galina
authors.initials: G
authors.lastname: Skibo
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA.
authors.forename: Bradley T
authors.initials: BT
authors.lastname: Hyman
authors.affiliation: Department of Neurology, MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, 114 16th Street, Rm. 2006, 02129, Charlestown, MA, USA. oberezovska@mgh.harvard.edu.
authors.forename: Oksana
authors.initials: O
authors.lastname: Berezovska
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D005089:Exocytosis / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism; D053764:Presenilin-1 / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism; D050863:Synaptotagmin I / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C508853:PSEN1 protein, human; D053764:Presenilin-1; C494310:SYT1 protein, human; D050863:Synaptotagmin I; C494311:Syt1 protein, mouse; C580804:presenilin 1, mouse; D053829:Amyloid Precursor Protein Secretases
keywords: Alzheimer’s disease; Amyloid β; Exocytosis; Presenilin 1; Synapse; Synaptotagmin 1