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Selective Serotonin Reuptake Inhibitors Within Cells: Temporal Resolution in Cytoplasm, Endoplasmic Reticulum, and Membrane

Nichols, Aaron L. and Blumenfeld, Zack and Luebbert, Laura and Knox, Hailey J. and Muthusamy, Anand K. and Marvin, Jonathan S. and Kim, Charlene H. and Grant, Stephen N. and Walton, David P. and Cohen, Bruce N. and Hammar, Rebekkah and Looger, Loren L. and Artursson, Per and Dougherty, Dennis A. and Lester, Henry A. (2022) Selective Serotonin Reuptake Inhibitors Within Cells: Temporal Resolution in Cytoplasm, Endoplasmic Reticulum, and Membrane. . (Unpublished)

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Selective serotonin reuptake inhibitors (SSRIs) are the most prescribed treatment for individuals experiencing major depressive disorder (MDD). The therapeutic mechanisms that take place before, during, or after SSRIs bind the serotonin transporter (SERT) are poorly understood, partially because no studies exist of the cellular and subcellular pharmacokinetic properties of SSRIs in living cells. We studied escitalopram and fluoxetine using new intensity-based drug-sensing fluorescent reporters (″iDrugSnFRs″) targeted to the plasma membrane (PM), cytoplasm, or endoplasmic reticulum (ER) of cultured neurons and mammalian cell lines. We also employed chemical detection of drug within cells and phospholipid membranes. The drugs attain equilibrium in neuronal cytoplasm and ER, at approximately the same concentration as the externally applied solution, with time constants of a few s (escitalopram) or 200-300 s (fluoxetine). Simultaneously, the drugs accumulate within lipid membranes by ≥ 18-fold (escitalopram) or 180-fold (fluoxetine), and possibly by much larger factors. Both drugs leave cytoplasm, lumen, and membranes just as quickly during washout. We synthesized membrane-impermeant quaternary amine derivatives of the two SSRIs. The quaternary derivatives are substantially excluded from membrane, cytoplasm, and ER for > 2.4 h. They inhibit SERT transport-associated currents 6- or 11-fold less potently than the SSRIs (escitalopram or fluoxetine derivative, respectively), providing useful probes for distinguishing compartmentalized SSRI effects. Although our measurements are orders of magnitude faster than the ″therapeutic lag″ of SSRIs, these data suggest that SSRI-SERT interactions within organelles or membranes may play roles during either the therapeutic effects or the ″antidepressant discontinuation syndrome″.

Item Type:Report or Paper (Discussion Paper)
Related URLs:
URLURL TypeDescription ItemData ItemJournal Article
Nichols, Aaron L.0000-0001-9341-0049
Blumenfeld, Zack0000-0002-4627-5582
Luebbert, Laura0000-0003-1379-2927
Knox, Hailey J.0000-0003-0608-2855
Muthusamy, Anand K.0000-0003-1041-914X
Marvin, Jonathan S.0000-0003-2294-4515
Kim, Charlene H.0000-0003-4048-5244
Grant, Stephen N.0000-0003-0923-8886
Walton, David P.0000-0002-9557-6461
Cohen, Bruce N.0000-0003-2913-6238
Hammar, Rebekkah0000-0001-5740-0353
Looger, Loren L.0000-0002-7531-1757
Artursson, Per0000-0002-3708-7395
Dougherty, Dennis A.0000-0003-1464-2461
Lester, Henry A.0000-0002-5470-5255
Additional Information:The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-ND 4.0 International license. We thank Stefan Petrovic for his stewardship of the isothermal titration calorimeter in the Caltech Center for Molecular Medicine, the Gradinaru lab and Caltech CLOVER Center for help with viral vectors, and Andres Collazo and Giada Spigolon at the Caltech Biological Imaging Facility. We thank Zoe Beatty, Kallol Bera, Eve Fine, Shan Huang, Elaine Lin, Stephen Mayo, Lin Tian, Andrea Treyer, Elizabeth Unger, and Lu Wei for advice and guidance. We also thank Purnima Deshpande for her excellent lab management. Funding. California Tobacco-Related Disease Research Program (TRDRP) (27FT-0022), Aaron L. Nichols. California Tobacco-Related Disease Research Program (TRDRP) (27IP-0057), Henry A. Lester. California Tobacco-Related Disease Research Program (TRDRP) (T29IR0455), Dennis A. Dougherty. NIH (GM-123582, MH120823), Henry A. Lester. NIH (DA049140, GM7616), Anand K. Muthusamy. Howard Hughes Medical Institute, Jonathan S. Marvin. Howard Hughes Medical Institute, Loren L. Looger. Leiden University International Studies Fund (LISF L18020-1-45), Laura Luebbert. Swedish Research Council, (01586), P. Artursson. European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie grant agreement (956851), R. Hammar The authors have declared no competing interest.
Funding AgencyGrant Number
California Tobacco-Related Disease Research Program27FT-0022
California Tobacco-Related Disease Research Program27IP-0057
California Tobacco-Related Disease Research ProgramT29IR0455
Howard Hughes Medical Institute (HHMI)UNSPECIFIED
Leiden UniversityLISF L18020-1-45
Swedish Research Council01586
Marie Curie Fellowship956851
Record Number:CaltechAUTHORS:20220812-829310000
Persistent URL:
Official Citation:Selective Serotonin Reuptake Inhibitors Within Cells: Temporal Resolution in Cytoplasm, Endoplasmic Reticulum, and Membrane Aaron L Nichols, Zack Blumenfeld, Laura Luebbert, Hailey J Knox, Anand K Muthusamy, Jonathan S Marvin, Charlene H Kim, Stephen N Grant, David P Walton, Bruce N Cohen, Rebekkah Hammar, Loren L Looger, Per Artursson, Dennis A Dougherty, Henry A Lester bioRxiv 2022.08.09.502705; doi:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116272
Deposited By: George Porter
Deposited On:15 Aug 2022 21:55
Last Modified:15 May 2023 22:42

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