{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T22:48:58Z","timestamp":1770763738822,"version":"3.50.0"},"posted":{"date-parts":[[2026,2,6]]},"group-title":"Biophysics","reference-count":36,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,2,6]],"date-time":"2026-02-06T00:00:00Z","timestamp":1770336000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,2,6]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                <jats:p>\n                  The sarco-endoplasmic reticulum Ca\u00b2\u207a-ATPase (SERCA) is a ubiquitous P-type ATPase that restores cytosolic Ca\n                  <jats:sup>2+<\/jats:sup>\n                  to the sarco-endoplasmic reticulum. SERCA is essential for cardiac Ca\n                  <jats:sup>2+<\/jats:sup>\n                  cycling and cellular energy metabolism. Several small molecules enhance SERCA function and show promise in models of metabolic and cardiovascular diseases. However, the structural basis for SERCA activation has remained unknown, hindering mechanism-driven lead optimization. Here we present cryo-EM structures of SERCA bound to two chemically distinct activators: the quinoline derivative CDN1163 (2.6 \u00c5 resolution) and a benzofuran derivative UM-52 (3.1 \u00c5 resolution). Biochemical assays show that both compounds stimulate Ca\n                  <jats:sup>2+<\/jats:sup>\n                  -dependent ATPase activity of SERCA without altering the apparent Ca\u00b2\u207a affinity. The structures reveal a previously unrecognized \u201cactivation hotspot\u201d in the transmembrane domain, a shallow groove formed by helices M3 and M4 and capped by M1. Despite low chemical similarity, both activators occupy the same pocket and share conserved interactions with Ser\n                  <jats:sup>265<\/jats:sup>\n                  , Trp\n                  <jats:sup>272<\/jats:sup>\n                  , and Phe\n                  <jats:sup>296<\/jats:sup>\n                  . These residues are unique to SERCA and help explain selectivity relative to other P-type ATPases. Activator binding stabilizes a catalytically competent conformation, shifting SERCA toward an E1-like state poised for ATP binding and coordinated movements of the M1-M4 bundle and the cytosolic domains. Notably, density consistent with a detergent acyl chain bridges an otherwise open cavity adjacent to the compound, suggesting that altered protein-lipid interactions may contribute to activation. Together, these findings define a structural framework for SERCA activation and provide a blueprint for rational design of next-generation SERCA activators.\n                <\/jats:p>\n                <jats:sec>\n                  <jats:title>SIGNIFICANCE STATEMENT<\/jats:title>\n                  <jats:p>\n                    SERCA pumps Ca\u00b2\u207a into the sarco-endoplasmic reticulum, enabling muscle relaxation and shaping calcium signals across tissues. Small-molecule SERCA activators improve cardiac and metabolic phenotypes in animal models, but drug development has been limited by the absence of a defined binding site and activation mechanism. We determined cryo-EM structures of SERCA bound to two distinct activators, CDN1163 and UM-52. Both compounds occupy a groove formed by transmembrane segments M3-M4, anchored by a hydrogen bond to the SERCA-specific Ser\n                    <jats:sup>265<\/jats:sup>\n                    and aromatic contacts near Trp\n                    <jats:sup>272<\/jats:sup>\n                    and Phe\n                    <jats:sup>296<\/jats:sup>\n                    . An acyl chain bridges a gap in the binding pocket toward M1, suggesting that protein-lipid coupling may play a role in SERCA activation. These results directly enable structure-mechanism guided design of next-generation selective SERCA activators.\n                  <\/jats:p>\n                <\/jats:sec>","DOI":"10.64898\/2026.02.05.703879","type":"posted-content","created":{"date-parts":[[2026,2,7]],"date-time":"2026-02-07T03:55:22Z","timestamp":1770436522000},"source":"Crossref","is-referenced-by-count":0,"title":["Supercharging the calcium pump: Identification of an activation hotspot on SERCA by cryo-EM"],"prefix":"10.64898","author":[{"given":"Vinh H.","family":"Nguyen","sequence":"first","affiliation":[{"name":"Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Carlos","family":"Cruz-Cort\u00e9s","sequence":"additional","affiliation":[{"name":"Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Joseph O.","family":"Primeau","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4745-9153","authenticated-orcid":false,"given":"M. Joanne","family":"Lemieux","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"L. Michel","family":"Espinoza-Fonseca","sequence":"additional","affiliation":[{"name":"Center for Arrhythmia Research, Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI 48109, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5990-8422","authenticated-orcid":false,"given":"Howard S.","family":"Young","sequence":"additional","affiliation":[{"name":"Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"54368","reference":[{"key":"2026021010205220000_2026.02.05.703879v1.1","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.M115.705012"},{"key":"2026021010205220000_2026.02.05.703879v1.2","doi-asserted-by":"crossref","unstructured":"O. Roopnarine et al., Fluorescence lifetime FRET assay for live-cell high-throughput screening of the cardiac SERCA pump yields multiple classes of small-molecule allosteric modulators. Sci Rep 13, 10673 (2023).","DOI":"10.1038\/s41598-023-37704-x"},{"key":"2026021010205220000_2026.02.05.703879v1.3","doi-asserted-by":"publisher","DOI":"10.1021\/acs.jmedchem.5c01192"},{"key":"2026021010205220000_2026.02.05.703879v1.4","doi-asserted-by":"crossref","first-page":"e202400763","DOI":"10.1002\/cmdc.202400763","article-title":"Quinoline- and Pyrimidine-based Allosteric Modulators of the Sarco\/Endoplasmic Reticulum Calcium ATPase","volume":"20","year":"2025","journal-title":"ChemMedChem"},{"key":"2026021010205220000_2026.02.05.703879v1.5","doi-asserted-by":"publisher","DOI":"10.1002\/cmdc.202500968"},{"key":"2026021010205220000_2026.02.05.703879v1.6","doi-asserted-by":"crossref","unstructured":"G. Sordi , A. Goti , H. S. Young , I. Palchetti , F. Tadini-Buoninsegni , Stimulation of Ca2+-ATPase transport activity by a small-molecule drug. ChemMedChem 16 (2021).","DOI":"10.1002\/cmdc.202100350"},{"key":"2026021010205220000_2026.02.05.703879v1.7","doi-asserted-by":"publisher","DOI":"10.1038\/nature00944"},{"key":"2026021010205220000_2026.02.05.703879v1.8","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.C900031200"},{"key":"2026021010205220000_2026.02.05.703879v1.9","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.M611653200"},{"key":"2026021010205220000_2026.02.05.703879v1.10","doi-asserted-by":"publisher","DOI":"10.1016\/j.bpj.2019.01.013"},{"key":"2026021010205220000_2026.02.05.703879v1.11","doi-asserted-by":"publisher","DOI":"10.1016\/j.bpj.2019.11.3385"},{"key":"2026021010205220000_2026.02.05.703879v1.12","doi-asserted-by":"publisher","DOI":"10.15252\/embj.2021108482"},{"key":"2026021010205220000_2026.02.05.703879v1.13","first-page":"pgad453","article-title":"Mechanisms for cardiac calcium pump activation by its substrate and a synthetic allosteric modulator using fluorescence lifetime imaging","volume":"3","year":"2024","journal-title":"PNAS Nexus"},{"key":"2026021010205220000_2026.02.05.703879v1.14","doi-asserted-by":"publisher","DOI":"10.1038\/nature11899"},{"key":"2026021010205220000_2026.02.05.703879v1.15","doi-asserted-by":"publisher","DOI":"10.1038\/nature11900"},{"key":"2026021010205220000_2026.02.05.703879v1.16","doi-asserted-by":"publisher","DOI":"10.1074\/jbc.M113.501585"},{"key":"2026021010205220000_2026.02.05.703879v1.17","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/0005-2736(72)90321-5","article-title":"Phospholipid orientation in sarcoplasmic membranes: spin-label ESR and proton MNR studies","volume":"282","year":"1972","journal-title":"Biochim Biophys Acta"},{"key":"2026021010205220000_2026.02.05.703879v1.18","doi-asserted-by":"publisher","DOI":"10.1016\/S0006-3495(90)82501-7"},{"key":"2026021010205220000_2026.02.05.703879v1.19","doi-asserted-by":"publisher","DOI":"10.1038\/227680a0"},{"key":"2026021010205220000_2026.02.05.703879v1.20","doi-asserted-by":"publisher","DOI":"10.1016\/S0006-3495(97)78898-2"},{"key":"2026021010205220000_2026.02.05.703879v1.21","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.71.3.622"},{"key":"2026021010205220000_2026.02.05.703879v1.22","doi-asserted-by":"crossref","first-page":"119699","DOI":"10.1016\/j.bbamcr.2024.119699","article-title":"Missense variants in phospholamban and cardiac myosin binding protein identified in patients with a family history and clinical diagnosis of dilated cardiomyopathy","volume":"1871","year":"2024","journal-title":"Biochim Biophys Acta Mol Cell Res"},{"key":"2026021010205220000_2026.02.05.703879v1.23","doi-asserted-by":"publisher","DOI":"10.1126\/science.aar5839"},{"key":"2026021010205220000_2026.02.05.703879v1.24","doi-asserted-by":"publisher","DOI":"10.1038\/nmeth.4169"},{"key":"2026021010205220000_2026.02.05.703879v1.25","doi-asserted-by":"publisher","DOI":"10.1107\/S2059798319011471\/HTTPS:\/\/GOLDBOOK.IUPAC.ORG\/E02002.HTML"},{"key":"2026021010205220000_2026.02.05.703879v1.26","doi-asserted-by":"publisher","DOI":"10.1107\/S0907444910007493"},{"key":"2026021010205220000_2026.02.05.703879v1.27","doi-asserted-by":"publisher","DOI":"10.1107\/S0907444909029436"},{"key":"2026021010205220000_2026.02.05.703879v1.28","doi-asserted-by":"publisher","DOI":"10.1093\/nar\/gkm216"},{"key":"2026021010205220000_2026.02.05.703879v1.29","doi-asserted-by":"publisher","DOI":"10.1002\/jcc.20084"},{"key":"2026021010205220000_2026.02.05.703879v1.30","doi-asserted-by":"publisher","DOI":"10.1002\/PRO.3943"},{"key":"2026021010205220000_2026.02.05.703879v1.31","doi-asserted-by":"publisher","DOI":"10.1021\/acs.jctc.1c01217"},{"key":"2026021010205220000_2026.02.05.703879v1.32","doi-asserted-by":"publisher","DOI":"10.1002\/jcc.20945"},{"key":"2026021010205220000_2026.02.05.703879v1.33","doi-asserted-by":"publisher","DOI":"10.1016\/j.bpj.2015.10.008"},{"key":"2026021010205220000_2026.02.05.703879v1.34","doi-asserted-by":"publisher","DOI":"10.1021\/ct400314y"},{"key":"2026021010205220000_2026.02.05.703879v1.35","doi-asserted-by":"publisher","DOI":"10.1021\/ACS.JCTC.9B00591\/SUPPL_FILE\/CT9B00591_SI_002.ZIP"},{"key":"2026021010205220000_2026.02.05.703879v1.36","doi-asserted-by":"publisher","DOI":"10.1016\/0263-7855(96)00018-5"}],"container-title":[],"original-title":[],"link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.64898\/2026.02.05.703879","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,2,10]],"date-time":"2026-02-10T18:21:04Z","timestamp":1770747664000},"score":1,"resource":{"primary":{"URL":"http:\/\/biorxiv.org\/lookup\/doi\/10.64898\/2026.02.05.703879"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,2,6]]},"references-count":36,"URL":"https:\/\/doi.org\/10.64898\/2026.02.05.703879","relation":{},"subject":[],"published":{"date-parts":[[2026,2,6]]},"subtype":"preprint"}}