{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"institution":[{"name":"bioRxiv"}],"indexed":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T05:07:00Z","timestamp":1779167220570,"version":"3.51.4"},"posted":{"date-parts":[[2026,5,18]]},"group-title":"Biochemistry","reference-count":0,"publisher":"openRxiv","license":[{"start":{"date-parts":[[2026,5,18]],"date-time":"2026-05-18T00:00:00Z","timestamp":1779062400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"funder":[{"name":"National Science Centre","award":["2023\/49\/N\/NZ5\/02175"],"award-info":[{"award-number":["2023\/49\/N\/NZ5\/02175"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"accepted":{"date-parts":[[2026,5,18]]},"abstract":"<jats:p>Missense mutations in the TPM2 gene encoding skeletal muscle tropomyosin Tpm2.2 cause congenital myopathies associated with hyper and hypocontractile phenotypes. Mutation-dependent defects in thin filament stability and length maintenance may contribute to sarcomere dysfunction. To address this possibility, four disease associated substitutions in Tpm2.2 were analyzed: hypercontractile D20H and E181K, and hypocontractile E41K and N202K. Recombinant proteins were examined in vitro for their effects on actin filament polymerization, stability, and cofilin-2 dependent filament length regulation in the absence and presence of troponin (+Ca2+).\nWild-type Tpm2.2 inhibited spontaneous actin polymerization and reduced polymerization cooperativity in the presence of cofilin-2. Hypercontractile substitutions D20H and E181K further decreased the polymerization rate, whereas hypocontractile variants had little effect. Under ATP-driven actomyosin interactions, E41K and N202K stabilized filaments, resulting in increased filament length, but this effect was abolished by troponin. All variants slightly decreased cofilin-2 affinity for F-actin without affecting cooperativity. Troponin prevented displacement of Tpm2.2 from the filament at increasing cofilin-2 occupancy, indicating concomitant binding of all proteins to the thin filament, consistent with a structural model based on high-resolution F-actin-Tpm-Tn and cofilactin structures.Tpm2.2-N202K inhibited cofilin-2-dependent depolymerization, whereas Tpm2.2-E181K increased susceptibility to depolymerization. Although cofilin-2 induced filament severing in all cases, the Tpm2.2-Tn complex protected filaments from disassembly. \nThese findings support a model in which the Tpm2.2-Tn complex forms a cooperative regulatory strand that constrains filament dynamics and transmits structural perturbations along the filament. Disease-causing substitutions differentially alter filament length and stability, potentially contributing to the pathogenesis of myopathies.<\/jats:p>","DOI":"10.64898\/2026.05.15.725491","type":"posted-content","created":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T04:10:20Z","timestamp":1779163820000},"source":"Crossref","is-referenced-by-count":0,"title":["Disease-associated mutations in TPM2 alter regulation of actin filament stability and cofilin-dependent dynamics"],"prefix":"10.64898","author":[{"given":"Recep","family":"Kucukdogru","sequence":"first","affiliation":[{"name":"Kazimierz Wielki University in Bydgoszcz"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Katarzyna","family":"Robaszkiewicz","sequence":"additional","affiliation":[{"name":"Kazimierz Wielki University in Bydgoszcz"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Malgorzata","family":"Siatkowska","sequence":"additional","affiliation":[{"name":"Kazimierz Wielki University in Bydgoszcz"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4518-3843","authenticated-orcid":false,"given":"Joanna","family":"Moraczewska","sequence":"additional","affiliation":[{"name":"Kazimierz Wielki University in Bydgoszcz"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"54368","container-title":[],"original-title":[],"link":[{"URL":"https:\/\/syndication.highwire.org\/content\/doi\/10.64898\/2026.05.15.725491","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,19]],"date-time":"2026-05-19T04:10:20Z","timestamp":1779163820000},"score":1,"resource":{"primary":{"URL":"http:\/\/biorxiv.org\/lookup\/doi\/10.64898\/2026.05.15.725491"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,18]]},"references-count":0,"URL":"https:\/\/doi.org\/10.64898\/2026.05.15.725491","relation":{},"subject":[],"published":{"date-parts":[[2026,5,18]]},"subtype":"preprint"}}