Tropomodulin and Leiomodin Differentially Nucleate Tropomyosin Assembly on Actin Filaments
- 1Institut Jacques Monod - CNRS
Abstract
Tropomyosins play a central role in the regulation of the actin cytoskeleton by assembling along filaments into rope-like, head-to-tail polymers ("clusters") along filaments that regulate the binding and activity of numerous actin-binding proteins. Importantly, in cells, tropomyosins do not decorate actin filaments uniformly; some filaments are devoid of tropomyosins, whereas others recruit specific isoforms. To explore the diversity of tropomyosin-isoform binding kinetics and identify factors that control their assembly, we designed tropomyosin constructs, bearing a natural N-terminal acetylation and targeted cysteine mutations for fluorescence labelling. We analysed the binding of different tropomyosin isoforms to individual actin filaments reconstituted inside a microfluidic chamber. We show that, despite significant differences in spontaneous nucleation and elongation rates, all tested tropomyosin isoforms can coassemble within the same clusters. In addition, we identified tropomodulin and leiomodin, two pointed-end-binding proteins, to efficiently nucleate the formation of tropomyosin clusters on actin filaments, for all tested tropomyosin isoforms. Notably, while tropomodulin nucleates tropomyosin clusters from the pointed end, leiomodin does so along the entire filament.
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BibTeX
@misc{bages2026tropomodulin,
title = {{Tropomodulin and Leiomodin Differentially Nucleate Tropomyosin Assembly on Actin Filaments}},
author = {C. Bages and D. Al Abiad and R. Pages and S. Brotzman and T. Dos Santos and G. Romet-Lemonne and R. Dominguez and A. JEGOU and H. Wioland},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.04.756620},
url = {https://www.biorxiv.org/content/10.64898/2026.10.04.756620v1},
note = {CC BY-NC},
}
RIS
TY - UNPB
TI - Tropomodulin and Leiomodin Differentially Nucleate Tropomyosin Assembly on Actin Filaments
AU - C. Bages
AU - D. Al Abiad
AU - R. Pages
AU - S. Brotzman
AU - T. Dos Santos
AU - G. Romet-Lemonne
AU - R. Dominguez
AU - A. JEGOU
AU - H. Wioland
PY - 2026
DA - 2026/10/04
PB - bioRxiv
DO - 10.64898/2026.10.04.756620
UR - https://www.biorxiv.org/content/10.64898/2026.10.04.756620v1
AB - Tropomyosins play a central role in the regulation of the actin cytoskeleton by assembling along filaments into rope-like, head-to-tail polymers ("clusters") along filaments that regulate the binding and activity of numerous actin-binding proteins. Importantly, in cells, tropomyosins do not decorate actin filaments uniformly; some filaments are devoid of tropomyosins, whereas others recruit specific isoforms. To explore the diversity of tropomyosin-isoform binding kinetics and identify factors that control their assembly, we designed tropomyosin constructs, bearing a natural N-terminal acetylation and targeted cysteine mutations for fluorescence labelling. We analysed the binding of different tropomyosin isoforms to individual actin filaments reconstituted inside a microfluidic chamber. We show that, despite significant differences in spontaneous nucleation and elongation rates, all tested tropomyosin isoforms can coassemble within the same clusters. In addition, we identified tropomodulin and leiomodin, two pointed-end-binding proteins, to efficiently nucleate the formation of tropomyosin clusters on actin filaments, for all tested tropomyosin isoforms. Notably, while tropomodulin nucleates tropomyosin clusters from the pointed end, leiomodin does so along the entire filament.
ER -