Metallothionein-3 attenuates the effect of Cu2+ ions on actin filaments

• Published in: Journal of inorganic biochemistry 2023-05, Vol.242, p.112157-112157, Article 112157
• Main Authors: Lakha, Rabina, Hachicho, Carla, Mehlenbacher, Matthew R., Wilcox, Dean E., Austin, Rachel N., Vizcarra, Christina L.
• Format: Article
• Language: English
• Subjects: Actin; Copper; Cytoskeleton; Metallothionein-3; Profilin; Zinc
• ISSN: 0162-0134; 1873-3344
• DOI: 10.1016/j.jinorgbio.2023.112157

Metallothionein 3 (MT-3) is a cysteine-rich metal-binding protein that is expressed in the mammalian central nervous system and kidney. Various reports have posited a role for MT-3 in regulating the actin cytoskeleton by promoting the assembly of actin filaments. We generated purified, recombinant mouse MT-3 of known metal compositions, either with zinc (Zn), lead (Pb), or copper/zinc (Cu/Zn) bound. None of these forms of MT-3 accelerated actin filament polymerization in vitro, either with or without the actin binding protein profilin. Furthermore, using a co-sedimentation assay, we did not observe Zn-bound MT-3 in complex with actin filaments. Cu2+ ions on their own induced rapid actin polymerization, an effect that we attribute to filament fragmentation. This effect of Cu2+ is reversed by adding either EGTA or Zn-bound MT-3, indicating that either molecule can chelate Cu2+ from actin. Altogether, our data indicate that purified recombinant MT-3 does not directly bind actin but it does attenuate the Cu-induced fragmentation of actin filaments. The metal binding protein MT-3 is a putative cytoskeletal regulator that is expressed in the central nervous system. We found that it can scavenge copper ions from actin filaments. [Display omitted] •Recombinant MT-3 has undetectable effects on actin polymerization dynamics.•Zinc-replete MT-3 removes copper ions from actin filaments.•The transfer of copper ions reverses copper-induced actin filament fragmentation.