C-Terminal Fragment of Filamin C Containing Immunoglobulin-Like Domains 19-24 Selectively Interacts with the Small Heat Shock Protein HspB7

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Maria A. Zamotina¹, Lidia K. Muranova¹, Pyotr A. Tyurin-Kuzmin², Nikolai N. Sluchanko³, and Nikolai B. Gusev^1,a*

¹Department of Biochemistry, Faculty of Biology, Lomonosov Moscow State University, 119991 Moscow, Russia

²Department of Biochemistry and Regenerative Biomedicine, Faculty of Medicine, Medical Research and Educational Institute, Lomonosov Moscow State University, 119991 Moscow, Russia

³Bach Institute of Biochemistry, Federal Research Center of Biotechnology of the Russian Academy of Sciences, 119071 Moscow, Russia

^* To whom correspondence should be addressed.

Received: October 10, 2025; Revised: November 4, 2025; Accepted: November 8, 2025

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Filamin C is an adapter protein involved in the regulation of cytoskeleton; it interacts with more than 90 protein partners, including small heat shock proteins (sHsps). However, the details of filamin C interaction with sHsps remain poorly characterized. Here, we used immunochemistry methods, size-exclusion chromatography, native gel electrophoresis, and chemical crosslinking to investigate the interactions of a long C-terminal fragment of filamin C containing immunoglobulin (Ig)-like domains 19-24 (FLNC19-24) with sHsps. Out of five analyzed sHsps (HspB1, phosphorylation-mimicking 3D mutant of HspB1, HspB5, HspB6, HspB7, and HspB8), only HspB7 formed complexes with FLNC19-24. Taking into account that HspB7 interacted with the isolated Ig-like domain 24 and filamin fragments containing Ig-like domains 22-24 and 19-24, we concluded that HspB7 is a bona fide partner of filamin C. Selective binding of the α-crystallin domain of HspB7 with the Ig-like domain 24 induced dissociation of filamin dimers, which might promote filamin C translocation in the cell and facilitate the repairs of damaged contractile apparatus.

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KEY WORDS: small heat shock proteins, filamin C, immunoglobulin-like domains

DOI: 10.1134/S0006297925603624

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