The Molecular Chaperone CCT Sequesters Gelsolin and Protects it from Cleavage by Caspase-3

• Published in: Journal of molecular biology Vol. 434; no. 5; p. 167399
• Main Authors: Cuéllar, Jorge, Vallin, Josefine, Svanström, Andreas, Maestro-López, Moisés, Bueno-Carrasco, María Teresa, Ludlam, W. Grant, Willardson, Barry M., Valpuesta, José M., Grantham, Julie
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 15.03.2022
• Subjects: actin; Actins - metabolism; Animals; Caspase 3 - metabolism; chaperonin; Chaperonin Containing TCP-1 - metabolism; Cryoelectron Microscopy; Gelsolin - chemistry; Gelsolin - metabolism; Mice; Proteolysis; structured illumination microscopy; TRiC; actin; cryoelectron microscopy; structured illumination microscopy; chaperonin; TRiC
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2021.167399

[Display omitted] •Gelsolin binds to the molecular chaperone CCT but is not a folding substrate.•Gelsolin and CCT co-localise close to sites of actin rearrangements.•CCT protects gelsolin from cleavage by caspase-3.•Cryo-electron microscopy reveals gelsolin binding deep in the chaperonin cavity.•Interactions with CCT may modulate gelsolin activity and influence actin dynamics. The actin filament severing and capping protein gelsolin plays an important role in modulation of actin filament dynamics by influencing the number of actin filament ends. During apoptosis, gelsolin becomes constitutively active due to cleavage by caspase-3. In non-apoptotic cells gelsolin is activated by the binding of Ca2+. This activated form of gelsolin binds to, but is not a folding substrate of the molecular chaperone CCT/TRiC. Here we demonstrate that in vitro, gelsolin is protected from cleavage by caspase-3 in the presence of CCT. Cryoelectron microscopy and single particle 3D reconstruction of the CCT:gelsolin complex reveals that gelsolin is located in the interior of the chaperonin cavity, with a placement distinct from that of the obligate CCT folding substrates actin and tubulin. In cultured mouse melanoma B16F1 cells, gelsolin co-localises with CCT upon stimulation of actin dynamics at peripheral regions during lamellipodia formation. These data indicate that localised sequestration of gelsolin by CCT may provide spatial control of actin filament dynamics.