CCT8

CCT8, or chaperonin-containing TCP1 subunit 8, is a protein that is a component of the cytosolic chaperonin complex known as TRiC (TCP-1 ring complex) or CCT. The TRiC/CCT complex consists of eight distinct subunits (CCT1–CCT8) arranged in two stacked rings. CCT8 participates as one subunit within the central folding chamber that encloses substrates during folding, using ATP-driven conformational changes to regulate substrate binding and release.

Functionally, CCT8 assists the folding of a subset of newly synthesized proteins in the cytosol, notably actin and tubulin, among others. The complex provides an isolated environment to facilitate proper folding and prevent aggregation, contributing to the maturation of a broad range of cytosolic proteins through an ATP-dependent cycle.

Localization and mechanism: CCT8 is a cytosolic protein and interacts with the other CCT subunits to form the functional TRiC/CCT complex. Its activity is coordinated with ATP binding and hydrolysis, which drives conformational changes essential for substrate encapsulation and release during the folding process.

Biological significance: The CCT/TRiC complex is essential for the maturation of many cytoskeletal and regulatory proteins. Proper folding of actin and tubulin is critical for cytoskeleton assembly, cell shape, division, and development. In model systems, depletion or dysfunction of CCT8 or the TRiC complex leads to growth defects and accumulation of misfolded substrates.

Genetics and evolution: The CCT8 gene is conserved across eukaryotes and is expressed broadly in mammalian tissues. Like other CCT subunits, it shows high sequence conservation, reflecting its essential role.

Research and medical relevance: Altered chaperonin function has been linked to diseases in some contexts; the specific contribution of CCT8 to human disease remains an area of ongoing investigation. CCT8 is used in research to study chaperonin assembly, substrate specificity, and cytoskeleton biogenesis.