CCT4 (chaperonin containing TCP1 subunit 4) is a core component of the TRiC/CCT molecular chaperone complex that facilitates ATP-dependent protein folding of actin, tubulin, and other cytosolic proteins 1. Within the hetero-oligomeric TRiC complex, CCT4 contributes to the negatively charged chamber hemisphere with weak affinity for unfolded substrates 2. Beyond its chaperonin function, CCT4 can form biologically active homo-oligomeric double-ring structures capable of ATP hydrolysis and substrate refolding 3. Additionally, monomeric CCT4 independently promotes tunneling nanotube formation and microtubule dynamics 4. Clinically, CCT4 dysregulation is implicated in multiple cancers. In glioblastoma, YB-1 protein promotes CCT4 translation, activating the mTOR pathway and driving tumor growth 5. In lung adenocarcinoma, CCT4 upregulation correlates with advanced stage, poor survival, reduced immune infiltration, and suppressed anti-tumor immunity through altered Th1/Th2 balance 6. Conversely, CCT4 is downregulated in Wilms tumor, suggesting context-dependent roles 7. Historically, a spontaneous Cct4 mutation in rats caused early-onset sensory neuropathy 8, indicating essential roles in neuronal proteostasis.