The chaperonin CCT8 controls proteostasis essential for T cell maturation, selection, and function

Revisiting the chaperonin T-complex protein-1 ring complex in human health and disease: A proteostasis modulator and beyond

BACKGROUND

Disrupted protein homeostasis (proteostasis) has been demonstrated to facilitate the progression of various diseases. The cytosolic T-complex protein-1 ring complex (TRiC/CCT) was discovered to be a critical player in orchestrating proteostasis by folding eukaryotic proteins, guiding intracellular localisation and suppressing protein aggregation. Intensive investigations of TRiC/CCT in different fields have improved the understanding of its role and molecular mechanism in multiple physiological and pathological processes.

MAIN BODY

In this review, we embark on a journey through the dynamic protein folding cycle of TRiC/CCT, unraveling the intricate mechanisms of its substrate selection, recognition, and intriguing folding and assembly processes. In addition to discussing the critical role of TRiC/CCT in maintaining proteostasis, we detail its involvement in cell cycle regulation, apoptosis, autophagy, metabolic control, adaptive immunity and signal transduction processes. Furthermore, we meticulously catalogue a compendium of TRiC-associated diseases, such as neuropathies, cardiovascular diseases and various malignancies. Specifically, we report the roles and molecular mechanisms of TRiC/CCT in regulating cancer formation and progression. Finally, we discuss unresolved issues in TRiC/CCT research, highlighting the efforts required for translation to clinical applications, such as diagnosis and treatment.

CONCLUSION

This review aims to provide a comprehensive view of TRiC/CCT for researchers to inspire further investigations and explorations of potential translational possibilities.

Proteostasis in T cell aging

Aging leads to a decline in immune cell function, which leaves the organism vulnerable to infections and age-related multimorbidities. One major player of the adaptive immune response are T cells, and recent studies argue for a major role of disturbed proteostasis contributing to reduced function of these cells upon aging. Proteostasis refers to the state of a healthy, balanced proteome in the cell and is influenced by synthesis (translation), maintenance and quality control of proteins, as well as degradation of damaged or unwanted proteins by the proteasome, autophagy, lysosome and cytoplasmic enzymes. This review focuses on molecular processes impacting on proteostasis in T cells, and specifically functional or quantitative changes of each of these upon aging. Importantly, we describe the biological consequences of compromised proteostasis in T cells, which range from impaired T cell activation and function to enhancement of inflamm-aging by aged T cells. Finally, approaches to improve proteostasis and thus rejuvenate aged T cells through pharmacological or physical interventions are discussed.

CCT8 promotes cell migration and tumor metastasis in lung adenocarcinomas

Chaperonins, which contain t-complex polypeptide 1 (CCT), are critical for correct protein folding to generate stable and functional protein conformations, which are important for cell growth and survival. However, little is known about the expression and prognostic significance of CCT8 (subunit 8 of the CCT complex chaperonin) in lung cancer. In this study, we demonstrated that CCT8 expression is frequently increased in human lung cancer. Survival analysis indicated that CCT8 expression is closely correlated with inferior overall survival in lung adenocarcinoma (LUAD), but not in lung squamous carcinoma (LUSC). Subsequently, ectopic expression of CCT8 facilitated cell migration and tumor metastasis, and vice versa. Mechanistically, CCT8 interacted and activated ATK. Inhibition of AKT suppressed CCT8-induced cell migration and tumor metastasis. Our findings support CCT8 as a biomarker for LUAD prognosis and as a target for LUAD therapy.

Multi-Omics Analysis and Verification of the Oncogenic Value of CCT8 in Pan-Cancers

Background

Chaperonin-containing TCP1 subunit 8 (CCT8) has been proved to be involved in the occurrence and development of some cancers. However, no study has reported the potential role of CCT8 in a pan-cancer manner.

Methods

TIMER2.0, GEPIA2, UALCAN and Sangerbox were used to explore the expression, prognosis and methylation of CCT8. We used cBioPortal, TISIDB, SangerBox, TIMER2.0 and TISMO to investigate the genetic alteration of CCT8 and the relationship of CCT8 with molecular subtype, immune subtype, immune infiltration and immunotherapy response. CCT8-related genes were screened out through GEPIA and STRING for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. CCK-8, the colony formation assay, the wound healing assay and the Transwell assay were performed to explore the influence of CCT8 on proliferation and migration.

Results

CCT8 was highly expressed in most cancers with a poor prognosis. The expression level of CCT8, which was affected by the promoter region methylation and genetic alteration, was related to the molecular and immune subtype of cancers. Interestingly, CCT8 was positively associated with the activated CD4 T cells and type 2 T-helper cells. CCT8 played a vital role in the cell cycle and RNA transport of cancers, and it significantly inhibited the proliferation and migration of lung adenocarcinoma cells when it was knocked down.

Conclusion

CCT8 plays an indispensable role in promoting the proliferation and migration of many cancers. CCT8 might be a biomarker of T-helper type 2 (Th2) cell infiltration and a promising therapeutic target for T-helper type 1(Th1)/Th2 imbalance.

Construction of Severe Eosinophilic Asthma Related Competing Endogenous RNA Network by Weighted Gene Co-Expression Network Analysis

Background: Currently, disease control in patients with severe eosinophilic asthma is not optimistic. Competing endogenous RNA (ceRNA) networks have been found to play a key role in asthma in recent years. However, it is unclear whether ceRNA networks play an important part in severe eosinophilic asthma. Methods: Firstly, gene expression profiles related to severe eosinophilic asthma were downloaded from the Gene Expression Omnibus (GEO) database. Secondly, the key modules were identified by the weighted gene co-expression network analysis (WGCNA). Thirdly, genes in modules highly associated with severe eosinophilic asthma were selected for further construction of the ceRNA network. Fourthly, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were performed on hub genes. Finally, the results of this study were validated on the GSE143303, GSE137268, and GSE147878 datasets. Results: 22 severe eosinophilic asthmatics and 13 healthy controls were extracted for WGCNA. We found that the genes in the black module (r = -0.75, p < 0.05) and yellow module (r = 0.65, p < 0.05) were highly associated with severe eosinophilic asthma. EP300 was discovered to serve the key connecting function in the ceRNA network. Surprisingly, lncRNAs seem to eliminate the role of EP300 in the black module and we discovered that CCT8 and miRNA-mRNA formed a circRNA-miRNA-mRNA network in the yellow module. We found that EP300 and FOXO3 in the black module were regulated by steroid hormones in the enrichment analysis, which were related to the medication used by the patient. Through validation of other datasets, we found that the hub genes in the yellow module were the key genes in the treatment of severe eosinophilic asthma. In particular, RPL17 and HNRNPK might specifically regulate severe eosinophilic asthma. Conclusion: RPL17 and HNRNPK might particularly regulate severe eosinophilic asthma. Our results could be useful to provide potential immunotherapy targets and prognostic markers for severe eosinophilic asthma.

The TRiCky Business of Protein Folding in Health and Disease

Maintenance of the cellular proteome or proteostasis is an essential process that when deregulated leads to diseases like neurological disorders and cancer. Central to proteostasis are the molecular chaperones that fold proteins into functional 3-dimensional (3D) shapes and prevent protein aggregation. Chaperonins, a family of chaperones found in all lineages of organisms, are efficient machines that fold proteins within central cavities. The eukaryotic Chaperonin Containing TCP1 (CCT), also known as Tailless complex polypeptide 1 (TCP-1) Ring Complex (TRiC), is a multi-subunit molecular complex that folds the obligate substrates, actin, and tubulin. But more than folding cytoskeletal proteins, CCT differs from most chaperones in its ability to fold proteins larger than its central folding chamber and in a sequential manner that enables it to tackle proteins with complex topologies or very large proteins and complexes. Unique features of CCT include an asymmetry of charges and ATP affinities across the eight subunits that form the hetero-oligomeric complex. Variable substrate binding capacities endow CCT with a plasticity that developed as the chaperonin evolved with eukaryotes and acquired functional capacity in the densely packed intracellular environment. Given the decades of discovery on the structure and function of CCT, much remains unknown such as the scope of its interactome. New findings on the role of CCT in disease, and potential for diagnostic and therapeutic uses, heighten the need to better understand the function of this essential molecular chaperone. Clues as to how CCT causes cancer or neurological disorders lie in the early studies of the chaperonin that form a foundational knowledgebase. In this review, we span the decades of CCT discoveries to provide critical context to the continued research on the diverse capacities in health and disease of this essential protein-folding complex.