Carbonic Anhydrase 3 Overexpression Modulates Signalling Pathways Associated with Cellular Stress Resilience and Proteostasis.

Carbonic anhydrase 3 (CA3) exhibits low enzymatic activity compared to other CA isoforms but contains two surface-exposed cysteine residues that undergo glutathionylation under oxidative stress. Highly expressed in muscle tissue, CA3 has been implicated in cellular protection, particularly through interactions with Bcl2-Associated Athanogene 3 (BAG3), modulating autophagy, while CA3 overexpression decreased hypoxia-induced apoptosis in cardiomyocytes. In this study, we investigated the impact of CA3 overexpression on cellular pathways in HEK293T, MDA-MB-231, and SVCT cells using RNA sequencing and proteomics. Gene Set Enrichment Analysis (GSEA) in HEK293T cells revealed the down-regulation of pathways related to protein synthesis, RNA processing, Roundabout signalling, selenocysteine-metabolism, and suppression of neurodegenerative disease-associated pathways. Human breast epithelial cell lines under normoxia and hypoxia showed down-regulation of similar pathways, although notably, hypoxic conditions also suppressed interferon α/β signalling. Proteomic analysis in HEK293T cells using HaloTag pull-down experiments identified putative novel CA3 binding partners, including heat shock 70 kDa proteins 1 and 8, and ribosomal protein S2 (RPS2). RANBP2 protein was consistently up-regulated after CA3 overexpression, irrespective of the presence of CA3 surface-exposed cysteines and HaloTag orientation. These findings suggest that CA3 modulates key cellular processes beyond its enzymatic role, contributing to stress resilience through pathway-level regulation and protein interactions, potentially impacting autophagy and neurodegenerative disease.