Integrative phosphoproteomics reveals kinase-mediated regulation of OCIAD1 and its roles in mitochondrial quality...

The ovarian cancer immunoreactive antigen domain-containing protein 1 (OCIAD1) is a mitochondrial protein implicated in mitochondrial morphology, energy metabolism, and differentiation. Although understudied, recent studies position it as a critical player in carcinogenesis and neurodegenerative disorders, making it a potentially druggable node in cellular signaling networks. However, the phosphoregulatory networks and the upstream kinases governing OCIAD1 remain unknown.

A large-scale literature mining and analysis of 177 phosphoproteomic datasets with differential expression of OCIAD1 was carried out to map its phosphoregulatory network. The predominant phosphosites were determined based on localization probability, detection frequency, and differential regulation. Multipronged computational approaches were employed to gather novel candidate kinases that may target OCIAD1 phosphosites. Co-differential phosphorylation analysis was conducted with other proteins, including interactors and candidate upstream kinases, to infer functional and regulatory associations.

The sites S108 and S123 emerged as predominant, together accounting for 70% of OCIAD1 phosphorylation. Co-differential phosphorylation analysis revealed associations with proteins involved in the cell cycle, DNA repair, autophagy, mitophagy, endocytosis, and apoptosis. Novel candidate kinases for OCIAD1 phosphosites were identified; notably, SRMS and YES1 emerged as potential upstream regulators of Y199. Furthermore, the phosphosites in the candidate kinases of sites, including PLK1 (T210), CDK13 (S383, S397), PRKD2 (S200), CIT (S1343), and RPS6KA3 (T577), showed strong positive co-differential regulation with OCIAD1 predominant sites, supporting their potential involvement as upstream kinases.

This study presents the first systematic map of the OCIAD1 phosphoregulatory network and provides candidate upstream kinases that may contribute to its phosphorylation, which warrant further experimental validation. The strong co-differential regulation of proteins involved in autophagy, mitophagy, endocytosis, and neurodegenerative pathways, as well as of kinases that orchestrate these processes, suggests that OCIAD1 phosphoregulatory network maybe involved in mitochondrial quality control and mitochondria-associated neurodegeneration, establishing a foundation for therapeutic investigations targeting OCIAD1 signaling.