TPD52 Inhibits Aldosterone Synthesis Through Suppression of CAMKK2 Signaling
Background: Aldosterone-producing adenomas (APA) are a major cause of primary aldosteronism. While gene mutations in APA trigger aldosterone overproduction via Calcium signaling, their precise regulatory mechanisms remain unclear. Our prior proteomic analysis identified significant upregulation of Tumor protein D52 (TPD52), an oncogene protein implicated in cancer progression, in APA. This study investigates the role of TPD52 in regulating aldosterone synthesis and its molecular mechanism. Method: TPD52 expression was validated in APA specimens. Gain- and loss-of-function studies in NCI-H295R cells were performed to assess its role in aldosterone synthesis. Mechanistic insights were obtained through transcriptomics and immunoprecipitation-mass spectrometry (IP-MS), with key results validated in NCI-H295R and HEK-293T cells. Results: TPD52 was upregulated in APA tissues. Functionally, TPD52 overexpression suppressed aldosterone synthesis in NCI-H295R cells, whereas its knockdown enhanced aldosterone production. Transcriptomics confirmed that TPD52 knockdown promoted CYP11B2 expression and aldosterone synthesis. IP-MS identified calcium/calmodulin-dependent protein kinase kinase 2 (CAMKK2) as a novel TPD52-interacting protein. This interaction suppressed phosphorylation of calmodulin-dependent protein kinase 4 (CAMK4) and CREB. Importantly, CAMKK2 overexpression rescued the TPD52-mediated suppression of CYP11B2 expression and aldosterone synthesis. Conclusion: TPD52 acts as a negative regulator of aldosterone synthesis by inhibiting the CAMKK2–CAMK4–CREB signaling axis. Overall design: RNA-seq profiling of  NCI-H295R cells, in which TPD52 expression was knocked down by lentivirus-delivered specific shRNA compared to a non-targeting shRNA control.