Identification and Validation of an Interaction between the E3 Ubiquitin Ligase WWP1 and the Transcriptional Co-Activator WBP2 in the Human Heart

Impaired proteostasis is one of the cellular hallmarks of aging, and the ubiquitin-proteosome system is a fundamental driver of proteostasis. As an E3 ubiquitin ligase, WW-domain containing protein 1 (WWP1) expression and activity are tightly regulated in cells, while its deregulation has been described in cancer, in neurodegenerative diseases, and in heart failure. However, the protein-protein interaction network of WWP1 is understudied, particularly in the heart. Here, we conducted a yeast-two hybrid (Y2H) screen of a human heart library and identified 21 putative WWP1 interactors, including 12 whose expression and potential function in the heart were previously unappreciated. Chief among these was WBP2 (WW domain binding protein 2), an oncogenic transcriptional co-activator. Utilizing immunofluorescence, it was confirmed that endogenous WWP1 co-localizes with WBP2 in human heart tissue, and, using the Y2H system, we showed that this interaction is dependent upon the associations between WW domains 1 and 3 from WWP1 and PY domains 2 and 3 of WBP2. In total, these data serve as a launching pad to identify broader protein networks regulated by WWP1 and the regions of interaction which might be targetable to reduce hallmarks of cellular aging.