Functional interaction between the ubiquitin-specific protease 25 and the SYK tyrosine kinase.

The SYK non-receptor tyrosine kinase is a key effector of immune receptors signaling in hematopoietic cells. Here, we identified and characterized a novel interaction between SYK and the ubiquitin-specific protease 25 (USP25). We report that the second SH2 domain of SYK physically interacts with a tyrosine-rich, C-terminal region of USP25 independently of tyrosine phosphorylation. Moreover, we showed that SYK specifically phosphorylates USP25 and alters its cellular levels. This study thus uncovers a new SYK substrate and reveals a novel SYK function, namely the regulation of USP25 cellular levels.