Synthesis and characterization of a novel phosphatidylinositol 5-phosphate (PI(5)P) photoaffinity probe.

Phosphatidylinositol 5-phosphate (PI(5)P) plays a crucial role in cellular signaling, cell proliferation, the DNA damage repair response, and gene transcription. However, the underlying mechanism of PI(5)P function in these cellular pathways is poorly understood. This lack of understanding results at least in part, from the dearth of available chemical tools to enable the investigation of PI(5)P interaction with target proteins in the corresponding biological systems. Here, we report the design and synthesis of a novel phosphatidylinositol 5-phosphate-based photoaffinity probe. The probe bound and photo-crosslinked to purified, recombinant hUHRF1 and TAF1 proteins that are known PI(5)P-interacting factors. Copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry with an azide-functionalized TAMRA dye allowed visualization of these proteins. We further show that the PI(5)P photoaffinity probe was functional in complex cell lysate by demonstrating protein crosslinking and fluorescent visualization with a TAMRA-azide. The data presented here validate the novel photoaffinity probe as a molecular tool for analyzing interactions and mapping the PI(5)P interactome.