Chemical proteomics reveals interactors of the alarmone diadenosine triphosphate in the cancer cell line H1299.

Intracellular dinucleoside polyphosphates (Np Ns) have been known for decades but the functional role remains enigmatic. Diadenosine triphosphate (Ap A) is one of the most prominent examples, and its intercellular concentration was shown to increase upon cellular stress. By employment of previously reported Ap A-based photoaffinity-labeling probes (PALPs) in chemical proteomics, we investigated the Ap A interactome in the human lung carcinoma cell line H1299. The cell line is deficient of the fragile histidine triade (Fhit) protein, a hydrolase of Ap A and tumor suppressor. Overall, the number of identified potential interaction partners was significantly lower than in the previously investigated HEK293T cell line. Gene ontology term analysis revealed that the identified proteins participate in similar pathways as for HEK293T, but the percentage of proteins involved in RNA-related processes is higher for H1299. The obtained results highlight similarities and differences of the Ap A interaction network in different cell lines and give further indications regarding the importance of the presence of Fhit.