Identification of transglutaminase 2 mediated polyaminated proteins in a hepatocellular cancer cell line

Polyamines are abundant metabolites that are involved in many cellular processes. Despite playing wide-ranging and essential roles in the cell, only a few examples of a specific polyamine function are known. Polyamination is the post-translational modification of a protein by polyamines (putrescine, spermidine or spermine). This reaction is catalyzed by transglutaminases (primarily TGM2) via a transamidation reaction that conjugates a polyamine to an acceptor glutamine in a target protein. Protein polyamination is poorly characterized due to technical challenges in detecting the polyaminated adduct, and is neglected in most proteomic surveys. We performed polyamination reactions using whole cell lysates from a mouse liver cancer cell line with elevated TGM2 expression. Two differently tagged polyamine analogs (Biotin-pentylamine and DNP-pentylamine) with distinct molecular masses were used, and the respective modified peptides were identified by mass spectrometry. 51 protein targets modified on 66 different sites were identified, in some cases with both donor polyamines. Many of the targets are involved in translation or cytoskeletal organization, and implicated in cancer.