Chemical proteomics reveals protein tyrosination extends beyond the alpha-tubulins in human cells.

Tubulin detyrosination-tyrosination cycle regulates the stability of microtubules. Thus far described on α-tubulins, the tyrosination level is maintained by a single tubulin-tyrosine ligase (TTL). However, the precise dynamics and tubulin isoforms which undergo (de)tyrosination in neurons are unknown. Here, we exploit the substrate promiscuity of the TTL to introduce an O-propargyl-L-tyrosine in cancer cell lines and neurons. Mass spectrometry-based chemical proteomics in neuroblastoma cells using the O-propargyl-L-tyrosine probe revealed previously discussed tyrosination of TUBA4A, MAPRE1, and other non-tubulin proteins. This finding was further corroborated in differentiating neurons. We present the method for tubulin tyrosination profiling in living cells. Our results show that detyrosination-tyrosination is not restricted to α-tubulins with coded C-terminal tyrosine and is thus involved in fine-tuning of the tubulin and non-tubulin proteins during neuronal differentiation.