The τ-tubulin kinase 2 2 (TTBK2 ) phosphorylates τ and tubulin, preferably in the nervous system
Aberrant TTBK2 activity was linked to the progression of the Alzheimer's disease (70, 71)
The protein resides primarily in the cytosol; however, Böhm et al. could also detect TTBK2 in a secreted form in human tears (72, 73)
Hitherto, no glycosylation of this protein has been described
CID-MS3 as well as ETD spectra of the O-glycopeptide 814KDHSATEPL823 \+HexNAc1Hex1NeuAc1 (m/z 877.822+), though, suggest the O-glycosylation of Thr820
ETD fragment ions at m/z 485.221+, 557.431+, and 1098.631+, corresponding to c4, c+15, and z4 ions, allowed discerning the exact glycosylation site
As TTBK2 is involved in ciliogenesis (74, 75), a process which requires the vesicle transport from the Golgi to the basal bodies and cilia, we speculate that TTBK2 might become O-glycosylated during this process