Dynamic interplay between nitration and phosphorylation of tubulin cofactor B in the control of microtubule dynamics

Abstract

Tubulin cofactor B (TCoB) plays an important role in microtubule dynamics by facilitating the dimerization of α- and β-tubulin. Recent evidence suggests that p21-activated kinase 1 (Pak1), a major signaling nodule in eukaryotic cells, phosphorylates TCoB on Ser-65 and Ser-128 and plays an essential role in microtubule regrowth. However, to date, no upstream signaling molecules have been identified to antagonize the functions of TCoB, which might help in maintaining the equilibrium of microtubules. Here, we discovered that TCoB is efficiently nitrated, mainly on Tyr-64 and Tyr-98, and nitrated-TCoB attenuates the synthesis of new microtubules. In addition, we found that nitration of TCoB antagonizes signaling-dependent phosphorylation of TCoB, whereas optimal nitration of TCoB requires the presence of functional Pak1 phosphorylation sites, thus providing a feedback mechanism to regulate phosphorylation-dependent MT regrowth. Together these findings identified TCoB as the third cytoskeleton protein to be nitrated and suggest a previously undescribed mechanism, whereby growth factor signaling may coordinately integrate nitric oxide signaling in the regulation of microtubule dynamics.

Tyrosine Nitration within the Proline-Rich Region of Tau in Alzheimer's Disease

“…The highly electronegative orthophosphate group likely would not permit the addition of a nitro group at the meta position of the same tyrosine ring. A balance between nitration and phosphorylation at specific amino acids may have some biological importance, 26,46 but this hypothesis requires further study.…”

Revisiting the tubulin folding pathway: new roles in centrosomes and cilia

“…Indeed, mutated forms of TBCB at its phosphorylation sites inhibit microtubule regrowth from the centrosome after nocodazole treatment and washout (80). More recently, it has been shown that TBCB, just like tau and a-tubulin, undergoes nitration, which inhibits the polymerization of new microtubules (81). The inhibition of microtubule regrowth in this case seems to be related to the fact that tyrosine nitration of TBCB inhibits its ability to undergo phosphorylation.…”

Nitrated Proteome in Human Embryonic Stem Cells

“…5 Further, nitration at a tyrosine residue can modulate phosphorylation of neighboring sites. 20 To examine the potential effect of nitration on signaling pathways, we first collected phosphorylation sites for the 23 NPs from the following three PTM databases (Phosphosite Plus, 29 Phosida, 30 Phospho.ELM…”

“…PTN exerts its functions by modulating phosphorylation of the nitrated tyrosine or neighboring serine/threonine residues. 20 Thus, the comparison between the detected nitrated and known phosphorylation sites can reveal functional implication of the nitrated sites. •) is necessarily needed to initiate this modification.…”