Microtubules (MTs) are cytoskeletal elements that play an essential role in cell division and cytoplasmic organization. MTs are dynamic polymers of a/beta-Tubulin heterodimers. At least two populations of MTs, called dynamic and stable according to their rates of turnover, are readily distinguishable in cells. The proteins associated with MTs (MAPs) are among the best-known factors that regulate MT dynamics and stability. In addition, a variety of different post-translational modifications may also regulate MT dynamics and stability. Phosphorylation is one of these modifications and it can occur on serine, threonine, and tyrosine residues in alpha- and beta-Tubulin isoforms. Multiple kinases can phosphorylate Ser-444 at the C-terminus of betaIII-Tubulin in vitro, and unphosphorylated Ser-444 may be an early marker for cells of neuronal lineage. Cdk1 can phosphorylate Ser-172 in beta-Tubulin during mitosis and this may impair tubulin incorporation into microtubules. In alpha-tubulin, PKC can phosphorylate Ser-165 leading to increased cell motility in human breast cells.
