Tubulin post-translational modifications in Schwann cells.

Microtubules (MTs), are heterodimers of α- and β-tubulin, generally involved in different cellular processes including mitosis, cell motility, intracellular transport, cell shape and polarization. In most eukaryotes tubulins, especially the α, are subjected to several post-translational modifications (PTMs) which include acetylation, tyrosination, detyrosination, Δ2 modification, polyglutamylation, that characterize different type of MTs and regulate the interactions between MTs and certain MAPs or motor proteins. Unlike neurons, in which presence and distributions of tubulin PTMs are most studied, in other neural cells little is known about the different tubulin PTMs amount, distribution and their functional role. So that, the purpose of the present work was to deepen the knowledge about the diverse tubulin PTMs in a commonly used immortalized Schwann cell line. Undifferentiated RT4-D6P2T rat schwannoma cells were cultured in standard conditions for 48 hours. Prior to reach complete confluence, cells were or fixed or collected and homogenized for underwent to immunofluorescence staining and Western blot procedures respectively. Our results, displayed some original data. Both Western blot analysis and immunofluorescence staining revealed significant levels of polyglutamylated and Δ2-modification α-tubulins, usually considered mainly expressed in neurons. In addition we found differences in amount and distribution of tubulin PTMs in Schwann cells. In details, Western blot analysis showed a higher amount of polyglutamylated and tyrosinated α-tubulin, whereas acetylated, Δ2 and detyrosinated α-tubulin were less expressed, in comparison with total α-tubulin. Immunofluorescence staining, highlighted the distribution of acetylated and detyrosinated α-tubulin along the Schwann cells prolongations, showing a pattern similar with neurons, were the detyrosinated and acetylated isoforms are usually most detectable in axons and dendrites. In contrast, polyglutamylated α-tubulin was more detectable close to the cell body of Schwann cells, whereas the Δ2-modification was mainly distributed round the nuclear profile, forming a characteristic and complete ring. The tyrosinated α-tubulin isoform, appeared uniformly distributed both in the cytoplasmic processes and to the cell body. Summing up, our investigation offers insight on several tubulin PTMs amount and distribution in Schwann cells. This could be a further contribution to better understand both the role played by different MTs in myelination processes and the possible microtubular involvment in the pathogenesis of certain Schwann cells disorders.