Detection, Distribution and Amount of Posttranslational α-Tubulin Modifications in Immortalized Rat Schwann Cells.

Microtubules (MTs), heterodimers of α- and ß-tubulin, are 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. Despite neurons, in which presence and distributions of tubulin PTMs are well evaluated, in glial cells like Schwann cells, little is known about the diverse 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. By Western blot analysis we found a higher amount of polyglutamylated and tyrosinated α-tubulin, whereas acetylated, Δ2 and detyrosinated α-tubulin were less expressed.  Immunofluorescence staining, highlighted the distribution of acetylated and detyrosinated α-tubulin along the Schwann cells prolongations. 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. 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 the role played by different MTs in Schwann cells biology and during the onset of certain disorders of peripheral nervous system.

Tubulin posttranslational modifications in in vitro matured prepubertal and adult ovine oocytes.

Microtubules (MTs), polymers of alpha/beta-tubulin heterodimers, are involved in crucial functions in eukaryotic cells. MTs physiology can be influenced by a variety of post-translational modifications (PTMs), including tyrosination, detyrosination, delta 2 modification, acetylation, polyglutamylation, polyglycylation. In mammalian oocytes, MTs are essential for meiosis, regulating the formation of meiotic spindle and chromosomes movements. Considering that the patterns of tubulin PTMs (tyrosination, detyrosination, acetylation, polyglutamylation and delta 2 modification) have not been investigated in ovine oocytes, this study has been designed to investigate their presence and quantification in in vitro matured (IVM) adult and prepubertal ovine oocytes. Oocytes from adult and lamb Sarda ewes, regularly slaughtered at the local abattoir, were in vitro matured, fixed, and processed by indirect immunofluorescence and confocal microscopy analyses at metaphase II stage. Our results revealed a well detectable signal for total, tyrosinated and acetylated α-tubulin in meiotic spindle of both sheep and lamb oocytes. On the other hand, no immunopositivity were appreciable for detyrosinated, polyglutamylated, and delta 2 tubulin in meiotic spindle of both sheep and lamb oocytes. As regard the tyrosinated and the acetylated α-tubulin PTMs, through the quantification of the fluorescence intensity, we did not find significant differences in their expression in meiotic spindle of sheep, while in lamb the acetylated tubulin levels were predominant in comparison with tyrosinated. Our results in addition to investigating for the first time the different tubulin PTMs in the spindle organization of ovine oocytes, showed a different microtubule pattern between adult and prepubertal oocytes. The microtubule cytoskeleton survey may thus suggest further cues to better understand skill-related problems in in the acquisition of oocyte competence.