Differential expression and cellular distribution of γ‐tubulin and βIII‐tubulin in medulloblastomas and human medulloblastoma cell lines

Abstract

In previous studies, we have shown overexpression and ectopic subcellular distribution of gamma-tubulin and betaIII-tubulin in human glioblastomas and glioblastoma cell lines (Katsetos et al., 2006, J Neuropathol Exp Neurol 65:455-467; Katsetos et al., 2007, Neurochem Res 32:1387-1398). Here we determined the expression of gamma-tubulin in surgically excised medulloblastomas (n = 20) and in the human medulloblastoma cell lines D283 Med and DAOY. In clinical tissue samples, the immunohistochemical distribution of gamma-tubulin labeling was pervasive and inversely related to neuritogenesis. Overexpression of gamma-tubulin was widespread in poorly differentiated, proliferating tumor cells but was significantly diminished in quiescent differentiating tumor cells undergoing neuritogenesis, highlighted by betaIII-tubulin immunolabeling. By quantitative real-time PCR, gamma-tubulin transcripts for TUBG1, TUBG2, and TUBB3 genes were detected in both cell lines but expression was less prominent when compared with the human glioblastoma cell lines. Immunoblotting revealed comparable amounts of gamma-tubulin and betaIII-tubulin in different phases of cell cycle; however, a larger amount of gamma-tubulin was detected in D283 Med when compared with DAOY cells. Interphase D283 Med cells exhibited predominantly diffuse cytoplasmic gamma-tubulin localization, in addition to the expected centrosome-associated distribution. Robust betaIII-tubulin immunoreactivity was detected in mitotic spindles of DAOY cells. Our data indicate that overexpression of gamma-tubulin may be linked to phenotypic dedifferentiation (anaplasia) and tumor progression in medulloblastomas and may potentially serve as a promising tumor marker.

Kinesin-14 and kinesin-5 antagonistically regulate microtubule nucleation by γ-TuRC in yeast and human cells

“…Our findings are of particular interest in regard to multiple clinically oriented studies525354555657585960 that demonstrate overexpression of γ-tubulin and other centrosomal proteins is characteristic of tumorigenesis and human malignancies in multiple tissues. In this case supernumerary microtubule-nucleating centrosomes are often observed and result in abnormal multipolar mitoses, aneuploidy and ultimately cell death585961.…”

“…Similarly, overexpression of γ-tubulin in malignant cells can also produce ectopic microtubule nucleation in the cytoplasm. This is thought to result from γ-tubulin-centrosome decoupling as well as subcellular sorting changes to soluble cytoplasmic pools or insoluble centrosomal complexes52575860 as well as insoluble cytoplasmic aggregates53. Interestingly, an increase in the percentage of soluble cytoplasmic γ-tubulin is associated with cell lines of higher aggressiveness and poorer prognosis versus those of low or moderate aggressiveness58.…”

The GTPase domain of gamma-tubulin is required for normal mitochondrial function and spatial organization

“…Thus, cell metabolism requires the synchronous production and coordinated transport of metabolites between cell compartments that might be assisted by the γ-tubulin meshwork. Notably, in various tumours and cell lines, the localization and expression of γ-tubulin are altered 38–40 . Thus, the function of γ-tubulin as a regulator of the metabolic status of a cell may be one of various mechanisms that provide tumour cells with metabolic advantages that favour tumour growth.…”

Growth-inhibitory effect of neurotrophin-3-secreting adipose tissue-derived mesenchymal stem cells on the D283-MED human medulloblastoma cell line

“…3a). The proportion of positive cells against Class III b-tubulin antibody, a neuronal differentiation marker [16][17][18], increased linearly as the concentration of NT-3 increased (P \ 0.001; Fig. 3b).…”