Biomedical subjects

B Brugg

Publications and source records attributed to B Brugg.

22 records · Page 2Linked to original sources

PubMed1993

Attenuation of microtubule-associated protein 1B expression by antisense oligodeoxynucleotides inhibits initiation of neurite outgrowth.

Microtubule-associated protein 1B, formerly also known as microtubule-associated protein 5, is the first structural microtubule accessory protein to appear in outgrowing axons. In PC12 pheochromocytoma cells microtubule-associated protein 1B levels increase several-fold after the addition of nerve growth factor and this increase is correlated with the initiation of process formation. To determine whether microtubule-associated protein 1B is essential for neurite outgrowth, we used antisense oligodeoxynucleotides to inhibit its expression in nerve growth factor-treated PC12 cells in the rat. The application of several different antisense oligodeoxynucleotides to the microtubule-associated protein 1B mRNA sequence inhibited both microtubule-associated protein 1B expression and neurite extension. Specificity was shown by the lack of effect of control sense oligonucleotides and by the lack of effect of the microtubule-associated protein 1B antisense oligodeoxynucleotides on the expression of either tubulin or microtubule-associated protein 3, another microtubule-associated protein whose synthesis is stimulated by nerve growth factor treatment of PC12 cells. After removal of the antisense oligodeoxynucleotides, microtubule-associated protein 1B expression recovered to normal levels and the cells grew normal neurites with the timing and morphological characteristics of normal nerve growth factor-induced outgrowth, indicating that the blockade was not because of non-specific toxic effects. These results indicate that microtubule-associated protein 1B is an essential component of the molecular mechanism underlying the formation of neuronal processes.

Animals↗

PubMed1991

Phosphorylation determines the binding of microtubule-associated protein 2 (MAP2) to microtubules in living cells.

The influence of phosphorylation on the binding of microtubule-associated protein 2 (MAP2) to cellular microtubules was studied by microinjecting MAP2 in various phosphorylation states into rat-1 fibroblasts, which lack endogenous MAP2. Conventionally prepared brain MAP2, containing 10 mol of endogenous phosphate per mol (MAP2-P10), was completely bound to cellular microtubules within 2-3 min after injection. MAP2 prepared in the presence of phosphatase inhibitors, containing 25 mol/mol of phosphate (MAP2-P25), also bound completely. However, MAP2 whose phosphate content had been reduced to 2 mol phosphate per mol by treatment with alkaline phosphatase in vitro (MAP2-P2) did not initially bind to microtubules, suggesting that phosphorylation of certain sites in MAP2 is essential for binding to microtubules. MAP2-P10 was further phosphorylated in vitro via an endogenously bound protein kinase activity, adding 12 more phosphates, giving a total of 22 mol/mol. This preparation (MAP2-P10+12) also did not bind to microtubules. Assay of the binding of these preparations to taxol-stabilized tubulin polymers in vitro confirmed that their binding to tubulin depended on the state of phosphorylation, but the results obtained in microinjection experiments differed in some cases from in vitro binding. The results suggest that the site of phosphate incorporation rather than the amount is the critical factor in determining microtubule binding activity of MAP2. Furthermore, the interaction of MAP2 with cellular microtubules may be influenced by additional factors that are not evident in vitro.

Animals↗

PubMed1988

PC12 cells express juvenile microtubule-associated proteins during nerve growth factor-induced neurite outgrowth.

Microtubule-associated proteins (MAPs) are believed to play an important role in regulating the growth of neuronal processes. The nerve growth factor-induced differentiation of PC12 pheochromocytoma cells is a widely used tissue culture model for studying this mechanism. We have found that contrary to previous suggestions, the major MAPs of adult brain, MAP1 and MAP2, are minor components of PC12 cells. Instead two novel MAPs characteristic of developing brain, MAP3 and MAP5, are present and increase more than 10-fold after nerve growth factor treatment; the timing of these increases coinciding with the bundling of microtubules and neurite outgrowth. Immunocytochemical staining showed that MAP3 and MAP5 are initially distributed throughout the cytoplasm. Subsequently MAP5 becomes associated with microtubules in both neurites and growth cones but MAP3 distribution remained diffuse. Thus MAP3 and MAP5, which are characteristic of developing neurons in the juvenile brain, are also induced in PC12 cells during neurite outgrowth in culture. In contrast MAP1, which is characteristic of mature neurons, does not increase during PC12 cell differentiation. These results provide evidence that one set of MAPs is expressed during neurite outgrowth and a different set during the maintenance of neuronal form. It also appears that the PC12 system is an appropriate model for studying the active neurite growth phase of neuronal differentiation but not for neuronal maturation.

Adrenal Gland Neoplasms↗

PubMed1988

A 70-kilodalton microtubule-associated protein (MAP2c), related to MAP2.

Microtubule-associated protein 2 (MAP2) from adult brain consists of a pair of high molecular mass (280 kilodaltons) polypeptides, MAP2a and MAP2b. Juvenile brain microtubules also contain a 70-kilodalton protein that cross-reacts with monoclonal antibodies against these high molecular weight MAP2s. We have analyzed the relationship between this 70-kilodalton protein and MAP2 by peptide mapping. Our results show that the 70-kilodalton species bears strong homology to the MAP2 molecules and that it is distinct from the tau MAPs. We propose the name MAP2c for this low molecular weight MAP2 species. MAP2c is developmentally regulated in brain, being more abundant in neonatal tissue than in the adult. In several cell lines, MAP2c is the sole MAP2 species expressed. We examined homogenates from both juvenile brain and MAP2c-containing cell lines for evidence of a protease activity that might be responsible for generating MAP2c from either MAP2a or MAP2b. No such activity was found, suggesting that MAP2c is an independently synthesized MAP2 species some 200 kilodaltons smaller than the previously recognized forms.

Adrenal Gland Neoplasms↗