A PROTEIN RELATED TO BRAIN MICROTUBULE-ASSOCIATED PROTEIN MAP1B IS A COMPONENT OF THE MAMMALIAN CENTROSOME

Citation
Je. Dominguez et al., A PROTEIN RELATED TO BRAIN MICROTUBULE-ASSOCIATED PROTEIN MAP1B IS A COMPONENT OF THE MAMMALIAN CENTROSOME, Journal of Cell Science, 107, 1994, pp. 601-611
Citations number
81
Categorie Soggetti
Cytology & Histology
Journal title
ISSN journal
00219533
Volume
107
Year of publication
1994
Part
2
Pages
601 - 611
Database
ISI
SICI code
0021-9533(1994)107:<601:APRTBM>2.0.ZU;2-S
Abstract
The centrosome is the main microtubule organizing center of mammalian cells. Structurally, it is composed of a pair of centrioles surrounded by a fibro-granular material (the pericentriolar material) from which microtubules are nucleated. However, the nature of centrosomal molecu les involved in microtubule nucleation is still obscure. Since brain m icrotubule-associated proteins (MAPs) lower the critical tubulin conce ntration required for microtubule nucleation in tubulin solution in vi tro, we have examined their possible association with centrosomes. By immunofluorescence, monoclonal and polyclonal antibodies raised agains t MAP1B stain the centrosome in cultured cells as well as purified cen trosomes, whereas antibodies raised against MAP2 give a completely neg ative reaction. The MAP1B-related antigen is localized to the pericent riolar material as revealed by immunoelectron microscopy. In preparati ons of purified centrosomes analyzed on polyacrylamide gels, a protein that migrates as brain MAP1B is present. After blotting on nitrocellu lose, it is decorated by anti-MAP1B antibodies and the amino acid sequ ence of proteolytic fragments of this protein is similar to brain MAP1 B. Moreover, brain MAP1B and its centrosomal counterpart share the sam e phosphorylation features and have similar peptide maps. These data s trongly suggest that a protein homologue to MAP1B is present in centro somes and it is a good candidate for being involved in the nucleating activity of the pericentriolar material.