Truncation of the Projection Domain of MAP4 (Microtubule-Associated Protein 4) Leads to Attenuation of Microtubule Dynamic Instability

Cell Structure and Function

Hirokazu Hotani²  Shin-ichi Hisanaga¹  Yoko Nagatomo²  Junko Iida¹  Sofy Permana²  Tomohiko J. Itoh² 

[1] Department of Biological Sciences, Graduate School of Science, Tokyo Metropolitan University;Division of Biological Sciences, Graduate School of Science, Nagoya University

关键词: microtubule;    dynamic instability;    MAP4;    projection domain;    dark-field microscopy;   

DOI  :  10.1247/csf.29.147

学科分类：分子生物学，细胞生物学和基因

来源: Japan Society for Cell Biology

【 摘 要 】

References(47)Cited-By(8)MAP4, a ubiquitous heat-stable MAP, is composed of an asymmetric structure common to the heat-stable MAPs, consisting of an N-terminal projection (PJ) domain and a C-terminal microtubule (MT)-binding (MTB) domain. Although the MTB domain has been intensively studied, the role of the PJ domain, which protrudes from MT-wall and does not bind to MTs, remains unclear. We investigated the roles of the PJ domain on the dynamic instability of MTs by dark-field microscopy using various PJ domain deletion constructs of human MAP4 (PJ1, PJ2, Na-MTB and KDM-MTB). There was no obvious difference in the dynamic instability between the wtMAP4 and any fragments at 0.1 μM, the minimum concentration required to stabilize MTs. The individual MTs stochastically altered between polymerization and depolymerization phases with similar profiles of length change as had been observed in the presence of MAP2 or tau. We also examined the effects at the increased concentrations of 0.7 μM, and found that in some cases the dynamic instability was almost entirely attenuated. The length of both the polymerization and depolymerization phases decreased and “pause-phases” were occasionally observed, especially in the case of PJ1, PJ2 or Na-MTB. No obvious change was observed in the increased concentration of wtMAP4 and KDM-MTB. Additionally, the profiles of MT length change were quite different in 0.7 μM PJ2. Relatively rapid and long depolymerization phases were sometimes observed among quite slow length changes. Perhaps, this unusual profile could be due to the uneven distribution of PJ2 along the MT lattice. These results indicate that the PJ domain of MAP4 participates in the regulation of the dynamic instability.

【 授权许可】

Unknown