title: alphaB-Crystallin-coated MAP microtubule resists nocodazole and calcium-induced disassembly.
abstract: alphaB-Crystallin, one of the small heat-shock proteins, is constitutively expressed in various tissues including the lens of the eye. It has been suggested that alphaB-crystallin provides lens transparency but its function in nonlenticular tissues is unknown. It has been reported that alphaB-crystallin is involved in the stabilization and the regulation of cytoskeleton, such as intermediate filaments and actin. In this study, we investigate the possibility whether alphaB-crystallin interacts with the third cytoskeleton component, microtubules (MTs). First, we precisely observed the cellular localization of alphaB-crystallin and MT networks in L6E9 myoblast cells and found a striking coincidence between them. MTs reconstituted from cell lysate contained alphaB-crystallin. Electron micrographs clearly showed direct interactions of purified alphaB-crystallin with the surface of microtubule-associated proteins (MAPs) attached to MTs. Purified alphaB-crystallin bound to MAP-MTs in a concentration-dependent manner. However, alphaB-crystallin did not bind MTs reconstituted from purified tubulin. Finally, we observed that alphaB-crystallin increased the resistance of MTs to depolymerization in cells and in vitro. Taken together, these results suggest that one of the functions of alphaB-crystallin is to bind MTs via MAP(s) and to give the MTs resistance to disassembly.
authors.affiliation: Department of Life Sciences, The Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Yoshinobu
authors.initials: Y
authors.lastname: Fujita
authors.forename: Eri
authors.initials: E
authors.lastname: Ohto
authors.forename: Eisaku
authors.initials: E
authors.lastname: Katayama
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Atomi
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D002460:Cell Line; D045744:Cell Line, Tumor; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism* / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology*; D016376:Oligonucleotides, Antisense; D011034:Podophyllotoxin / Q000494:pharmacology; D011485:Protein Binding; D051381:Rats; D038203:alpha-Crystallin B Chain / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D008869:Microtubule-Associated Proteins; D016376:Oligonucleotides, Antisense; D038203:alpha-Crystallin B Chain; D011034:Podophyllotoxin; D015739:Nocodazole; D002118:Calcium