title: CacyBP/SIP interacts with tubulin in neuroblastoma NB2a cells and induces formation of globular tubulin assemblies.
abstract: CacyBP/SIP, originally identified as a S100A6 (calcyclin) target, was later shown to interact with some other members of the S100 family as well as with Siah-1 and Skp1 proteins. Recently, it has been shown that CacyBP/SIP is up-regulated during differentiation of cardiomyocytes. In this work we show that the level of CacyBP/SIP is higher in differentiated neuroblastoma NB2a cells than in undifferentiated ones and that in cells overexpressing CacyBP/SIP the level of GAP-43, a marker of differentiation, was increased. Since the process of differentiation is accompanied by an extensive rearrangement of microtubules, we examined whether CacyBP/SIP interacted with tubulin. By applying cross-linking experiments we found that these two proteins bind directly. The dissociation constant of the tubulin-CacyBP/SIP complex determined by the surface plasmon resonance technique is 1.57 x 10(-7 )M which suggests that the interaction is tight. The interaction and co-localization of CacyBP/SIP and tubulin was also demonstrated by co-immunoprecipitation, affinity chromatography and immunofluorescence methods. Light scattering measurements and electron microscopy studies revealed that CacyBP/SIP, but not its homologue, Sgt1, increased tubulin oligomerization. Altogether, our results suggest that CacyBP/SIP, via its interaction with tubulin, might contribute to the differentiation of neuroblastoma NB2a cells.
authors.affiliation: Nencki Institute of Experimental Biology, 3 Pasteur Street, 02-093 Warsaw, Poland.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Schneider
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Nieznanski
authors.forename: Ewa
authors.initials: E
authors.lastname: Kilanczyk
authors.forename: Paweł
authors.initials: P
authors.lastname: Bieganowski
authors.forename: Jacek
authors.initials: J
authors.lastname: Kuznicki
authors.forename: Anna
authors.initials: A
authors.lastname: Filipek
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D002457:Cell Extracts; D003432:Cross-Linking Reagents / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D047468:Immunoprecipitation; D051379:Mice; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008969:Molecular Sequence Data; D009391:Nephelometry and Turbidimetry; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology*; D011485:Protein Binding / Q000187:drug effects; D020836:Protein Structure, Quaternary; D021381:Protein Transport / Q000187:drug effects; D013552:Swine; D014404:Tubulin / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: C111922:Cacybp protein, mouse; D002135:Calcium-Binding Proteins; D002457:Cell Extracts; D003432:Cross-Linking Reagents; D014404:Tubulin