title: Immunolocalization of phospho-S6 kinases: a new way to detect mitosis in tissue sections and in cell culture.
abstract: During a study on the mTor pathway in the rat kidney we observed a striking increase of the phosphorylation of the S6 kinase in mitosis. In cryostat sections of perfusion-fixed tissue mitotic cells appeared as bright spots in immunofluorescence using an antibody specific for the phosphorylation site Thr421/Ser424. They were easily spotted in overviews with the objective 4x and 10x. Immunofluorescence was weak during the interphase. During the prophase it increased in both the nucleus and the cytoplasm and it remained bright during the subsequent phases of mitosis. All mitotic cells which were found in tubules and in the interstitium of the kidney using a chromatin stain displayed the bright immunofluorescence for phospho-S6 kinase. The same phenomenon was observed in rat liver and in mouse kidney as well as in a human cell line. Provided a rapid fixation, mitotic cells could be identified with the immunoperoxidase technique in paraffin sections of immersion-fixed tissue. This is the first report of phosphorylation of S6 kinase during mitosis in vivo. Thus, immunohistochemistry with anti-phospho-S6 kinase (Thr421/Ser424) appears to provide a convenient way to detect mitotic cells at low magnification.
authors.affiliation: Institute of Anatomy, University of Zurich, and Clinic of Nephrology, University Hospital, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmidt
authors.forename: Patricia
authors.initials: P
authors.lastname: Wahl
authors.forename: Rudolf P
authors.initials: RP
authors.lastname: Wüthrich
authors.forename: Alexander
authors.initials: A
authors.lastname: Vogetseder
authors.forename: Nicolas
authors.initials: N
authors.lastname: Picard
authors.forename: Brigitte
authors.initials: B
authors.lastname: Kaissling
authors.forename: Michel
authors.initials: M
authors.lastname: Le Hir
mesh_terms: D000818:Animals; D002460:Cell Line; D005455:Fluorescent Antibody Technique; D006801:Humans; D007124:Immunoenzyme Techniques; D051379:Mice; D008938:Mitosis; D010766:Phosphorylation; D051381:Rats; D019893:Ribosomal Protein S6 Kinases / Q000302:isolation & purification / Q000378:metabolism*; D013194:Staining and Labeling
chemical_list: D019893:Ribosomal Protein S6 Kinases