title: Characterization of SKAP/kinastrin isoforms: the N-terminus defines tissue specificity and Pontin binding.
abstract: Small Kinetochore-Associated Protein (SKAP)/Kinastrin is a multifunctional protein with proposed roles in mitosis, apoptosis and cell migration. Exact mechanisms underlying its activities in these cellular processes are not completely understood. SKAP is predicted to have different isoforms, however, previous studies did not differentiate between them. Since distinct molecular architectures of protein isoforms often influence their localization and functions, this study aimed to examine the expression profile and functional differences between SKAP isoforms in human and mouse. Analyses of various human tissues and cells of different origin by RT-PCR, and by Western blotting and immunocytochemistry applying newly generated anti-SKAP monoclonal antibodies revealed that human SKAP exists in two protein isoforms: ubiquitously expressed SKAP16 and testis/sperm-specific SKAP1. In mouse, SKAP1 expression is detectable in testis at 4 weeks postnatally, when the first wave of spermatogenesis in mice is complete and the elongated spermatids are present in the testes. Furthermore, we identified Pontin as a new SKAP1 interaction partner. SKAP1 and Pontin co-localized in the flagellar region of human sperm suggesting a functional relevance for SKAP1-Pontin interaction in sperm motility. Since most previous studies on SKAP were performed with the testis-specific isoform SKAP1, our findings provide a new basis for future studies on the role of SKAP in both human somatic cells and male germ cells, including studies on male fertility.
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany.
authors.forename: Anita
authors.initials: A
authors.lastname: Cindric Vranesic
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany.
authors.forename: Juliane
authors.initials: J
authors.lastname: Reiche
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute e.V. Jena, 07745 Jena, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Hoischen
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Wohlmann
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Bratsch
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany.
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Friedrich
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute e.V. Jena, 07745 Jena, Germany.
authors.forename: Berkay
authors.initials: B
authors.lastname: Günes
authors.affiliation: Department of Andrology, University Hospital Hamburg-Eppendorf, 20246 Hamburg, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Cappallo-Obermann
authors.affiliation: Department of Andrology, University Hospital Hamburg-Eppendorf, 20246 Hamburg, Germany.
authors.forename: Christiane
authors.initials: C
authors.lastname: Kirchhoff
authors.affiliation: Leibniz Institute on Aging - Fritz Lipmann Institute e.V. Jena, 07745 Jena, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Diekmann
authors.affiliation: Department of Urology, University Hospital Ulm, 89075 Ulm, Germany.
authors.forename: Cagatay
authors.initials: C
authors.lastname: Günes
authors.affiliation: Department of Biochemistry II, Jena University Hospital, 07743 Jena, Germany otmar.huber@med.uni-jena.de.
authors.forename: Otmar
authors.initials: O
authors.lastname: Huber
mesh_terms: D000818:Animals; D017209:Apoptosis; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism*; D008938:Mitosis; D009928:Organ Specificity / Q000235:genetics; D000072417:Protein Domains / Q000235:genetics; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D013081:Sperm Motility; D013091:Spermatogenesis; D013094:Spermatozoa / Q000378:metabolism; D013737:Testis / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; C555984:KNSTRN protein, human; D008869:Microtubule-Associated Proteins; D020033:Protein Isoforms; C000612101:SKAP protein, mouse