Expression and phosphorylation of TOPK during spermatogenesis.
Among normal organs and tissues, the MAPKK-like mitotic protein kinase TOPK is expressed exclusively in the testis. We analyzed the expression and phosphorylation of TOPK to address the functional role of this kinase during spermatogenesis. TOPK protein is expressed mainly in the cytosol of spermatocytes and spermatids, but not in spermatids and spermatogonia in situ. TOPK-Thr-9, a cdk1/cyclin B target residue, was specifically phosphorylated during mitotic and meiotic phases, while TOPK-Thr-198, a key amino acid for the ATP pocket, was constantly phosphorylated irrespective of the cell cycle. These data indicate that spermatogenic germ cells with vital proliferation activity express TOPK. As TOPK-Thr-9 was phosphorylated during both mitosis and meiosis, TOPK was indicted to play a role in cytokinesis and/or chromosomal segregation but not in DNA replication.
Fujibuchi
Taketsugu
T
Department of Pathology, Division of Molecular Pathology, National University Corporation, Ehime University School of Medicine, Toh-on, Ehime 791-0295, Japan.
Abe
Yasuhito
Y
Takeuchi
Takashi
T
Ueda
Norifumi
N
Shigemoto
Kazuhiro
K
Yamamoto
Haruyasu
H
Kito
Katsumi
K
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D000937:Antigen-Antibody Reactions; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases; D008938:Mitosis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism*; D012680:Sensitivity and Specificity; D013087:Spermatids / Q000378:metabolism; D013090:Spermatocytes / Q000378:metabolism; D013091:Spermatogenesis / Q000235:genetics* / Q000502:physiology*
D000906:Antibodies; D017346:Protein Serine-Threonine Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; C409022:PDZ-binding kinase