Oncogenic role of nuclear accumulated Aurora-A.
Aurora-A, also known as Aik, BTAK, or STK15, is a centrosomal serine/threonine protein kinase, which is proto-oncogenic and is overexpressed in a wide range of human cancers. Besides gene amplification and mRNA overexpression, proteolytic resistance mechanisms are thought to contribute to overexpression of Aurora-A. However, it is not yet clear how overexpressed Aurora-A affects the expression of transformed phenotype. Here, we found that nuclear accumulation of Aurora-A was critical for transformation activity. Cellular protein fractionation experiments and immunoblot analysis demonstrated a predominance of Aurora-A in the nuclear soluble fraction in head and neck cancer cells. Indirect immunofluorescence using confocal laser microscopy confirmed nuclear Aurora-A in head and neck cancer cells, while most oral keratinocytes exhibited only centrosomal localization. The expression of nuclear export signal-fused Aurora-A demonstrated that the oncogenic transformation activity was lost on disruption of the nuclear localization. Thus, the cytoplasmic localization of overexpressed Aurora-A previously demonstrated by immunohistochemical analysis is not likely to correspond to that in intact cancer cells. This study identifies an alternative mode of Aurora-A overexpression in cancer, through nuclear rather than cytoplasmic functions. We suggest that substrates of Aurora-A in the cell nuclear soluble fraction can represent a novel therapeutic target for cancer.
Tatsuka
Masaaki
M
Department of Life Sciences, Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Hiroshima 727-0023, Japan.
Sato
Sunao
S
Kanda
Akifumi
A
Miki
Tomoharu
T
Kamata
Nobuyuki
N
Kitajima
Shojiro
S
Kudo
Yasusei
Y
Takata
Takashi
T
D000818:Animals; D064096:Aurora Kinase A; D064127:Aurora Kinases; D041702:BALB 3T3 Cells; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism*; D002471:Cell Transformation, Neoplastic; D018385:Centrosome / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006258:Head and Neck Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D020641:Polymorphism, Single Nucleotide; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection
D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; C576917:AURKA protein, human; C576918:Aurka protein, mouse; D064096:Aurora Kinase A; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases