Aurora-A kinase interacting protein 1 (AURKAIP1) promotes Aurora-A degradation through an alternative ubiquitin-independent pathway.
Mitotic Aurora-A is an oncogene, which undergoes a cell-cycle-dependent regulation of both its synthesis and degradation. Overexpression of Aurora-A leads to aneuploidy and cellular transformation in cultured cells. It has been shown that the cell-cycle-dependent turnover of Aurora-A is mediated by Cdh1 (CDC20 homologue 1) through the anaphase-promoting complex/cyclosome (APC/C)-ubiquitin-proteasome pathway. We have described previously the identification of an Aurora-A kinase interacting protein, AURKAIP1 (formerly described as AIP), which is also involved in the destabilization of Aurora-A through the proteasome-dependent degradation pathway. In an attempt to investigate the mechanism of AURKAIP1-mediated Aurora-A degradation, we report here that AURKAIP1 targets Aurora-A for degradation in a proteasome-dependent but Ub (ubiquitin)-independent manner. AURKAIP1 inhibits polyubiquitination of Aurora-A. A non-interactive AURKAIP1 mutant that cannot destabilize Aurora-A restores ubiquitination of Aurora-A. An A-box mutant of Aurora-A, which cannot be targeted for proteasome-dependent degradation by Cdh1, can still be degraded by AURKAIP1. Inhibition of cellular ubiquitination either by expression of dominant negative Ub mutants or by studies in ts-20 (temperature sensitive-20) CHO (Chinese-hamster ovary) cell line lacking the E1 Ub activating enzyme at the restrictive temperature, cannot abolish AURKAIP1-mediated degradation of Aurora-A. AURKAIP1 specifically decreases the stability of Aurora-A in ts-20 CHO cells at the restrictive temperature, while cyclinB1 and p21 are not affected. This demonstrates that there exists an Ub-independent alternative pathway for Aurora-A degradation and AURKAIP1 promotes Aurora-A degradation through this Ub-independent yet proteasome-dependent pathway.
Lim
Shen Kiat
SK
Laboratory of Gene Structure and Expression, Division of Cellular and Molecular Research, National Cancer Centre, Singapore 169610, Singapore.
Gopalan
Ganesan
G
D019943:Amino Acid Substitution; D000818:Animals; D064096:Aurora Kinase A; D064127:Aurora Kinases; D002453:Cell Cycle; D005434:Flow Cytometry; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D051379:Mice; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D017384:Sequence Deletion; D025801:Ubiquitin / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D011994:Recombinant Proteins; D025801:Ubiquitin; C103265:aryl hydrocarbon receptor-interacting protein; C576918:Aurka protein, mouse; D064096:Aurora Kinase A; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases