Protein Kinase Profile of Sperm and Eggs: Cloning and Characterization of Two Novel Testis-Specific Protein Kinases (AIE1, AIE2) Related to Yeast and Fly Chromosome Segregation Regulators

Abstract

We have analyzed the general protein kinase expression profile in mouse sperm and eggs. A total of 41 different kinases were identified. In this study, we describe two novel protein kinases, designated AIE1 (mouse) and AIE2 (human), which share high amino acid identities with the serine/threonine (S/T) kinase domain of yeast Ip11, fly aurora, and frog Eg2. Mutations in Ip11 and aurora have been reported to cause abnormal chromosome segregation and centrosome separation. Both AIE1 and AIE2 contain a typical S/T kinase domain (251 aa) flanked by a short polypeptide at both ends. Two other AIE-related kinases (STK-1 and IAK1/Ayk1) were also identified in mature mouse oocytes. The central kinase domain of AIE1 revealed 77.6% and 66.3% identity with that of STK-1 and IAK1/Ayk1, but much less homology was found in the sequence outside the kinase domain. Northern blot analysis revealed that both AIE1 and AIE2 are specifically expressed in testis, whereas STK-1 and IAK1/Ayk1 are expressed in many tissues rich in proliferating cells. An in vitro kinase assay showed that AIE1 can phosphorylate casein, AIE1 itself, and an uncharacterized cellular protein (p16). The kinase activity of AIE1 can be destroyed by heat inactivation. In summary, we suggest that AIE is a new member of the S/T kinase family, which may be regulated in a fashion distinct from other AIE-related kinases.

Aurora-A: the maker and breaker of spindle poles

“…Whereas there is only one Aurora protein in yeast (the founding member of the family Ipl1 in Saccharomyces cerevisiae and Ark1 in Schizosaccharomyces pombe), metazoans have at least two aurora genes: aurora-a and aurora-b (reviewed in Andrews et al, 2003). A third member of the family, aurora-c, is specifically expressed during meiosis in the mammalian testis, where it behaves similarly to Aurora-B (Bernard et al, 1998;Kimmins et al, 2007;Kimura et al, 1999;Tang et al, 2006;Tseng et al, 1998). The catalytic domain of the Aurora kinases is highly conserved; sequences outside this region are more divergent.…”

On the role of aurora-A in centrosome function

“…Many aurora kinases have then been found in various organisms giving birth to as many different confusing names as publications, and Erich Nigg proposed the nomenclature aurora-A, -B and -C (Nigg, 2001). Aurora-C expression seems to be restricted to spermatogenesis at the time when cells assemble the two meiotic spindles (Hu et al, 2000;Tseng et al, 1998). Aurora-B is a chromosome passenger involved in cytokinesis and chromosome architecture (Adams et al, 2000(Adams et al, , 2001Giet and Glover, 2001).…”

The mitotic serine/threonine kinase Aurora2/AIK is regulated by phosphorylation and degradation

“…Overexpression of Aurora2/STK15 in NIH3T3 cells results in abnormal centrosome numbers and transformation of the cells (Zhou et al, 1998). A third family member, Aik3/AIE2, is localized at the centrosome only in anaphase and expression levels of Aik3 are elevated in several cancer cell lines (Kimura et al, 1997;Bernard et al, 1998;Tseng et al, 1998). Thus, there is compelling evidence that the Aurora/Ipl1 family of serine/threonine kinases are important regulators of mitosis.…”