Cep55 is a centrosome protein that plays a role in mitotic exit and cytokinesis []. It is a regulator of the PI3K/AKT pathway and has been linked to cancers [].
This domain family is found in eukaryotes, and is approximately 40 amino acids in length. This domain is the active domain of CEP55. CEP55 is a protein involved in cytokinesis, specifically in abscission of the plasma membrane at the midbody. To perform this function, CEP55 complexes with ESCRT-I (by a Proline rich sequence in its TSG101 domain) and ALIX. This is the domain on CEP55 which binds to both TSG101 and ALIX. It also acts as a hinge between the N and C termini. This domain is called EABR.
TEX14 is an inactive serine/threonine-protein kinase because the active site aspartic acid residue has been replaced. It localizes to germ cell intercellular bridges during spermatogenesis. In germ cell cytokinesis a permanent intercellular bridge connecting the daughter cells through a large cytoplasmic channel forms, unlike in somatic cells. This bridge does not form in TEX14 deficient mice and male mice are sterile []; female knockout mice are fertile []. TEX14 binds to CEP55, which is a stable component of the intercellular bridge, via a GPPX3Y motif and preventing proteins with a similar motif (such as ALIX and TSG101) from binding to CEP55 []. During mitosis, TEX14 is recruited to kinetochores by Plk1 and without TEX14, kinetochores are unable to bind other essential components leading to chromosome instability. Phosphorylation of TEX14 by Plk1 leads to its degradation, which is essential for metaphase-to-anaphase transition and chromosome segregation []. TEX14 contains ankyrin repeat-containing domains and a protein kinase domain.
