CEP55

CEP55, or centrosomal protein of 55 kDa, is a highly conserved protein essential for cytokinesis in animal cells. The human CEP55 gene encodes a coiled-coil–rich protein that localizes to the centrosome during interphase and to the midbody during cytokinesis, where it participates in the final separation of daughter cells.

CEP55 contains extended coiled-coil regions that enable self-assembly and interactions with other cytokinetic factors. Its midbody localization is tightly regulated by phosphorylation: cyclin-dependent kinase 1 (CDK1) and polo-like kinase 1 (PLK1) phosphorylate CEP55 to prevent premature recruitment; at late mitosis, dephosphorylation by phosphatases such as PP2A unmasks the midbody-targeting signals and allows CEP55 to accumulate at the midbody.

At the midbody, CEP55 acts as a scaffold to recruit components of the ESCRT machinery, notably TSG101 and ALIX (PDCD6IP), which in turn recruit ESCRT-III subunits such as CHMP4B. This assembly drives the membrane scission event that completes abscission, ensuring proper cytokinesis. CEP55 function is thereby essential for final separation of daughter cells and for genome stability.

Loss of CEP55 function or depletion disrupts cytokinesis, leading to multinucleation and aneuploidy. In various cancers, CEP55 expression is often dysregulated, with overexpression linked to tumor progression and poor prognosis; CEP55 is studied as a potential biomarker and, in some contexts, as a therapeutic target.