Clues to CD2-associated protein involvement in cytokinesis.

Cytokinesis requires membrane trafficking coupled to actin remodeling and involves a number of trafficking molecules. CD2-associated protein (CD2AP) has been implicated in dynamic actin remodeling and membrane trafficking that occurs during endocytosis leading to the degradative pathway. In this study, we present several arguments for its implication in cytokinesis. First, endogenous CD2AP was found concentrated in the narrow region of the midzone microtubules during anaphase and in the midbody during late telophase. Moreover, we found that CD2AP is a membrane- and not a microtubule-associated protein. Second, the overexpression of the first two Src homology 3 domains of CD2AP, which are responsible for this localization, led to a significant increase in the rate of cell multinucleation. Third, the CD2AP small interfering RNA interfered with the cell separation, indicating that CD2AP is required for HeLa cells cytokinesis. Fourth, using the yeast two-hybrid system, we found that CD2AP interacted with anillin, a specific cleavage furrow component, and the two proteins colocalized at the midbody. Both CD2AP and anillin were found phosphorylated early in mitosis and also CD2AP phosphorylation was coupled to its delocalization from membrane to cytosol. All these observations led us to propose CD2AP as a new player in cytokinesis.