Cytokinesis mediated through the recruitment of cortexillins into the cleavage furrow

The fact that substrate‐anchored Dictyostelium cells undergo cytokinesis in the absence of myosin II underscores the importance of other proteins in enabling the cleavage furrow to constrict. Cortexillins, a pair of actin‐bundling proteins, are required for normal cleavage. They are targeted to the incipient furrow in wild‐type and, more prominently, in myosin II‐null cells. No other F‐actin bundling or cross‐linking protein tested is co‐localized. Green fluorescent protein fusions show that the N‐terminal actin‐binding domain of cortexillin I is dispensable and the C‐terminal region is sufficient for translocation to the furrow and the rescue of cytokinesis. Cortexillins are suggested to have a targeting signal for coupling to a myosin II‐independent system that directs transport of membrane proteins to the cleavage furrow.