Cooperation between Imp2p and Cdc15p imparts stiffness to the constricting contractile ring in fission yeast.

Abstract

The contractile ring must anchor to the plasma membrane and cell wall to transmit its tension to the plasma membrane. F-BAR domain containing proteins including Cdc15p and Imp2p in fission yeast are likely candidate anchoring proteins based on their mutant phenotypes. Cdc15p is a node component, links the actin bundle to the plasma membrane, recruits Bgs1p to the division plane, prevents contractile ring sliding, and contributes to the stiffness of the contractile ring. Less is known about Imp2p. We found that similarly to Cdc15p, Imp2p contributes to the stiffness of the contractile ring and assembles into protein clusters. Imp2p clusters contain [~]8 Imp2p dimers and depend on the actin network for their stability at the division plane. Importantly, Imp2p and Cdc15p reciprocally affect the amount of the other in the contractile ring indicating that the two proteins influence each other during cytokinesis and may explain their similar phenotypes.