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Membrane blebbing during apoptosis results from caspase-mediated activation of ROCK I
M L Coleman1, E A Sahai, M Yeo
1CRC Centre for Cell and Molecular Biology, Chester Beatty Laboratories, The Institute of Cancer Research, 237 Fulham Road, London SW3 6JB, UK.
Abstract:
The execution phase of apoptosis is characterized by marked changes in cell morphology that include contraction and membrane blebbing. The actin-myosin system has been proposed to be the source of contractile force that drives bleb formation, although the biochemical pathway that promotes actin-myosin contractility during apoptosis has not been identified. Here we show that the Rho effector protein ROCK I, which contributes to phosphorylation of myosin light-chains, myosin ATPase activity and coupling of actin-myosin filaments to the plasma membrane, is cleaved during apoptosis to generate a truncated active form. The activity of ROCK proteins is both necessary and sufficient for formation of membrane blebs and for re-localization of fragmented DNA into blebs and apoptotic bodies.