In vivo and in vitro effects of a protease inhibitor (E-64) on cell division of Xenopus eggs

Microinjection of E-64 into single blastomeres of Xenopus embryos at the 2-cell stage arrested cell division. In vitro treatment of cultured individual cells at the blastular embryonic stage with E-64 c also arrested the cleavages. We examined the effects of E-64 on the proteasome and calcium-activated protease in Xenopus embryos in vitro. E-64 inhibited calpain-like protease activity. Calpain-like protease activity was stimulated during cleavage. These results indicated that a calpain-like protease might be involved in the cell division of early Xenopus embryos.