title: Identification of actin as a substrate of ICE and an ICE-like protease and involvement of an ICE-like protease but not ICE in VP-16-induced U937 apoptosis.
abstract: Human leukemia U937 cells are induced to undergo apoptosis by several chemotherapeutic agents; however, the cellular components involved in the process have not yet been identified. We found that an actin-cleavage activity (ACA) was activated in the VP-16-treated U937 cytosolic fraction and 15K- and 30K-actin fragments were produced. This ACA was inhibited by inhibitors of interleukin-1 beta-converting enzyme (ICE)/ced-3 family proteases, such as Z-Asp-CH2-DCB, YVAD-CHO, TPCK, TLCK, and iodoacetamide. Differing from ICE, the ACA could not process pro-IL-1 beta to mature IL-1 beta. Although ICE can cleave actin in vitro, ICE activity was not activated in the VP-16 treated U937 cells. These results indicate that actin is a potential substrate of ICE and ICE-like proteases, and that VP-16 preferentially activate an ICE-like protease, but not ICE itself, in U937 cells.
authors.affiliation: Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Mashima
authors.forename: M
authors.initials: M
authors.lastname: Naito
authors.forename: N
authors.initials: N
authors.lastname: Fujita
authors.forename: K
authors.initials: K
authors.lastname: Noguchi
authors.forename: T
authors.initials: T
authors.lastname: Tsuruo
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D017209:Apoptosis / Q000187:drug effects; D020170:Caspase 1; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D004789:Enzyme Activation; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D008969:Molecular Sequence Data; D013379:Substrate Specificity; D014407:Tumor Cells, Cultured
chemical_list: D000199:Actins; D005047:Etoposide; D003546:Cysteine Endopeptidases; D020170:Caspase 1