Harvey N L, Daish T, Mills K, Dorstyn L, Quinn L M, Read S H, Richardson H, Kumar S
Hanson Centre for Cancer Research, Institute of Medical and Veterinary Science, Frome Road, Adelaide, SA 5000, Australia.
J Biol Chem. 2001 Jul 6;276(27):25342-50. doi: 10.1074/jbc.M009444200. Epub 2001 May 3.
Caspases are main effectors of apoptosis in metazoans. Genome analysis indicates that there are seven caspases in Drosophila, six of which have been previously characterized. Here we describe the cloning and characterization of the last Drosophila caspase, DAMM. Similar to mammalian effector caspases, DAMM lacks a long prodomain. We show that the DAMM precursor, along with the caspases DRONC and DECAY, is partially processed in cells undergoing apoptosis. Recombinant DAMM produced in Escherichia coli shows significant catalytic activity on a pentapeptide caspase substrate. Low levels of damm mRNA are ubiquitously expressed in Drosophila embryos during early stages of development. Relatively high levels of damm mRNA are detected in larval salivary glands and midgut, and in adult egg chambers. Ectopic expression of DAMM in cultured cells induces apoptosis, and similarly, transgenic overexpression of DAMM, but not of a catalytically inactive DAMM mutant, in Drosophila results in a rough eye phenotype. We demonstrate that expression of the catalytically inactive DAMM mutant protein significantly suppresses the rough eye phenotype due to the overexpression of HID, suggesting that DAMM may be required in a hid-mediated cell death pathway.
半胱天冬酶是后生动物细胞凋亡的主要效应因子。基因组分析表明，果蝇中有七种半胱天冬酶，其中六种此前已被鉴定。在此，我们描述了果蝇最后一种半胱天冬酶DAMM的克隆与鉴定。与哺乳动物的效应半胱天冬酶相似，DAMM缺乏一个长的前结构域。我们发现，DAMM前体与半胱天冬酶DRONC和DECAY一起，在经历凋亡的细胞中会被部分加工。在大肠杆菌中产生的重组DAMM对五肽半胱天冬酶底物显示出显著的催化活性。在果蝇胚胎发育早期，低水平的damm mRNA在各处均有表达。在幼虫唾液腺、中肠以及成虫卵室中检测到相对高水平的damm mRNA。在培养细胞中异位表达DAMM会诱导细胞凋亡，同样地，在果蝇中过表达DAMM（而非催化失活的DAMM突变体）会导致粗糙眼表型。我们证明，催化失活的DAMM突变体蛋白的表达显著抑制了由于HID过表达导致的粗糙眼表型，这表明DAMM可能在hid介导的细胞死亡途径中是必需的。
