Demarchi F, Bertoli C, Greer P A, Schneider C
L.N.C.I.B. Laboratorio Nazionale Consorzio Interuniversitario Biotecnologie AREA Science Park, Padriciano 99, 34012 Trieste, Italy.
Cell Death Differ. 2005 May;12(5):512-22. doi: 10.1038/sj.cdd.4401592.
We have shown that C2 ceramide, a cell-permeable analog of this lipid second messenger, triggers an NF-kappaB dependent survival pathway that counteracts cell death. Activation of NF-kappaB and subsequent induction of prosurvival genes relies on calpain activity and is prevented on silencing of the calpain small subunit (Capn4) that is required for the function of ubiquitous calpains. We have demonstrated that p105 (NF-kappaB1) and its proteolytic product p50 can be targets of micro- and milli-calpain in vitro and that a p50 deletion mutant, lacking both the N- and the C-terminal ends, is resistant to calpain-mediated degradation. Capn4 silencing results in stabilization of endogenous p105 and p50 in diverse human cell lines. Furthermore, p105 processing and activation of NF-kappaB survival genes in response to C2 ceramide is impaired in Capn4-/- mouse embryonic fibroblasts defective in calpain activity. Altogether, these data argue for the existence of a ceramide-calpain-NF-kappaB axis with prosurvival functions.
我们已经证明，C2神经酰胺这种可穿透细胞的脂质第二信使类似物，能触发一条依赖NF-κB的存活途径，从而对抗细胞死亡。NF-κB的激活以及随后促存活基因的诱导依赖于钙蛋白酶的活性，而在钙蛋白酶小亚基（Capn4）沉默时则会受到抑制，Capn4是普遍存在的钙蛋白酶发挥功能所必需的。我们已经证明，p105（NF-κB1）及其蛋白水解产物p50在体外可能是微钙蛋白酶和毫微钙蛋白酶的作用靶点，并且一个缺失N端和C端的p50缺失突变体对钙蛋白酶介导的降解具有抗性。Capn4沉默导致多种人类细胞系中内源性p105和p50的稳定。此外，在钙蛋白酶活性有缺陷的Capn4基因敲除小鼠胚胎成纤维细胞中，p105的加工以及对C2神经酰胺应答时NF-κB存活基因的激活均受到损害。总之，这些数据表明存在一条具有促存活功能的神经酰胺-钙蛋白酶-NF-κB轴。
