Incomplete Caspase 3 Activation and Mitigation of Apoptosis in Hibernating Ground Squirrels, Spermophilus lateralis
Incomplete Caspase 3 Activation and Mitigation of Apoptosis in Hibernating Ground Squirrels, Spermophilus lateralis
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DOI：
10.1086/722708
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发表时间：
2022-10
影响因子：
1.6
通讯作者：
Michael D Treat;Anthony J. Marlon;F. van Breukelen
中科院分区：
文献类型：
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作者：
Michael D Treat;Anthony J. Marlon;F. van Breukelen
冬眠的金毛地松鼠，嗜精子（callospermoophilus），能够耐受促凋亡的条件，如低体温、厌食、酸中毒和缺血/再灌注。避免广泛的细胞凋亡是冬眠动物存活的关键。Caspase 3是细胞凋亡的关键执行者，可切割大多数凋亡靶点。在促凋亡条件下，失活的procaspase 3 （32 kDa）在裂解成17和12 kDa片段（分别为p32、p17和p12）时被激活。Caspase 3激活导致极端的酶激活。细胞活性增加10万倍，随后发生凋亡。在促凋亡冬眠季节是否发生广泛的细胞凋亡？Western blots显示p17在冬眠期间增加了~ 2倍，表明caspase 3激活。然而，体外半胱天冬酶3活性测定没有发现活性的极端增加。caspase 3的下游靶点ICAD （caspase激活的脱氧核糖核酸酶抑制剂）和PARP（聚（adp核糖）聚合酶）在冬眠期间没有升高的裂解，这与caspase 3的激活不一致。多种组织的TUNEL（末端脱氧核苷酸转移酶介导的脱氧尿苷三磷酸镍端标记）检测发现，冬季只有0.001%-0.009%的细胞TUNEL阳性，表明冬眠期间凋亡可以忽略不计。通常，caspase 3的激活会产生强烈的凋亡承诺。我们发现，尽管活性caspase 3增加了2倍，冬眠动物没有下游的caspase 3活性或广泛的细胞凋亡。一个系统级的方法提示一个不完整的信号级联，其中一些caspase 3在冬眠期间的激活并不一定导致真正的细胞凋亡。
Hibernating golden-mantled ground squirrels, Spermophilus [Callospermophilus] lateralis, tolerate proapoptotic conditions, such as low body temperature, anorexia, acidosis, and ischemia/reperfusion. Avoiding widespread apoptosis is critical for hibernator survival. Caspase 3, the key executioner of apoptosis, cleaves a majority of apoptotic targets. Under proapoptotic conditions, inactive procaspase 3 (32 kDa) is activated when cleaved into 17- and 12-kDa fragments (p32, p17, and p12, respectively). Caspase 3 activation results in extreme enzymatic activation. Activity increases >10,000-fold followed by apoptotic execution. Is widespread apoptosis occurring during the proapoptotic hibernation season? Western blots showed p17 increased ∼2-fold during hibernation, indicating caspase 3 activation. However, in vitro caspase 3 activity assays found no extreme increases in activity. Downstream caspase 3 targets ICAD (inhibitor of caspase-activated deoxyribonuclease) and PARP (poly (ADP-ribose) polymerase) did not experience elevated cleavage during hibernation, which is inconsistent with caspase 3 activation. TUNEL (terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling) assays from multiple tissues found only 0.001%–0.009% of cells were TUNEL positive during winter, indicating negligible apoptosis during hibernation. Typically, caspase 3 activation generates a strong commitment toward apoptosis. We found that despite a ∼2-fold increase in active caspase 3, hibernators experience no downstream caspase 3 activity or widespread apoptosis. A systems-level approach suggests an incomplete signaling cascade wherein some caspase 3 activation during hibernation does not necessarily lead to bona fide apoptosis.