Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, USA.
PLoS One. 2012;7(11):e48601. doi: 10.1371/journal.pone.0048601. Epub 2012 Nov 15.
During pregnancy, the heart develops physiological hypertrophy. Proteasomal degradation has been shown to be altered in various models of pathological cardiac hypertrophy. Since the molecular signature of pregnancy-induced heart hypertrophy differs significantly from that of pathological heart hypertrophy, we investigated whether the cardiac proteasomal proteolytic pathway is affected by pregnancy in mice. We measured the proteasome activity, expression of proteasome subunits, ubiquitination levels and reactive oxygen production in the hearts of four groups of female mice: i) non pregnant (NP) at diestrus stage, ii) late pregnant (LP), iii) one day post-partum (PP1) and iv) 7 days post-partum (PP7). The activities of the 26 S proteasome subunits β1 (caspase-like), and β2 (trypsin-like) were significantly decreased in LP (β1∶83.26 ± 1.96%; β2∶74.74 ± 1.7%, normalized to NP) whereas β5 (chymotrypsin-like) activity was not altered by pregnancy but significantly decreased 1 day post-partum. Interestingly, all three proteolytic activities of the proteasome were restored to normal levels 7 days post-partum. The decrease in proteasome activity in LP was not due to the surge of estrogen as estrogen treatment of ovariectomized mice did not alter the 26 S proteasome activity. The transcript and protein levels of RPN2 and RPT4 (subunits of 19 S), β2 and α7 (subunits of 20 S) as well as PA28α and β5i (protein only) were not significantly different among the four groups. High resolution confocal microscopy revealed that nuclear localization of both core (20S) and RPT4 in LP is increased ∼2-fold and is fully reversed in PP7. Pregnancy was also associated with decreased production of reactive oxygen species and ubiquitinated protein levels, while the de-ubiquitination activity was not altered by pregnancy or parturition. These results indicate that late pregnancy is associated with decreased ubiquitin-proteasome proteolytic activity and oxidative stress.
在怀孕期间，心脏会发生生理性肥大。已经证明，蛋白酶体降解在各种病理性心肌肥大模型中都发生了改变。由于妊娠引起的心肌肥大的分子特征与病理性心肌肥大有很大的不同，因此我们研究了在怀孕的小鼠中，心脏蛋白酶体的蛋白水解途径是否受到影响。我们测量了四组雌性小鼠的心脏蛋白酶体活性、蛋白酶体亚基表达、泛素化水平和活性氧产生：i）非怀孕（NP）在动情期，ii）晚期怀孕（LP），iii）产后 1 天（PP1），iv）产后 7 天（PP7）。在 LP 中，26S 蛋白酶体亚基β1（半胱天冬酶样）和β2（胰凝乳蛋白酶样）的活性显著降低（β1：83.26±1.96%；β2：74.74±1.7%，相对于 NP 归一化），而β5（糜蛋白酶样）活性不受怀孕影响，但产后 1 天显著降低。有趣的是，产后 7 天所有三种蛋白酶体的蛋白水解活性都恢复到正常水平。LP 中蛋白酶体活性的降低不是由于雌激素激增所致，因为卵巢切除小鼠的雌激素治疗并未改变 26S 蛋白酶体的活性。在四组中，RPN2 和 RPT4（19S 亚基）、β2 和α7（20S 亚基）的转录物和蛋白质水平以及 PA28α和β5i（仅蛋白质）没有明显差异。高分辨率共聚焦显微镜显示，LP 中核心（20S）和 RPT4 的核定位增加了约 2 倍，并在 PP7 中完全逆转。怀孕还与活性氧物质和泛素化蛋白水平的降低有关，而怀孕或分娩并未改变去泛素化活性。这些结果表明，晚期怀孕与泛素蛋白酶体蛋白水解活性和氧化应激降低有关。
