Institut für Biochemie/CCM, Charité-Universitätsmedizin Berlin, Monbijoustr 2, Berlin 10117, Germany.
Cardiovasc Res. 2010 Jan 15;85(2):367-75. doi: 10.1093/cvr/cvp217. Epub 2009 Jun 28.
The proteasome is the proteolytically active core of the ubiquitin-proteasome system, which regulates vital processes and which can cause various diseases when it malfunctions. Therefore, the proteasome has become an attractive target for pharmaceutical interventions. Inhibition of the cardiac proteasome by specific proteasome inhibitors has been shown to attenuate cardiac hypertrophy and ischaemia reperfusion injury of the heart. We have resolved the cardiac proteasome into its subtypes and have addressed the key question of how proteasome inhibitors affect single cardiac proteasomal subtypes.
The 20S proteasome from rat heart was dissected into three different subpopulations (groups I-III), each comprising 4-7 different subtypes. The major group (group II) comprises standard proteasome subtypes; the two minor subpopulations (groups I and III) contain intermediate proteasome subtypes. All subtypes exhibit chymotrypsin-, trypsin-, and caspase-like activity but to different degrees. We have tested the effect of two common proteasome inhibitors on the chymotrypsin-like activity of all subtypes: 20-30 nmol/L MG132 caused 50% inhibition of all subtypes from groups I and II, whereas 100 nmol/L was necessary to affect group III subtypes to the same extent. However, another inhibitor, bortezomib (VELCADE), already used clinically, inhibited 50% of the activity of group III proteasome subtypes even below 20 nmol/L, a concentration showing almost no effect on group I and II proteasome subtypes. The caspase-like activity of group II proteasome subtypes was not affected by MG132 and was inhibited by bortezomib only at concentrations above 100 nmol/L.
These data show that different inhibitors have differential inhibitory effects on the various cardiac proteasome subtypes. Different cardiac subtypes are inhibited by the same dose of proteasome inhibitor to a different extent.
蛋白酶体是泛素-蛋白酶体系统中具有蛋白水解活性的核心，该系统调节重要的生命过程，当其功能失调时会导致各种疾病。因此，蛋白酶体已成为药物干预的一个有吸引力的靶点。特异性蛋白酶体抑制剂抑制心脏蛋白酶体已被证明可减轻心脏肥大和心脏缺血再灌注损伤。我们已经将心脏蛋白酶体解析为其亚型，并解决了蛋白酶体抑制剂如何影响单一心脏蛋白酶体亚型的关键问题。
从大鼠心脏中分离出的 20S 蛋白酶体分为三个不同的亚群（I-III 组），每组包含 4-7 种不同的亚型。主要亚群（II 组）包含标准蛋白酶体亚型；两个较小的亚群（I 和 III 组）包含中间蛋白酶体亚型。所有亚型均表现出胰凝乳蛋白酶样、胰蛋白酶样和半胱天冬酶样活性，但程度不同。我们已经测试了两种常见的蛋白酶体抑制剂对所有亚型的胰凝乳蛋白酶样活性的影响：20-30 nmol/L 的 MG132 引起 I 组和 II 组的所有亚型的 50%抑制，而 100 nmol/L 则需要以相同的程度影响 III 组的亚型。然而，另一种抑制剂硼替佐米（VELCADE），已在临床上使用，即使在低于 20 nmol/L 的浓度下，也能抑制 50%的 III 组蛋白酶体亚型的活性，而对 I 组和 II 组蛋白酶体亚型的作用几乎可以忽略不计。MG132 不影响 II 组蛋白酶体亚型的半胱天冬酶样活性，只有在浓度高于 100 nmol/L 时才会抑制硼替佐米的活性。
这些数据表明，不同的抑制剂对各种心脏蛋白酶体亚型具有不同的抑制作用。不同的心脏亚型被相同剂量的蛋白酶体抑制剂抑制的程度不同。
