Identification of the Immunoproteasome as a Novel Regulator of Skeletal Muscle Differentiation
Identification of the Immunoproteasome as a Novel Regulator of Skeletal Muscle Differentiation
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DOI：
10.1128/mcb.00622-13
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发表时间：
2014-01-01
影响因子：
5.3
通讯作者：
Gomes, Aldrin V.
中科院分区：
文献类型：
--
作者：
Cui, Ziyou;Hwang, Soyun Michelle;Gomes, Aldrin V.
虽然肌发生的许多分子细节已被广泛研究，但免疫蛋白酶体（iproteasomes）在肌发生分化中的功能仍然未知。我们在这里表明，i-蛋白酶体亚基的mRNA，组成型和诱导型蛋白酶体亚基的蛋白质水平，以及20 S和26 S蛋白酶体的蛋白水解活性在骨骼肌C2 C12细胞分化过程中显著上调。通过短发夹RNA（shRNA）敲低i-蛋白酶体催化亚基PSMB 9降低PSMB 9和PSMB 8的表达，而不影响蛋白酶体的其他催化亚基。PSMB 9敲除和i-蛋白酶体特异性抑制剂的使用均降低26 S蛋白酶体活性并阻止C2 C12分化。抑制i-蛋白酶体也损害人骨骼肌成肌细胞分化。抑制的i-蛋白酶体增加蛋白质氧化，这些氧化的蛋白质被认为是更容易被外源性i-蛋白酶体降解。下调的i-蛋白酶体也增加了促凋亡蛋白，包括Bax，以及裂解的半胱天冬酶3，裂解的半胱天冬酶9，和裂解的聚（ADP-核糖）聚合酶（PARP），这表明，受损的分化是可能发生的，因为显着增加的细胞凋亡。这些结果首次证明，i-蛋白酶体，独立于组成型蛋白酶体，是小鼠C2 C12细胞的骨骼肌分化的关键。
While many of the molecular details of myogenesis have been investigated extensively, the function of immunoproteasomes (iproteasomes) in myogenic differentiation remains unknown. We show here that the mRNA of i-proteasome subunits, the protein levels of constitutive and inducible proteasome subunits, and the proteolytic activities of the 20S and 26S proteasomes were significantly upregulated during differentiation of skeletal muscle C2C12 cells. Knockdown of the i-proteasome catalytic subunit PSMB9 by short hairpin RNA (shRNA) decreased the expression of both PSMB9 and PSMB8 without affecting other catalytic subunits of the proteasome. PSMB9 knockdown and the use of i-proteasome-specific inhibitors both decreased 26S proteasome activities and prevented C2C12 differentiation. Inhibition of the i-proteasome also impaired human skeletal myoblast differentiation. Suppression of the i-proteasome increased protein oxidation, and these oxidized proteins were found to be more susceptible to degradation by exogenous i-proteasomes. Downregulation of the i-proteasome also increased proapoptotic proteins, including Bax, as well as cleaved caspase 3, cleaved caspase 9, and cleaved poly(ADP-ribose) polymerase (PARP), suggesting that impaired differentiation is likely to occur because of significantly increased apoptosis. These results demonstrate for the first time that i-proteasomes, independent of constitutive proteasomes, are critical for skeletal muscle differentiation of mouse C2C12 cells.