Inactivation of the inhA-encoded fatty acid synthase II (FASII) enoyl-acyl carrier protein reductase induces accumulation of the FASI end products and cell lysis of Mycobacterium smegmatis
Inactivation of the inhA-encoded fatty acid synthase II (FASII) enoyl-acyl carrier protein reductase induces accumulation of the FASI end products and cell lysis of Mycobacterium smegmatis
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DOI：
10.1128/jb.182.14.4059-4067.2000
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发表时间：
2000-07-01
影响因子：
3.2
通讯作者：
Jacobs, WR
中科院分区：
文献类型：
--
作者：
Vilchèze, C;Morbidoni, HR;Jacobs, WR
异烟肼（INH）是一种一线抗结核药物，其作用机制很复杂，因为已发现至少5种不同基因（katG、inhA、ahpC、kasA和ndh）的突变与异烟肼耐药相关。尽管这种复杂性，优势的证据暗示inhA，其编码的脂肪酸合成酶II（FASII）的烯酰-酰基载体蛋白还原酶，作为INH的主要目标。然而，结核分枝杆菌的INH治疗引起二十六烷酸（C-26：0）的积累，这是阻断烯酰还原酶所意外的结果。为了测试InhA的失活是否与INH治疗分枝杆菌相同，我们分离了耻垢分枝杆菌inhA基因中的温度敏感性突变，该突变使InhA在42 ℃下失活。InhA的热失活导致真菌酸生物合成的抑制，十六烷酸（C-16：0）的减少和伴随的二十四烷酸（C-24：0）的增加，与INH处理的细胞中所见的方式相当。类似地，牛分枝杆菌BCG的INH处理引起分枝菌酸生物合成的抑制、C-16：0的减少和伴随的C-26：0的积累。此外，InhA灭活的细胞，如INH处理的细胞，经历了剧烈的形态变化，导致细胞溶解。这些数据表明，单独的InhA失活足以诱导饱和脂肪酸的积累、细胞壁改变和细胞裂解，并且与InhA是INH的主要靶标一致。
The mechanism of action of isoniazid (INH), a first-line antituberculosis drug, is complex, as mutations in at least five different genes (katG, inhA, ahpC, kasA, and ndh) have been found to correlate with isoniazid resistance. Despite this complexity, a preponderance of evidence implicates inhA, which codes for an enoyl-acyl carrier protein reductase of the fatty acid synthase II (FASII), as the primary target of INH. However, INH treatment of Mycobacterium tuberculosis causes the accumulation of hexacosanoic acid (C-26:0), a result unexpected for the blocking of an enoyl-reductase. To test whether inactivation of InhA is identical to INH treatment of mycobacteria, we isolated a temperature-sensitive mutation in the inhA gene of Mycobacterium smegmatis that rendered InhA inactive at 42 degrees C. Thermal inactivation of InhA in ill, smegmatis resulted in the inhibition of mycolic acid biosynthesis, a decrease in hexadecanoic acid (C-16:0) and a concomitant increase of tetracosanoic acid (C-24:0) in a manner equivalent to that seen in INH-treated cells. Similarly, INH treatment of Mycobacterium bovis BCG caused an inhibition of mycolic acid biosynthesis, a decrease in C-16:0, and a concomitant accumulation of C-26:0. Moreover, the InhA-inactivated cells, like INH-treated cells, underwent a drastic morphological change, leading to cell lysis. These data show that InhA inactivation, alone, is sufficient to induce the accumulation of saturated fatty acids, cell wall alterations, and cell lysis and are consistent with InhA being a primary target of INH.