Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, USA.
PLoS Pathog. 2010 Aug 12;6(8):e1001040. doi: 10.1371/journal.ppat.1001040.
Previous work revealed that conditional depletion of the core proteasome subunits PrcB and PrcA impaired growth of Mycobacterium tuberculosis in vitro and in mouse lungs, caused hypersusceptibility to nitric oxide (NO) and impaired persistence of the bacilli during chronic mouse infections. Here, we show that genetic deletion of prcBA led to similar phenotypes. Surprisingly, however, an active site mutant proteasome complemented the in vitro and in vivo growth defects of the prcBA knockout (Delta prcBA) as well as its NO hypersensitivity. In contrast, long-term survival of M. tuberculosis in stationary phase and during starvation in vitro and in the chronic phase of mouse infection required a proteolytically active proteasome. Inhibition of inducible nitric oxide synthase did not rescue survival of Delta prcBA, revealing a function beyond NO defense, by which the proteasome contributes to M. tuberculosis fitness during chronic mouse infections. These findings suggest that proteasomal proteolysis facilitates mycobacterial persistence, that M. tuberculosis faces starvation during chronic mouse infections and that the proteasome serves a proteolysis-independent function.
先前的工作表明，核心蛋白酶体亚基 PrcB 和 PrcA 的条件性缺失会损害结核分枝杆菌在体外和小鼠肺部的生长，导致对一氧化氮（NO）的超敏反应，并在慢性小鼠感染期间损害细菌的持续存在。在这里，我们表明 prcBA 的基因缺失导致了类似的表型。然而，令人惊讶的是，活性位点突变的蛋白酶体补充了 prcBA 敲除（Delta prcBA）及其对 NO 的超敏反应的体外和体内生长缺陷。相比之下，结核分枝杆菌在静止期和体外饥饿期以及在慢性感染期的长期存活需要一个具有蛋白水解活性的蛋白酶体。诱导型一氧化氮合酶的抑制不能挽救 Delta prcBA 的存活，这揭示了蛋白酶体在慢性小鼠感染期间通过除了 NO 防御之外的功能有助于结核分枝杆菌的适应性。这些发现表明蛋白酶体的蛋白水解有助于分枝杆菌的持续存在，结核分枝杆菌在慢性小鼠感染期间面临饥饿，并且蛋白酶体具有非依赖于蛋白水解的功能。
