Swanson M S, Isberg R R
Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
Infect Immun. 1995 Sep;63(9):3609-20. doi: 10.1128/iai.63.9.3609-3620.1995.
Legionella pneumophila replicates within a membrane-bounded compartment that is studded with ribosomes. In this study we investigated whether these ribosomes originate from the cytoplasmic pool or are associated with host endoplasmic reticulum (ER). Immunofluorescence and electron microscopic localization studies of ER proteins in macrophages infected with L. pneumophila indicated that the bacteria reside in a compartment surrounded by ER. An L. pneumophila mutant that grows slowly in macrophages was slow to associate with host ER, providing genetic evidence in support of the hypothesis that this specialized vacuole is required for intracellular bacterial growth. Ultrastructural studies, in which the ER luminal protein BiP was labeled by immunoperoxidase cytochemistry, revealed that L. pneumophila replication vacuoles resemble nascent autophagosomes. Furthermore, short-term amino acid starvation of macrophages, which stimulated host autophagosomes. Furthermore, short-term amino acid starvation of macrophages, which stimulated host autophagy, increased association of the bacteria with the ER and enhanced bacterial growth. These results are compatible with the hypothesis that L. pneumophila exploits the autophagy machinery of macrophages to establish an intracellular niche favorable for replication.
嗜肺军团菌在布满核糖体的膜结合区室中进行复制。在本研究中，我们调查了这些核糖体是源自细胞质池还是与宿主内质网（ER）相关联。对感染嗜肺军团菌的巨噬细胞中ER蛋白进行的免疫荧光和电子显微镜定位研究表明，细菌存在于被ER包围的区室中。一种在巨噬细胞中生长缓慢的嗜肺军团菌突变体与宿主ER结合的速度较慢，这为支持这种特殊液泡是细胞内细菌生长所必需的这一假说提供了遗传学证据。通过免疫过氧化物酶细胞化学标记ER腔蛋白BiP的超微结构研究表明，嗜肺军团菌复制液泡类似于新生自噬体。此外，巨噬细胞的短期氨基酸饥饿刺激了宿主自噬，增加了细菌与ER的结合并促进了细菌生长。这些结果与嗜肺军团菌利用巨噬细胞的自噬机制来建立有利于复制的细胞内生态位这一假说相符。
