Kima P E, Burleigh B, Andrews N W
Section of Microbial Pathogenesis, Boyer Center for Molecular Medicine, Yale University School of Medicine, New Haven, CT 06536, USA.
Cell Microbiol. 2000 Dec;2(6):477-86. doi: 10.1046/j.1462-5822.2000.00071.x.
To gain entry into non-phagocytic cells, Trypanosoma cruzi trypomastigotes recruit lysosomes to the host cell surface. Lysosome fusion at the site of parasite entry leads to the formation of a parasitophorous vacuole with lysosomal properties. Here, we show that increased expression of the lysosomal membrane glycoprotein Lamp-1 at the cell surface renders CHO cells more susceptible to trypomastigote invasion in a microtubule-dependent fashion. Mutation of critical residues in the lysosome-targeting motif of Lamp-1 abolished the enhancement of T. cruzi invasion. This suggests that interactions dependent on Lamp-1 cytoplasmic tail motifs, and not the surface-exposed luminal domain, modulate T. cruzi entry. Measurements of Ca2+-triggered exocytosis of lysosomes in these cell lines revealed an enhancement of beta-hexosaminidase release in cells expressing wild-type Lamp-1 on the plasma membrane; this effect was not observed in cell lines transfected with Lamp-1 cytoplasmic tail mutants. These results also implicate Ca2+-regulated lysosome exocytosis in cell invasion by T. cruzi and indicate a role for the Lamp-1 cytosolic domain in promoting more efficient fusion of lysosomes with the plasma membrane.
为了进入非吞噬细胞，克氏锥虫锥鞭毛体将溶酶体募集到宿主细胞表面。寄生虫进入部位的溶酶体融合导致形成具有溶酶体特性的寄生泡。在此，我们表明细胞表面溶酶体膜糖蛋白Lamp-1表达的增加使CHO细胞以微管依赖的方式更易受到锥鞭毛体的侵袭。Lamp-1溶酶体靶向基序中关键残基的突变消除了克氏锥虫侵袭的增强。这表明依赖于Lamp-1细胞质尾基序而非表面暴露的腔结构域的相互作用调节克氏锥虫的进入。对这些细胞系中Ca2+触发的溶酶体胞吐作用的测量显示，在质膜上表达野生型Lamp-1的细胞中β-己糖胺酶释放增强；在用Lamp-1细胞质尾突变体转染的细胞系中未观察到这种效应。这些结果还表明Ca2+调节的溶酶体胞吐作用参与了克氏锥虫的细胞侵袭，并表明Lamp-1胞质结构域在促进溶酶体与质膜更有效融合中起作用。
