Department of Pediatrics, David Geffen School of Medicine, University of California, Los Angeles, California.
Veterans Affairs Greater Los Angeles Health Care System, Los Angeles, California.
Am J Physiol Gastrointest Liver Physiol. 2020 May 1;318(5):G931-G945. doi: 10.1152/ajpgi.00266.2019. Epub 2020 Mar 16.
infection always induces gastritis, which may progress to ulcer disease or cancer. The mechanisms underlying mucosal injury by the bacteria are incompletely understood. Here, we identify a novel pathway for -induced gastric injury, the impairment of maturation of the essential transport enzyme and cell adhesion molecule, Na-K-ATPase. Na-K-ATPase comprises α- and β-subunits that assemble in the endoplasmic reticulum (ER) before trafficking to the plasma membrane. Attachment of to gastric epithelial cells increased Na-K-ATPase ubiquitylation, decreased its surface and total levels, and impaired ion balance. did not alter degradation of plasmalemma-resident Na-K-ATPase subunits or their mRNA levels. Infection decreased association of α- and β-subunits with ER chaperone BiP and impaired assembly of α/β-heterodimers, as was revealed by quantitative mass spectrometry and immunoblotting of immunoprecipitated complexes. The total level of BiP was not altered, and the decrease in interaction with BiP was not observed for other BiP client proteins. The -induced decrease in Na-K-ATPase was prevented by BiP overexpression, stopping protein synthesis, or inhibiting proteasomal, but not lysosomal, protein degradation. The results indicate that impairs chaperone-assisted maturation of newly made Na-K-ATPase subunits in the ER independently of a generalized ER stress and induces their ubiquitylation and proteasomal degradation. The decrease in Na-K-ATPase levels is also seen in vivo in the stomachs of gerbils and chronically infected children. Further understanding of -induced Na-K-ATPase degradation will provide insights for protection against advanced disease. This work provides evidence that decreases levels of Na-K-ATPase, a vital transport enzyme, in gastric epithelia, both in acutely infected cultured cells and in chronically infected patients and animals. The bacteria interfere with BiP-assisted folding of newly-made Na-K-ATPase subunits in the endoplasmic reticulum, accelerating their ubiquitylation and proteasomal degradation and decreasing efficiency of the assembly of native enzyme. Decreased Na-K-ATPase expression contributes to -induced gastric injury.
感染总会引起胃炎，进而可能发展为溃疡病或癌症。细菌引起黏膜损伤的机制尚不完全清楚。在这里，我们发现了一种新的途径，即 - 诱导的胃损伤，这种损伤会损害必需的转运酶和细胞粘附分子 Na-K-ATPase 的成熟。Na-K-ATPase 由 α-和 β-亚基组成，这些亚基在运输到质膜之前在内质网（ER）中组装。与胃上皮细胞的附着增加了 Na-K-ATPase 的泛素化，降低了其表面和总水平，并损害了离子平衡。 并没有改变质膜驻留的 Na-K-ATPase 亚基的降解或其 mRNA 水平。感染降低了 α-和 β-亚基与内质网伴侣蛋白 BiP 的结合，并通过定量质谱和免疫沉淀复合物的免疫印迹显示，α/β 异二聚体的组装受损。BiP 的总水平没有改变，并且没有观察到其他 BiP 客户蛋白与 BiP 的相互作用减少。通过过表达 BiP、阻止蛋白质合成或抑制蛋白酶体而不是溶酶体蛋白质降解来防止 - 诱导的 Na-K-ATPase 减少。结果表明， 独立于普遍的内质网应激，破坏新合成的 Na-K-ATPase 亚基在内质网中伴侣蛋白辅助的成熟，并诱导它们的泛素化和蛋白酶体降解。在沙土鼠和慢性感染儿童的胃中也可以看到体内的 Na-K-ATPase 水平降低。进一步了解 - 诱导的 Na-K-ATPase 降解将为预防晚期疾病提供依据。这项工作提供了证据，即在急性感染培养的细胞和慢性感染的患者和动物的胃上皮细胞中， 降低了 Na-K-ATPase 的水平，这是一种重要的转运酶。细菌干扰新合成的 Na-K-ATPase 亚基在内质网中 BiP 辅助的折叠，加速它们的泛素化和蛋白酶体降解，并降低天然酶的组装效率。Na-K-ATPase 表达的减少导致 - 诱导的胃损伤。
