New York University School of Medicine--Langone Health, Departments of Medicine and Pathology, Division of Translational Medicine, 550 First Ave, New York, NY 10016, USA.
University of Exeter Medical School, Exeter EX1 2LU, Devon UK.
Int J Mol Sci. 2019 Jan 18;20(2):408. doi: 10.3390/ijms20020408.
The endoplasmic reticulum (ER) chaperone protein, calreticulin (CRT), is essential for proper glycoprotein folding and maintaining cellular calcium homeostasis. During ER stress, CRT is overexpressed as part of the unfolded protein response (UPR). In addition, CRT can be released as a damage-associated molecular pattern (DAMP) molecule that may interact with pathogen-associated molecular patterns (PAMPs) during the innate immune response. One such PAMP is lipopolysaccharide (LPS), a component of the gram-negative bacterial cell wall. In this report, we show that recombinant and native human placental CRT strongly interacts with LPS in solution, solid phase, and the surface of gram-negative and gram-positive bacteria. Furthermore, LPS induces oilgomerization of CRT with a disappearance of the monomeric form. The application of recombinant CRT (rCRT) to size exclusion and anion exchange chromatography shows an atypical heterogeneous elution profile, indicating that LPS affects the conformation and ionic charge of CRT. Interestingly, LPS bound to CRT is detected in sera of bronchiectasis patients with chronic bacterial infections. By ELISA, rCRT dose-dependently bound to solid phase LPS via the N- and C-domain globular head region of CRT and the C-domain alone. The specific interaction of CRT with LPS may be important in PAMP innate immunity.
内质网伴侣蛋白钙网织蛋白（CRT）对于糖蛋白的正确折叠和维持细胞内钙稳态至关重要。在 ER 应激期间，CRT 作为未折叠蛋白反应（UPR）的一部分过表达。此外，CRT 可以作为一种损伤相关分子模式（DAMP）分子释放，在先天免疫反应中可能与病原体相关分子模式（PAMP）相互作用。一种这样的 PAMP 是脂多糖（LPS），革兰氏阴性细菌细胞壁的组成部分。在本报告中，我们表明重组和天然人胎盘 CRT 与 LPS 在溶液、固相以及革兰氏阴性和革兰氏阳性细菌的表面强烈相互作用。此外，LPS 诱导 CRT 的油团聚，单体形式消失。重组 CRT（rCRT）在排阻和阴离子交换层析中的应用显示出非典型的异质洗脱谱，表明 LPS 影响 CRT 的构象和离子电荷。有趣的是，在患有慢性细菌感染的支气管扩张症患者的血清中检测到与 LPS 结合的 CRT。通过 ELISA，rCRT 剂量依赖性地通过 CRT 的 N 和 C 结构域球状头部区域以及 C 结构域本身与固相 LPS 结合。CRT 与 LPS 的特异性相互作用可能在 PAMP 先天免疫中很重要。
