Quantitative Organellar Proteomics Analysis of Rough Endoplasmic Reticulum from Normal and Acute Pancreatitis Rat Pancreas

The rough endoplasmic reticulum (RER) is a central organelle for synthesizing and processing digestive enzymes and alteration of ER functions may participate in the pathogenesis of acute pancreatitis (AP). To comprehensively characterize the normal and diseased RER subproteome, this study quantitatively compared the protein compositions of pancreatic RER between normal and AP animals using isobaric tags (iTRAQ) and 2D LC-MALDI-MS/MS. A total of 469 unique proteins were revealed from four independent experiments using two different AP models. These proteins belong to a large number of functional categories including ribosomal proteins, translocon subunits, chaperones, secretory proteins, and glyco- and lipid-processing enzymes. A total of 37 RER proteins (25 unique in arginine-induced, 6 unique in caerulein-induced and 6 common in both models of AP) showed significant changes during AP including translational regulators and digestive enzymes, whereas only mild changes were found in some ER chaperones. The six proteins common to both AP models included a decrease in pancreatic triacylglycerol lipase precursor, Erp27, and prolyl 4-hydroxylase beta polypeptide as well as a dramatic increase in fibrinogen alpha, beta and gamma chains. These results suggest that the early stages of AP involve changes of multiple RER proteins that may affect the synthesis and processing of digestive enzymes.

粗面内质网（rough endoplasmic reticulum, RER）是合成与加工消化酶的核心细胞器，内质网功能异常可能参与急性胰腺炎（acute pancreatitis, AP）的发病机制。为全面表征正常与病变状态下的RER亚蛋白质组，本研究采用同位素相对和绝对定量标签（isobaric tags, iTRAQ）联合二维液相色谱-基质辅助激光解吸电离串联质谱（2D LC-MALDI-MS/MS），对正常与AP模型动物的胰腺RER蛋白质组成进行定量比较。本研究通过两种不同的AP模型开展4次独立实验，共鉴定得到469种独特蛋白质，这些蛋白质涵盖大量功能类别，包括核糖体蛋白（ribosomal proteins）、易位复合物亚基（translocon subunits）、分子伴侣（chaperones）、分泌蛋白（secretory proteins）以及糖脂加工酶（glyco- and lipid-processing enzymes）等。在AP进程中，共有37种RER蛋白（精氨酸诱导模型特有25种、雨蛙素诱导模型特有6种、两种AP模型共有的6种）发生显著变化，其中包括翻译调控因子与消化酶；而部分内质网分子伴侣仅出现轻微表达变化。两种AP模型共有的6种差异蛋白包括：胰三酰甘油脂肪酶前体（pancreatic triacylglycerol lipase precursor）、Erp27以及脯氨酰4-羟化酶β亚基（prolyl 4-hydroxylase beta polypeptide）表达下调，而纤维蛋白原α、β及γ链（fibrinogen alpha, beta and gamma chains）的表达则显著上调。本研究结果表明，AP早期阶段涉及多种RER蛋白的表达改变，这些变化可能影响消化酶的合成与加工过程。