以分子動力模擬探討正常及瓜胺酸化膠原蛋白與整合素的結合力

Abstract

類風溼關節炎是一種自體免疫性疾病，會導致全身關節反覆性發炎，長期下來使關節內部的軟骨或硬骨破壞及變形。根據近年的研究，從類風溼關節炎或一般骨關節炎患者的關節腔內所提取的滑膜液，發現類風溼關節炎的自身抗原-瓜胺酸化的第二型和第三型膠原蛋白，被證實與關節炎的致病機制密切相關。更有研究發現，滑膜纖維母細胞會分泌相關促進發炎的因子，被認為是關鍵的治療標靶；而整合素α1、α2、α10和α11由於能夠調節其附著與遷移，被認為是重要的細胞膜受體蛋白。總結上述發現，瞭解瓜胺酸化對膠原蛋白與四種整合素結合的影響非常重要。 雖然有許多研究已經證實瓜胺酸化與發炎機制相關，然而仍不清楚瓜胺酸化對膠原蛋白與四種整合素結合的影響，因此本研究將透過分子動力模擬，探討微觀尺度下，正常的GLOGER與瓜胺酸化的GLOGER和整合素α1、α2、α10、α11結合後的結構差異，以及正常的GAOGER與瓜胺酸化的GAOGER和整合素α2結合後的結構差異，以解釋實驗數據中結合強度的影響，並提供未來炎症相關藥物設計的方向。 本研究發現瓜胺酸化會大幅減弱GLOGER與α11的氫鍵作用，使得Cit12C側鏈與E220不再產生氫鍵，甚至E11D也不再與α11產生氫鍵，導致氫鍵幾乎喪失。其餘三者有各自的機制緩和瓜胺酸化，例如Cit12C骨架與α2仍保持氫鍵；α1機制如下，雖然瓜胺酸化使得Cit12B側練不在與E298和E255產生氫鍵，卻因為Cit12C側鏈偏移與D259產生新的氫鍵，以及E11D與R218仍保持氫鍵，緩和了瓜胺酸化的影響；α10則是藉由E11D與R219產生更強的氫鍵。這些重要的發現，解釋了瓜胺酸化對膠原蛋白與四種整合素結合不同的反應，也提供未來實驗數據對照的合理解釋。

Rheumatoid arthritis is an autoimmune disease that can cause repetitive inflammation of joints throughout the body, which can destroy and deform the cartilage or hard bones in the joints over a long period of time. According to recent studies, the synovial fluid extracted from the joint cavity of patients with rheumatoid arthritis or general osteoarthritis has discovered the autoantigens of rheumatoid arthritis-citrullinated type II and type III collagen. It has been proved to be closely related to the pathogenic mechanism of arthritis. More studies have found that synovial fibroblasts secrete related factors that promote inflammation and are considered to be key therapeutic targets; integrins α1, α2, α10, and α11 are considered important because they can regulate their attachment and migration cell membrane receptor protein. Summarizing the above findings, it is very important to understand the effect of citrulline on the binding of collagen to the four integrins. Although many studies have confirmed that citrulline is related to the mechanism of inflammation, it is still not clear how citrulline affects the binding of collagen to the four integrins. Therefore, this study will use molecular dynamics simulation to explore the normal GLOGER on a microscopic scale. The structural difference after combining with citrullinated GLOGER and integrin α1, α2, α10, and α11, as well as the structural difference between normal GAOGER and citrullinated GAOGER and integrin α2, to explain the binding strength in the experimental data Influence and provide direction for future inflammation-related drug design. This study found that citrulline acidification would greatly weaken the hydrogen bond between GLOGER and α11, so that the side chain of Cit12C and E220 no longer generate hydrogen bonds, and even E11D no longer generates hydrogen bonds with α11, resulting in almost loss of hydrogen bonds. The other three have their own mechanisms to alleviate citrulline acidification. For example, the main chain of Cit12C still maintains hydrogen bonds with α2; the mechanism of α1 is as follows. Although citrulline acidification prevents Cit12B from forming hydrogen bonds with E298 and E255, the side chain of Cit12C is biased. It creates a new hydrogen bond with D259, and E11D and R218 still maintain the hydrogen bond, alleviating the effect of citrulline acidification; α10 uses E11D and R219 to generate stronger hydrogen bonds. These important findings explain the different responses of citrulline to the binding of collagen to the four integrins, and also provide a reasonable explanation for future experimental data comparison.