11月22日,，國(guó)際知名學(xué)術(shù)期刊《美國(guó)科學(xué)院院刊》（PNAS）在線發(fā)表了中科院上海生科院生化與細(xì)胞所陳劍峰課題組的最新研究成果,，闡明了陽(yáng)離子-π相互作用對(duì)于整合素α4β7的親和性及其相關(guān)信號(hào)轉(zhuǎn)導(dǎo)的新調(diào)節(jié)機(jī)制。
白細(xì)胞的遷移運(yùn)動(dòng)是炎癥反應(yīng)病理過程中的重要步驟和關(guān)鍵環(huán)節(jié),。整合素作為一類重要的細(xì)胞表面粘附分子,，是直接介導(dǎo)白細(xì)胞遷移運(yùn)動(dòng)的重要蛋白，與炎癥反應(yīng)關(guān)系密切,。整合素α4β7主要表達(dá)在淋巴細(xì)胞表面,，負(fù)責(zé)介導(dǎo)淋巴細(xì)胞從血液循環(huán)進(jìn)入腸道和中樞神經(jīng)系統(tǒng)，其功能的異常與人類自身免疫疾病密切相關(guān),，如潰瘍性結(jié)腸炎、克羅恩病等,。整合素與配體的結(jié)合及其介導(dǎo)的信號(hào)轉(zhuǎn)導(dǎo)是受到嚴(yán)格的調(diào)控的,。這種精確的動(dòng)態(tài)調(diào)控的機(jī)制一直以來都是整合素研究領(lǐng)域的熱點(diǎn)。
前期的研究表明,，整合素β亞基I結(jié)構(gòu)域中的specific determining loop（SDL）與SyMBS是兩個(gè)重要的整合素功能調(diào)控元件,。SDL具有非常柔性的結(jié)構(gòu)，與整合素識(shí)別配體的特異性有關(guān),；而SyMBS金屬離子結(jié)合位點(diǎn)是整合素活化所必須的,，但是它們的精細(xì)調(diào)控機(jī)制還不清楚。
陳劍峰課題組的潘有東博士等人發(fā)現(xiàn)了整合素α4β7的SDL與SyMBS通過一個(gè)特殊的陽(yáng)離子-p相互作用相連接,。該陽(yáng)離子-p相互作用的喪失嚴(yán)重影響了高親和性α4β7介導(dǎo)的細(xì)胞穩(wěn)定粘附,，但是對(duì)低親和性α4β7介導(dǎo)的細(xì)胞滾動(dòng)粘附影響很小。此外,，α4β7介導(dǎo)的細(xì)胞運(yùn)動(dòng)也受到抑制,。缺失該陽(yáng)離子-π相互作用會(huì)引起α4β7胞內(nèi)區(qū)的部分分離，產(chǎn)生一種異常的outside-in信號(hào),，引起FAK表達(dá)及其磷酸化的上調(diào),。胞內(nèi)paxillin蛋白水平上調(diào)、paxillin與α4β7的結(jié)合增強(qiáng),，進(jìn)而抑制了整合素介導(dǎo)的細(xì)胞鋪展,。研究還發(fā)現(xiàn)陽(yáng)離子-π相互作用的喪失會(huì)提高paxillin的磷酸化水平并抑制talin的剪切，從而穩(wěn)定了粘著斑,。同時(shí),，整合素通過inside-out信號(hào)的活化過程也依賴于該陽(yáng)離子-π相互作用。該研究首次提出了陽(yáng)離子-p相互作用調(diào)控整合素的功能,，揭示了整合素SyMBS位點(diǎn)通過該陽(yáng)離子-π相互作用聯(lián)系SDL,、協(xié)同調(diào)控α4β7的功能。該發(fā)現(xiàn)不僅揭示了整合素功能的一個(gè)新調(diào)控機(jī)制，還對(duì)陽(yáng)離子-π相互作用在蛋白中的生理功能提供了新的證據(jù),。
該研究課題獲得國(guó)家科技部973項(xiàng)目,、國(guó)家自然科學(xué)基金委、中國(guó)科學(xué)院和上海市科委的經(jīng)費(fèi)資助,。（生物谷Bioon.com）
生物谷推薦英文摘要：
PNAS doi: 10.1073/pnas.1015487107
Cation-π interaction regulates ligand-binding affinity and signaling of integrin α4β7
YouDong Pana, Kun Zhanga, JunPeng Qia, Jiao Yuea, Timothy A. Springerb,1, and JianFeng Chena,1
aLaboratory of Molecular Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China; and
bThe Immune Disease Institute, Children’s Hospital Boston, and Department of Pathology, Harvard Medical School, 3 Blackfan Circle, Boston, MA 02115
Integrin α4β7 mediates rolling and firm adhesion of leucocytes, two of the critical steps in leukocyte migration and tissue specific homing. Affinity of α4β7 for ligand is dynamically regulated by three interlinked metal ion-binding sites in β7-subunit I domain. In this study, we found that Phe185 (F185), a highly conserved aromatic residue in β7-subunit, links the specificity-determining loop and the synergistic metal ion-binding site (SyMBS) through cation-π interaction. Mutations of F185 that disrupted the SyMBS cation-F185 interaction led to deficient firm cell adhesion mediated by high affinity α4β7, and only slightly affected rolling adhesion mediated by low affinity α4β7. Disruption of SyMBS cation-F185 interaction induced partial extension of integrin ectodomain and separation of cytoplasmic tails, and impaired α4β7-mediated bidirectional signaling. In addition, loss of SyMBS cation-F185 interaction increased paxillin expression and promoted paxillin-integrin binding, leading to deficient cell spreading. Furthermore, integrin α4β7-mediated cell migration was decreased by the abolishment of SyMBS cation-F185 interaction. Thus, these findings reveal a cation-π interaction playing vital roles in the regulation of integrin affinity, signaling, and biological functions.
