An1, LiFang Sun, Kun Zhang, Jie Liu, Ling Lu, and JianFeng Chen2 From the State Essential Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, ChinaBackground: Integrin four 7 is exceptional for mediating rolling and firm adhesion of lymphocytes pre- and post-activation. Results: Disrupting the disulfide bond-stabilized W1 4- 1 loop in the four -propeller domain impaired four 7-mediated, low-affinity ligand binding and bidirectional signaling. Conclusion: The W1 4- 1 loop regulates integrin ligand binding and signaling. Significance: Our findings reveal a certain molecular basis for four 7-mediated rolling cell adhesion. Integrin 4 7 mediates rolling and firm adhesion of lymphocytes pre- and post-activation, which is distinct from most integrins only mediating firm cell adhesion upon activation. This two-phase cell adhesion suggests a exceptional molecular basis for the dynamic interaction of four 7 with its ligand, mucosal addressin cell adhesion molecule 1 (MAdCAM-1). Here we report that a disulfide bond-stabilized W1 4- 1 loop in four -propeller domain plays critical roles in regulating integrin four 7 affinity and signaling. Either breaking the disulfide bond or deleting the disulfide bond-occluded segment within the W1 4- 1 loop inhibited rolling cell adhesion supported by the lowaffinity interaction amongst MAdCAM-1 and inactive four 7 but negligibly impacted firm cell adhesion supported by the highaffinity interaction among MAdCAM-1 and Mn2 -activated 4 7.Formula of (R)-3-Amino-1-methyl-piperidine Furthermore, disrupting the disulfide bond or deleting the disulfide bond-occluded segment not just blocked the conformational transform and activation of four 7 triggered by talin or phorbol-12-myristate-13-acetate by means of inside-out signaling but also disrupted integrin-mediated outside-in signaling and impaired phosphorylation of focal adhesion kinase and paxillin.Price of 1287752-84-4 Therefore, these findings reveal a certain molecular basis for four 7-mediated rolling cell adhesion along with a novel regulatory element of integrin affinity and signaling.PMID:22664133 Integrins are a household of / heterodimeric cell adhesion molecules that mediate cell-cell, cell-matrix, and cell-pathogen* Thiswork was supported by National Standard Investigation System of China Grant 2010CB529703; by National Organic Science Foundation of China Grants 31190061, 31271487, and 30970604; by Science and Technologies Commission of Shanghai Municipality Grant 11JC1414200; by Shanghai Pujiang System Grant 08PJ14106; by China Postdoctoral Science Foundation Grants 2011M500079 and 2012T50445; and by Postdoctoral Analysis System from Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences Grant 2012KIP503. We acknowledge the support from the Sanofi-Aventis Shanghai Institutes for Biological Sciences (SA-SIBS) scholarship system. 1 Both authors contributed equally to this operate. two To whom correspondence must be addressed: Institute of Biochemistry and Cell Biology, 320 YueYang Road, Shanghai 200031, China. Tel.: 86-2154921142; Fax: 86-21-54921658; E-mail: [email protected] and signal bidirectionally across the plasma membrane (1). Distinct from most integrins that mediate only firm cell adhesion upon activation, a compact subset of integrins, which includes 4 7, four 1, six four, and L 2, can mediate rolling and firm cell adhesion pre- and post-activation (2?). Integrin 4 7 is expressed exclusively on lymphocytes, and its main ligand, mucosal addressin cell adhesion molecule 1.