The leukocyte integrins aM?2 and ax?2 are widely important in inflammatory responses of myeloid cells. They bind ligands including ICAM-1, iC3b, and fibrin. Upon cell activation, integrins change shape and can bind ligand, a phenomenon known as inside-out signaling. Understanding the molecular basis of this structural alteration is of great importance. The long-term goal of this application is to understand at the atomic level 1) how allostery in aM?2 and ax?2 integrins is transmitted from the juxtamembrane regions through the lower legs, upper legs, and ? I domain, to the ligand-binding a I domain, 2) how ligands such as iC3b bind, and 3) how small molecule antagonists inhibit ligand binding by disrupting allostery. Mutations predicted to better stabilize the high affinity, open conformation of ax and aM I domains than current mutations will be examined, and the best ones used in studies of ligand binding and allostery. A structure of the aM I domain bound to domain 3 of ICAM-1 will reveal the mechanism of ligand binding; a ternary complex of the CCL and aM I domains bound to a domain 1-3 fragment will reveal how integrins cooperate to bind a single ligand and how binding sites are organized to allow this. Electron microscopy will reveal how domain-domain orientations change between bent, extended-closed, and extended-open conformations, how allostery is transmitted from one domain to another, and how activating Fab and small molecule antagonists alter allosteric transitions. Structural studies will examine how the overall disposition of the thioester domain in C3 changes from C3 to C3b to iC3b, and how the ax and aM I domain and intact ectodomains specifically recognize iC3b. A crystal structure of the ax?2 ectodomain in the bent conformation will define at the atomic level the structure of the low affinity state. The structure of interfaces between the ? -propeller and a I domain and between the a I domain and ? I domain will reveal important information about how allostery is transmitted. Mutational studies will define the physiologic function of the bent conformation on cell surfaces. Co-crystal structures with small molecule antagonists will reveal binding sites important for development of therapeutics for inflammatory and autoimmune diseases. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
9R01AI072765-26A1
Application #
7197632
Study Section
Cellular and Molecular Immunology - A Study Section (CMIA)
Program Officer
Palker, Thomas J
Project Start
1988-05-15
Project End
2011-12-31
Budget Start
2007-01-01
Budget End
2007-12-31
Support Year
26
Fiscal Year
2007
Total Cost
$568,200
Indirect Cost
Name
Immune Disease Institute, Inc.
Department
Type
DUNS #
059709394
City
Boston
State
MA
Country
United States
Zip Code
02115
Xu, Shutong; Wang, Jianchuan; Wang, Jia-Huai et al. (2017) Distinct recognition of complement iC3b by integrins ?X?2 and ?M?2. Proc Natl Acad Sci U S A 114:3403-3408
Sen, Mehmet; Springer, Timothy A (2016) Leukocyte integrin ?L?2 headpiece structures: The ?I domain, the pocket for the internal ligand, and concerted movements of its loops. Proc Natl Acad Sci U S A 113:2940-5
Sen, Mehmet; Yuki, Koichi; Springer, Timothy A (2013) An internal ligand-bound, metastable state of a leukocyte integrin, ?X?2. J Cell Biol 203:629-42
Chen, Xing; Yu, Yamei; Mi, Li-Zhi et al. (2012) Molecular basis for complement recognition by integrin ?X?2. Proc Natl Acad Sci U S A 109:4586-91
Chen, Xing; Xie, Can; Nishida, Noritaka et al. (2010) Requirement of open headpiece conformation for activation of leukocyte integrin alphaXbeta2. Proc Natl Acad Sci U S A 107:14727-32
Xie, Can; Zhu, Jianghai; Chen, Xing et al. (2010) Structure of an integrin with an alphaI domain, complement receptor type 4. EMBO J 29:666-79
Mi, Li-Zhi; Grey, Michael J; Nishida, Noritaka et al. (2008) Functional and structural stability of the epidermal growth factor receptor in detergent micelles and phospholipid nanodiscs. Biochemistry 47:10314-23
Vorup-Jensen, Thomas; Chi, Lianli; Gjelstrup, Louise C et al. (2007) Binding between the integrin alphaXbeta2 (CD11c/CD18) and heparin. J Biol Chem 282:30869-77
Luo, Bing-Hao; Carman, Christopher V; Springer, Timothy A (2007) Structural basis of integrin regulation and signaling. Annu Rev Immunol 25:619-47
Nishida, Noritaka; Xie, Can; Shimaoka, Motomu et al. (2006) Activation of leukocyte beta2 integrins by conversion from bent to extended conformations. Immunity 25:583-94

Showing the most recent 10 out of 13 publications