Mutation of a conserved asparagine in the I-like domain promotes constitutively active integrins alphaLbeta2 and alphaIIbbeta3.
The leukocyte beta2 integrins are heterodimeric adhesion receptors required for a functional immune system. Many leukocyte adhesion deficiency-1 (LAD-1) mutations disrupt the expression and function of beta2 integrins. Herein, we further characterized the LAD-1 mutation N329S in the beta2 inserted (I)-like domain. This mutation converted alphaLbeta2 from a resting into a high affinity conformer because alphaLbeta2N329S transfectants adhered avidly to ligand intercellular adhesion molecule (ICAM)-3 in the absence of additional activating agent. An extended open conformation is adopted by alphaLbeta2N329S because of its reactivity with the beta2 activation reporter monoclonal antibodies MEM148 and KIM127. A corresponding mutation in beta3 generated constitutively active alphaIIbbeta3 that adhered to fibrinogen. This Asn is conserved in all human beta subunits, and it resides before the last helix of the I-like domain, which is known to be important in activation signal propagation. By mutagenesis studies and review of existing integrin structures, we conjectured that this conserved Asn may have a primary role in shaping the I-like domain by stabilizing the conformation of the alpha7 helix and the beta6-alpha7 loop in the I-like domain.
Cheng
Ming
M
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
Foo
Shen-Yun
SY
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
Shi
Min-Long
ML
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
Tang
Ren-Hong
RH
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
Kong
Le-Sheng
LS
Computational Research Group, Temasek Life Sciences Laboratory, 1 Research Link, National University of Singapore, Singapore 117604, Singapore.
Law
S K Alex
SKA
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Electronic address: alaw@ntu.edu.sg.
Tan
Suet-Mien
SM
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551. Electronic address: smtan@ntu.edu.sg.
D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism; D001216:Asparagine / Q000737:chemistry*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D009154:Mutation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000235:genetics*; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D015703:Antigens, CD; D015815:Cell Adhesion Molecules; C483616:ICAM3 protein, human; D016169:Lymphocyte Function-Associated Antigen-1; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D018799:Intercellular Adhesion Molecule-1; D001216:Asparagine