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Related Concept Videos

Integrins01:10

Integrins

Animal and protozoan cells do not have cell walls to help maintain shape and provide structural stability. Instead, these eukaryotic cells secrete a sticky mass of carbohydrates and proteins into the spaces between adjacent cells. This network of proteins and molecules is called an extracellular matrix or ECM.
Some ECM proteins assemble into a basement membrane to which the remaining components adhere. Proteoglycans typically form the bulk of the ECM while fibrous proteins, like collagen,...
Complement System01:27

Complement System

The complement system is a group of approximately 20 plasma proteins that strengthen the body's defenses against infections through opsonization, inflammation, and cell lysis. Opsonization involves coating pathogens with complement proteins, making them more recognizable and facilitating phagocyte engulfment. Certain complement proteins induce inflammation that attracts immune cells to the site of infection. Cell lysis involves the destruction of pathogens through the formation of a membrane...
Activation of Integrins01:15

Activation of Integrins

Integrins bind ligands and transmit information from outside the cell to inside or vice-versa through an "outside-in signaling" or "inside-out signaling."
In "outside-in signaling," external factors in the extracellular space bind to exposed ligand binding sites on integrins. This causes the inactive protein to undergo a conformational change to become active. Integrins are often clustered on the cell membrane. Repetitive and regularly spaced ligand binding events provide an effective stimulus.
Immunoglobulin-like Cell Adhesion Molecules01:31

Immunoglobulin-like Cell Adhesion Molecules

Immunoglobulin-like cell adhesion molecules or Ig-CAMs are a versatile group of cell surface glycoproteins belonging to the immunoglobulin protein superfamily. Ig-CAMs possess the characteristic immunoglobulin protein domains and other domains such as the fibronectin type III domain. The Ig domains are glycosylated to varying degrees in different Ig-CAMs.
Ig-CAMs exhibit either homophilic binding (to other Ig-CAMs) or heterophilic binding (to other ligands such as integrins). While most Ig-CAMs...
Intracellular Signaling Affects Focal Adhesions01:17

Intracellular Signaling Affects Focal Adhesions

Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer's hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some...
Selectins01:25

Selectins

Cell adhesion is  an essential aspect of multicellularity. While stable cell interactions usually occur between cells of the same type, transient cell interactions occur between cells of different tissue types, such as between neutrophils and endothelial cells. Selectins are one class of cell adhesion molecules (CAMs) that bind carbohydrate ligands to form transient cell adhesion. They are rod-like proteins with a long extracellular part of variable length ending with the lectin domain, which...

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High-resolution Melting PCR for Complement Receptor 1 Length Polymorphism Genotyping: An Innovative Tool for Alzheimer's Disease Gene Susceptibility Assessment
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Molecular basis for complement recognition by integrin αXβ2.

Xing Chen1, Yamei Yu, Li-Zhi Mi

  • 1Immune Disease Institute, Children's Hospital Boston, and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA.

Proceedings of the National Academy of Sciences of the United States of America
|March 7, 2012
PubMed
Summary
This summary is machine-generated.

Integrin alpha(X)beta(2) binds to complement fragment iC3b, enabling pathogen recognition and phagocytosis. This study reveals the specific binding sites on both the integrin and iC3b using electron microscopy.

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Area of Science:

  • Immunology
  • Structural Biology
  • Biochemistry

Background:

  • Integrin alpha(X)beta(2) is a key complement receptor involved in innate immunity.
  • It mediates the recognition and phagocytosis of pathogens opsonized by complement fragments like iC3b.
  • Understanding the molecular basis of this interaction is crucial for immune response mechanisms.

Purpose of the Study:

  • To elucidate the structural basis of the interaction between integrin alpha(X)beta(2) and its ligand iC3b.
  • To identify the specific binding sites on both the integrin and the complement fragment.

Main Methods:

  • Negative-stain electron microscopy (EM) was employed to visualize the complex.
  • EM class averages were used to define the interaction interface.

Main Results:

  • The study identified the binding site on iC3b to be within the C3c moiety, specifically at the interface of the MG3 and MG4 domains.
  • Integrin alpha(X)beta(2) binds via its alpha(X) alpha I domain, utilizing the metal ion-dependent adhesion site.
  • Similar binding was observed between alpha(X)beta(2) and the C3c fragment.

Conclusions:

  • The structural insights provided by EM clarify how integrin alpha(X)beta(2) recognizes complement-opsonized targets.
  • This detailed understanding of the binding interface can inform strategies for modulating immune responses.