Integrins

Definition

Integrins are a family of transmembrane cell surface receptors that mediate cell-cell and cell-extracellular matrix (ECM) adhesion. They play crucial roles in various cellular processes, including cell migration, differentiation, and signaling, making them important in the context of virulence factors of eukaryotic pathogens and pathogen recognition and phagocytosis.

5 Must Know Facts For Your Next Test

1. Integrins are composed of two non-covalently linked subunits, alpha and beta, which together form a heterodimeric receptor.
2. Integrins can transmit signals bidirectionally, from the extracellular environment to the cell interior (outside-in signaling) and from the cell interior to the extracellular environment (inside-out signaling).
3. Binding of integrins to their ligands, such as components of the extracellular matrix, can activate intracellular signaling cascades that regulate cell survival, proliferation, and migration.
4. Pathogens, including viruses, bacteria, and parasites, can exploit integrins as receptors to facilitate their entry into host cells and promote infection.
5. Phagocytic cells, such as macrophages and neutrophils, use integrins to recognize and bind to pathogens, leading to their engulfment and destruction through phagocytosis.

Review Questions

• Explain how integrins function as virulence factors for eukaryotic pathogens.
  • Eukaryotic pathogens, such as viruses, bacteria, and parasites, can exploit integrins as receptors to facilitate their entry into host cells and promote infection. Pathogens may bind to specific integrin subunits, triggering signaling cascades that allow the pathogen to gain access to the host cell, evade immune defenses, and establish a successful infection. By hijacking the host cell's integrin-mediated adhesion and signaling pathways, pathogens can enhance their ability to colonize, replicate, and spread within the host organism.
• Describe the role of integrins in pathogen recognition and phagocytosis.
  • Phagocytic cells, such as macrophages and neutrophils, utilize integrins to recognize and bind to pathogens, leading to their engulfment and destruction through phagocytosis. Integrins on the surface of phagocytes can interact with specific ligands or molecules expressed on the pathogen, triggering a signaling cascade that activates the phagocytic process. This integrin-mediated recognition and binding facilitate the efficient identification, internalization, and elimination of invading microorganisms, playing a crucial role in the host's innate immune response.
• Analyze how the bidirectional signaling capabilities of integrins contribute to their importance in both virulence and host defense mechanisms.
  • The ability of integrins to transmit signals bidirectionally, from the extracellular environment to the cell interior (outside-in signaling) and from the cell interior to the extracellular environment (inside-out signaling), is a key feature that makes them important in the context of both virulence factors of eukaryotic pathogens and pathogen recognition and phagocytosis. Pathogens can exploit the outside-in signaling of integrins to gain entry and manipulate host cells, while phagocytic cells can utilize the inside-out signaling of integrins to recognize, bind, and eliminate invading microorganisms. This dynamic and versatile nature of integrins highlights their critical role in mediating complex host-pathogen interactions and the delicate balance between pathogenesis and host defense mechanisms.

Related terms

Cell Adhesion Molecules (CAMs): Cell adhesion molecules are proteins expressed on the cell surface that facilitate binding between cells or between a cell and the extracellular matrix. Integrins are a type of CAM.

Extracellular Matrix (ECM): The extracellular matrix is a complex network of macromolecules, such as collagen, fibronectin, and laminin, that provide structural and biochemical support to surrounding cells. Integrins mediate cell-ECM interactions.

Focal Adhesions: Focal adhesions are large, dynamic protein complexes through which the actin cytoskeleton of a cell connects to the extracellular matrix. Integrins are a key component of focal adhesions.