cell adhesion molecule

Examples of cell adhesion molecule in the following topics:

• Adaptive Immunity and the Immunoglobulin Superfamily

  • These membrane molecules function as B cell receptors for antigens.
  • The immunoglobulin superfamily (IgSF) is a large group of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells.
  • Members of the IgSF include cell surface antigen receptors, co-receptors, and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors, and intracellular muscle proteins.
  • When a B cell encounters its triggering antigen, it gives rise to many large cells known as plasma cells.
  • Each of the plasma cells manufactures millions of identical antibody molecules and pours them into the bloodstream.

• Desmosomes

  • A desmosome is a type of cell junction that attaches to keratin in the cytoplasm and is a localized structure adjoining two cells.
  • The cell adhesion proteins of the desmosome - desmoglein and desmocollin - are members of the cadherin family of cell adhesion molecules.
  • The symptoms of the diseases are caused by the subsequent disruption to the desmosome-keratin filament complex leading to a breakdown in cell adhesion in the skin.
  • A desmosome, also known as macula adherens (Latin: adhering spot), is a cell structure specialized for cell-to-cell adhesion in animal cells.
  • A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes.

• Basement Membranes and Diseases

  • This is achieved by cell-matrix adhesions through substrate adhesion molecules (SAMs).
  • The basement membrane also acts as a mechanical barrier, preventing malignant cells from invading the deeper tissues.
  • Basement membrane proteins have been found to accelerate differentiation of endothelial cells.
  • It is caused by a mutation in the integrin α6β4 cell-adhesion molecule on either the alpha or beta subunit.

• Cellular Differentiation

  • Three basic categories of cells make up the mammalian body: germ cells, somatic cells, and stem cells.
  • Hematopoietic stem cells (adult stem cells) from the bone marrow that give rise to red blood cells, white blood cells, and platelets
  • Mesenchymal stem cells (adult stem cells) from the bone marrow that give rise to stromal cells, fat cells, and types of bone cells;
  • Epithelial stem cells (progenitor cells) that give rise to the various types of skin cells
  • A pathway that is guided by the cell adhesion molecules is created as the cellular blastomere differentiates from the single-layered blastula to the three primary layers of germ cells in mammals, namely the ectoderm, mesoderm and endoderm (listed from most distal, or exterior, to the most proximal, or interior).

• Adherens Junctions

  • Zonula means small zone or belt-like, and adherens refers to adhesion (sticking together). 
  • As a result, the zonula adherens often runs like a belt around the entire cell in a continuous fashion, and it acts as an adhesion belt.
  • These are transmembrane adhesion proteins, whose main portions are located in the extracellular space.
  • Each cell’s cadherin molecule also contains a tail that inserts itself inside its respective cell. 
  • The extracellular portions of the cadherin molecules of adjacent cells are bonded together by calcium ions (or another protein in some cases). 

• Hemidesmosomes

  • While desmosomes link two cells together, hemidesmosomes attach one cell to the extracellular matrix.
  • Rather than using desmogleins, hemidesmosomes use desmopenetrin cell adhesion proteins.
  • Hemidesmosomes are asymmetrical and are found in epithelial cells connecting the basal face to other cells.
  • An example configuration of a hemidesmosome might consist of cytosolic keratin, non-covalently bonded to a cytosolic plectin plaque, which is bonded to a single-pass transmembrane adhesion molecule such as the α6β4 integrin.
  • The integrin might then attach to one of many multi-adhesive proteins such as laminin, resident within the extracellular matrix, thereby forming one of many potential adhesions between cell and matrix.

• Surface Tension and Capillary Action

  • Attractive forces between molecules of different types are called adhesive forces.
  • In this section we examine effects of cohesive and adhesive forces in liquids.
  • In the bulk of the liquid, each molecule is pulled equally in every direction by neighboring liquid molecules, resulting in a net force of zero.
  • The molecules at the surface do not have other molecules on all sides of them and therefore are pulled inwards.
  • The effect can be seen in the drawing-up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper, in some non-porous materials such as liquified carbon fiber, and in a cell.

• Capillary Action

  • The molecules in any sample of matter experience intermolecular forces, which are attractive or repulsive forces between atoms or molecules within the sample.
  • On the other hand, when intermolecular forces occur between different types of molecules (especially when they are part of different phases of matter), they are referred to as adhesive forces, or resulting in adhesion.
  • The molecules in a sample of water in contact with a glass surface experience attractive forces toward the glass molecules.
  • This effect can be seen in the drawing-up of liquids between the hairs of a paintbrush, in a thin tube, in porous materials such as paper, in some non-porous materials (such as liquified carbon fiber), or in a cell.
  • A convex meniscus occurs when the molecules have a stronger attraction to each other (cohesion) than to the material of the container (adhesion), causing the surface of the liquid to cave downward.

• Injuring the Plasma Membrane

  • The plasma membrane or cell membrane is a biological membrane that separates the interior of all cells from the outside environment.
  • The plasma membrane is selectively permeable to ions and organic molecules.
  • Plasma membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity, and cell signaling.
  • Fungi, bacteria, and plants also have the cell wall which provides a mechanical support for the cell and precludes the passage of larger molecules.
  • The plasma membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell and in attaching to the extracellular matrix and other cells to help group cells together to form tissues .

• Adhesions

  • If this is allowed to happen, tissue repair cells such as macrophages, fibroblasts and blood vessel cells, penetrate into the fibrinous adhesion, and lay down collagen and other matrix substances to form a permanent fibrous adhesion.
  • In the case of adhesive capsulitis of the shoulder (also known as frozen shoulder), adhesions grow between the shoulder joint surfaces, restricting motion.
  • Abdominal adhesions (or intra-abdominal adhesions) are most commonly caused by abdominal surgical procedures but may also be caused by pelvic inflammatory disease or endometriosis.
  • Small bowel obstruction (SBO) is another significant consequence of post-surgical adhesions.
  • The majority of fibrinous adhesions will disappear in due course.