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Cell Junctions

  1. Joachim Wegener

Published Online: 15 JUN 2011

DOI: 10.1002/9780470015902.a0001275.pub2

eLS

eLS

How to Cite

Wegener, J. 2011. Cell Junctions. eLS. .

Author Information

  1. Universität Regensburg, Regensburg, Germany

Publication History

  1. Published Online: 15 JUN 2011

Abstract

For any multicellular organism to function, it is a prerequisite that its individual cells interact with each other. These interactions are realised by cell-to-cell junctions that provide mechanical stability, information exchange or occlusion of extracellular diffusion pathways between neighbouring cells. The latter is an unconditional prerequisite for the formation of interfaces within the organism or between organism and environment. In order to provide these different physiological functions the corresponding cell junctions have their individual molecular architecture but share some common construction principles. For all of them transmembrane proteins are required that interact with corresponding structures on the surface of the opposing cell to form either mechanically stable interconnections, tight diffusion barriers, aqueous channels or well-defined nanometre gaps for the fast diffusion of signal molecules. In most cases these transmembrane proteins interact with intracellular adapter proteins or the cytoskeleton, which is critical for their correct functionality.

Key Concepts:

  • More than 200 different cell types act together in the tissues and organs of the human body.

  • Cellular cooperation in multicellular organisms is based on various cellular interactions and cell junctions.

  • From a functional viewpoint cell junctions can be grouped into: (1) occluding junctions, (2) mechanical junctions and (3) communicating junctions.

  • Barrier-forming epithelial and endothelial cells, which build up interfacial tissues between two fluid compartments, express tight junctions that occlude the diffusion pathway between adjacent cells.

  • Tight junctions are mainly composed of different transmembrane proteins (occludin, members of the claudin family, etc.) that use their extracellular domains to interact with the corresponding protein domains on the adjacent cell surface to block the intercellular cleft.

  • Mechanical stability of epithelial cell layers is based on adherens junctions and desmosomes that both provide a stable mechanical linkage between the intracellular cytoskeletons of adjacent cells.

  • Exchange of signalling molecules or metabolites smaller than 1000 g mol−1 is provided by gap junctions (electrical synapses) who form aqueous channels between neighbouring cells.

  • Plant cells show a special kind of communicating junctions, the plasmodesmata.

  • Electrical communication between two neurons or a neuron and muscle cells is provided by chemical synapses, which relay electrochemical signals by a pulse of neurotransmitters.

Keywords:

  • tight junctions;
  • adherens junctions;
  • desmosomes;
  • gap junctions;
  • plasmodesmata;
  • synapses