Cell junctions are large protein complexes found in the plasma membrane, which provide a conncection between neighboring cells or between cells and the extracellular matrix (ECM). The major types of cell junctions are adherens junctions, desmosomes, hemidesmosomes, gap junctions and tight junctions. Adherens junctions, desmosomes and hemidesmosomes are different types of anchoring junctions that provide adherens between cytoskeletal filaments in one cell and cytoskeletal filaments in another cell, or to components in the ECM. Gap junctions, or communicating junctions, enables direct chemical communication between cells by allowing diffusion between their cytosols. Tight junctions are found in epithelial tissues and serve to block the passage of water and solutes between epithelial layers.
Staining of cell junctions can be observed at contact sites between neighbouring cells, and are more prominent in certain cell types, such as epithelial cells. Cell junctions are sometimes prominent along long stretches of the plasma membrane, but may also be seen only in smaller patches.
Read more about the proteome of cell junctions as substructures of the plasma membrane.