Cell adhesion

Cell adhesion is the process by which cells interact and attach to neighbouring cells through specialised molecules of the cell surface. This process can occur either through direct contact between cell surfaces such as cell junctions or indirect interaction, where cells attach to surrounding extracellular matrix, a gel-like structure containing molecules released by cells into spaces between them. Cells adhesion occurs from the interactions between cell-adhesion molecules (CAMs), transmembrane proteins located on the cell surface. Cell adhesion links cells in different ways and can be involved in signal transduction for cells to detect and respond to changes in the surroundings. Other cellular processes regulated by cell adhesion include cell migration and tissue development in multicellular organisms. Alterations in cell adhesion can disrupt important cellular processes and lead to a variety of diseases, including cancer and arthritis. Cell adhesion is also essential for infectious organisms, such as bacteria or viruses, to cause diseases. CAMs are classified into four major families: integrins, immunoglobulin (Ig) superfamily, cadherins, and selectins. Cadherins and IgSF are homophilic CAMs, as they directly bind to the same type of CAMs on another cell, while integrins and selectins are heterophilic CAMs that bind to different types of CAMs. Each of these adhesion molecules has a different function and recognizes different ligands. Defects in cell adhesion are usually attributable to defects in expression of CAMs. In multicellular organisms, bindings between CAMs allow cells to adhere to one another and creates structures called cell junctions. According to their functions, the cell junctions can be classified as: Anchoring junctions (adherens junctions, desmosomes and hemidesmosomes), which maintain cells together and strengthens contact between cells.