tetraspan

Tetraspan is a term that appears in several disciplines, most often as shorthand for proteins characterized by four transmembrane segments. In biology, the term is sometimes used informally to refer to the tetraspanin family, a group of cell-surface proteins that organize membranes by forming tetraspanin-enriched microdomains.

Tetraspanins are typically around 200–300 amino acids long and contain four transmembrane helices, a short cytoplasmic tail, and two extracellular loops, with the large extracellular loop mediating many protein–protein interactions. They function as organizers of membrane architecture, aiding in cell adhesion, migration, signal transduction, and, in some cases, viral entry. The family includes well-known members such as CD9, CD63, and CD81 in humans. Tetraspanins interact with a broad network of partner proteins, including integrins, growth factor receptors, and immunoreceptors, to coordinate cellular responses.

Beyond biology, “tetraspan” is not a standardized technical term in most fields. Some writers use it descriptively to refer to objects or structures with four spans or four-fold symmetry, but such usage is informal and varies by context. There is no universal specification or measurement associated with the term outside its informal reference to four-span configurations.

In scientific contexts, the precise and widely accepted term for these proteins is tetraspanin. When encountered as “tetraspan” alone, it is typically an informal shorthand and should be interpreted from the surrounding domain-specific usage. See also: tetraspanin.