Entactine

Entactine, more commonly known as nidogen, is a basement membrane glycoprotein that serves as a crosslinking component within the extracellular matrix. It is secreted by various cell types, including epithelial, endothelial, and mesenchymal cells, and localizes to basement membranes across many tissues.

In humans, entactin refers to two closely related proteins produced by the NID1 and NID2 genes, encoding nidogen-1 and nidogen-2. These large secreted glycoproteins contain multiple globular domains arranged along rod-like regions and mediate interactions with major basement membrane networks. The G3 domain of nidogen binds laminin, while other regions interact with the collagen IV network and other basement membrane constituents such as perlecan. Through these interactions, nidogens help couple laminin networks to collagen IV networks, contributing to basement membrane assembly, stability, and integrity.

Distribution and function are broad: nidogen is found in the basement membranes of most organs, including skin, vasculature, kidney, lung, and nervous tissue. By anchoring laminin and collagen IV, entactin/nidogen supports tissue architecture and influences processes such as cell adhesion, migration, and differentiation during development and tissue remodeling.

Clinical and research notes indicate that altered nidogen expression or fragmentation is observed in certain pathological contexts, including cancer and fibrotic diseases. Animal studies show that loss of nidogen can compromise basement membranes, with some redundancy between NID1 and NID2; double deficiencies tend to yield more pronounced defects.

See also: Basal lamina, Laminin, Collagen IV, Perlecan, Nidogen.