The laminin family nomenclature
Laminins are multidomain, heterotrimeric, glycoproteins, composed of three different subunits; an α-chain, β-chain and γ-chain, that can be found in five (α1-5), three (β1-3) and three (γ1-3) genetic variants respectively. A β4 subunit has also been identified in mammals but little is known about it (Yurchenco, 2015). Furthermore, the α3 subunit exists as two splice variants. (Aumailley et al., 2005; Miner & Yurchenco, 2004). There are to date at least 16 distinct isoforms identified in mammals and their names derive from their combination of the subunits, thus, laminin-521 contains an α5, a β2 and a γ1 chain (Aumailley et al., 2005).
Laminin molecular structure
The laminin protein is assembled through a coiled-coil of the three chains, stabilized by inter-chain disulfide bonds. The assembled laminin molecule forms a cross-like structure where the N-terminal ends of the α, β, and γ chains forms the short arms and the coiled-coiled C-terminal ends forms the long arm (Aumailley et al., 2005; Miner & Yurchenco, 2004).
The N terminal ends of the α, β, and γ chains vary in length and typically are capped by laminin globular domains (LN), connected to a semi-flexible rod consisting of a variable number of laminin epidermal growth factor–like (LE) domains. They also contain internal globular domains, such as laminin 4 (L4), a laminin four (LF) and modified LF (LFx). The laminin coiled-coil domain of the β-chains also contain a small globular motif (Lβ). The α chains also have five globular domains (LG1–5) at the C terminus end with a short hinge-like segment between the third and fourth globule (Yurchenco, 2015; Aumailley et al., 2005).
- A simplified laminin nomenclature. Aumailley et al. Matrix Biol., 2005
- Laminin functions in tissue morphogenesis. Miner & Yurchenco. Annu Rev Cell Dev Biol., 2004
- Integrating Activities of Laminins that Drive Basement Membrane Assembly and Function. Yurchenco. Current Topics in Membranes, 2015