Laminins

Laminins are a family of large, cross-shaped glycoproteins that are a major component of basement membranes, specialized extracellular matrices that underlie epithelia and surround many tissues. They are heterotrimers composed of one alpha, one beta, and one gamma chain, of which several isoforms exist (LAMA1–5, LAMB1–5, LAMC1–3). The combination of chains gives rise to numerous laminin isoforms, such as laminin-111 (alpha1beta1gamma1) and laminin-521 (alpha5beta2gamma1).

Each laminin monomer has a long coiled-coil region formed by the N-terminus and a short arm with LN domains that mediate polymerization into a network within the basement membrane; the C-terminal globular LG domains mediate interactions with cell surface receptors such as integrins and dystroglycan, enabling cell adhesion and signaling.

Laminins organize basement membranes, influence cell adhesion, migration, differentiation, and polarization, and regulate processes during development, tissue maintenance, wound healing, and angiogenesis. Key receptors include integrins (e.g., α6β1, α3β1, α7β1) and dystroglycan; interactions with other matrix components such as heparan sulfate proteoglycans can occur in some contexts.

In kidneys, the laminin network supports glomerular filtration; in neuromuscular and vascular tissues, laminins guide development and maintenance of specialized structures. Mutations in laminin genes cause congenital muscular dystrophies and other basement membrane disorders; LAMA2-related dystrophy is a well-known example. Laminins are produced by many cell types, including epithelial cells, Schwann cells, muscle cells, endothelial cells, and neurons, and are secreted to assemble the basement membrane. They are also used as culture substrates to promote cell adhesion, survival, and differentiation in vitro.