Laminin

Laminin is a large, noncollagenous, basement membrane glycoprotein regulating differentiation, migration, and adhesion of normal and tumor cells. Laminin consists of three different polypeptides bound by disulfide bonds into a cross-shaped molecule. Laminin binds cells via integrins, making it an effective substrate for stimulating and enhancing cell migration and neurite outgrowth. In placental laminin, the A chain is replaced with merosin, and in laminin found near the neuromuscular junction, the B1 chain is replaced by s-laminin (synapse laminin).

Various laminin subtypes have specific binding properties. For example, laminin-5 provides an attachment substrate for both adhesion and migration in epithelial cells, fibroblasts, neurons and leukocytes. Compared to fibronectin, collagen, or vitronectin, epithelial cells adhere to laminin-5 faster and spread to a larger extent. Furthermore, laminin-5 can be used at coating concentrations ≤1 µg/mL, approximately 10-fold lower than most other ECM proteins (Koshikawa et al., 2000).

Mouse anti-Laminin-5 (Epiligrin) staining of human colon carcinoma.

Mouse anti-Laminin-5 (Epiligrin) (Merck cat. no. MAB1947) staining of human colon carcinoma.

Merosin (Laminin-2)

Merosin is a basement membrane-associated ECM protein, similar in size and structure to other laminins. Merosin is found in placenta, peripheral nerve, and is the predominant laminin variant in skeletal muscle basement membranes. Defects in the protein result in a devastating form of congenital muscular dystrophy (MDC1A). The protein structure consists of three laminin chains (a b g) . Merosin forms a link between the peripheral membrane protein a-dystroglycan and the basal lamina. Binding to cells via a high affinity receptor, merosin and other laminins are thought to mediate the attachment, migration and organization of cells into tissues during embryonic development by interacting with other extracellular matrix components.