27.10: Laminins are the Adhesive Proteins of Basal Lamina
Laminins are heterotrimeric proteins with high molecular mass found in the extracellular matrix. Each laminin molecule is composed of three chains, viz. alpha, beta, and gamma, coded by five, four, and three paralogous genes, respectively. Laminins are categories based on the compositions of the three chains.
In humans, the five forms of alpha chains are LAMA 1, LAMA 2, LAMA 3, LAMA 4, and LAMA 5. The four forms of beta chains are LAMB 1, LAMB 2, LAMB 3, and LAMB 4. The three forms of gamma chains are LAMC 1, LAMC 2 and LAMC 3.
In the extracellular matrix, the laminins associate with each other to form a mesh. This mesh is associated with other macromolecules like perlecan, entactin, and type IV collagen to form a framework for the basal lamina. Laminins also connect with the cell by binding to their integrins or dystroglycan.
Biologically laminins help in influencing cell adhesion, differentiation, and migration. Laminins are essential for the survival and maintenance of the tissue. Defective laminins can lead to improper muscle formation, skin blistering, and issues related to kidney filtration. Laminins also play an essential role in neural development and peripheral nerve repair.