Laminin

Glycoprotein of the extracellular matrix. Laminins are found in all basal laminae, and have binding sites for cell surface receptors.

Together with collagen type IV and proteoglycans, laminins form the basement membranes.Other important components of the basal lamina are fibronectins, integrins. Laminins connect integrins to the basal lamina in a protein complex. Fibronectin, however, connects integrins with collagen fibers of different types. Types.

15 isoforms of laminin are known so far. These are distributed tissue-specifically in the animal organism. The laminin molecule consists of an alpha-, a beta- and a γ-protein chain, which assemble in heterotrimeric form to the respective laminin molecule. So far, the following combinations of protein chains have been detected in the different isoforms of lamininis:

• Laminin-1: α1β1γ1 (Laminin-111).
• Laminin-2: α2β1γ1 (laminin-211)
• Laminin-3: α1β2γ1 (laminin-121)
• Laminin-4: α2β2γ1 (laminin-221)
• Laminin-5: α3β3γ2 (laminin-332)
• Laminin-6: α3β1γ1 (laminin-311)
• Laminin-7: α3β2γ1 (laminin-321)
• Laminin-8: α4β1γ1 (laminin-411)
• Laminin-9: α4β2γ1 (laminin-421)
• Laminin-10: α5β1γ1 (laminin-511)
• Laminin-11: α5β2γ1 (laminin-521)
• Laminin-12: α2β1γ3 (laminin-231)
• Laminin-13: α3β2γ3 (laminin-323)
• Laminin-14: α4β2γ3 (laminin-423)
• Laminin-15: α5β2γ3 (laminin-523)

The laminin molecule consists of an alpha, a beta and a gamma protein chain, which are combined in a special structure to form the laminin molecule. The molecule has 4 arms, 3 of which can form bonds with other laminin molecules. The remaining, longer arm binds to cell surfaces. Laminin is of great importance for cell adhesion. In addition, laminin stimulates the growth of neurites in cell cultures, has a chemotactic effect and can trigger cell differentiation.

Antibodies against laminin 5 are found in a subset of scarring pemphigoid.

Mutation in the genes for laminin-5(LAMA3, LAMB3, LAMC2) mapped on chromosomes 1q25/1q31 lead to the clinical picture of epidermolysis bullosa junctionalis, generalized severe and intermediate (hsitoric: Herzlitz and non-Herlitz). The absence of the protein in the skin leads to extreme skin fragility.

1. Kon A et al. (1998) Laminin 5 genes and Herlitz junctional epidermolysis bullosa: novel mutations and polymorphisms in the LAMB3 and LAMC2 genes. Mutations in brief no. 190. online. Hum Mutat 12: 288.
2. Laimer M et al (2010) Herlitz junctional epidermolysis bullosa. Dermatol Clin 28:55-60.