Abundant structural component of the basal lamina; critical to the stability of the extracellular matrix and to the adhesion of cells to the basement membrane. Family of heterotrimeric glycoproteins composed of a heavy chain, designated α (also known as A) and 2 light chains, designated β (B1) and γ (B2), which are linked by disulfide bonds to form an asymmetrical cross-shaped structure. Eight genetically distinct laminin subunits have been identified: α1, α2, α3, β1, β2, β3, γ1, and γ2. Seven different assembly forms (laminins-1 to -7) are known and appear to be tissue specific and developmentally regulated. Exhibits diverse biological activities. Influences adhesion, growth, morphology and differentiation of a variety of cells via specific receptors including several of the integrin type. Isoln from murine Engelbreth-Holm-Swarm (EHS) tumor: R. Timpl et al., J. Biol. Chem. 254, 9933 (1979). Review of biological activities: H. K. Kleinman et al., J. Cell. Biochem. 27, 317-325 (1985); of role in neural development: V. Nurcombe, Pharmacol. Ther. 56, 247 (1992). Tissue distribution: E. Engvall et al., Cell Regul. 1, 731 (1990). Review of laminin binding proteins and receptors: R. P. Mecham, Annu. Rev. Cell Biol. 7, 71-91 (1991); and role in metastasis: V. Castronovo, Invasion Metastasis 13, 1-30 (1993). Structure and function of laminin isoforms: E. Engvall, Kidney Int. 43, 2-6 (1993); K. Tryggvason, Curr. Opin. Cell Biol. 5, 877-882 (1993). Nomenclature: R. E. Burgeson et al., Matrix Biol. 14, 209 (1994). Review of structure: R. Timpl, J. C. Brown, ibid. 275-281.
Prototype laminin produced by murine EHS tumor. Contains α1 (also known as A or Ae), β1 (B1, B1e) and γ1 (B2, B2e) subunits.
Variant found in striated muscle, placental trophoblast and Schwann cell basement membranes. Contains α2 (also known as M or Am), β1 and γ1 subunits. Identification: I. Leivo, E. Engvall, Proc. Natl. Acad. Sci. USA 85, 1544 (1988); K. Ehrig et al., ibid. 87, 3264 (1990).
Contains α1, β2 (also known as s or B1s), and γ1 chains. Identification in neuromuscular junction: D. D. Hunter et al., Nature 338, 229 (1989).
Contains α3, β3, and γ2 subunits. Isoln from human keratinocytes: P. Rousselle et al., J. Cell Biol. 114, 567 (1991). Review of role in progression of cancer: J. Lohi, Int. J. Cancer 94, 763-767 (2001).