Laminins are the key proteins for proper basement membrane assembly

Basement membrane composition is highly cell-surface selective and for proper assembly, laminins are the key proteins. Laminin molecules self-assemble via a thermodynamically unfavorable nucleation binding followed by a calcium-dependent polymerization of the LN domains in the short-arms of the α, β, and γ chains (Yurchenco et al., 1985; Carafoli et al., 2012; Yurchenco & Cheng, 1993; Purvis & Hohenester, 2012). The sheet-like laminin network binds to other proteins in the basement membrane. Laminin interact with nidogen via LE motifs of the γ1 and γ3 chains (Gersdorff et al., 2005; Takagi et al., 2003; Stetefeld et al., 1996), and the Lβ domain of the β chains binds to agrin (Domogatskaya et al., 2012). Laminin is linked to collagen IV through nidogen and heparin interactions, forming a covalently stabilized network (Hohenester & Yurchenco, 2013). 

Laminin cell membrane receptor interactions

The laminin network formation is facilitated by cooperatively cell surface binding via the domains in the C-terminal end (Yurchenco, 2015). There are many binding sites on the full-length laminin molecule which can interact with cell membrane receptors, in particular integrins, α-dystroglycan (αDG), and sulfated glycolipids (SGLs). 

Integrins are important laminin receptors that initiates intracellular signaling pathways. Integrins are heterodimeric transmembrane membrane proteins consisting of an α and an β subunit. There has been at least 24 distinct integrins identified and the type and quantity of integrins on each cell are cell- and tissue-specific (Campbell & Humphries, 2011). The α5-laminins (especially LN-511) exhibit the broadest degree of integrin binding interactions (Miner et al., 1995). In contrast, the α2-laminins interact only with the α7β1 integrin and dystroglycan. The integrin α6 chain forms the major receptors for ECM laminins and integrin α6β1 binds to most laminin isoforms (Colognato & Yurchenco, 2000).

The molecular mechanism underlying the laminin-mediated signaling to integrins and other signaling receptors is still not clear. Studies indicate that the LG domains in C-terminal region of laminins are highly involved in laminin recognition by integrins and that the integrins that bind to laminin LG domains also require that the coiled coil be present (Deutzmann et al., 1990; Sung et al., 1993). A short C-terminal γ1 segment that contain a critical glutamic acid that extends out beyond the coiled-coil have also shown to play an important role (Ido et al., 2007). αDG binds primarily to the LG4 C-terminal domain and, to a lesser degree, to the LG1-3 domains of the laminins. SGLs bind to the LG4 and LG5 domains (Wizemann et al., 2003; Yu & Talts, 2003; Aumailley et al., 2005). Integrins and SGLs also interact with some of the N-terminal globular domains (Aumailley et al., 2005; Yurchenco, 2011). LG4 and N-terminal LE domains also binds to sydecans which regulates cell adhesion and motility (Okamoto et al., 2003; Ogawa et al. 2007). Beside direct interaction, laminin may also link to cell surface α-DG through secreted protein agrin (Denzer et al., 1998) or perlecan (Talts et al., 1999).

Only the intact, full length laminin molecules can replicate a biological relevant milieu for the cells

The expression of laminin isoforms in the basement membrane is heterogeneous and tissue specific. Without the right combination of laminin isoforms cells and tissues becomes dysfunctional. Laminin binding to cell membrane receptors elicit both mechanical and chemical signals in the cell, regulating organization of the cytoskeleton, cell adhesion, motility, proliferation and differentiation. Laminin-laminin linkage induces individual laminin affinities to surface binding molecules and the changes in the laminin polymer stiffness may alter the signaling strength (Yurchenco, 2015). Laminins are capable of co-signaling with growth factors and efficiently buffers endogenously produced growth factors (Rodin et al., 2014), which adds to the mechanistic complexity. Cell polarization generated by laminin interactions can also affect the cellular response to treatments with growth factor (Domogatskaya et al., 2012).

A fractionated or truncated laminin molecule or laminins isolated from tissue, lack many of the laminin domains which is needed by the cells for the proper extracellular network to form and to for stimulation of correct cellular signal transductions. Hence, only the intact, full length laminin is able to replicate the full biological relevance. Emphasizing on biology by mimicking the natural matrix protein composition is one of the most important aspects to achieve phenotypically relevant, stable cell cultures and reproducible protocols. 


  • A simplified laminin nomenclature. Aumailley et al. Matrix Biol., 2005
  • Integrin structure, activation, and interactions. Campbell & Humphries. Cold Spring Harb Perspect Biol., 2011
  • Crystal structures of the networkforming short-arm tips of the laminin b1 and g1 chains. Carafoli et al. PLOS One, 2012
  • Form and function: the laminin family of heterotrimers. Colognato & Yurchenco. Dev Dyn., 2000
  • Electron microscopic structure of agrin and mapping of its binding site in laminin-1. Denzer et al. EMBO J., 1998
  • Cell adhesion, spreading and neurite stimulation by laminin fragment E8 depends on maintenance of secondary and tertiary structure in its rod and globular domain. Deutzmann et al. Eur J Biochem., 1990
  • Functional diversity of laminins. Domogatskaya et al. Annu Rev Cell Dev Biol., 2012
  • Laminin γ3 chain binds to nidogen and is located in murine basement membranes. Gersdorff et al. J. Biol. Chem., 2005
  • Laminins in basement membrane assembly. Hohenester & Yurchenco. Cell Adhesion & Migration, 2013
  • The requirement of the glutamic acid residue at the third position from the carboxyl termini of the laminin gamma chains in integrin binding by laminins. Ido et al. Journal of Biological Chemistry, 2007
  • Extracellular distribution of diffusible growth factors controlled by heparan sulfate proteoglycans during mammalian embryogenesis. Matsuo & Kimura-Yoshida. Phil Trans R Soc., 2014
  • Clonal derivation and single-cell expansion of hPSCs on Laminin-521: Clonal culturing of human embryonic stem cells on laminin-521/E-cadherin matrix in defined and xeno-free environment. Rodin et al. Nat Commun., 2014a
  • Molecular cloning of a novel laminin chain, alpha 5, and widespread expression in adult mouse tissues. Miner et al. Journal of Biological Chemistry, 1995
  • The short arm of laminin gamma2 chain of laminin-5 (laminin-332) binds syndecan-1 and regulates cellular adhesion and migration by suppressing phosphorylation of integrin beta4 chain. Ogawa et al. Mol Biol Cell., 2007
  • Normal human keratinocytes bind to the alpha3LG4/5 domain of unprocessed laminin-5 through the receptor syndecan-1. Okamoto et al. J Biol Chem., 2003
  • Laminin network formation studied by reconstitution of ternary nodes in solution. Purvis & Hohenester. J Biol Chem., 2012
  • Crystal structure of three consecutive laminin-type epidermal growth factor-like (LE) modules of laminin gamma1 chain harboring the nidogen binding site. Stetefeld et al. J Mol Biol., 1996
  • Cell and heparin binding in the distal long arm of laminin: identification of active and cryptic sites with recombinant and hybrid glycoprotein. Sung et al., J Cell Biol., 1993
  • Complex between nidogen and laminin fragments reveals a paradigmatic beta-propeller interface. Takagi et al. Nature, 2003
  • Binding of the G domains of laminin alpha1 and alpha2 chains and perlecan to heparin, sulfatides, alpha-dystroglycan and several extracellular matrix proteins. Talts et al. EMBO J., 1999
  • Distinct requirements for heparin and alpha-dystroglycan binding revealed by structure-based mutagenesis of the laminin alpha2 LG4-LG5 domain pair. Wizemann et al. J Mol Biol., 2003
  • Beta1 integrin and alpha-dystroglycan binding sites are localized to different laminin-G-domain-like (LG) modules within the laminin alpha5 chain G domain. Yu & Talts. Biochem. J., 2003
  • Self-assembly and calcium-binding sites in laminin. A three-arm interaction model. Yurchenco & Cheng. Journal of Biological Chemistry, 1993
  • Laminin polymerization in vitro. Evidence for a two-step assembly with domain specificity. Yurchenco et al. Journal of Biological Chemistry, 1985
  • Basement membranes: cell scaffoldings and signaling platforms. Yurchenco. Cold Spring Harbor Perspectives in Biology, 3, 2011
  • Integrating Activities of Laminins that Drive Basement Membrane Assembly and Function. Yurchenco. Current Topics in Membranes, 2015