The initial process of laminin (LM) deposition onto the cell surface depends upon interactions with the LG domain located at the alpha chain C-terminus. This domain contains binding sites for alpha-dystroglycan, sulfated glycolipids, heparan sulfate chains and integrins. The LM binding site for the major LM-binding integrins alpha6beta1, alpha6beta4, alpha3beta1 and alpha7beta1 (Belkin & Stepp 2000) is located in LG motifs 1-3 of LM alpha (LMA) chains (Hirosaki et al. 2000 - LMA3, unidentified integrin, Shang et al. 2001 - rat LMA3, human alpha3beta1, Smirnov et al. 2002 - LMA2 with mouse alpha6beta1, Talts et al. 2000 - mouse LMA4 with integrin alpha6beta1, Yu & Talts 2003 - mouse LMA5 with integrin alpha3beta1, Nishiuchi et al. 2006 - LMA1and LMA2 with alpha7beta1).
Recombinant integrins vary in their laminin specificities: alpha3beta1 and alpha6beta4 have a clear specificity for LM-332 and -511/512, integrin alpha6beta1 has a broad specificity, binding all LM isoforms with a preference for LM-111, -332 and -511/521. Alpha7beta1 variants do not bind LM-332. Alpha7 isoform X1beta1 binds all LM except LM-332, with a preference for LM-211/221 and LM-511/521, while alpha7 isoform X2beta1 binds preferentially to LM-111 and LM-211/221. LM-511/521 has the highest affinity for all LM-binding integrins except alpha7 isoform X2beta1, while LM-411 has low affinity only for alpha6beta1 and alpha7 isoform X1beta1 (Nishiuchi et al. 2006 - all human reagents except mouse LM-111).
The N-terminal globular domains of LMA1 (Colognato-Pyke et al. 1995 - mouse LM, rat alpha1 and beta1 integrins) and alpha-2 chains (Colognato et al. 1997 - mouse LMA1, human LMA2, human integrins) can bind integrins alpha1beta1 and alpha2beta1. The N-terminal globular VI domains of LMA5 and LMA1 can bind integrin subunits alpha3, alpha2, alpha4, alpha6 (not LMA1) and beta1 (Nielsen & Yamada 2001 - using mouse LMA1 and LMA5 against Cercopithecus aethiops integrins). The IVa domain (L4a) domain of the LMA5 chain can bind integrin alphaVbeta3 (mouse LMA5, human integrin, Sasaki & Timpl 2001). The LM gamma-2 chain has been reported to bind alpha2beta1 integrin (Decline & Rousselle 2001). The N-terminal globular domains of some alpha chains can also bind sulfatides, which may also link the LM molecules to the cell surface.
The relative importance of these interactions is unclear (Yurchenko & Patton 2009).
Integrins and dystroglycan indirectly connect the LM network to the actin cytoskeleton.