Laminin (925-933)

Synthetic peptides interacting with the 67-kd laminin receptor can reduce retinal ischemia and inhibit hypoxia-induced retinal neovascularization

The high-affinity 67-kd laminin receptor (67LR) is expressed by proliferating endothelial cells during retinal neovascularization. The role of 67LR has been further examined experimentally by administration of selective 67LR agonists and antagonists in a murine model of proliferative retinopathy. These synthetic 67LR ligands have been previously shown to stimulate or inhibit endothelial cell motility in vitro without any direct effect on proliferation. In the present study, a fluorescently labeled 67LR antagonist (EGF(33-42)) was injected intraperitoneally into mice and its distribution in the retina was assessed by confocal scanning laser microscopy. Within 2 hours this peptide was localized to the retinal vasculature, including preretinal neovascular complexes, and a significant amount had crossed the blood retinal barrier. For up to 24 hours postinjection, the peptide was still present in the retinal vascular walls and, to a lesser extent, in the neural retina. Non-labeled EGF(33-42) significantly inhibited pre-retinal neovascularization in comparison to controls treated with phosphate-buffered saline or scrambled peptide (P < 0.0001). The agonist peptide (Lam beta 1(925-933)) also significantly inhibited proliferative retinopathy; however, it caused a concomitant reduction in retinal ischemia in this model by promoting significant revascularization of the central retina (P < 0.001). Thus, 67LR appears to be an important target receptor for the modulation of retinal neovascularization. Agonism of this receptor may be valuable in reducing the hypoxia-stimulated release of angiogenic growth factors which drives retinal angiogenesis.

Promotion of human oral squamous cell carcinoma adhesion in vitro by the carboxy-terminal globular domain of laminin

The domains of laminin utilized by cells from human squamous-cell carcinoma (SCC) to promote adhesion were investigated. The ability of cultured SCC cells to adhere to surfaces adsorbed with laminin, laminin fragments, or laminin peptides was examined in a direct, solid-phase adhesion assay. The cells adhered in a concentration-dependent and saturable manner to laminin and E3 and E8 fragments of elastase-digested laminin. These results suggest that SCC cells adhere to at least two distinct sites within the carboxy terminal long arm of laminin. In contrast, SCC cells adhered poorly to the 440-kDa chymotrypsin-resistant fragment of laminin, and the E1' and E4 elastase-digested fragments of laminin, suggesting that the short arms, including the cross-region, of laminin does not contain binding sites for these cells. Synthetic peptides GD-2 and -6, comprised of amino acid sequences derived from the E3 fragment, promoted the adhesion of SCC cells in a concentration-dependent and saturable manner. The specific interaction of SCC cells with GD-2 was demonstrated by competition assays in which soluble GD-2 and anti-peptide GD-2 IgG inhibited cell adhesion to GD-2. The anti-peptide GD-2 IgG partially inhibited the adhesion of SCC cells to the E3 fragment and intact laminin, but not to fibronectin. These results suggest that SCC cells recognize the sequence of GD-2 within laminin. The role of integrins in mediating the adhesion of SCC cells to laminin and GD-2 was then investigated.(ABSTRACT TRUNCATED AT 250 WORDS)

High glucose, high insulin, and their combination rapidly induce laminin-beta1 synthesis by regulation of mRNA translation in renal epithelial cells

Laminin is a glycoprotein that contributes to renal extracellular matrix expansion in diabetes. We investigated regulation of laminin-beta1 synthesis in murine renal proximal tubular epithelial cells by 30 mmol/l glucose (high glucose), 1 nmol/l insulin (high insulin), and their combination (high glucose+high insulin), simulating conditions observed during progression of type 2 diabetes. Compared with 5 mmol/l glucose and no insulin (control), high glucose alone, high insulin alone, or high glucose+high insulin together increased laminin-beta1 chain protein synthesis within 5 min, lasting for up to 60 min with no change in laminin-beta1 mRNA levels. Cycloheximide, but not actinomycin-D, abrogated increased laminin-beta1 synthesis. High glucose, high insulin, and high glucose+high insulin stimulated phosphorylation of 4E-BP1, a repressor binding protein for eukaryotic initiation factor 4E (eIF4E), that was dependent on activation of phosphatidylinositol 3-kinase, Akt, and mammalian target of rapamycin. High glucose, high insulin, and high glucose+high insulin also promoted release of eIF4E from 4E-BP1, phosphorylation of eIF4E, and increase in eIF4E association with eIF4G, critical events in the initiation phase of mRNA translation. High glucose, high insulin, and high glucose+high insulin increased Erk phosphorylation, which is an upstream regulator of eIF4E phosphorylation, and PD098059, which is a MEK inhibitor that blocks Erk activation, abolished laminin-beta1 synthesis. This is the first demonstration of rapid increment in laminin-beta1 synthesis by regulation of its mRNA translation by cells exposed to high glucose, high insulin, or high glucose+high insulin.