Glycosaminoglycan silencing by engineered CXCL12 variants.

We have engineered GPCR (G protein-coupled receptor) knock-out and high GAG-binding affinity into CXCL12α to inhibit CXCL12α-induced cell migration. Compared to wtCXCL12, the mutant CXCL12α (Δ8 L29K V39K) exhibited a 5.6-fold and a 2.2-fold affinity increase for heparin and heparan sulfate, respectively. From NaCl-based heparin displacement chromatography we concluded that more amino acid replacements would lead to altered GAG (glycosaminoglycan) ligand specificity. GAG silencing by this mutant was shown in a murine seeding model of human cancer cells, whereby a greatly reduced number of liver metastases was detected when the animals were treated intravenously with 1mg/kg CXCL12α (Δ8 L29K V39K) before cancer cell application.

A combinatorial approach to biophysically characterise chemokine-glycan binding affinities for drug development.

Chemokine binding to glycosaminoglycans (GAGs) is recognised to be an important step in inflammation and other pathological disorders like tumor growth and metastasis. Although different ways and strategies to interfere with these interactions are being pursued, no major breakthrough in the development of glycan-targeting drugs has been reported so far. We have engineered CXCL8 towards a dominant-negative form of this chemokine (dnCXCL8) which was shown to be highly active in various inflammatory animal models due to its inability to bind/activate the cognate CXCL8 GPC receptors on neutrophils in combination with its significantly increased GAG-binding affinity [1]. For the development of GAG-targeting chemokine-based biopharmaceuticals, we have established a repertoire of methods which allow the quantification of protein-GAG interactions. Isothermal fluorescence titration (IFT), surface plasmon resonance (SPR), isothermal titration calorimetry (ITC), and a novel ELISA-like competition assay (ELICO) have been used to determine Kd and IC50 values for CXCL8 and dnCXCL8 interacting with heparin and heparan sulfate (HS), the proto-typical members of the GAG family. Although the different methods gave different absolute affinities for the four protein-ligand pairs, the relative increase in GAG-binding affinity of dnCXCL8 compared to the wild type chemokine was found by all methods. In combination, these biophysical methods allow to discriminate between unspecific and specific protein-GAG interactions.

Characterization of two bacterial hydroxynitrile lyases with high similarity to cupin superfamily proteins.

Hydroxynitrile lyases (HNLs) catalyze the cleavage of cyanohydrins. In the reverse reaction, they catalyze the formation of carbon-carbon bonds by enantioselective condensation of hydrocyanic acid with carbonyls. In this study, we describe two proteins from endophytic bacteria that display activity in the cleavage and the synthesis reaction of (R)-mandelonitrile with up to 74% conversion of benzaldehyde (enantiopreference ee 89%). Both showed high similarity to proteins of the cupin superfamily which so far were not known to exhibit HNL activity.