LDL receptor-GFP fusion proteins: new tools for the characterization of disease-causing mutations in the LDL receptor gene

The function of a series of LDL receptor GFP fusion proteins with different, flexible, unstructured spacer regions was analysed. An optimised version of the fusion protein was used to analyse the effect of a LDL receptor mutation (W556S) found in FH patients and characterized as transport defective. In cultured liver cells this mutation was found to inhibit the transport of LDL receptor GFP fusion protein to the cell surface, thus leading to impaired internalisation of fluorescent labelled LDL. Co-locallisation studies confirmed the retention of the mutant protein in the endoplasmic reticulum.