Functional characterization of two low density lipoprotein receptor gene mutations by fluorescence flow cytometric assessment of receptor activity instimulated human T-lymphocytes

We report a functional characterization of the W23X and W66G low density li poprotein (LDL) receptor gene mutations. The authors used two-color fluores cence flow cytometry to measure LDL receptor activity in stimulated T-lymph ocytes, prepared from patients heterozygous for the W23X or W66G mutation, and compared the results with measurements of LDL receptor activity in stim ulated T-lymphocytes prepared from unrelated healthy control subjects. It w as found that the W23X mutation significantly reduced LDL receptor expressi on and LDL binding and internalization, and that the W66G mutation signific antly reduced LDL receptor expression and LDL binding. LDL internalization in patients heterozygous for the W66G mutation was not significantly reduce d. The data support the concepts that the W23X mutation prevents production of LDL receptors (class I) and that the W66G mutation produces LDL recepto rs unable to recycle normally in cells (class V).