Journal of Lipid Research, Vol 28, 1515-1521, Copyright © 1987 by Lipid Research, Inc.
Detection of the low density lipoprotein (LDL) receptor on nitrocellulose paper with colloidal gold-LDL conjugates
PD Roach, M Zollinger and SP Noel
Departement de Biochimie, Universite de Montreal, Canada.
Gold-low density lipoprotein (LDL) conjugates were used to detect the LDL
receptor on nitrocellulose paper. Solubilized rat liver membrane proteins
were subjected to electrophoresis and electroblotted onto nitrocellulose
paper. The receptor was then detected as a red band (within 10 min) by
overlaying with the LDL conjugates. The coloration was prevented by
unlabeled LDL, EDTA, and suramin but not by unlabeled HDL3. In the dot blot
assay, detection with the colloidal gold-LDL conjugates was as sensitive as
both the autoradiographic method with 125I-labeled LDL and the biotinylated
LDL method; the estimated limit of detection by scanning densitometry was
1.6 femtomoles of receptor protein. When the coloration obtained with the
colloidal gold-LDL conjugates was intensified by photochemical silver
staining, down to 200 attomoles of the LDL receptor could be detected. In
this assay, the EDTA-sensitive binding of colloidal gold-LDL to solubilized
hepatic membrane proteins was 12 times higher for rats treated with 17
alpha-EE than for normal rats. The use of colloidal gold-LDL conjugates is
therefore a very easy, safe, inexpensive, fast and sensitive method for the
detection of the LDL receptor on nitrocellulose paper. Furthermore, with
silver staining and scanning densitometry, the colloidal gold-LDL
conjugates could be used in a dot blot assay to quantify tissue and cell
LDL receptors down to attomolar levels.