Inhibition of the binding of low-density lipoprotein to its cell surface receptor in human fibroblasts by positively charged proteins

✍ Scribed by Brown, Michael S. ;Deuel, Thomas F. ;Basu, Sandip K. ;Goldstein, Joseph L.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1978
• Tongue: English
• Weight: 701 KB
• Volume: 8
• Category: Article
• ISSN: 0091-7419
• DOI: 10.1002/jss.400080302

✦ Synopsis

A group of proteins and polyarnino acids with positively charged domains were shown to inhibit the binding of 1251-LDL t o its receptor on the surface of human fibroblasts. The list of inhibitory proteins included platelet factor 4 (which has a cluster of lysine residues at its carboxyl terminus), two lysinerich histones, poly-L-lysines of chain length greater than 4, and protamine. These proteins were effective in the concentration range of 5-50 pg/ml. Two other positively charged proteins, lysozyme and avidin, did not inhibit 125 I-LDL binding. Kinetic studies suggested that protamine was not acting simply as a competitive inhibitor with regard to the LDL receptor. In light of previous data showing that polyanions such as heparin and polyphosphates also inhibit '251-LDL binding t o its cell surface receptor, the current findings suggest that charge interactions are important in this binding reaction. In a related series of studies, a number of glycoproteins and their asialo derivatives as well as a number of sugar phosphates failed t o inhibit i251-LDL binding t o its receptor in fibroblasts.