Monoacylation of ribonuclease A enables its transport across an in vitro model of the blood-brain barrier

A major challenge in correcting disorders affecting the central nervous sys tem is to induce blood-brain barrier (BBB) crossing of exogenous biological compounds such as proteins or specific nucleic acid sequences. Fatty acids , due to their high membrane affinity and low toxicity, are good potential candidates to promote this barrier crossing when covalently bound to protei ns. In this paper, we report that regiospecific monoacylation of ribonuclea se A (RNase A) enables its transport across an in vitro model of the BBB. M yristoylated, palmitoylated and stearoylated RNases A were prepared using r eversed micelles as microreactors. All the purified acylated RNases A kept their original enzymatic activity. A single fatty acid moiety was linked to RNase A through the alpha-amino group of its N-terminal lysine as shown by powerful analytical techniques. The ability of monoacylated RNases A to cr oss an in vitro model of the BBB is strictly dependent on the acyl chain le ngth, which must be at least 16 carbon atoms long. (C) 1998 Elsevier Scienc e B,V. All rights reserved.