Surface display of LRP1-IV and ApoE3 on E. coli for the development of new drug delivery systems across the blood-brain barrier

Gisbert Fenoy C, Raudszus B, Langer K, Jose J

Abstract

Nanoparticles and nano‑scaled carriers are the major tools designed for the delivery of drugs into the brain a. They overcome the accessibility troubles of drugs when treating brain tumours, Alzheimer’s disease, or other neurological disorders. The small molecules attached to the nano‑structures can target membrane receptors in the blood-brain barrier (BBB), and probably via receptor‑mediated transcytosis, the whole system enters the brain b. The low density lipoprotein receptor-related protein (LRP1), one of the most expressed receptors on the BBB, could mainly be responsible for this transport c. In the work presented, a strategy to improve this transport, consisting of the in vitro identification of new specific LRP1 binding partners, has been designed. E.coli cells displaying recombinant proteins via the autodisplay technology, were used as a platform to allow protein-protein interaction studies d. As a proof of principle, the fourth ligand‑binding domain of LRP1 (LRP1‑IV) was successfully surface displayed on E.coli, and was shown to be functional due to the binding to its natural ligand Apolipoprotein E3 (ApoE3) and fluorescently‑labeled ApoE3. Surface display of ApoE3 on E. coli and fragments of it were also achieved, and can now be used for binding studies with purified LRP1‑IV. The next step will be to investigate and quantify the interaction between ApoE3 fragments or other peptides and purified LRP1‑IV, to determine which molecules could be the best for the modification of nanoparticles to accurately target the brain.