Gb3-binding lectins as potential carriers for transcellular drug delivery

ABSTRACT

Objectives: Epithelial cell layers as well as endothelia forming the blood-brain barrier can drastically reduce the efficiency of drug targeting. Our goal was to investigate lectins recognizing the glycosphingolipid globotriaosylceramide (Gb3) for their potential as carriers for transcytotic drug delivery.

Methods: We utilized an in vitro model based on Madin-Darby canine kidney cells transfected with Gb3 synthase to characterize transcytosis of the Gb3-binding lectins LecA from Pseudomonas aeruginosa and the B-subunit of Shiga toxin (StxB).

Results: Both lectins were rapidly transcytosed from the apical to the basolateral plasma membrane and vice versa. Whereas StxB proceeded on retrograde and transcytotic routes, LecA avoided retrograde transport. This differential trafficking could be explained by our observation that LecA and StxB segregated into different domains during endocytosis. Furthermore, inhibiting the small GTPase Rab11a, which organizes trafficking through apical recycling endosomes, blocked basolateral to apical transcytosis of both lectins.

Conclusions: Gb3-binding lectins are promising candidates for transcytotic drug delivery. Our findings highlight that LecA and StxB, which both bind Gb3 but exhibit dissimilar valence and molecular structures of their carbohydrate binding sites and can take divergent intracellular trafficking routes. This opens up the possibility of developing tailor-made glycosphingolipid-binding carrier lectins, which take optimized trafficking pathways.

KEYWORDS:

• Apical recycling endosome
• LecA
• MDCK cells
• Rab11
• Shiga toxin
• transcytosis

Acknowledgments

The authors thank Alessia Landi for proofreading the manuscript and helpful scientific discussions.

Declaration of interest

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

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Funding

W Römer acknowledges support by the Excellence Initiative of the German Research Foundation (EXC 294 and GSC-4 Spemann Graduate School), the Baden-Württemberg Stiftung (Zukunftsoffensive IV Innovation und Exzellenz), a German Research Foundation Grant Number [RO 4341/2-1] and a starting grant from the European Research Council (Programme ‘Ideas’, ERC-2011-StG 282105).