Bacterial Magnetosomes as Novel Platform for the Presentation of Immunostimulatory, Membrane-Bound Ligands in Cellular Biotechnology.

Frank Mickoleit,Valérie Jérôme,Ruth Freitag,Dirk Schüler

doi:10.1002/adbi.201900231

Abstract

Cell-cell interactions involving specific membrane proteins are critical triggers in cellular development. Ex vivo strategies to mimic these effects currently use soluble proteins or (recombinant) presenter cells, albeit with mixed results. A promising alternative are bacterial magnetosomes, which can be selectively transformed into cell-free membrane-protein presenters by genetic engineering. In this study, the human CD40 Ligand (CD40L), a key ligand for B cell activation, is expressed on the particle surface. Functionality is demonstrated on sensor cells expressing the human CD40 receptor. Binding of CD40L magnetosomes to these cells triggers a signaling cascade leading to the secretion of embryonic alkaline phosphatase. Concomitantly, the CD40-CD40L interaction is strong enough to allow cell recovery by magnetic sorting. Overall, this study demonstrates the potential of magnetosomes as promising cell-free tools for cellular biotechnology, based on the display of membrane-bound target molecules, thereby creating a biomimetic interaction.

Highlights

Cell–cell interactions involving specific membrane proteins are critical triggers in cellular development
A substitute membrane-bound ligands (L) with cellular receptors are of high presentation system with reduced drawbacks and efficacy compainterest in tissue engineering, and for directed stem cell dif- rable to the natural membrane-bound CD40 Ligand (CD40L) is highly desirable
Such a solution may be provided by bacterial magnetosomes, to mimic such reactions ex vivo use soluble multimers of the biogenic nanoparticles produced by magnetotactic bacteria

Summary

Introduction

Cell–cell interactions involving specific membrane proteins are critical triggers in cellular development. To study effects of ligand density, three variants of CD40L displaying magnetosomes were generated using two Mam proteins with different abundances, namely MamC and MamG (60 or 165 copies per particle, respectively),[12,14] as anchors. Protein bands in the expected molecular mass range were detected for the magnetosome membrane fractions of all three recombinant strains (Figure 3A).

Results

Conclusion