Claudin-4: functional studies beyond the tight junction.

Claudin-4 is an unusual member of the claudin family; in addition to its role in epithelial tight junction barrier function, it is a receptor for the Clostridium perfringens enterotoxin. We have also found that claudin-4 is regulated in mucosal epithelium M cells, both in increased expression of the protein and in redistribution into endocytosis vesicles. Our ongoing studies are studying the potential for developing ligands specific to claudin-4 for targeted delivery of cargo such as proteins and poly(DL-lactide-co-glycolide) nanoparticles to mucosal M cells.

Intranasal M cell uptake of nanoparticles is independently influenced by targeting ligands and buffer ionic strength.

In mucosal tissues, epithelial M cells capture and transport microbes across the barrier to underlying immune cells. Previous studies suggested that high affinity ligands targeting M cells may be used to deliver mucosal vaccines; here, we show that particle composition and dispersion buffer ionic strength can independently influence their uptake in vivo. First, addition of a poloxamer 188 to nanoparticle formulations increased uptake of intranasally administered nanoparticles in vivo, but the effect was dependent on the presence of the M cell-targeting ligand.

Claudin 4-targeted protein incorporated into PLGA nanoparticles can mediate M cell targeted delivery.

Polymer-based microparticles are in clinical use mainly for their ability to provide controlled release of peptides and compounds, but they are also being explored for their potential to deliver vaccines and drugs as suspensions directly into mucosal sites. It is generally assumed that uptake is mediated by epithelial M cells, but this is often not directly measured. To study the potential for optimizing M cell uptake of polymer microparticles in vivo, we produced sub-micron size PLGA particles incorporating a recombinant protein.

Membrane transduction of oligoarginine in HeLa cells is not mediated by macropinocytosis.

The mechanism in which small cationic oligopeptides are able to reach the cytosol of cells is controversial. Macropinocytosis has been recently suggested as a major mechanism for internalization of these peptides. In this report, the involvement of macropinocytosis on cytosolic localization of oligoarginine was quantitatively investigated in HeLa cells.