THERMOSTABLE EXOSHELLS AS TOOLS FOR RECOMBINANT PROTEIN EXPRESSION AND IN VIVO DELIVERY

Abstract

We have engineered a thermostable protein nanoparticle (tES) to improve both expression and stabilization of recombinant proteins using a single technology. tES provides steric accommodation and charge complementation to GFPuv, horseradish peroxidase (HRP), and Renilla luciferase, and Photinus pyralis luciferase, improving yields of functional in vitro folding by approximately 100 fold. Encapsulated enzymes retain the ability to metabolize small molecule substrates, presumably via four 4.5-nm pores present in the tES shell. Thermolabile proteins can be released from tES assembly with mild pH titration followed by proteolysis. Each tES accommodates exactly two molecules of HRP and that the internalized enzymes can hydrolyze indole-3-acetic acid (IAA) into reactive intermediates. tES specifically mediates endocytotic uptake of the enzyme into MDA-MB-231 and systemic treatment with IAA in the presence of locally administered tES(+)/tES-HRP results in complete tumor regression. Our findings support the potential use of thermostable shells in the therapeutic delivery of macroglobular proteins.