One mechanism of emergent anticancer multidrug resistance is the induction of an ATP-dependent, membrane transport system, P-glycoprotein, P-gp, a pump which effluxes anticancer agents. We offer a peptide ligand design scheme as an agent source alternative to currently prominent empirically discovered small molecule inhibitors of substrate and/or nucleotide binding which often fail because they themselves are subject to and/or induce the P-gp pump in tumor cells. Our new scheme for computational hierarchical hydrophobic mode analysis and membrane protein mode matched peptide design target membrane protein extracellular loops and induce conformational transitions manifested by either positive or negative allosteric changes in their responses to their natural ligands and with approximately 30-50% hit rates. The cooperative conformational motions of P-gp?s nearly symmetric halves required for normal function make this approach different from and perhaps more promising than the more common binding-site targeted, small molecule inhibitors. Work since the previous submission suggest that these receptor hydrophobic mode matched algorithmic peptides, reversed in sequence and expressed in D amino acids, retro-inverso forms, less likely to be subject to the action and induction of the P-gp pump as well as the actions of peptidases (thus more easily deliverable, even orally), have similar effects in magnitude and direction as their ortho congeners. Hydrophobic mode-matched, algorithmically designed, conformationally active allosteric ortho and retro-inverso peptide agents will be tested against cancer drug transport and ATP utilization in spheroblasts, right sided vesicles and whole cell prokaryote systems expressing human P-gp. Ligand mode specificity will be addressed using 50 peptides generated from randomized eigenvector templates. The non-multidrug ATP-dependent transporter MDR3 will serve as a control for target specificity. Evidence that the anticipated 30% (75) or more of the 250 normal vector generated candidate algorithmic peptides will down regulate, impair or abrogate transport by this Phase I study using this in vitro simple cell system will encourage a Phase I submission for expanded peptide design and testing in P-gp expressing in vitro and in vivo mammalian cells systems as well as drug resistant human tumor cell lines.
| Selz, Karen A; Mandell, Arnold J; Shlesinger, Michael F et al. (2004) Designing human m1 muscarinic receptor-targeted hydrophobic eigenmode matched peptides as functional modulators. Biophys J 86:1308-31 |
