title: Neuropilin-1 and heparan sulfate proteoglycans cooperate in cellular uptake of nanoparticles functionalized by cationic cell-penetrating peptides.
abstract: Cell-penetrating peptides (CPPs) have been widely used to deliver nanomaterials and other types of macromolecules into mammalian cells for therapeutic and diagnostic use. Cationic CPPs that bind to heparan sulfate (HS) proteoglycans on the cell surface induce potent endocytosis; however, the role of other surface receptors in this process is unclear. We describe the convergence of an HS-dependent pathway with the C-end rule (CendR) mechanism that enables peptide ligation with neuropilin-1 (NRP1), a cell surface receptor known to be involved in angiogenesis and vascular permeability. NRP1 binds peptides carrying a positive residue at the carboxyl terminus, a feature that is compatible with cationic CPPs, either intact or after proteolytic processing. We used CPP and CendR peptides, as well as HS- and NRP1-binding motifs from semaphorins, to explore the commonalities and differences of the HS and NRP1 pathways. We show that the CendR-NRP1 interaction determines the ability of CPPs to induce vascular permeability. We also show at the ultrastructural level, using a novel cell entry synchronization method, that both the HS and NRP1 pathways can initiate a macropinocytosis-like process and visualize these CPP-cargo complexes going through various endosomal compartments. Our results provide new insights into how CPPs exploit multiple surface receptor pathways for intracellular delivery.
authors.affiliation: Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Hong-Bo
authors.initials: HB
authors.lastname: Pang
authors.affiliation: Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA. ; Center for Nanomedicine and Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610, USA.
authors.forename: Gary B
authors.initials: GB
authors.lastname: Braun
authors.affiliation: Cancer Center, Sanford Burnham Prebys Medical Discovery Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA. ; Center for Nanomedicine and Department of Molecular, Cellular, and Developmental Biology, University of California, Santa Barbara, Santa Barbara, CA 93106-9610, USA.
authors.forename: Erkki
authors.initials: E
authors.lastname: Ruoslahti
keywords: CendR pathway; cell-penetrating peptide; intracellular delivery; neuropilin-1; synchronized ultrastructural imaging; vascular permeability