A novel Pyk2-derived peptide inhibits invadopodia-mediated breast cancer metastasis.

Dissemination of cancer cells from the primary tumor into distant body tissues and organs is the leading cause of death in cancer patients. While most clinical strategies aim to reduce or impede the growth of the primary tumor, no treatment to eradicate metastatic cancer exists at present. Metastasis is mediated by feet-like cytoskeletal structures called invadopodia which allow cells to penetrate through the basement membrane and intravasate into blood vessels during their spread to distant tissues and organs. The non-receptor tyrosine kinase Pyk2 is highly expressed in breast cancer, where it mediates invadopodia formation and function via interaction with the actin-nucleation-promoting factor cortactin. Here, we designed a cell-permeable peptide inhibitor that contains the second proline-rich region (PRR2) sequence of Pyk2, which binds to the SH3 domain of cortactin and inhibits the interaction between Pyk2 and cortactin in invadopodia. The Pyk2-PRR2 peptide blocks spontaneous lung metastasis in immune-competent mice by inhibiting cortactin tyrosine phosphorylation and actin polymerization-mediated maturation and activation of invadopodia, leading to reduced MMP-dependent tumor cell invasiveness. The native structure of the Pyk2-PRR2:cortactin-SH3 complex was determined using nuclear magnetic resonance (NMR), revealing an extended class II interaction surface spanning the canonical binding groove and a second hydrophobic surface which significantly contributes to ligand affinity. Using structure-guided design, we created a mutant peptide lacking critical residues involved in binding that failed to inhibit invadopodia maturation and function and consequent metastatic dissemination in mice. Our findings shed light on the specific molecular interactions between Pyk2 and cortactin and may lead to the development of novel strategies for preventing dissemination of primary breast tumors predicted at the time of diagnosis to be highly metastatic, and of secondary tumors that have already spread to other parts of the body.

The Disordered Cellular Multi-Tasker WIP and Its Protein-Protein Interactions: A Structural View.

WASp-interacting protein (WIP), a regulator of actin cytoskeleton assembly and remodeling, is a cellular multi-tasker and a key member of a network of protein-protein interactions, with significant impact on health and disease. Here, we attempt to complement the well-established understanding of WIP function from cell biology studies, summarized in several reviews, with a structural description of WIP interactions, highlighting works that present a molecular view of WIP's protein-protein interactions. This provides a deeper understanding of the mechanisms by which WIP mediates its biological functions. The fully disordered WIP also serves as an intriguing example of how intrinsically disordered proteins (IDPs) exert their function. WIP consists of consecutive small functional domains and motifs that interact with a host of cellular partners, with a striking preponderance of proline-rich motif capable of interactions with several well-recognized binding partners; indeed, over 30% of the WIP primary structure are proline residues. We focus on the binding motifs and binding interfaces of three important WIP segments, the actin-binding N-terminal domain, the central domain that binds SH3 domains of various interaction partners, and the WASp-binding C-terminal domain. Beyond the obvious importance of a more fundamental understanding of the biology of this central cellular player, this approach carries an immediate and highly beneficial effect on drug-design efforts targeting WIP and its binding partners. These factors make the value of such structural studies, challenging as they are, readily apparent.

Hybrid-silica nanoparticles as a delivery system of the natural biocide carvacrol.

Bacterial resistance to common antibiotics necessitates innovative solutions. The phenolic antimicrobial compound carvacrol, a major ingredient in the Essential Oils (EOs) of oregano and thyme, has the advantages of natural compounds such as Generally Recognized As Safe (GRAS) status, but needs an appropriate delivery system designed to overcome its drawbacks (such as low aqueous solubility, easy phenol oxidation, heat/light inactivation, distinct odor). An alkoxysilane incorporating the carvacrol moiety is synthesized and subsequently employed to fabricate hybrid silica nanoparticles (NPs) with carvacrol covalently bound to the silica matrix. The enzymatically hydrolyzable carbamate bond turns these NPs into a release-on-demand nanoscale system for the biocide carvacrol. Characterization of both silane linker and hybrid silica NPs, including quantification of the bioactive compound in the bulk and on the NP surface, is accomplished by spectroscopic methods, including X-ray Photoelectron Spectroscopy (XPS), and Thermo-Gravimetric Analysis (TGA), Dynamic Light Scattering (DLS), ζ-potential measurements, as well as electron microscopy. Preliminary biological testing with E. coli proves an antibacterial effect. The carbamoylation reaction employed to synthesize the hybrid silica precursor might be readily applied to other bioactive phenolic compounds.

Proteinaceous microspheres as a delivery system for carvacrol and thymol in antibacterial applications.

There is an urgent need for new materials with antimicrobial activity. Phenolic essential oil (EO) compounds with Generally Recognized As Safe (GRAS) status are attractive candidates, but they need suitable delivery systems to overcome specific drawbacks. Core-shell microspheres (MSs) of Bovine Serum Albumin (BSA) or Human Serum Albumin (HSA) encapsulating such active compounds in the oil phase are a delivery system that is novel in combination with phenolic EO compounds. Moreover, the EO compounds can also be assembled in an oil shell around a protein core by choosing an appropriate oil phase. A facile sonochemical fabrication method, which can be easily scaled-up, is developed with full characterization of the resulting EO-containing MSs by optical and electron microscopy. Bacterial growth experiments with E. coli including TEM of treated cells confirm antibacterial activity. In the case of carvacrol, the corresponding MSs are found to be both more bioactive and more stable than the free biocide.