Discovery and Optimization of Salicylic Acid-Derived Sulfonamide Inhibitors of the WD Repeat-Containing Protein 5-MYC Protein-Protein Interaction.

The treatment of tumors driven by overexpression or amplification of MYC oncogenes remains a significant challenge in drug discovery. Here, we present a new strategy toward the inhibition of MYC via the disruption of the protein-protein interaction between MYC and its chromatin cofactor WD Repeat-Containing Protein 5. Blocking the association of these proteins is hypothesized to disrupt the localization of MYC to chromatin, thus disrupting the ability of MYC to sustain tumorigenesis. Utilizing a high-throughput screening campaign and subsequent structure-guided design, we identify small-molecule inhibitors of this interaction with potent in vitro binding affinity and report structurally related negative controls that can be used to study the effect of this disruption. Our work suggests that disruption of this protein-protein interaction may provide a path toward an effective approach for the treatment of multiple tumors and anticipate that the molecules disclosed can be used as starting points for future efforts toward compounds with improved drug-like properties.

In-depth analyses of kinase-dependent tyrosine phosphoproteomes based on metal ion-functionalized soluble nanopolymers.

The ability to obtain in-depth understanding of signaling networks in cells is a key objective of systems biology research. Such ability depends largely on unbiased and reproducible analysis of phosphoproteomes. We present here a novel proteomics tool, polymer-based metal ion affinity capture (PolyMAC), for the highly efficient isolation of phosphopeptides to facilitate comprehensive phosphoproteome analyses. This approach uses polyamidoamine dendrimers multifunctionalized with titanium ions and aldehyde groups to allow the chelation and subsequent isolation of phosphopeptides in a homogeneous environment. Compared with current strategies based on solid phase micro- and nanoparticles, PolyMAC demonstrated outstanding reproducibility, exceptional selectivity, fast chelation times, and high phosphopeptide recovery from complex mixtures. Using the PolyMAC method combined with antibody enrichment, we identified 794 unique sites of tyrosine phosphorylation in malignant breast cancer cells, 514 of which are dependent on the expression of Syk, a protein-tyrosine kinase with unusual properties of a tumor suppressor. The superior sensitivity of PolyMAC allowed us to identify novel components in a variety of major signaling networks, including cell migration and apoptosis. PolyMAC offers a powerful and widely applicable tool for phosphoproteomics and molecular signaling.

Role of the protein tyrosine kinase Syk in regulating cell-cell adhesion and motility in breast cancer cells.

The expression of the Syk protein tyrosine kinase in breast cancer cells is inversely correlated with invasive growth and metastasis. The expression of Syk inhibits cell motility while supporting the formation of cell clusters by enhancing cell-cell contacts and promoting the redistribution of the adhesion proteins cortactin and vinculin to these contacts. Syk associates physically with cortactin and catalyzes its phosphorylation on tyrosine. The clustering of integrins leads to the phosphorylation of Syk and of numerous cellular proteins in a manner dependent on the activity of the kinase and on the presence of tyrosine 342 located in the linker B region. The ability of Syk to participate in integrin-mediated protein tyrosine phosphorylation correlates well with its ability to inhibit cell motility.