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Scavenger receptors clear pathogens, transport lipid, and mediate polyanionic ligand uptake in macrophages, but their expression and role in skin is poorly understood. Although the epidermal barrier typically excludes nucleic acid entry, topically applied, spherically-arranged oligonucleotide nanoconjugates (spherical nucleic acids or SNAs) penetrate mouse skin, 3D skin equivalents, and human skin. We explored the mechanism of SNA uptake in normal human epidermal keratinocytes (NHEKs) and 3D skin equivalents. NHEKs and 3D raft treatment with class A scavenger receptor (SR-A) inhibitors reduced SNA uptake by >80%. Human epidermis expresses SR-As scavenger receptor class A type 3 (SCARA3) and, to a lesser extent, macrophage receptor with collagenous structure (MARCO). Simultaneous lentiviral knockdown of SCARA3 and MARCO reduced SNA uptake in NHEKs and 3D rafts after topical application, affirming a role for SR-As in SNA uptake and 3D raft penetration. Incubation of NHEKs at 4°C or with sodium azide prevented SNA uptake, suggesting active endocytosis. Endocytosis inhibitors, immunofluorescence, immunoprecipitation, and knockdown studies localized functional SR-As to flotillin-1 (FLOT-1)-containing lipid rafts throughout the epidermis and caveolin-1 (CAV-1)-containing rafts only in the upper epidermis. These studies suggest a central role for SR-A complexes in epidermal lipid rafts in mediating uptake of nucleic acid-laden nanoparticles.

p53 is an important tumor-suppressor protein that is mutated in more than 50% of cancers. Strategies for restoring normal p53 function are complicated by the oncogenic properties of mutant p53 and have not met with clinical success. To counteract mutant p53 activity, a variety of drugs with the potential to reconvert mutant p53 to an active wildtype form have been developed. However, these drugs are associated with various negative effects such as cellular toxicity, nonspecific binding to other proteins, and inability to induce a wildtype p53 response in cancer tissue. Here, we report on the effects of a curcumin analog, HO-3867, on p53 activity in cancer cells from different origins. We found that HO-3867 covalently binds to mutant p53, initiates a wildtype p53-like anticancer genetic response, is exclusively cytotoxic toward cancer cells, and exhibits high anticancer efficacy in tumor models. In conclusion, HO-3867 is a p53 mutant–reactivating drug with high clinical anticancer potential.

The glmS riboswitch is unique among gene-regulating riboswitches and catalytic RNAs. This is because its own metabolite, glucosamine-6-phosphate (GlcN6P), binds to the riboswitch and catalytically participates in the RNA self-cleavage reaction, thereby providing a novel negative feedback mechanism. Given that a number of pathogens harbor the glmS riboswitch, artificial actuators of this potential RNA target are of great interest. Structural/kinetic studies point to the 2-amino and 6-phosphate ester functionalities in GlcN6P as being crucial for this actuation. As a first step toward developing artificial actuators, we have synthesized a series of nine GlcN6P analogs bearing phosphatase-inert surrogates in place of the natural phosphate ester. Self-cleavage assays with the Bacillus cereus glmS riboswitch give a broad SAR. Two analogs display significant activity, namely, the 6-deoxy-6-phosphonomethyl analog (5) and the 6-O-malonyl ether (13). Kinetic profiles show a 22-fold and a 27-fold higher catalytic efficiency, respectively, for these analogs vs glucosamine (GlcN). Given their nonhydrolyzable phosphate surrogate functionalities, these analogs are arguably the most robust artificial glmS riboswitch actuators yet reported. Interestingly, the malonyl ether (13, extra O atom) is much more effective than the simple malonate (17), and the "sterically true" phosphonate (5) is far superior to the chain-truncated (7) or chain-extended (11) analogs, suggesting that positioning via Mg coordination is important for activity. Docking results are consistent with this view. Indeed, the viability of the phosphonate and 6-O-malonyl ether mimics of GlcN6P points to a potential new strategy for artificial actuation of the glmS riboswitch in a biological setting, wherein phosphatase-resistance is paramount.