Spermidine promotes lysozyme tolerance and acid stress resistance in Streptococcus pyogenes M3

Streptococcus pyogenes are Gram-positive opportunistic pathogens residing in the human nasopharynx and skin. Changes in environmental conditions, such as pH, temperature and availability of essential ions, can stimulate the expression of S. pyogenes virulence factors. One such factor could be the availability of an extracellular pool of polyamines. Polyamines are synthesized from amino acids, and are universally present in the environment. Polyamines have been implicated in the ecology of pathogenesis by modulating quorum sensing, host adaptation and virulence. Polyamines mediate pathogenesis and help the pathogen resist environmental stress. In this study, we investigated the ability of the polyamine, spermidine, to promote acid stress survival of S. pyogenes. S. pyogenes does not synthesize spermidine, but the extracellular pool of spermidine constituted by the host and microbiome could be utilized as a signalling molecule. We report that spermidine promotes acid stress resistance in S. pyogenes. Moreover, spermidine affects the morphology of S. pyogenes by decreasing the cell size and increasing the dltA gene expression. Along with dltA, spermidine upregulated the gene expression of cell wall-modifying genes such as mur, pgdA, pepO and srtA, which might help the bacteria to resist acidic stress.

Cancer Cell-Sticky Hydrogels to Target the Cell Membrane of Invading Glioblastomas

Owing to their remarkable infiltrative traits, glioblastomas develop unclear tumor margins toward the brain, hampering the complete resection. Since the remaining invasive cells tend to have resistance to therapeutics and cause recurrence around the surgical voids, this has been a major challenge for glioblastoma treatment. Thus, we design a cancer cell-sticky hydrogel (CSH) that interacts with the glioblastoma cells to impede their invasive motility by modifying the cell membrane with active thiol-enriched interfaces. Highly reactive thiols at the cell surface can make the infiltrated cancer cells adhere to the hydrogel, resulting in increased cell adhesion and decreased motility. Cotreatment with the CSH and chemical inhibitors of the major proinvasive molecules, focal adhesion kinase and hyaluronic acid synthase, maximized the invasion-inhibitory effect. In addition, a significant decrease in tumor mass was achieved via CSH implantation in mouse models. Overall, our results highlight the use of the CSH to inhibit the aggressive invasion as a novel therapeutic strategy against glioblastoma.

Lipid-Oligonucleotide Conjugates for Simple and Efficient Cell Membrane Engineering and Bioanalysis

Cell membrane modification is important for tissue engineering, cell-based therapies, and cell biology studies. Recently, oligonucleotides have attracted considerable attention to remodel and functionalize live cell membranes. In particular, a type of amphiphilic lipid-oligonucleotide conjugates have been rationally designed and synthesized for this purpose. These conjugates have enabled a rapid, straightforward and efficient cell membrane modification. Taking advantage of the highly precise and programmable self-assembly of DNAs and RNAs, lipid-oligonucleotide conjugates have been used for membrane bioanalysis, therapeutics, building artificial membrane structures, and regulating cell-surface and cell-cell interactions. In this review, we have summarized the current knowledge in the design, synthesis, and regulating membrane properties of lipid-oligonucleotide conjugates. In addition, their state-of-the-art applications in cell membrane engineering and bioanalysis have been illustrated.