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Sialoadhesin (Sn, Siglec-1, CD169) is a member of the sialic acid binding Ig-like lectin (siglec) family expressed on macrophages. Its macrophage specific expression makes it an attractive target for delivering antigens to tissue macrophages via Sn-mediated endocytosis. Here we describe a novel approach for delivering antigens to macrophages using liposomal nanoparticles displaying high affinity glycan ligands of Sn. The Sn-targeted liposomes selectively bind to and are internalized by Sn-expressing cells, and accumulate intracellularly over time. Our results show that ligand decorated liposomes are specific for Sn, since they are taken up by bone marrow derived macrophages that are derived from wild type but not Sn(-/-) mice. Importantly, the Sn-targeted liposomes dramatically enhance the delivery of antigens to macrophages for presentation to and proliferation of antigen-specific T cells. Together, these data provide insights into the potential of cell-specific targeting and delivery of antigens to intracellular organelles of macrophages using Sn-ligand decorated liposomal nanoparticles.

The significance of sialic acid substituents for modulating the affinity of siglec binding and the utility of high affinity sialoside ligands as biological probes of siglec-2 (CD22) is demonstrated. A sialoside analogue array facilitates the synthesis of sialoside analogues in small quantity for subsequent screening for high affinity ligands of siglecs and other sialoside binding GBPs.

The implementation of a new strategy for labeling the exterior surface of a virus capsid is described by considering the compatibility of the protein particles with glycosyltransferase enzymes and chemoenzymatic reaction conditions. The resulting structures have multivalent arrays of glycan ligands favorable for binding to a cell surface glycan receptor in a highly specific manner.

The p38 signal transduction pathway can be activated transiently or constitutively, depending on the contexts in which the activation occurs. However, the biological consequence of constitutive activation of p38 is largely unknown. After screening 300 transcriptional cofactors, we identified CRTC2 as a downstream substrate of constitutively activated p38. Constitutive, rather than transient, activation of p38 led to hyperphosphorylation of CRTC2, resulting in CRTC2 cytosolic relocation and subsequent inactivation of cyclic AMP response element (CRE)-mediated transcription. Interestingly, the cytosolic translocation of CRTC2 depended on phosphorylation accumulation at multiple sites (≥11 phosphoserine/phosphothreonine residues) but not on specific sites. The hyperphosphorylation-driven nucleocytoplasmic transport of CRTC2 may not be a rare case of nuclear export of proteins, as we also observed that constitutively activated p38 promoted FOS nuclear export in a hyperphosphorylation-dependent manner. Collectively, our study uncovered a previously unknown mechanism of inactivation of selected transcription, which results from hyperphosphorylation-driven nucleocytoplasmic transport of cofactors or transcription factors mediated by constitutively active kinase. [ABSTRACT FROM AUTHOR]

A photothermal pH-reporting nanoprobe was developed for intraoperative tumor detection by "turn-on" fluorescence of the probe inside viable tumor cells, photothermal tumor therapy, and in situ monitoring of tumor killing by non-fluorescence of the probe in damaged cells. [ABSTRACT FROM AUTHOR]

CD22 is a B cell-specific sialic acid-binding immunoglobulin-like lectin (Siglec) whose function as a regulator of B cell signaling is modulated by its interaction with glycan ligands bearing the sequence NeuAcu2-6Gal. To date, only highly multivalent polymeric ligands (n = 450) have achieved sufficient avidity to bind to CD22 on native B cells. Here we demonstrate that a synthetic bifunctional molecule comprising a ligand of CD22 linked to an antigen (nitrophenol; NP) can use a monoclonal anti-NP IgM as a decavalent protein scaffold to efficiently drive assembly of IgM-CD22 complexes on the surface of native B cells. Surprisingly, anti-NP antibodies of lower valency, IgA (n = 4) and IgG (n = 2), were also found to drive complex formation, though with lower avidity. Ligands bearing alternate linkers of variable length and structure were constructed to establish the importance of a minimal length requirement, and versatility in the structural requirement. We show that the ligand drives assembly of IgM complexes exclusively on the surface of B cells and not other classes of white blood cells that do not express CD22, which lends itself to the possibility of targeting B cells in certain hematopoietic malignancies. [ABSTRACT FROM AUTHOR]