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Introduction Immune checkpoint blockade (ICB) Abs that target programmed death 1 (PD-1) and cytotoxic T lymphocyte-associated protein 4 (CTLA-4), which are focused on activating and mobilizing the body's immune system [...], The inability of [CD8.sup.+] effector T cells (Teffs) to reach tumor cells is an important aspect of tumor resistance to cancer immunotherapy. The recruitment of these cells to the tumor microenvironment (TME) is regulated by integrins, a family of adhesion molecules that are expressed on T cells. Here, we show that 7HP349, a small-molecule activator of lymphocyte function-associated antigen-1 (LFA-1) and very late activation antigen-4 (VLA-4) integrin cell-adhesion receptors, facilitated the preferential localization of tumor-specific T cells to the tumor and improved antitumor response. 7HP349 monotherapy had modest effects on anti-programmed death 1-resistant (anti-PD-1-resistant) tumors, whereas combinatorial treatment with anti-cytotoxic T lymphocyte-associated protein 4 (anti-CTLA-4) increased [CD8.sup.+] Teff intratumoral sequestration and synergized in cooperation with neutrophils in inducing cancer regression. 7HP349 intratumoral [CD8.sup.+] Teff enrichment activity depended on CXCL12. We analyzed gene expression profiles using RNA from baseline and on treatment tumor samples of 14 melanoma patients. We identified baseline CXCL12 gene expression as possibly improving the likelihood or response to anti-CTLA-4 therapies. Our results provide a proof-of-principle demonstration that LFA-1 activation could convert a T cellexclusionary TME to a T cell-enriched TME through mechanisms involving cooperation with innate immune cells.

Thebiophysical chemistry of macromolecular complexes confer their functionalcharacteristics. We investigate the mechanisms that make the AB5 holotoxinof Vibrio cholerae(CT) a significantlymore pathogenic molecule than the enterotoxin of Escherichiacoli(LT) with which it shares 88% similarity andwhose structure is homologous with a backbone RMSD of 0.84 Åand imposes its deleterious effects though the same process to constitutivelyADP-ribosylate adenylate cyclase. We present computational data thatcharacterizes the impact of amino acid variations in the A2 tail,which helps to explain experimental data that demonstrate CT’shigher toxicity. A hydrophobic patch on the B pentamer interface andits interactions with the A subdomain are partially disrupted by thesubstitution of an aspartic acid (LT) for glycine in CT. CT’sholotoxin has less solvent accessible surface area (94 Å2vs 54 Å2) and higher contact area (280 Å2vs 241 Å2) with S228, which is a gatekeeper,partially controlling the diffusion of water into the pore. CT excludeswater from the top of the central pore whereas LT allows much morewater to interact. These biophysical properties of the toxins leadto their differential toxicity and resulting impact to human health. [ABSTRACT FROM AUTHOR]

Serotonin (5-hydroxytryptamine; 5-HT) signaling through the 5-HT2C receptor (5-HT2C) is essential in normal physiology, whereas aberrant 5-HT2C function is thought to contribute to the pathogenesis of multiple neural disorders. The 5-HT2C interacts with specific protein partners, but the impact of such interactions on 5-HT2C function is poorly understood. Here, we report convergent cellular and behavioral data that the interaction between the 5-HT2C and protein phosphatase and tensin homolog (PTEN) serves as a regulatory mechanism to control 5-HT2C-mediated biology but not that of the closely homologous 5-HT2AR. A peptide derived from the third intracellular loop of the human 5-HT2C [3L4F (third loop, fourth fragment)] disrupted the association, allosterically augmented 5-HT2C-mediated signaling in live cells, and acted as a positive allosteric modulator in rats in vivo. We identified the critical residues within an 8 aa fragment of the 3L4F peptide that maintained efficacy (within the picomolar range) in live cells similar to that of the 3L4F peptide. Last, molecular modeling identified key structural features and potential interaction sites of the active 3L4F peptides against PTEN. These compelling data demonstrate the specificity and importance of this protein assembly in cellular events and behaviors mediated by 5-HT2C signaling and provide a chemical guidepost to the future development of drug-like peptide or small-molecule inhibitors as neuroprobes to study 5-HT2C allostery and therapeutics for 5-HT2C-mediated disorders. [ABSTRACT FROM AUTHOR]