Inflammatory pathologies caused by phagocytes lead to numerous debilitating conditions, including chronic pain and blindness due to age-related macular degeneration. Many members of the sialic acid-binding immunoglobulin-like lectin (Siglec) family are immunoinhibitory receptors whose agonism is an attractive approach for antiinflammatory therapy. Here, we show that synthetic lipid-conjugated glycopolypeptides can insert into cell membranes and engage Siglec receptors in
- NSF-PAR ID:
- 10209526
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 118
- Issue:
- 3
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- Article No. e2012408118
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Glyco-immune checkpoint receptors , molecules that inhibit immune cell activity following binding to glycosylated cell-surface antigens, are emerging as attractive targets for cancer immunotherapy. Defining biologically relevant ligands that bind and activate such receptors, however, has historically been a significant challenge. Here, we present a CRISPRi genomic screening strategy that allowed unbiased identification of the key genes required for cell-surface presentation of glycan ligands on leukemia cells that bind the glyco-immune checkpoint receptors Siglec-7 and Siglec-9. This approach revealed a selective interaction between Siglec-7 and the mucin-type glycoprotein CD43. Further work identified a specific N-terminal glycopeptide region of CD43 containing clusters of disialylated O-glycan tetrasaccharides that form specific Siglec-7 binding motifs. Knockout or blockade of CD43 in leukemia cells relieves Siglec-7-mediated inhibition of immune killing activity. This work identifies a potential target for immune checkpoint blockade therapy and represents a generalizable approach to dissection of glycan–receptor interactions in living cells. -
Abstract Chemotaxis is a fundamental process whereby bacteria seek out nutrient sources and avoid harmful chemicals. For the symbiotic soil bacterium
Sinorhizobium meliloti , the chemotaxis system also plays an essential role in the interaction with its legume host. The chemotactic signaling cascade is initiated through interactions of an attractant or repellent compound with chemoreceptors or methyl‐accepting chemotaxis proteins (MCPs).S. meliloti possesses eight chemoreceptors to mediate chemotaxis. Six of these receptors are transmembrane proteins with periplasmic ligand‐binding domains (LBDs). The specific functions of McpW and McpZ are still unknown. Here, we report the crystal structure of the periplasmic domain of McpZ (McpZPD) at 2.7 Å resolution. McpZPD assumes a novel fold consisting of three concatenated four‐helix bundle modules. Through phylogenetic analyses, we discovered that this helical tri‐modular domain fold arose within the Rhizobiaceae family and is still evolving rapidly. The structure, offering a rare view of a ligand‐free dimeric MCP‐LBD, reveals a novel dimerization interface. Molecular dynamics calculations suggest ligand binding will induce conformational changes that result in large horizontal helix movements within the membrane‐proximal domains of the McpZPD dimer that are accompanied by a 5 Å vertical shift of the terminal helix toward the inner cell membrane. These results suggest a mechanism of transmembrane signaling for this family of MCPs that entails both piston‐type and scissoring movements. The predicted movements terminate in a conformation that closely mirrors those observed in related ligand‐bound MCP‐LBDs. -
Activating mutations in
PIK3CA are frequent in human breast cancer, and phosphoinositide 3-kinase alpha (PI3Kα) inhibitors have been approved for therapy. To characterize determinants of sensitivity to these agents, we analyzedPIK3CA -mutant cancer genomes and observed the presence of multiplePIK3CA mutations in 12 to 15% of breast cancers and other tumor types, most of which (95%) are double mutations. DoublePIK3CA mutations are in cis on the same allele and result in increased PI3K activity, enhanced downstream signaling, increased cell proliferation, and tumor growth. The biochemical mechanisms of dual mutations include increased disruption of p110α binding to the inhibitory subunit p85α, which relieves its catalytic inhibition, and increased p110α membrane lipid binding. DoublePIK3CA mutations predict increased sensitivity to PI3Kα inhibitors compared with single-hotspot mutations. -
SUMMARY Sorghum anthracnose caused by the fungus
Colletotrichum sublineola (Cs ) is a damaging disease of the crop. Here, we describe the identification ofANTHRACNOSE RESISTANCE GENES (ARG4 andARG5 ) encoding canonical nucleotide‐binding leucine‐rich repeat (NLR) receptors.ARG4 andARG5 are dominant resistance genes identified in the sorghum lines SAP135 and P9830, respectively, that show broad‐spectrum resistance toCs . Independent genetic studies using populations generated by crossing SAP135 and P9830 with TAM428, fine mapping using molecular markers, comparative genomics and gene expression studies determined thatARG4 andARG5 are resistance genes againstCs strains. Interestingly,ARG4 andARG5 are both located within clusters of duplicate NLR genes at linked loci separated by ~1 Mb genomic region. SAP135 and P9830 each carry only one of theARG genes while having the recessive allele at the second locus. Only two copies of theARG5 candidate genes were present in the resistant P9830 line while five non‐functional copies were identified in the susceptible line. The resistant parents and their recombinant inbred lines carrying eitherARG4 orARG5 are resistant to strains Csgl1 and Csgrg suggesting that these genes have overlapping specificities. The role ofARG4 andARG5 in resistance was validated through sorghum lines carrying independent recessive alleles that show increased susceptibility.ARG4 andARG5 are located within complex loci displaying interesting haplotype structures and copy number variation that may have resulted from duplication. Overall, the identification of anthracnose resistance genes with unique haplotype stucture provides a foundation for genetic studies and resistance breeding. -
Abstract Structural variation in plant genomes is a significant driver of phenotypic variability in traits important for the domestication and productivity of crop species. Among these are traits that depend on functional meristems, populations of stem cells maintained by the CLAVATA-WUSCHEL (CLV-WUS) negative feedback-loop that controls the expression of the WUS homeobox transcription factor. WUS function and impact on maize development and yield remain largely unexplored. Here we show that the maize dominant
Barren inflorescence3 (Bif3 ) mutant harbors a tandem duplicated copy of theZmWUS1 gene,ZmWUS1-B , whose novel promoter enhances transcription in a ring-like pattern. Overexpression ofZmWUS1-B is due to multimerized binding sites for type-B RESPONSE REGULATORs (RRs), key transcription factors in cytokinin signaling. Hypersensitivity to cytokinin causes stem cell overproliferation and major rearrangements ofBif3 inflorescence meristems, leading to the formation of ball-shaped ears and severely affecting productivity. These findings establishZmWUS1 as an essential meristem size regulator in maize and highlight the striking effect of cis-regulatory variation on a key developmental program.