Malaria is caused by Plasmodium parasites and remains a significant health concern for almost half the world's population. There are estimated to be > 240 million malaria cases and approximately 600,000 malaria-related deaths annually, mainly due to infection with P. falciparum parasites. Parasite drug resistance is impacting malaria prevention and control efforts, and as part of the malaria eradication agenda, new drugs with novel mechanisms of action are needed. Histone/lysine deacetylase (HDAC) enzymes play essential roles in Plasmodium biology and are potential targets for the development of new antiplasmodial agents. In this study, a panel of 24 HDAC inhibitors with hydroxamic acid zinc binding group, a pentyloxyamide connecting unit linker region and substituted 4-phenyl and 4(pyridinyl)thiazole cap groups were investigated for in vitro activity against asexual intraerythrocytic stage P. falciparum parasites, the life cycle stage responsible for the clinical symptoms of malaria. The most potent compound (4o) had a P. falciparum IC50 of 20 nM and >250-fold greater selectivity for P. falciparum versus human cells. Compound 4o was also active against exoerythrocytic stage parasites (IC50 24 nM), which are a target for malaria prevention. In contrast, 4o lacked potent activity against late-stage gametocytes (IC50 > 2 μM), which are a target for malaria transmission-blocking drugs. Compound 4o and analogues caused in situ hyperacetylation of P. falciparum histone H4, indicating deacetylase inhibition. Furthermore, 4o was found to stabilise PfHDAC1 in P. falciparum protein lysates using solvent-induced protein stability Western blot assays with anti-PfHDAC1 antibody. Together, these data provide new structure-activity relationship and mechanistic insights on pentyloxyamide-based HDAC inhibitors as potential therapeutic starting points for malaria.
Copyright © 2025 The Authors. Published by Elsevier Ltd.. All rights reserved.

Plant lectins have garnered attention for their roles as laboratory probes and potential therapeutics. Here, we report the discovery and characterization of Cucumis melo agglutinin (CMA1), a new R-type lectin from melon. Our findings reveal CMA1's unique glycan-binding profile, mechanistically explained by its 3D structure, augmenting our understanding of R-type lectins. We expressed CMA1 recombinantly and assessed its binding specificity using multiple glycan arrays, covering 1,046 unique sequences. This resulted in a complex binding profile, strongly preferring C2-substituted, beta-linked galactose (both GalNAc and Fuca1-2Gal), which we contrasted with the established R-type lectin Ricinus communis agglutinin 1 (RCA1). We also report binding of specific glycosaminoglycan subtypes and a general enhancement of binding by sulfation. Further validation using agglutination, thermal shift assays, and surface plasmon resonance confirmed and quantified this binding specificity in solution. Finally, we solved the high-resolution structure of the CMA1 N-terminal domain using X-ray crystallography, supporting our functional findings at the molecular level. Our study provides a comprehensive understanding of CMA1, laying the groundwork for further exploration of its biological and therapeutic potential.
Copyright © 2024, Lundstrøm et al.

Plasmodium falciparum is a unicellular eukaryotic parasite that causes malaria in humans. The parasite is spread by Anopheles mosquitoes after ingestion of sexual stage parasites known as gametocytes. Malaria transmission depends on parasites switching from the disease-causing asexual blood forms to male and female gametocytes. The current protocol allows the simultaneous isolation of male and female parasites from the same population to study this critical lifecycle stage in a sex-specific manner. We have generated a transgenic P. falciparum cell line that expresses a GFP-tagged parasite protein in female, but not male, parasites. Gametocyte production is stress induced and, through a series of steps, sexual stage parasites are enriched relative to uninfected red blood cells or red blood cells infected with asexual stage parasites. Finally, male and female gametocytes are separated by fluorescence-activated cell sorting. This protocol allows for the separation of up to 12 million live male and female parasites from the same population, which are amenable to further analysis.Copyright © 2021 The Authors; exclusive licensee Bio-protocol LLC.

CD4 and chemokine receptors mediate HIV-1 attachment and entry. They are, however, insufficient to explain the preferential viral infection of central memory T cells. Here, we identify L-selectin (CD62L) as a viral adhesion receptor on CD4+ T cells. The binding of viral envelope glycans to L-selectin facilitates HIV entry and infection, and L-selectin expression on central memory CD4+ T cells supports their preferential infection by HIV. Upon infection, the virus downregulates L-selectin expression through shedding, resulting in an apparent loss of central memory CD4+ T cells. Infected effector memory CD4+ T cells, however, remain competent in cytokine production. Surprisingly, inhibition of L-selectin shedding markedly reduces HIV-1 infection and suppresses viral release, suggesting that L-selectin shedding is required for HIV-1 release. These findings highlight a critical role for cell surface sheddase in HIV-1 pathogenesis and reveal new antiretroviral strategies based on small molecular inhibitors targeted at metalloproteinases for viral release.

Innate immunity is the first line of defense against pathogens and predators. To initiate a response, it relies on the detection of invaders, where lectin-carbohydrate interactions play a major role. O-Methylated glycans were previously identified as non-self epitopes and conserved targets for defense effector proteins belonging to the tectonin superfamily. Here, we present two crystal structures of Tectonin 2 from the mushroom Laccaria bicolor in complex with methylated ligands, unraveling the molecular basis for this original specificity. Furthermore, they revealed the formation of a ball-shaped tetramer with 24 binding sites distributed at its surface, resembling a small virus capsid. Based on the crystal structures, a methylation recognition motif was identified and found in the sequence of many tectonins from bacteria to human. Our results support a key role of tectonins in innate defense based on a distinctive and conserved type of lectin-glycan interaction.Copyright © 2018 Elsevier Ltd. All rights reserved.