Kinesin-13, a Motor Protein, is Regulated by Polo-like Kinase in Giardia lamblia

Optimization of 18 S rRNA metabarcoding for the simultaneous diagnosis of intestinal parasites

Recent advancements in next-generation sequencing (NGS) technologies have created new opportunities for comprehensive screening of multiple parasite species. In this study, we cloned the 18 S rDNA V9 region of 11 species of intestinal parasites into plasmids. Equal amounts and concentrations of these 11 plasmids were pooled, and amplicon NGS targeting the 18 S rDNA V9 region was performed using the Illumina iSeq 100 platform. A total of 434,849 reads were identified, and all 11 parasite species were detected, although the number of output reads for each parasite varied. The read count ratio, in descending order, was as follows: Clonorchis sinensis, 17.2%; Entamoeba histolytica, 16.7%; Dibothriocephalus latus, 14.4%; Trichuris trichiura, 10.8%; Fasciola hepatica, 8.7%; Necator americanus, 8.5%; Paragonimus westermani, 8.5%; Taenia saginata, 7.1%; Giardia intestinalis, 5.0%; Ascaris lumbricoides, 1.7%; and Enterobius vermicularis, 0.9%. We found that the DNA secondary structures showed a negative association with the number of output reads. Additionally, variations in the amplicon PCR annealing temperature affected the relative abundance of output reads for each parasite. These findings can be applied to improve parasite detection methodologies and ultimately enhance efforts to control and prevent intestinal parasitic infections.

Tubulin as a potential molecular target for resveratrol in Giardia lamblia trophozoites, in vitro and in silico approaches

Giardia lamblia is a globally distributed protozoan parasite that causes intestinal disease. Recently, there is an increase in refractory cases of giardiasis to chemotherapeutic agents, and drugs available cause side effects that may limit its use or cause therapeutic non-compliance. Therefore, search for alternative and less harmful drugs to treat giardiasis is an important task. In this sense, resveratrol (RSV) is a polyphenol with a wide range of pharmacological effects such as antimicrobial, anticarcinogenic and antioxidant. The aim of this study was to evaluate the effects of RSV on Giardia lamblia trophozoites in vitro and in silico, focusing on tubulin affectation, a major protein of the Giardia cytoskeleton which participates in relevant processes for cell survival. In vitro determinations showed that RSV inhibits parasite growth and adherence, causes morphological changes, and induces apoptosis-like cell death through tubulin alterations demonstrated by immunolocalization and Western blot assays. Bioinformatic analysis by molecular docking suggested that RSV binds to Giardia tubulin interface heterodimer, sharing binding residues to those reported with depolymerization inhibitors. These findings suggest that RSV affects microtubular dynamics and make it an interesting compound to study for its safety and antigiardiasic potential.

Functional Differentiation of Cyclins and Cyclin-Dependent Kinases in Giardia lamblia

Cyclin-dependent kinases (CDKs) are serine/threonine kinases that control the eukaryotic cell cycle. Limited information is available on Giardia lamblia CDKs (GlCDKs), GlCDK1 and GlCDK2. After treatment with the CDK inhibitor flavopiridol-HCl (FH), division of Giardia trophozoites was transiently arrested at the G1/S phase and finally at the G2/M phase. The percentage of cells arrested during prophase or cytokinesis increased, whereas DNA synthesis was not affected by FH treatment. Morpholino-mediated depletion of GlCDK1 caused arrest at the G2/M phase, while GlCDK2 depletion resulted in an increase in the number of cells arrested at the G1/S phase and cells defective in mitosis and cytokinesis. Coimmunoprecipitation experiments with GlCDKs and the nine putative G. lamblia cyclins (Glcyclins) identified Glcyclins 3977/14488/17505 and 22394/6584 as cognate partners of GlCDK1 and GlCDK2, respectively. Morpholino-based knockdown of Glcyclin 3977 or 22394/6584 arrested cells in the G2/M phase or G1/S phase, respectively. Interestingly, GlCDK1- and Glcyclin 3977-depleted Giardia showed significant flagellar extension. Altogether, our results suggest that GlCDK1/Glcyclin 3977 plays an important role in the later stages of cell cycle control and in flagellar biogenesis. In contrast, GlCDK2 along with Glcyclin 22394 and 6584 functions from the early stages of the Giardia cell cycle. IMPORTANCE Giardia lamblia CDKs (GlCDKs) and their cognate cyclins have not yet been studied. In this study, the functional roles of GlCDK1 and GlCDK2 were distinguished using morpholino-mediated knockdown and coimmunoprecipitation. GlCDK1 with Glcyclin 3977 plays a role in flagellum formation as well as cell cycle control of G. lamblia, whereas GlCDK2 with Glcyclin 22394/6584 is involved in cell cycle control.