Rika Umemiya-Shirafuji

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Autophagic process is one of the best examples of a conserved mechanism of survival in eukaryotes. At the molecular level there are impressive similarities between unicellular and multicellular organisms, but there is increasing evidence that the same process may be used for different ends, i.e., survival or death, at least at cellular levels. Arthropods(More)
Ovarian development and egg maturation are crucial processes for the success of reproduction in ticks. Three full-length cDNAs encoding the precursor of major yolk protein, vitellogenin, were obtained from cDNA libraries of the Haemaphysalis longicornis tick and designated as HlVg-1, HlVg-2 and HlVg-3. The HlVg mRNAs were found in fed females with major(More)
BACKGROUND Lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) is a bifunctional enzyme catalyzing the first two steps of lysine catabolism in plants and mammals. However, to date, the properties of the lysine degradation pathway and biological functions of LKR/SDH have been very little described in arthropods such as ticks. (More)
Ticks are long-lived hematophagous arthropods and have tolerance to starvation. They can survive without food during the host-seeking period for several months to years. To understand how ticks obtain energy over a long period of non-feeding (starvation), we focused on autophagy, a crucial proteolysis system via the lysosomes for various cellular processes(More)
Autophagy is the intracellular protein degradation process which is induced by starvation. Ticks have a unique tolerance for starvation, and it is possible that this tolerance is associated with their longevity. Previously, we isolated the homologues of four autophagy-related (ATG) genes in the hard tick, Haemaphysalis longicornis, suggesting that autophagy(More)
Scavenger receptors (SRs) are cell-surface proteins and exhibit distinctive ligand-binding properties, recognizing a wide range of ligands that include microbial surface constituents and intact microbes. The class B scavenger receptor CD36 (SRB) is predominantly expressed by macrophages and is considered important in innate immunity. We here show the(More)
Ticks are obligate hematophagous parasites and important vectors of diseases. The large amount of blood they consume contains great quantities of iron, an essential but also toxic element. The function of ferritin, an iron storage protein, and iron metabolism in ticks need to be further elucidated. Here, we investigated the function a newly identified(More)
RNA interference is an efficient method to silence gene and protein expressions. Here, the class B scavenger receptor CD36 (SRB) mediated the uptake of exogenous dsRNAs in the induction of the RNAi responses in ticks. Unfed female Haemaphysalis longicornis ticks were injected with a single or a combination of H. longicornis SRB (HlSRB) dsRNA, vitellogenin-1(More)
Ticks grow rapidly during blood feeding, and their body weight may ultimately increase 100-fold more than that before feeding. The molecular mechanisms controlling growth during blood feeding in ticks remain largely unknown. The conserved insulin/PI3K/Akt signaling pathway regulates growth and metabolism in eukaryotes. Here, we show evidence for the(More)
Human defensins play a fundamental role in the initiation of innate immune responses to some microbial pathogens. In this paper, we show that human α-defensin-5 displays a parasiticidal role against Toxoplasma gondii, the causative agent of toxoplasmosis. Exposure of the tachyzoite form of T. gondii to defensin induced aggregation and significantly reduced(More)