Evaluation of Modulators of cAMP-Response in Terms of Their Impact on Cell Cycle and Mitochondrial Activity of Leishmania donovani

Evolutionary analysis of globin domains from kinetoplastids

Globin (Gb) domains function in sensing gaseous ligands like oxygen and nitric oxide. In recent years, Gb domain containing heme binding adenylate cyclases (OsAC or GbAC) emerged as significant modulator of Leishmania response to hypoxia and oxidative stress. During progression of life cycle stages, kinetoplastids experience altered condition in insect vectors or other hosts. Moreover, marked diversity in life style has been accounted among kinetoplastids. Distribution and abundance of Gb-domains vary between different groups of kinetoplastids. While in bodonoids, Gbs are not combined with any other functional domains, in trypanosomatids it is either fused with adenylate cyclase (AC) or oxidoreductase (OxR) domains. In salivarian trypanosomatids and Leishmania (Viannia) subtypes, no gene product featuring Gbs can be identified. In this context, evolution of Gb-domains in kinetoplastids was explored. GbOxR derived Gbs clustered with bacterial flavohemoglobins (fHb) including one fHb from Advenella, an endosymbiont of monoxeneous trypanosomatids. Codon adaptation and other evolutionary analysis suggested that OsAC (LmjF.28.0090), the solitary Gb-domain featuring gene product in Leishmania, was acquired via possible horizontal gene transfer. Substantial functional divergence was estimated between orthologues of genes encoding GbAC or GbOxR; an observation also reflected in structural alignment and heme-binding residue predictions. Orthologue-paralogue and synteny analysis indicated genomic reduction in GbOxR and GbAC loci for dixeneous trypanosomatids.

MiR-139-5p has an antidepressant-like effect by targeting phosphodiesterase 4D to activate the cAMP/PKA/CREB signaling pathway

Background

Phosphodiesterase 4D (PDE4D) inhibitor is commonly used to treat depression, but side effects seriously decrease its efficacy. PDE4D was a downstream target mRNA of miR-139-5p. Therefore, we examined the effects of hippocampal miR-139-5p gain- and loss-of-function on depression-like behaviors, the expression level of PDE4D, and hippocampus neurogenesis.

Methods

Bioinformatic analyses were carried out to to screen differential genes. Quantitative real-time polymerase chain reaction (qRT-PCR) and luciferase reporter assay were used to confirm the relationship between miR-139-5p and PDE4D. MiR-139-5p mimics, miR-139-5p inhibitor, or miR-NC were used to explore the function of miR-139-5p in HT-22 cells. We further explored the role of miR-139-5p in vivo using AAV-injection. Elisa, western blotting, and fluorescence in situ hybridization (FISH) were used to detect the expression of miR-139-5p and PDE4D in CRC tissues.

Results

Here, we showed that PDE4D messenger RNA (mRNA) was a direct target of microRNA (miR)-139-5p, which was downregulated in a chronic ultra-mild stress (CUMS)-induced depression mouse model. Moreover, in experiments in vitro, miR-139-5p mimic repressed PDE4D expression in HT-22 cells, but promoted phosphorylated cyclic-AMP response element-binding protein (p-CREB) and brain-derived neurotrophic factor (BDNF) expression. Interestingly, adeno-associated virus (AAV)-miR-139-5p downregulated susceptibility to stress-induced depression-like behaviors in mice. AAV-miR-139-5p suppressed PDE4D in mouse hippocampal cells, increasing expression level of cyclic adenosine monophosphate (cAMP), p-CREB, and BDNF, and stimulating mouse hippocampal neurogenesis.

Conclusions

Our findings suggested that miR-139-5p acted like an antidepressant by targeting PDE4D, thereby regulating the cAMP/protein kinase A (PKA)/CREB/BDNF pathway to improve depression.

Extracellular Vesicles in Trypanosomatids: Host Cell Communication

Trypanosoma cruzi, Trypanosoma brucei and Leishmania (Trypanosomatidae: Kinetoplastida) are parasitic protozoan causing Chagas disease, African Trypanosomiasis and Leishmaniases worldwide. They are vector borne diseases transmitted by triatomine bugs, Tsetse fly, and sand flies, respectively. Those diseases cause enormous economic losses and morbidity affecting not only rural and poverty areas but are also spreading to urban areas. During the parasite-host interaction, those organisms release extracellular vesicles (EVs) that are crucial for the immunomodulatory events triggered by the parasites. EVs are involved in cell-cell communication and can act as important pro-inflammatory mediators. Therefore, interface between EVs and host immune responses are crucial for the immunopathological events that those diseases exhibit. Additionally, EVs from these organisms have a role in the invertebrate hosts digestive tracts prior to parasite transmission. This review summarizes the available data on how EVs from those medically important trypanosomatids affect their interaction with vertebrate and invertebrate hosts.

Nutrient sensing in Leishmania: Flagellum and cytosol

Parasites are by definition organisms that utilize resources from a host to support their existence, thus, promoting their ability to establish long-term infections and disease. Hence, sensing and acquiring nutrients for which the parasite and host compete is central to the parasitic mode of existence. Leishmania are flagellated kinetoplastid parasites that parasitize phagocytic cells, principally macrophages, of vertebrate hosts and the alimentary tract of sand fly vectors. Because nutritional supplies vary over time within both these hosts and are often restricted in availability, these parasites must sense a plethora of nutrients and respond accordingly. The flagellum has been recognized as an "antenna" that plays a core role in sensing environmental conditions, and various flagellar proteins have been implicated in sensing roles. In addition, these parasites exhibit non-flagellar intracellular mechanisms of nutrient sensing, several of which have been explored. Nonetheless, mechanistic details of these sensory pathways are still sparse and represent a challenging frontier for further experimental exploration.