Down-regulation of TUFM impairs host cell interaction and virulence by Paracoccidioides brasiliensis

Role of paracoccin on Paracoccidioides brasiliensis virulence and susceptibility to antifungal drugs in the Galleria mellonella larvae model

Paracoccin (PCN), a Paracoccidioides brasiliensis glycoprotein, has been reported to play roles in fungal biology and paracoccidioidomycosis pathogenesis. Lectin and chitinase domains account for the PCN's dual roles as an immunomodulatory agent and virulence factor. Soluble PCN injected in P. brasiliensis infected mice, by interacting with TLRs' N-glycans, drives the host immune response toward a protective Th1 axis. Otherwise, mice infection with yeasts overexpressing PCN (ov-PCN) revealed that PCN acts as a fungal virulence factor, thanks to its chitinase activity on the cell wall, resulting in resistance to phagocytes' fungicidal activity and development of severe paracoccidioidomycosis. Because antifungal drug administration follows the disease diagnosis, we studied the PCN effect on yeast resistance or susceptibility to antifungal agents. Using a paracoccidioidomycosis model developed in Galleria mellonella larvae, we confirmed the observation, in the murine host, that ov-PCN yeasts display maximum virulence compared to wild-type (wt-PCN) or PCN-silenced (kd-PCN) yeasts. PCN overexpression accounted for the highest susceptibility of P. brasiliensis to antifungal and reduced relative mRNA expression of genes encoding proteins related to cell wall remodeling. The lowest virulence, detected in infection with kd-PCN yeasts, correlated with the lowest susceptibility to antifungals and impact on genes for cell wall remodeling. So, we defined that the grade of endogenous PCN production influences the P. brasiliensis virulence and susceptibility to antifungal drugs, as well as the expression of genes related to cell wall remodeling. We postulate that this variable gene expression is mechanistically associated with P. brasiliensis virulence changes.

Silencing TUFM Inhibits Development of Monocrotaline-Induced Pulmonary Hypertension by Regulating Mitochondrial Autophagy via AMPK/mTOR Signal Pathway

Pulmonary arterial hypertension (PAH) is an extremely malignant cardiovascular disease which mainly involves the uncontrollable proliferation of the pulmonary arterial smooth muscular cells (PASMCs). Recent studies have confirmed that mitochondria play an important role in the pathogenesis of pulmonary hypertension through sensing cell hypoxia, energy metabolism conversion, and apoptosis. As a mitochondrial membrane protein, TUFM has been regarded to be related to mitochondrial autophagy (mitophagy), apoptosis, and oxidative stress. Considering these factors are closely associated with the pathogenesis of PAH, we hypothesize that TUFM might play a role in the development of PAH. Our preliminary examination has showed TUFM mainly expressed in the PASMCs, and the subsequent test indicated an increased TUFM expression in the SMCs of pulmonary arteriole in monocrotaline- (MCT-) induced PAH rat model compared with the normal rat. The TUFM knockdown (Sh-TUFM) or overexpressed (OE-TUFM) rats were used to establish PAH by treating with MCT. A notable lower pulmonary arterial systolic pressure together with slightly morphological changes of pulmonary arteriole was observed in the Sh-TUFM group compared with the single MCT-induced PAH group. Increased levels of P62 and Bax and reduced LC3II/I, BECN1, and Bcl2 were detected in the Sh-TUFM group, while the expressions of these proteins in the OE-TUFM group were contrast to the results of the Sh-TUFM group. To elucidate the possible mechanism underlying biological effect of TUFM in PAH, PASMCs were treated with silence or overexpression of TUFM and then exposed to hypoxia condition. An obviously high levels of P62 and Bax along with a decreased LC3 II/I, BECN1, ULK1, Atg12, Atg13, and Bcl2 levels were noticed in cells with silence of TUFM. Moreover, the phosphorylated AMPK and mTOR which was well known in mitophagy modulating vary by the alternation of TUFM. These observations suggested that TUFM silence inhibits the development of MCT-induced PAH via AMPK/mTOR pathway.

On the relationship between Pathogenic Potential and Infective Inoculum

Pathogenic Potential (PP) is a mathematical description of an individual microbe, virus, or parasite's ability to cause disease in a host, given the variables of inoculum, signs of disease, mortality, and in some instances, median survival time of the host. We investigated the relationship between pathogenic potential (PP) and infective inoculum (I) using two pathogenic fungi in the wax moth Galleria mellonella with mortality as the relevant outcome. Our analysis for C. neoformans infection revealed negative exponential relationship between PP and I. Plotting the log(I) versus the Fraction of animals with signs or symptoms (Fs) over median host survival time (T) revealed a linear relationship, with a slope that varied between the different fungi studied and a y-intercept corresponding to the inoculum that produced no signs of disease. The I vs Fs/T slope provided a measure of the pathogenicity of each microbial species, which we call the pathogenicity constant or kPath. The kPath provides a new parameter to quantitatively compare the relative virulence and pathogenicity of microbial species for a given host. In addition, we investigated the PP and Fs/T from values found in preexisting literature. Overall, the relationship between Fs/T and PP versus inoculum varied among microbial species and extrapolation to zero signs of disease allowed the calculation of the lowest pathogenic inoculum (LPI) of a microbe. Microbes tended to fall into two groups: those with positive linear relationships between PP and Fs/T vs I, and those that had a negative exponential PP vs I relationship with a positive logarithmic Fs/T vs I relationship. The microbes with linear relationships tended to be bacteria, whereas the exponential-based relationships tended to be fungi or higher order eukaryotes. Differences in the type and sign of the PP vs I and Fs/T vs I relationships for pathogenic microbes suggest fundamental differences in host-microbe interactions leading to disease.

Drk1, a Dimorphism Histidine Kinase, Contributes to Morphology, Virulence, and Stress Adaptation in Paracoccidioides brasiliensis

P. brasiliensis is a thermally dimorphic fungus belonging to Paracoccidioides complex, causative of a systemic, endemic mycosis limited to Latin American countries. Signal transduction pathways related to important aspects as surviving, proliferation according to the biological niches are linked to the fungal pathogenicity in many species, but its elucidation in P. brasiliensis remains poorly explored. As Drk1, a hybrid histidine kinase, plays regulators functions in other dimorphic fungi species, mainly in dimorphism and virulence, here we investigated its importance in P. brasilensis. We, therefore generated the respective recombinant protein, anti-PbDrk1 polyclonal antibody and a silenced strain. The Drk1 protein shows a random distribution including cell wall location that change its pattern during osmotic stress condition; moreover the P. brasiliensis treatment with anti-PbDrk1 antibody, which does not modify the fungus's viability, resulted in decreased virulence in G. mellonella model and reduced interaction with pneumocytes. Down-regulating PbDRK1 yielded phenotypic alterations such as yeast cells with more elongated morphology, virulence attenuation in G. mellonella infection model, lower amount of chitin content, increased resistance to osmotic and cell wall stresses, and also caspofungin, and finally increased sensitivity to itraconazole. These observations highlight the importance of PbDrk1 to P. brasiliensis virulence, stress adaptation, morphology, and cell wall organization, and therefore it an interesting target that could help develop new antifungals.

Mitochondrial Protein Translation: Emerging Roles and Clinical Significance in Disease

Mitochondria are one of the most important organelles in cells. Mitochondria are semi-autonomous organelles with their own genetic system, and can independently replicate, transcribe, and translate mitochondrial DNA. Translation initiation, elongation, termination, and recycling of the ribosome are four stages in the process of mitochondrial protein translation. In this process, mitochondrial protein translation factors and translation activators, mitochondrial RNA, and other regulatory factors regulate mitochondrial protein translation. Mitochondrial protein translation abnormalities are associated with a variety of diseases, including cancer, cardiovascular diseases, and nervous system diseases. Mutation or deletion of various mitochondrial protein translation factors and translation activators leads to abnormal mitochondrial protein translation. Mitochondrial tRNAs and mitochondrial ribosomal proteins are essential players during translation and mutations in genes encoding them represent a large fraction of mitochondrial diseases. Moreover, there is crosstalk between mitochondrial protein translation and cytoplasmic translation, and the imbalance between mitochondrial protein translation and cytoplasmic translation can affect some physiological and pathological processes. This review summarizes the regulation of mitochondrial protein translation factors, mitochondrial ribosomal proteins, mitochondrial tRNAs, and mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) in the mitochondrial protein translation process and its relationship with diseases. The regulation of mitochondrial protein translation and cytoplasmic translation in multiple diseases is also summarized.

Updates in Paracoccidioides Biology and Genetic Advances in Fungus Manipulation

The dimorphic fungi of the Paracoccidioides genus are the causative agents of paracoccidioidomycosis (PCM). This disease is endemic in Latin America and primarily affects workers in rural areas. PCM is considered a neglected disease, despite being a disabling disease that has a notable impact on the public health system. Paracoccidioides spp. are thermally dimorphic fungi that present infective mycelia at 25 °C and differentiate into pathogenic yeast forms at 37 °C. This transition involves a series of morphological, structural, and metabolic changes which are essential for their survival inside hosts. As a pathogen, the fungus is subjected to several varieties of stress conditions, including the host immune response, which involves the production of reactive nitrogen and oxygen species, thermal stress due to temperature changes during the transition, pH alterations within phagolysosomes, and hypoxia inside granulomas. Over the years, studies focusing on understanding the establishment and development of PCM have been conducted with several limitations due to the low effectiveness of strategies for the genetic manipulation of Paracoccidioides spp. This review describes the most relevant biological features of Paracoccidioides spp., including aspects of the phylogeny, ecology, stress response, infection, and evasion mechanisms of the fungus. We also discuss the genetic aspects and difficulties of fungal manipulation, and, finally, describe the advances in molecular biology that may be employed in molecular research on this fungus in the future.

One Century of Study: What We Learned about Paracoccidioides and How This Pathogen Contributed to Advances in Antifungal Therapy

Paracoccidioidomycosis (PCM) is a notable fungal infection restricted to Latin America. Since the first description of the disease by Lutz up to the present day, Brazilian researchers have contributed to the understanding of the life cycle of this pathogen and provided the possibility of new targets for antifungal therapy based on the structural and functional genomics of Paracoccidioides. In this context, in silico approaches have selected molecules that act on specific targets, such as the thioredoxin system, with promising antifungal activity against Paracoccidioides. Some of these are already in advanced development stages. In addition, the application of nanostructured systems has addressed issues related to the high toxicity of conventional PCM therapy. Thus, the contribution of molecular biology and biotechnology to the advances achieved is unquestionable. However, it is still necessary to transcend the boundaries of synthetic chemistry, pharmaco-technics, and pharmacodynamics, aiming to turn promising molecules into newly available drugs for the treatment of fungal diseases.

Molecular characterization of siderophore biosynthesis in Paracoccidioides brasiliensis

Iron is an essential nutrient for all organisms. For pathogenic fungi, iron is essential for the success of infection. Thus, these organisms have developed high affinity iron uptake mechanisms to deal with metal deprivation imposed by the host. Siderophore production is one of the mechanisms that fungal pathogens employ for iron acquisition. Paracoccidioides spp. present orthologous genes encoding the enzymes necessary for the biosynthesis of hydroxamates, and plasma membrane proteins related to the transport of these molecules. All these genes are induced in iron deprivation. In addition, it has been observed that Paracoccidioides spp. are able to use siderophores to scavenge iron. Here we observed that addition of the xenosiderophore ferrioxamine B FOB) to P. brasiliensis culture medium results in repression (at RNA and protein levels) of the SidA, the first enzyme of the siderophore biosynthesis pathway. Furthermore, SidA activity was reduced in the presence of FOB, suggesting that P. brasiliensis blocks siderophores biosynthesis and can explore siderophores in the environment to scavenge iron. In order to support the importance of siderophores on Paracoccidioides sp. life and infection cycle, silenced mutants for the sidA gene were obtained by antisense RNA technology. The obtained AsSidA strains displayed decreased siderophore biosynthesis in iron deprivation conditions and reduced virulence to an invertebrate model.