Biology subjects

Rodriguez, R. A.

Publications and source records attributed to Rodriguez, R. A..

6 recordsLinked to original sources

bioRxiv2025

The Rpd3 histone deacetylase is critical for temperature-mediated morphogenesis and virulence in the human fungal pathogen Histoplasma

Adaptive responses to environmental stimuli are integral to the survival and virulence of microbial pathogens. The thermally dimorphic human fungal pathogen Histoplasma senses temperature to transition between a mold form in soil and a pathogenic yeast in mammalian hosts. The contributions of chromatin-modifying enzymes to the ability of Histoplasma to appropriately respond to temperature have never been explored. Through chemical inhibition and genetics, we determined that the class I histone deacetylase (HDAC) RPD3 is required for normal Histoplasma yeast morphology at 37 {degrees}C. Rpd3 regulated the expression of key morphology-specific genes, including critical virulence factors and transcription factors (TFs), was required for normal DNA-binding activity of yeast-promoting TFs, and influenced histone acetylation levels at the loci of putative pro-filamentation TFs. Furthermore, Rpd3 was required for virulence in a macrophage model of infection. Taken together, Rpd3 is a critical regulatory component that both activates the pathogenesis program and represses the filamentation program to enable thermal dimorphism in Histoplasma. This work uncovers the crucial role that chromatin regulation plays in temperature response of this ubiquitous pathogen.

microbiology↗

bioRxiv2025

Rapid gain and loss of a chromosome drives key morphology and virulence phenotypes in Histoplasma, a fungal pathogen of humans

Heritable phenotypic switches are fundamental to the ability of cells to respond to specific conditions. Such switches are key to the success of environmental pathogens, which encounter disparate conditions as they transition between the environment and host. We determine that the copy number of chromosome seven in the thermally dimorphic fungus Histoplasma dramatically affects the rate of transition. Though Histoplasma is haploid, a second copy of this chromosome is present in natural isolates of multiple Histoplasma species and is gained and lost at a high rate. Cells carrying two copies of this chromosome exhibit aspects of the environmental transcriptome even under host-like conditions and have a competitive advantage in the transition to the environmental form. Conversely, these cells are considerably less virulent than euploid cells and have a competitive disadvantage in the mouse model of infection. Chromosome seven contains a previously unstudied transcription factor that, when overexpressed in euploid Histoplasma, is sufficient to promote some of the key phenotypes of aneuploidy. We hypothesize that rapid gain and loss of this chromosome benefits Histoplasma by increasing phenotypic variation, thus helping populations of cells survive abrupt transitions between environment and host.

genetics↗

bioRxiv2025

A remarkable expansion of secreted cysteine knot proteins reveals novel virulence factors in the human fungal pathogen Histoplasma

Identifying fungal secreted factors that influence host infection remains a key challenge in microbial pathogenesis. While secreted effectors, particularly small cysteine-rich proteins, are well characterized in plant fungal pathogens, their counterparts in mammalian pathogens remain elusive. We applied criteria from plant fungal effectors to the mammalian fungal pathogen Histoplasma, yielding a set of putative effectors highly enriched for knottins, proteins that adopt a distinctive cysteine knot fold. Using a novel algorithm, we further identified 25 putative knottins in the Histoplasma genome, revealing a significant expansion of knottin genes. Knottin domains are found in diverse molecules but play an unknown role in virulence. Functional studies of individual Histoplasma knottins demonstrated their critical roles in intracellular survival and host cell lysis during macrophage infection as well as virulence in vivo. These findings highlight the importance of knottins in fungal pathogenesis and suggest their broader relevance for discovering conserved mechanisms of host manipulation.

microbiology↗

bioRxiv2024

Changing dynamics of Aedes aegypti invasion and vector-borne disease risk for rural communities in the Peruvian Amazon

Aedes aegypti, the primary vector of dengue virus, is predominantly considered an urban mosquito, especially in the Americas, where its reemergence began in cities after the end of continent-wide eradication campaigns. The results of our study diverge from this narrative, demonstrating the recent and widespread rural invasion of Ae. aegypti along major shipping routes in the northern Peruvian Amazon between the major cities of Iquitos, Pucallpa, and Yurimaguas. We identified Ae. aegypti populations in 29 of 30 sites surveyed across a rural to urban gradient and characterized mosquito larval habitats and Ae. aegypti adult metrics. Households, regardless of community size, were more likely to be positive for Ae. aegypti adult(s) and had a higher number of Ae. aegypti adults if a mosquito larval habitat was identified on the property, compared to houses without a larval habitat. In multiple instances, adult Ae. aegypti indices in rural villages were equal to or greater than indices in dengue-endemic cities, suggesting the entomological risk level in some rural areas is sufficient to sustain dengue transmission. Fourteen rural sites were sampled in transects from the community river port into town. In seven of these sites, houses closer to the port were significantly more likely to be infested with Ae. aegypti adults than houses further from the ports, and four additional sites had a marginal relationship to the same effect. This pattern suggests that many rural sites are invaded via adult Ae. aegypti disembarking from boats at the port, finding nearby oviposition sites, and advancing stepwise into town. The existence of the pattern also suggests that many of the sites are still experiencing active invasion, with sections of towns still Ae. aegypti-free. Only one site shows a strong signal of invasion via the egg or larval stage, with a focus of Ae. aegypti far removed from the port. The widespread infestation of Ae. aegypti in rural areas is a major public health threat given the far distance of communities to hospital care. It is important to implement control measures now before the mosquito gains a stronger foothold in zones of active invasion.

ecology↗

bioRxiv2020

Quantitative study of unsaturated transport of glycerol through aquaglyceroporin that has high affinity for glycerol

Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=37 SRC="FIGDIR/small/152512v1_ufig1.gif" ALT="Figure 1"> View larger version (9K): org.highwire.dtl.DTLVardef@19dcc7forg.highwire.dtl.DTLVardef@dce74dorg.highwire.dtl.DTLVardef@d599b4org.highwire.dtl.DTLVardef@15e24f5_HPS_FORMAT_FIGEXP M_FIG C_FIG ABSTRACTThe structures of several aquaglyceroporins have been resolved to atomic resolution showing two or more glycerols bound inside a channel and confirming a glycerol-facilitators affinity for its substrate glycerol. However, the kinetics data of glycerol transport experiments all point to unsaturated transport that is characteristic of low substrate affinity in terms of the Michaelis-Menten kinetics. In this article, we present an in silico-in vitro research focused on AQP3, one of the human aquaglyceroporins that is natively expressed in the abundantly available erythrocytes. We conducted 2.1 s in silico simulations of AQP3 embedded in a model erythrocyte membrane with intracellular-extracellular asymmetries in leaflet lipid compositions and compartment salt ions. From the equilibrium molecular dynamics (MD), we elucidated the mechanism of glycerol transport at high substrate concentrations. From the steered MD simulations, we computed the Gibbs free-energy profile throughout the AQP3 channel. From the free-energy profile, we quantified the kinetics of glycerol transport that is unsaturated due to glycerol-glycerol interaction mediated by AQP3 resulting in the concerted movement of two glycerol molecules for the transport of one glycerol molecule across the cell membrane. We conducted in vitro experiments on glycerol uptake into human erythrocytes for a wide range of substrate concentrations and various temperatures. The experimental data quantitatively validated our theoretical-computational conclusions on the unsaturated glycerol transport through AQP3 that has high affinity for glycerol.

biophysics↗

bioRxiv2017

Computing Osmotic Permeabilities of Aquaporins AQP4, AQP5, and GlpF from Near-Equilibrium Simulations

O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=79 SRC=\"FIGDIR/small/102343_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (20K):\norg.highwire.dtl.DTLVardef@c57ff0org.highwire.dtl.DTLVardef@527a79org.highwire.dtl.DTLVardef@e6bde6org.highwire.dtl.DTLVardef@bd53cf_HPS_FORMAT_FIGEXP M_FIG C_FIG Measuring or computing the single-channel permeability of aquaporins/aquaglyceroporins (AQPs) has long been a challenge. The measured values scatter over an order of magnitude but the corresponding Arrhenius activation energies converge in the current literature. Osmotic flux through an AQP was simulated as water current forced through the channel by kilobar hydraulic pressure or theoretically approximated as single-file diffusion. In this paper, we report large scale simulations of osmotic current under sub M gradient through three water channels (the water-specific AQP4 and AQP5 along with aquaglyceroporin GlpF) using the mature particle mesh Ewald technique (PME) for which the established force fields have been optimized with known accuracy. These simulations were implemented with hybrid periodic boundary conditions devised to avoid the artifactitious mixing across the membrane in a regular PME simulation. The computed single-channel permeabilities at 5{degrees}C and 25{degrees}C are in agreement with recently refined experiments on GlpF. The Arrhenius activation energies extracted from our simulations for all the three AQPs agree with the in vitro measurements. The single-file diffusion approximations from our large-scale simulations are consistent with the current literature on smaller systems. From these unambiguous agreements among the in vitro and in silico studies, we observe the quantitative accuracy of the all-atom force fields of the current literature for water-channel biology. We also observe that AQP4, that is particularly rich in the central nervous system, is more efficient in water conduction and more temperature-sensitive than other water-specific channel proteins.

biophysics↗