Biology subjects

Porter, C. J.

Publications and source records attributed to Porter, C. J..

4 recordsLinked to original sources

bioRxiv2025

Metabolic, epigenetic and transcriptomic alterations in postnatal 16p11.2 deficient murine astrocytes

Autism Spectrum Disorders (ASD) are associated with metabolic dysregulation. While astrocytes are integral to cerebral metabolism, their molecular and functional changes in ASD are poorly known. Using early postnatal primary cortical astrocytes from a mouse model of 16p11.2 deletion ASD syndrome (16p11.2df/+ mice), we observed core molecular alterations with sex-specific profiles, suggesting divergent energetic pathways and epigenetic regulation. Targeted metabolomics revealed opposing phenotypes in male versus female 16p11.2df/+ astrocytes, particularly for alpha-ketoglutaric acid. Functionally, 16p11.2df/+astrocytes exhibited elevated phosphorylation in low glucose culture conditions, and reduced glycolysis in high glucose. Epigenetic profiling of male 16p11.2df/+astrocytes revealed differentially hydroxymethylated and methylated regions, with foci on chromosomes 3 and 13. Finally, bulk RNA sequencing in male and female mutant astrocytes indicated differential gene expression with profound sex differences, mostly affecting pathways related to cellular morphology. By establishing 16p11.2df/+ astroglial molecular signatures, this study refines our understanding of glial changes in ASD.

cell biology↗

bioRxiv2022

Functional promiscuity of small multidrug resistance transporters from Staphylococcus aureus, Pseudomonas aeruginosa, and Francisella tularensis

Small multidrug resistance (SMR) transporters efflux toxic substrates from bacterial cells and were recently divided into two subfamilies: specific toxic metabolite transporters and promiscuous drug exporters. These drug exporters are thought to function similarly to EmrE, the model system for this subfamily of SMR transporters. Studies of EmrE homologs indicate that they are able to confer resistance to EmrE substrates in E. coli and in their native organisms. Recent work from our lab showed that functional EmrE can confer resistance or susceptibility in vivo depending on the drug substrate. Here, we test whether this functional promiscuity of EmrE extends to SMR transporters from three additional human or animal pathogens: SAsmr from Staphylococcus aureus, PAsmr from Pseudomonas aeruginosa, and FTsmr from Francisella tularensis. We find that these SMR homologs can confer either resistance or susceptibility to different toxic substrates in E. coli. This demonstrates that the ability of a single transporter to lead to opposite biological outcomes when transporting different substrates is a general property of the promiscuous multidrug transporters in the SMR family. It also suggests the potential for novel antibiotic development targeting these transporters with small molecules that trigger susceptibility. Such a strategy does not require that the target be the primary mode for antibiotic resistance because the goal is not simple inhibition of activity, but rather activation of an alternative transport function that is detrimental to bacteria.

microbiology↗

bioRxiv2021

Fatty acid binding proteins shape the cellular response to activation of the glucocorticoid receptor

Glucocorticoids are steroid hormones that are essential for life in mammals. Therapeutically, they are some of the most cost-effective drugs for the treatment of inflammatory diseases ranging from skin rashes to COVID-19, but their use is limited by adverse effects. Glucocorticoids exert their effects via the glucocorticoid receptor, a type I nuclear hormone receptor which modulates gene expression. The transcriptional activity of some related, but nuclear restricted, type II nuclear hormone receptors can be enhanced by a family of intracellular transport proteins, the fatty acid binding proteins (FABPs). We find that the transcriptional activity of the GR can be altered by a sub-set of FABP family members dependent on the GR-ligand. The ability of some FABPs to selectively promote or limit the transcriptional activity of the GR in a ligand-dependent manner could facilitate the discovery of drugs that narrow GR activity to only the desired subset of therapeutically relevant genes.

pharmacology and toxicology↗

bioRxiv2021

Functional phenotyping of small multidrug resistance proteins from Staphylococcus aureus and Francisella tularensis reveals functional homology to EmrE

Small multidrug resistance (SMR) transporters efflux toxic substrates from bacterial cells. These transporters were recently divided into two subfamilies: the GdX-like and EmrE-like SMRs. The EmrE-like subfamily of SMRs is predicted to contain transporters that are highly promiscuous in both substrate specificity and mechanism based on extensive characterization of the founding member of this subfamily, EmrE. However, there is only limited functional analysis of other members of this family from pathogenic strains such as Staphylococcus aureus and Francisella tularensis. Here, we use a small compound screen to explore the substrate specificity and diversity of EmrE-subfamily SMRs from these two bacterial species and confirm that they are functionally more like EmrE than the GdX-like subfamily of toxic-metabolite transporters. The results of these experiments lay the foundation for understanding the complex substrate specificity profiles of SMR family transporters and assess the potential for targeting these transporters for future antibiotic development, either broadly or in a species-specific manner.

microbiology↗