Biology subjects

Barasa, L.

Publications and source records attributed to Barasa, L..

3 recordsLinked to original sources

bioRxiv2026

Reciprocal regulation between the protein arginine deiminases and mSWI/SNF chromatin remodelers controls skeletal muscle differentiation and regeneration

Protein arginine deiminases (PADs) post-translationally convert arginine to citrulline on target proteins and serve as regulators of multiple cellular functions. PAD enzymes have been implicated in autoimmune disorders, cancer, and other diseases. Inhibiting PAD activity is currently being pursued clinically for therapeutic purposes. However, little is known about PAD function in normal developmental or homeostatic processes. Here we show that multiple PAD isoforms contribute to primary myoblast differentiation by binding to regulatory regions of target genes. Furthermore, we demonstrate a novel, reciprocal requirement for PADs and mammalian SWI/SNF (mSWI/SNF) chromatin remodeling enzymes; PAD enzymes are required for the expression and binding of specific mSWI/SNF enzyme subunits to target gene regulatory sequences while mSWI/SNF enzymes are required for the expression and binding of PAD enzymes. In vivo, the PADs contribute to mouse skeletal muscle regeneration after injury, with PAD4 specifically identified as a required regulator. This work identifies the PADs as critical cofactors in the initiation of skeletal muscle differentiation and reveals previously unappreciated connections between two major co-activator families during normal tissue development. Moreover, the results reveal important considerations for ongoing therapeutic approaches to myriad human diseases that utilize inhibitors of each enzyme family.

molecular biology↗

bioRxiv2025

SARM1, the executioner of axon degeneration, is an ADP-ribosyl transferase and autoMARylation negatively regulates its activation

Axon degeneration is a hallmark of nearly all neurodegenerative diseases. SARM1 plays a central role in this process by degrading NAD+ into nicotinamide and ADPR or cADPR. SARM1 also catalyzes a base exchange reaction between NAD+-phosphate (NADP+) and nicotinic acid (NA) to generate NAADP. These second messengers (i.e., ADPR, cADPR, and NAADP), and NAD+ consumption, are thought to drive axon degeneration. Herein, we identify a fourth reaction catalyzed by SARM1: mono-ADP-ribosylation (MARylation). Specifically, we show that SARM1 MARylates itself and other proteins with a catalytic efficiency (kcat/Km) higher than its NAD+ hydrolase activity. We further show that auto-MARylation promotes a phase transition and renders SARM1 responsive to regulation by NMN. Notably, endogenous SARM1 is MARylated at mitochondria, suggesting that MARylation may regulate SARM1 localization. Together, these findings uncover new regulatory mechanisms and expand the known signaling functions of SARM1. SignificanceSARM1 is an NAD+ hydrolase that executes axon degeneration in myriad neurodegenerative diseases. In addition to NAD+ hydrolysis, SARM1 catalyzes NAD+ cyclization and a base exchange reaction with NADP+ and nicotinic acid. These studies show that SARM1 also catalyzes the transfer of single ADPR moieties to proteins, including itself. Notably, we show that this auto-modification regulates SARM1 activity, allowing the protein to respond to NMN and to permit the phase transition. We also show that endogenous SARM1 is modified at the mitochondria, suggesting that this post-translational modification regulates SARM1 subcellular localization. These findings offer valuable mechanistic insights into SARM1 regulation that will ultimately inform the development of inhibitors targeting SARM1 for neurodegenerative diseases.

biochemistry↗

bioRxiv2024

High-throughput screening of more than 30,000 compounds for anthelmintics against gastrointestinal nematode parasites

Gastrointestinal nematodes (GINs) are amongst the most common parasites of humans, livestock, and companion animals. GIN parasites infect 1-2 billion people worldwide, significantly impacting hundreds of millions of children, pregnant women, and adult workers, thereby perpetuating poverty. Two benzimidazoles with suboptimal efficacy are currently used to treat GINs in humans as part of mass drug administrations, with many instances of lower-than-expected or poor efficacy and possible resistance. Thus, new anthelmintics are urgently needed. However, screening methods for new anthelmintics using human GINs typically have low throughput. Here, using our novel screening pipeline that starts with human hookworms, we screened 30,238 unique small molecules from a wide range of compound libraries, including ones with generic diversity, repurposed drugs, natural derivatives, known mechanisms of action, as well as multiple target-focused libraries (e.g., targeting kinases, GPCRs, and neuronal proteins). We identified 55 compounds with broad-spectrum activity against adult stages of two evolutionary divergent GINs, hookworms (Ancylostoma ceylanicum) and whipworms (Trichuris muris). Based on known databases, the targets of these 55 compounds were predicted in nematode parasites. One novel scaffold from the diversity set library, F0317-0202, showed good activity (high motility inhibition) against both GINs. To better understand this novel scaffolds structure-activity relationships (SAR), we screened 28 analogs and created SAR models highlighting chemical and functional groups required for broad-spectrum activity. These studies validate our new and efficient screening pipeline at the level of tens of thousands of compounds and provide an important set of new GIN-active compounds for developing novel and broadly-active anthelmintics.

pharmacology and toxicology↗