Tal, S. | Search bioRxiv

bioRxiv2024

Activity-dependent COX-2 proteolysis generates a catalytically inactive fragment that affects aerobic respiration

Cyclooxygenase-2 (COX-2) catalyzes arachidonic acid (AA) into PGH2, the single source of all prostaglandins (PGs), ligands that activate multiple inflammatory pathways. AA catalysis quickly results in suicide inactivation, rendering the enzyme catalytically inactive. We show that the catalytic activity also leads to controlled cleavage of COX-2, an event that is differentially regulated by fatty acids, and blocked by COX inhibitors. We also observe COX-2 cleavage in human colon tumors. Using mass spectrometry, we identify two adjacent cleavage points within the catalytic domain, which give rise to COX-2 fragments that are catalytically inactive and localize to different cellular compartments. One of these fragments significantly alters the expression of mitochondrial electron transport genes and functional assays show that it leads to reduced mitochondrial function, increased lactate production, and enhanced proliferation. We propose that in addition to its role in generating PGs, COX-2 has subsequent PG-independent cellular functions that may account for the complex role of COX-2 in proliferative diseases and chronic inflammation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/588559v2_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@15d589corg.highwire.dtl.DTLVardef@1648e5eorg.highwire.dtl.DTLVardef@bededcorg.highwire.dtl.DTLVardef@1195684_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

CRISPR Spacers Acquired from Plasmids Primarily Target Backbone Genes, Making Them Valuable for Predicting Potential Hosts and Host Range

In recent years, there has been a surge in metagenomic studies focused on identifying plasmids in environmental samples. While these studies have unearthed numerous novel plasmids, enriching our understanding of their environmental roles, a significant gap remains: the scarcity of information regarding the bacterial hosts of these newly discovered plasmids. Furthermore, even when plasmids are identified within bacterial isolates, the reported host is typically limited to the original isolate, with no insight into alternative hosts or the plasmids potential host range. Given that plasmids depend on hosts for their existence, investigating plasmids without knowledge of potential hosts offers only a partial perspective. This study introduces a method for identifying potential hosts and host ranges for plasmids through alignment with CRISPR spacers. To validate the method, we compared the PLSDB plasmids database with the CRISPR spacers database, yielding host predictions for 46% of the plasmids. When compared to reported hosts, our predictions achieved an 84% concordance at the family level and 99% concordance at the phylum level. Moreover, the method frequently identified multiple potential hosts for a plasmid, thereby enabling predictions of alternative hosts and the host range. Notably, we found that CRISPR spacers predominantly target plasmid backbone genes while sparing functional genes, such as those linked to antibiotic resistance, aligning with our hypothesis that CRISPR spacers are acquired from plasmid-specific regions rather than insertion elements from diverse sources. Lastly, we illustrate the network of connections among different bacterial taxa through plasmids, revealing potential pathways for horizontal gene transfer. IMPORTANCEPlasmids are notorious for their role in distributing antibiotic resistance genes, but they may also carry and distribute other environmentally important genes. Since plasmids are not free-living entities and rely on host bacteria for survival and propagation, predicting their hosts is essential. This study presents a method for predicting potential hosts for plasmids and offers insights into the potential paths for spreading functional genes between different bacteria. Understanding plasmid-host relationships is crucial for comprehending the ecological and clinical impact of plasmids and implications for various biological processes.

microbiology↗

bioRxiv2023

Synapsin E-domain is essential for α-synuclein function

The cytosolic proteins synucleins and synapsins are thought to play cooperative roles in regulating synaptic vesicle (SV) recycling, but mechanistic insight is lacking. Here we identify the synapsin E-domain as an essential functional binding-partner of -synuclein (-syn). Synapsin E-domain allows -syn functionality, binds to -syn, and is necessary and sufficient for enabling effects of -syn at the synapse. Together with previous studies implicating the E-domain in clustering SVs, our experiments advocate a cooperative role for these two proteins in maintaining physiologic SV clusters.

neuroscience↗