Biology subjects

Collins, C. A.

Publications and source records attributed to Collins, C. A..

7 recordsLinked to original sources

bioRxiv2025

Pyruvate kinase deficiency links metabolic perturbations to neurodegeneration and axonal protection

Neurons rely on tightly regulated metabolic networks to sustain their high-energy demands, particularly through the coupling of glycolysis and oxidative phosphorylation. Here, we investigate the role of pyruvate kinase (PyK), a key glycolytic enzyme, in maintaining axonal and synaptic integrity in the Drosophila melanogaster neuromuscular system. Using genetic deficiencies in PyK, we show that disrupting glycolysis induces progressive synaptic and axonal degeneration and severe locomotor deficits. These effects require the conserved dual leucine zipper kinase (DLK), Jun N-terminal kinase (JNK), and activator protein 1 (AP-1) Fos transcription factor axonal damage signaling pathway and the SARM1 NADase enzyme, a key driver of axonal degeneration. As both DLK and SARM1 regulate degeneration of injured axons (Wallerian degeneration), we probed the effect of PyK loss on this process. Consistent with the idea that metabolic shifts may influence neuronal resilience in context-dependent ways, we find that pyk knockdown delays Wallerian degeneration following nerve injury, suggesting that reducing glycolytic flux can promote axon survival under stress conditions. This protective effect is partially blocked by DLK knockdown and fully abolished by SARM1 overexpression. Together, our findings help bridge metabolism and neurodegenerative signaling by demonstrating that glycolytic perturbations causally activate stress response pathways that dictate the balance between protection and degeneration depending on the systems state. These results provide a mechanistic framework for understanding metabolic contributions to neurodegeneration and highlight the potential of metabolism as a target for therapeutic strategies. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/647282v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@1bba464org.highwire.dtl.DTLVardef@25bdd2org.highwire.dtl.DTLVardef@1d12611org.highwire.dtl.DTLVardef@1a3d96_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

LDL receptor-mediated endocytosis of Escherichia coli α-hemolysin mediates renal epithelial toxicity

Pore-forming toxins (PFTs) are secreted bacterial effector molecules that disrupt host cell membranes. The -hemolysin (HlyA) of uropathogenic Escherichia coli (UPEC) can exert damage to various mammalian cell types. While a candidate toxin receptor (CD11a/CD18 [LFA-1] integrin) exists on myeloid cells, the mechanism of HlyA cytotoxicity to epithelial cells remains undefined. We show that HlyA secretion by UPEC exacerbates renal tubular epithelial injury during ascending pyelonephritis in mice. A CRISPR-Cas9 loss-of-function screen in renal collecting duct cells identified clathrin-mediated endocytosis as required for HlyA cytotoxicity. HlyA internalization induces lysosomal permeabilization, facilitating protease release, cytoplasmic acidification, and mitochondrial dysfunction leading to rapid cell death. This mechanism contrasts with the described actions of other PFTs (plasma membrane poration and osmotic cytolysis). We also identify the low-density lipoprotein receptor (LDLR) as an epithelial receptor for HlyA; genetic or competitive inhibition of the HlyA-LDLR interaction prevented cytotoxicity. Our studies define a new mechanism of action for HlyA, in which its toxicity to epithelial cells requires LDLR-mediated, clathrin-dependent internalization. These results suggest therapeutic avenues for mitigating HlyA-induced damage during E. coli infections.

microbiology↗

bioRxiv2024

Axonal injury signaling is restrained by a spared synaptic branch

The intrinsic ability of injured neurons to degenerate and regenerate their axons facilitates nervous system repair, however this ability is not engaged in all neurons and injury locations. Here we investigate the regulation of a conserved axonal injury response pathway with respect to the location of damage in branched motoneuron axons in Drosophila larvae. The dileucine zipper kinase DLK, (also known as MAP3K12 in mammals and Wallenda (Wnd) in Drosophila), is a key regulator of diverse responses to axonal injury. In three different populations of motoneurons, we observed the same striking result that Wnd/DLK signaling becomes activated only in response to injuries that remove all synaptic terminals. Injuries that spare even a small part of a synaptic terminal fail to activate Wnd/DLK signaling, despite the presence of extensive axonal degeneration. The regulation of injury-induced Wnd/DLK signaling occurs independently of its previously known regulator, the Hiw/PHR ubiquitin ligase. We propose that Wnd/DLK signaling regulation is linked to the trafficking of a synapse-to-nucleus axonal cargo and that this mechanism enables neurons to respond to impairments in synaptic connectivity.

neuroscience↗

bioRxiv2024

Sarm1 is not necessary for activation of neuron-intrinsic growth programs yet required for the Schwann cell repair response and peripheral nerve regeneration.

Upon peripheral nervous system (PNS) injury, severed axons undergo rapid SARM1-dependent Wallerian degeneration (WD). In mammals, the role of SARM1 in PNS regeneration, however, is unknown. Here we demonstrate that Sarm1 is not required for axotomy induced activation of neuron-intrinsic growth programs and axonal growth into a nerve crush site. However, in the distal nerve, Sarm1 is necessary for the timely induction of the Schwann cell (SC) repair response, nerve inflammation, myelin clearance, and regeneration of sensory and motor axons. In Sarm1-/- mice, regenerated fibers exhibit reduced axon caliber, defective nerve conduction, and recovery of motor function is delayed. The growth hostile environment of Sarm1-/- distal nerve tissue was demonstrated by grafting of Sarm1-/- nerve into WT recipients. SC lineage tracing in injured WT and Sarm1-/- mice revealed morphological differences. In the Sarm1-/- distal nerve, the appearance of p75NTR+, c-Jun+ SCs is significantly delayed. Ex vivo, p75NTR and c-Jun upregulation in Sarm1-/- nerves can be rescued by pharmacological inhibition of ErbB kinase. Together, our studies show that Sarm1 is not necessary for the activation of neuron intrinsic growth programs but in the distal nerve is required for the orchestration of cellular programs that underlie rapid axon extension.

neuroscience↗

bioRxiv2023

Androgen exposure impairs neutrophil maturation and function within the infected kidney

Urinary tract infections (UTIs) in men are uncommon but carry increased risk for severe pyelonephritis and other complications. In models of Escherichia coli UTI, male C3H/HeN mice uniformly develop high-titer pyelonephritis (most with renal abscesses) in a testosterone-dependent manner, but the mechanisms underlying this phenotype are unknown. Here, using female mouse models, we show that androgen exposure impairs neutrophil maturation in the upper and lower urinary tract, compounded by an additional reduction of neutrophil function specifically within the infected kidney, enabling persistent high-titer infection and promoting abscess formation. Following intravesical inoculation with uropathogenic E. coli (UPEC), kidneys of androgen-exposed C3H mice showed delayed local pro-inflammatory cytokine responses while robustly recruiting neutrophils. These were enriched for an end-organ-specific population of aged but immature neutrophils (CD49d+, CD101-). Compared to their mature counterparts, these aged immature kidney neutrophils exhibited reduced functions in vitro, including impaired degranulation and diminished phagocytic activity, while splenic, bone marrow, and bladder neutrophils did not display these alterations. Further, aged immature neutrophils exhibited little phagocytic activity within intratubular UPEC communities in vivo. Experiments with B6 conditional androgen receptor (AR)-deficient mice indicated rescue of the maturation defect when AR was deleted in myeloid cells. We conclude that the recognized enhancement of UTI severity by androgens reflects urinary tract-specific impairment of neutrophil maturation (largely via cell-intrinsic AR signaling) and kidney-specific reduction in neutrophil antimicrobial capacity, resulting in failure to control renal bacterial infection.

immunology↗

bioRxiv2022

The phloem-resident protein OCTOPUS is a novel regulator of flg22-induced responses in Arabidopsis thaliana

Phloem is a critical tissue that transports photosynthates and extracellular signals in vascular plants. Although a functional phloem is necessary for plant health, it is also an ideal environment for pathogens to access host nutrients to promote pathogenesis. Even though many vascular pathogens induce economically relevant crop damage, very little is known about the mechanism(s) by which phloem cells detect potential pathogens and signal to minimize damage. Our lab searched existing phosphoproteomic databases, mining for proteins that were phosphorylated in response to the defense-elicitor flagellin, or flg22, AND were expressed in vascular cells, and we identified Octopus (OPS). OPS is polarly associated with the plasma membrane (PM) of sieve element cells and promotes their differentiation from procambial precursor cells by inhibiting the function of BIN2 in brassinosteroid-related signaling. The observation that OPS is differentially phosphorylated in response to flg22 led us to the examine whether OPS may function in flg22-induced signaling using Arabidopsis T-DNA insertion mutants lacking a functional OPS. In wild-type (WT) seedlings, flg22 binds to the PM receptor flagellin sensing 2 (FLS2) to initiate three branches of a signaling cascade that culminates in increased expression of distinct marker genes. Ultimately these signaling pathways lead to the restriction of pathogen growth. Two independent alleles of ops were treated with 100 M flg22 and marker genes from all three branches of FLS2 signaling exhibited higher expression than WT. We also found that in the absence of any flg22, ops mutants displayed increased flg22 signaling responses. Our results indicate that OPS may function as a negative regulator of flg22-induced signaling events and is one of very few phloem-resident proteins with a documented role in flg22 signaling. These results indicate that the phloem may be able to sense and response to the threat of bacterial pathogens in a unique way.

plant biology↗

bioRxiv2020

Vps13D is required for mitochondrial fission and mitophagy triggered by fission defects in Drosophila neurons

A healthy population of mitochondria, maintained by proper fission, fusion, and degradation, is critical for the long-term survival and function of neurons. Here, our discovery of mitophagy intermediates in fission-impaired Drosophila neurons brings new perspective into the relationship between mitochondrial fission and mitophagy. Neurons lacking either the ataxia disease gene Vps13D or the dynamin related protein Drp1 contain enlarged mitochondria that are engaged with autophagy machinery and also lack matrix components due to rupture. Reporter assays combined with genetic studies imply that mitophagy both initiates and is completed in Drp1 impaired neurons, but fails to complete in Vps13D impaired neurons, which accumulate compromised mitochondria within stalled mito-phagophores. Our findings imply that in fission-defective neurons, mitophagy becomes induced, and that the lipid channel containing protein Vps13D has separable functions in mitochondrial fission and phagophore elongation.

cell biology↗