Biology subjects

Ackley, B. D.

Publications and source records attributed to Ackley, B. D..

2 recordsLinked to original sources

bioRxiv2018

The C. elegans CHP1 homolog, pbo-1, functions in innate immunity by regulating the pH of the intestinal lumen

Caenorhabditis elegans are soil-dwelling nematodes and models for understanding innate immunity and infection. Previous work has described a regularly-timed pH change in the intestine of Caenorhabditis elegans called the pH wave. To characterize this wave and its function in the worm, we developed a novel fluorescent dye (KR35) that accumulates in the intestine and sensitively responds to dynamic changes in pH. Here, we use KR35 to show that mutations in the Ca2+-binding protein, PBO-1 abrogate the pH wave, causing the anterior intestine to be constantly acidic. Surprisingly, pbo-1 mutants were also more susceptible to infection by several bacterial pathogens. We could suppress pathogen susceptibility in pbo-1 mutants by treating the animals with pH-buffering bicarbonate, suggesting the pathogen susceptibility is a function of the acidity of the intestinal pH. Furthermore, we use KR35 to show that pathogens completely neutralize the pH in the intestine of wild type, but not pbo-1 mutants. C. elegans is known to increase production of reactive oxygen species (ROS), such as H2O2, in response to pathogens, which is an important component of pathogen defense. We show that pbo-1 mutants exhibited decreased H2O2 in response to pathogens, which could also be partially restored in pbo-1 animals treated with bicarbonate. Ultimately, our results support a model whereby pbo-1 functions during infection to permit pH changes in the intestine that are important for fighting pathogens.\n\nAuthor SummaryInnate immunity is critical for host defense against pathogens. However, questions remain about how the host senses and responds to pathogen invasion. Using a pH-sensitive fluorescent dye and a Caenorhabditis elegans pathogen infection model we show that pathogens induce changes in pH of the worm intestine. We also show that intestinal pH directly affects production of reactive oxygen species (e.g. H2O2) important for pathogen defense. Our results show that pH regulation is an important component of the innate immune response to pathogens.

microbiology↗

bioRxiv2018

Intermediate filaments EXC-2 and IFA-4 Maintain Luminal Structure of the Tubular Excretory Canals in Caenorhabditis elegans

The excretory canals of Caenorhabditis elegans are a model for understanding the maintenance of apical morphology in narrow single-celled tubes. Light and electron microscopy shows that mutants in exc-2 start to form canals normally, but these swell to develop large fluid-filled cysts that lack a complete terminal web at the apical surface, and accumulate filamentous material in the canal lumen. Here, whole-genome sequencing and gene rescue show that exc-2 encodes intermediate filament protein IFC-2. EXC-2/IFC-2 protein, fluorescently tagged via CRISPR/Cas9, is located at the apical surface of the canals independently of other intermediate filament proteins. EXC-2 is also located in several other tissues, though the tagged isoforms are not seen in the larger intestinal tube. Tagged EXC-2 binds via pulldown to intermediate filament protein IFA-4, which is also shown to line the canal apical surface. Overexpression of either protein results in narrow but shortened canals. These results are consistent with a model whereby three intermediate filaments in the canals, EXC-2, IFA-4, and IFB-1, restrain swelling of narrow tubules in concert with actin filaments that guide the extension and direction of tubule outgrowth, while allowing the tube to bend as the animal moves.\n\nArticle SummaryThe C. elegans excretory canals form a useful model for understanding formation of narrow tubes. exc-2 mutants start to form normal canals that then swell into fluid-filled cysts. We show that exc-2 encodes a large intermediate filament (IF) protein previously not thought to be located in the canals. EXC-2 is located at the apical (luminal) membrane, binds to another IF protein, and appears to be one of three IF proteins that form a flexible meshwork to maintain the thin canal diameter. This work provides a genetically useful model for understanding the interactions of IF proteins with other cytoskeletal elements to regulate tube size and growth.

developmental biology↗