Park, Eun Chan et al. (2013) International Worm Meeting "Mitochondrial Dynamics And Behavioral Plasticity In Response To Oxygen Deprivation Are Linked Through HIF-1."

Salazar-Vasquez, Nathaly, Ghose, Piya, Park, Eun Chan, Tabakin, Alexandra, Rongo, Christopher

[International Worm Meeting, 2013]

C. elegans can survive extreme oxygen deprivation (anoxia, < 0.1% O2) by entering into a suspended animation state during which locomotory behavior and development arrest. Upon re-exposure to normoxic conditions (21 % O2), animals resume their behavior and normal development. The underlying mechanism of this stress response is not well understood. Here we show that neuronal mitochondria undergo fission in response to anoxia co-temporaneously with the onset of suspended animation, followed by re-fusion upon re-oxygenation, suggesting that mitochondrial dynamics might contribute to anoxia-induced suspended animation. We find that the hypoxia response pathway, including EGL-9 and HIF-1, regulates the reconstitution of mitochondria following re-oxygenation. Under conditions of normal oxygen, EGL-9 represses the activity of HIF-1, a transcription factor that promotes the expression of hypoxia-response genes. Loss of function mutations in egl-9 result in rapid re-fusion of mitochondria and behavioral recovery from suspended animation following re-oxygenation; both phenotypes require HIF-1 activity. In addition, the mitochondria are significantly larger in egl-9 mutants after re-oxygenation than they were prior to anoxia exposure - a phenotype that resembles the stress-induced mitochondria hyperfusion (SIMH) that has been observed in mammalian cells. Both the changes in mitochondrial dynamics and suspended animation recovery of egl-9 mutants can be rescued by expressing wild-type EGL-9 solely in neurons. Mitochondrial hyperfusion and rapid recovery observed in egl-9 mutants following anoxia are modulated by STL-1, a mammalian stomatin-like protein (SLP2) homologue that is reported to function in SIMH. Our results suggest the existence of a conserved stress response involving changes in mitochondrial fission and fusion, and demonstrate that the behaviors executed by a simple neural circuit can be regulated through changes in mitochondrial dynamics.

Park, Eun Chan et al. (2011) International Worm Meeting "HIF-1 Independent Glutamate Receptor Trafficking as a Novel Neuroprotective Response to Hypoxic Insult."

Shao, Zhiyong, Xu, Shawn, Rongo, Christopher, Kang, Lijun, Park, Eun Chan, Powell-Coffman, Jo Anne, Ghose, Piya

[International Worm Meeting, 2011]

Ischemic stroke results in excitotoxicity via hypoxia, glutamate receptor (GluR) overactivation and deregulated calcium homeostasis. Changes in GluR trafficking can occur in response to hypoxia, but the nature of those changes, whether they protect or exacerbate excitotoxicity, remains controversial. Here we examine how hypoxia and the known hypoxia response pathway alter the trafficking of the C. elegans GluR GLR-1. GLR-1 acts in the command interneurons mediating an escape response by triggering reversals in locomotion. Synaptically localized GLR-1 receptors can be observed using a GLR-1::GFP chimeric protein. Recently, we observed a change in GLR-1 trafficking in response to hypoxic treatment: receptors become trapped in internal endosome-like accretions and animals behave similar to glr-1 knockouts. Loss of function mutations in egl-9, a prolyl hydroxylase that normally inhibits the cellular response to hypoxia by hydroxylating key proline residues on the transcription factor HIF-1, mimics the effects of hypoxia on GLR-1 trafficking and depresses both glutamate-activated currents and GLR-1- mediated behaviors. HIF-1, the canonical substrate of EGL-9 activity, is not required for this effect; instead, we find that EGL-9 physically interacts with LIN-10, a PTB/PDZ-domain protein that promotes GLR-1 membrane recycling. We find that normal oxygen levels induce a specific EGL-9 isoform to colocalize with LIN-10 in dendrites, where it prevents the phosphorylation of LIN-10 by the proline-directed kinase CDK-5. Un-phosphorylated LIN-10 is recruited to endosomes, where it mediates GLR-1 recycling. By contrast, under hypoxic conditions, EGL-9 is inhibited by lack of oxygen, allowing CDK-5 to inhibit LIN-10 by directly phosphorylating its proline-rich N-terminus. This results in LIN-10 delocalization and the trapping of GLR-1 in endosomes. Mutations in either cdk-5 or the proline residues of the CDK-5 phosphorylation sites in LIN-10 block the effects of hypoxia and egl-9 mutations, suggesting a novel kinase regulatory mechanism in which EGL-9 regulates CDK-5 kinase activity by hydroxylating its substrate prolines, thus precluding substrate phosphorylation by CDK-5. We propose that neurons use this novel neuroprotective mechanism to respond to hypoxia by inhibiting receptor membrane recycling so as to reduce GluR synaptic abundance.

Ghose, Piya et al. (2009) International Worm Meeting "The Effect of Hypoxia on Neuronal Necrosis and Glutamate Receptor Trafficking."

Rongo, Christopher, Ghose, Piya, Park, Eun Chan

[International Worm Meeting, 2009]

Neurons in the brain are sensitive to oxygen levels, undergoing necrosis within minutes after hypoxia (e.g., oxygen deprivation during ischemic stroke). This neuronal toxicity is mediated in part by the excitatory neurotransmitter glutamate, which is released at high levels during hypoxia, and the ionotropic glutamate receptors (GluRs) that are trafficked to postsynaptic membranes. However, the mechanistic relationship between hypoxia, GluR function and subcellular trafficking, and excitotoxic necrosis has not been fully elucidated. Here we examine the effects of hypoxia and mutations in hypoxia response factors on necrosis and GluR trafficking in C. elegans. In C. elegans, an excitotoxic-like necrosis can be modeled in vivo by expressing a constitutively active G alpha S subunit in neurons. Activated G alpha S modulates the activity of yet unknown ion channels, resulting in the necrosis of a subset of neurons that express it (1). The resulting intermediate necrosis phenotype affords us the ability to screen for factors that either enhance or suppress neuronal necrosis, including hypoxia. The C. elegans GluR GLR-1 is expressed in these same neurons, where it functions to mediate locomotion reversal behavior (2,3) and is trafficked to synaptic connections (4). We find that hypoxic treatment enhances the necrosis caused by activated G alpha S expression, and alters the trafficking of GLR-1 in these same neurons. We anticipate that our studies will further elucidate the mechanisms of neuronal damage after hypoxia. By identifying the molecular mechanisms that regulate GluR signaling and necrosis in response to hypoxia, we hope to provide useful therapeutic targets for the prevention of nervous system damage after hypoxia exposure.(*co-first author) References 1. Berger, A.J. et al., G alphas-induced neurodegeneration in Caenorhabditis elegans. J Neurosci. 18,2871-80 (1995). 2. Hart, A.C. et al., Synaptic code for sensory modalities revealed by C. elegans GLR-1 glutamate receptor. Nature. 378,82-5 (1995). 3. Maricq, A.V. et al., Mechanosensory signalling in C. elegans mediated by the GLR-1 glutamate receptor. Nature. 378,78-81 (1995). 4. Rongo, C. et al., LIN-10 is a shared component of the polarized protein localization pathways in neurons and epithelia. Cell 94,51-759, 1998.

Zhao C et al. (1993) Worm Breeder's Gazette "Cloning of the lin-32 Gene"

Emmons SW, Zhao C

[Worm Breeder's Gazette, 1993]

Cloning of the lin-32 gene Connie Zhao and Scott W. Emmons, Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461

Bargmann C (2024) Neuron "Cori Bargmann."

Bargmann C

[Neuron, 2024]

In an interview with Neuron, Cori Bargmann discusses C.&#xa0;elegans as a model organism, the importance of considering the animal's own world (thinking like a worm), choosing a scientific problem, and her experience as head of science at the Chan Zuckerberg Initiative and co-chair of the BRAIN Initiative.

Tabakin, Alexandra L. et al. (2013) International Worm Meeting "Mitochondrial dynamics in response to oxygen deprivation."

Salazar-Vasquez, Nathaly, Ghose, Piya, Park, Eun Chan, Rongo, Christopher, Tabakin, Alexandra L.

[International Worm Meeting, 2013]

Mitochondria play a critical role in the oxygen-dependent generation of cellular energy. Many aerobic organisms encounter oxygen-deprived environments and thus must have adaptive mechanisms to survive such stress. How mitochondria are regulated in the face of oxygen deprivation stress is not well understood. Here we examine mitochondrial dynamics, including organelle fission and fusion, in C. elegans neurons in response to anoxia. We find that anoxia triggers mitochondrial fission, and that DRP-1, a key component of the mitochondrial fission machinery, is required for this fission. Subsequent reoxygenation results in mitochondrial refusion. We observed that mutations in egl-9, a prolyl hydroxylase oxygen sensor, resulted in mitochondrial hyperfusion (fusion beyond the normal levels present prior to anoxia) upon reoxygenation. This hyperfusion phenotype requires the hypoxia inducible factor-1 (HIF-1), the canonical substrate of EGL-9. Hyperfusion also requires STL-1, a poorly characterized mitochondrial scaffolding protein. Finally, we found that anoxia triggers a behavioral arrest (suspended animation), and that normal neurological behavior was restored upon reoxygenation. Mutants for egl-9 demonstrated a rapid recovery from suspended animation compared to wild type; this rapid recovery also required HIF-1 and STL-1. Our results suggest that C. elegans neurons modulate mitochondrial fission and fusion in response to stress to help organisms adapt to low oxygen environments and to modify neurological function; moreover, this modulation is regulated and rapidly reversible.

Emmons SW et al. (1994) Worm Breeder's Gazette "Strain Names for non-C. elegans Species."

Emmons SW, Fitch DHA, Leroi AM

[Worm Breeder's Gazette, 1994]

Strain names for non-C. elegans species Scott W. Emmonst, Armand Leroit, and David Fitch, Department of Molecular Genetics, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, Department of Biology, New York University, RmlOO9 Main Bldg., Washington Square, New York, NY 10003

Lim, Yunki et al. (2019) International Worm Meeting "The mitophagy receptor FUNDC1 contributes to hypoxia-reoxygenation injury in C. elegans."

Park, Eun Chan, Berry, Brandon, Wojtovich, Andrew, Rongo, Christopher, Nehrke, Keith, Brookes, Paul S., Lim, Yunki

[International Worm Meeting, 2019]

Mitochondria are the metabolic hub of the cell and have a nearly pervasive impact on pathophysiology. Hence, the molecular components and signaling pathways that comprise mitochondrial quality control are tightly regulated and critical for normal stress responses. Among these are pathways for sensing mitochondrial proteostasis such as the mitochondrial unfolded protein response (UPRmt) and for recycling damaged mitochondria such as mitophagy. FUNDC1 (FUN14 domain containing 1) is a mitochondrial outer membrane protein and a hypoxia-induced mitophagy receptor that regulates hypoxic cell death in mammals. Here, using mito-mKeima (pH-dependent dual excitation fluorophore protein) to monitor mitophagy, we show that T06D8.7/fndc-1 encodes the C. elegans FUNDC1 ortholog and is required to protect nematodes from hypoxia-reoxygenation (H/R) injury. Consistent with previous results demonstrating protection from H/R injury by activation of the UPRmt, loss of the central UPRmt transcription factor atfs-1 suppresses H/R protection. However, canonical UPRmt reporter genes were not activated in the fndc-1(lf) mutant, suggesting that protection was seen in fndc-1(lf) worms may occur through a novel or restricted arm of the UPRmt pathway. Mechanistically, mitochondrial respiration was not impacted by the loss of fndc-1; instead, increased ATP levels and changes in the expression of genes that regulate glycolysis underlie metabolic rewiring in the mutant. Since these changes also depend upon atfs-1, our results highlight a connection between FNDC-1-mediated mitophagy and a restricted branch of the UPRmt that impacts metabolism and subsequent susceptibility to H/R injury.

(2019) Development "The people behind the papers - Daniel Osorio, Elaine Chan, Joana Saramago and Ana Carvalho."

[Development, 2019]

Animal cytokinesis is driven by an actomyosin ring that assembles at the cell equator and constricts to physically separate the two daughters. Although myosin is known to be essential for cytokinesis in multiple systems, whether this requirement reflects its motor or actin crosslinking activities has recently been a matter of contention. A new paper in Development now addresses this problem using the first divisions of the <i>Caenorhabditis elegans</i> embryo as a model. We caught up with the paper's three first authors Daniel Osorio, Elaine Chan and Joana Saramago, and their supervisor Ana Carvalho, Principal Investigator at the University of Porto's i3S consortium, to find out more about the story.

Cirillo, L. et al. (2015) International Worm Meeting "Coordinating Cdk1 and Plk1 activation for mitotic entry in early C. elegans embryos and human cells."

Pindard, L., Thomas, Y., Martino, L., Santamaria, A., Gotta, M., Schwager, F., Van Hove, L., Panbianco, C., Cirillo, L.

[International Worm Meeting, 2015]

Entry into mitosis is regulated by several kinases including Cdk1, Aurora A and Plk1. However, how the activity of these kinases is coordinated in space and time is not fully understood. Our laboratories have recently shown that SPAT-1, an activator of Plk1, is phosphorylated by Cdk-1 at several sites in C. elegans. Our in vivo and in vitro data revealed that phosphorylation of the N-terminal sites is crucial to promote the interaction with PLK-1 and its activation. Together, our results suggest the existence of a positive feedback loop that connects CDK-1 and PLK-1 via SPAT-1 and ensures a robust control of cell division timing during embryonic development.The human ortholog of SPAT-1, Bora, regulates several aspects of mitosis (Bruinsma et al. 2014, Chan et al 2008, Macurek et al. 2008, Seki et al. 2008). Although phosphorylation of Bora is not strictly required to activate Plk1 (Seki et al. 2008, our unpublished data) we find that Cdk1 phosphorylation of Bora greatly increases Plk1 activation in vitro. We have mapped the Cdk1 phosphorylation sites of Bora. Based on the results obtained in C. elegans, we have mutated a number of N-terminal sites and found that Bora ability to activate Plk1 is greatly reduced in vitro. We are currently testing the function of these sites in human cells by monitoring these mutants in vivo. Our data will help to shed light on the activation mechanisms of Plk1 by Bora. Since Plk1 is overexpressed in many cancers, understanding the precise mechanisms of activation of this kinase will help the design of anti-cancer drugs.References:Bruinsma W. et al. J Cell Sci. 2014; Chan EH. et al. Chromosoma. 2008; Macurek L. et al. Nature. 2008; Seki A. et al. Science. 2008.