Melissa Richardson et al. (2008) Development & Evolution Meeting "Protein Synthesis in the Germline: The Role of IFE-1"

Elizabeth Cronland, Susan Strome, Brett Keiper, Melissa Richardson

[Development & Evolution Meeting, 2008]

Fertility and embryonic viability are measures of efficient germ cell growth and differentiation. During oogenesis, spermatogenesis and embryogenesis cells initially proliferate then differentiate into specific tissues. New proteins are required for both cell growth and differentiation, requiring qualitative and quantitative changes in protein synthesis. During late gametogenesis and early embryogenesis the expression of the appropriate proteins is a primary function of translational control. Translational control of mRNAs is mediated in part by eukaryotic initiation factor 4E (eIF4E). eIF4E binds the methylated 5' cap of mRNA and recruits it to the ribosome. C.elegans encodes five isoforms of eIF4E (termed IFE-1-5). IFE-1 is expressed primarily in the germline and is the only isoform that associates with P granules by binding directly to PGL-1. P granules also contain stored mRNAs needed for oogenesis and early embryogenesis. Using a strain that lacks IFE-1, we assessed the translational efficiency of maternal mRNAs bound and not bound to P granules by polysome fractionation. Translation of pos-1, pal-1, mex-1, oma-1 and glp-1 mRNA was inefficient in the ife-1(-/-) strain relative to wild type worms. GAPDH mRNA translation was not effected. We also observed differences in the expression of their products, in particular, MEX-1 during oogenesis. In males, secondary spermatocytes fail to complete late stages of maturation in absence of IFE-1. Preliminary evidence shows these immature spermatocytes induce CED-4/Apaf-1 expression, suggesting they undergo apoptosis. In ife-1(-/-) worms fertility was decreased by 80% due to decreased viability of both oocytes and spermatocytes. Our data indicates an essential role for eIF4E (IFE-1 isoform) in late oogenesis and spermatogenesis. We suggest IFE-1 preferentially recruits regulated mRNAs at critical times during germ cell development (Supported by NSF Grant MCB-0321017 to BDK).

Richardson CE et al. (2019) Annu Rev Neurosci "Neurite Development and Repair in Worms and Flies."

Shen K, Richardson CE

[Annu Rev Neurosci, 2019]

How the nervous system is wired has been a central question of neuroscience since the inception of the field, and many of the foundational discoveries and conceptual advances have been made through the study of invertebrate experimental organisms, including Caenorhabditis elegans and Drosophila melanogaster. Although many guidance molecules and receptors have been identified, recent experiments have shed light on the many modes of action for these pathways. Here, we summarize the recent progress in determining how the physical and temporal constraints of the surrounding environment provide instructive regulations in nervous system wiring. We use Netrin and its receptors as an example to analyze the complexity of how they guide neurite outgrowth. In neurite repair, conserved injury detection and response-signaling pathways regulate gene expression and cytoskeletal dynamics. We also describe recent developments in the research on molecular mechanisms of neurite regeneration in worms and flies. Expected final online publication date for the Annual Review of Neuroscience Volume 42 is July 8, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Richardson SJ (2002) Clin Chem Lab Med "The evolution of transthyretin synthesis in vertebrate liver, in primitive eukaryotes and in bacteria."

Richardson SJ

[Clin Chem Lab Med, 2002]

Thyroid hormones are evolutionarily old signal molecules, which can partition between compartments by partitioning into lipid membranes. The role of thyroid hormone distributor proteins is to ensure that sufficient thyroid hormone remains in the bloodstream. Of particular interest is the role of transthyretin, synthesised by the liver and secreted into the blood. In this review, three hypotheses are presented, suggesting the selection pressures leading to the onset of transthyretin synthesis in the liver during evolution. A thyroid hormone distribution network would be a selection advantage over a single protein performing this function. Similarly to the situation in eutherians, hepatic transthyretin synthesis in marsupials is under negative acute phase regulation. The overall three-dimensional structure of transthyretin did not change appreciably during vertebrate evolution. The region of the primary sequence which evolved most was the N-terminal region of the subunit. The N-termini of transthyretin changed from longer and more hydrophobic in reptiles/birds, to shorter and more hydrophilic in eutherians. These changes are correlated with a change in preference from binding of triiodothyronine, to binding thyroxine. As the rest of the molecule had not changed significantly during vertebrate evolution, the gene coding for transthyretin must have evolved prior to the divergence of the vertebrates from the non-vertebrates. Five open reading frames in the genomes of C. elegans (2), S. dublin, S. pombe and E. coli were identified. The protein products are predicted to form tetramers similar to transthyretins. Two possible functions of these proteins are suggested.

Richardson CE et al. (2010) Nature "An essential role for XBP-1 in host protection against immune activation in C. elegans."

Richardson CE, Kim DH, Kooistra T

[Nature, 2010]

The detection and compensatory response to the accumulation of unfolded proteins in the endoplasmic reticulum (ER), termed the unfolded protein response (UPR), represents a conserved cellular homeostatic mechanism with important roles in normal development and in the pathogenesis of disease. The IRE1-XBP1/Hac1 pathway is a major branch of the UPR that has been conserved from yeast to human. X-box binding protein 1 (XBP1) is required for the differentiation of the highly secretory plasma cells of the mammalian adaptive immune system, but recent work also points to reciprocal interactions between the UPR and other aspects of immunity and inflammation. We have been studying innate immunity in the nematode Caenorhabditis elegans, having established a principal role for a conserved PMK-1 p38 mitogen-activated protein kinase (MAPK) pathway in mediating resistance to microbial pathogens. Here we show that during C. elegans development, XBP-1 has an essential role in protecting the host during activation of innate immunity. Activation of the PMK-1-mediated response to infection with Pseudomonas aeruginosa induces the XBP-1-dependent UPR. Whereas a loss-of-function xbp-1 mutant develops normally in the presence of relatively non-pathogenic bacteria, infection of the xbp-1 mutant with P. aeruginosa leads to disruption of ER morphology and larval lethality. Unexpectedly, the larval lethality phenotype on pathogenic P. aeruginosa is suppressed by loss of PMK-1-mediated immunity. Furthermore, hyperactivation of PMK-1 causes larval lethality in the xbp-1 mutant even in the absence of pathogenic bacteria. Our data establish innate immunity as a physiologically relevant inducer of ER stress during C. elegans development and indicate that an ancient, conserved role for XBP-1 may be to protect the host organism from the detrimental effects of mounting an innate immune response to microbes.

Richardson CE et al. (2011) PLoS Genet "Physiological IRE-1-XBP-1 and PEK-1 signaling in Caenorhabditis elegans larval development and immunity."

Kim DH, Richardson CE, Kinkel S

[PLoS Genet, 2011]

Endoplasmic reticulum (ER) stress activates the Unfolded Protein Response, a compensatory signaling response that is mediated by the IRE-1, PERK/PEK-1, and ATF-6 pathways in metazoans. Genetic studies have implicated roles for UPR signaling in animal development and disease, but the function of the UPR under physiological conditions, in the absence of chemical agents administered to induce ER stress, is not well understood. Here, we show that in Caenorhabditis elegans XBP-1 deficiency results in constitutive ER stress, reflected by increased basal levels of IRE-1 and PEK-1 activity under physiological conditions. We define a dynamic, temperature-dependent requirement for XBP-1 and PEK-1 activities that increases with immune activation and at elevated physiological temperatures in C. elegans. Our data suggest that the negative feedback loops involving the activation of IRE-1-XBP-1 and PEK-1 pathways serve essential roles, not only at the extremes of ER stress, but also in the maintenance of ER homeostasis under physiological conditions.

Richardson CE et al. (2019) PLoS Biol "A hormone receptor pathway cell-autonomously delays neuron morphological aging by suppressing endocytosis."

Shen K, Richardson CE, Yee C

[PLoS Biol, 2019]

Neurons have a lifespan that parallels that of the organism and are largely irreplaceable. Their unusually long lifespan predisposes neurons to neurodegenerative disease. We sought to identify physiological mechanisms that delay neuron aging in Caenorhabditis elegans by asking how neuron morphological aging is arrested in the long-lived, alternate organismal state, the dauer diapause. We find that a hormone signaling pathway, the abnormal DAuer Formation (DAF) 12 nuclear hormone receptor (NHR) pathway, functions cell-intrinsically in the dauer diapause to arrest neuron morphological aging, and that same pathway can be cell-autonomously manipulated during normal organismal aging to delay neuron morphological aging. This delayed aging is mediated by suppressing constitutive endocytosis, which alters the subcellular localization of the actin regulator T cell lymphoma Invasion And Metastasis 1 (TIAM-1), thereby decreasing age-dependent neurite growth. Intriguingly, we show that suppressed endocytosis appears to be a general feature of cells in diapause, suggestive that this may be a mechanism to halt the growth and other age-related programs supported by most endosome recycling.

Richardson CE et al. (2014) Elife "PTRN-1, a microtubule minus end-binding CAMSAP homolog, promotes microtubule function in Caenorhabditis elegans neurons."

Goodman MB, Shen K, Richardson CE, Perrino J, Spilker KA, Cueva JG

[Elife, 2014]

In neuronal processes, microtubules (MTs) provide structural support and serve as tracks for molecular motors. While it is known that neuronal MTs are more stable than MTs in non-neuronal cells, the molecular mechanisms underlying this stability are not fully understood. In this study, we used live fluorescence microscopy to show that the C. elegans CAMSAP protein PTRN-1 localizes to puncta along neuronal processes, stabilizes MT foci, and promotes MT polymerization in neurites. Electron microscopy revealed that ptrn-1 null mutants have fewer MTs and abnormal MT organization in the PLM neuron. Animals grown with a MT depolymerizing drug caused synthetic defects in neurite branching in the absence of ptrn-1 function, indicating that PTRN-1 promotes MT stability. Further, ptrn-1 null mutants exhibited aberrant neurite morphology and synaptic vesicle localization that is partially dependent on dlk-1. Our results suggest that PTRN-1 represents an important mechanism for promoting MT stability in neurons. DOI: http://dx.doi.org/10.7554/eLife.01498.001.

Richardson, Claire E. et al. (2011) International Worm Meeting "Physiological IRE-1-XBP-1 and PERK/PEK-1 Signaling in C. elegans Intestinal Homeostasis and Immunity."

Kim, Dennis H., Kinkel, Stephenie, Richardson, Claire E.

[International Worm Meeting, 2011]

Endoplasmic reticulum (ER) stress activates the Unfolded Protein Response (UPR), a compensatory signaling response mediated by the IRE-1, PERK/PEK-1, and ATF-6 transmembrane proteins. Genetic studies have implicated roles for UPR signaling in animal development, but the function of the UPR under physiological conditions, in the absence of chemical agents administered to induce ER stress, is not well understood. Here, we show that in Caenorhabditis elegans, XBP-1 deficiency results in dramatically increased activities of IRE-1 and PEK-1, reflecting constitutive ER stress under basal physiological conditions. Innate immune activation and elevated physiological temperatures exacerbate this basal ER stress and necessitate IRE-1- XBP-1 and PEK-1 signaling for development and survival. Our data suggest that the negative feedback loops involving the activation of the IRE-1-XBP-1 and PERK/PEK-1 pathways serve essential roles not only at the extremes of exogenously imposed ER stress, but also in the maintenance of ER homeostasis under physiological conditions.

Richardson, Claire E. et al. (2009) International Worm Meeting "The IRE-1 Branch of the Unfolded Protein Response Functions in C. elegans Pathogen Resistance During Larval Development."

Kim, Dennis H., Kooistra, Tristan, Richardson, Claire E.

[International Worm Meeting, 2009]

The Unfolded Protein Response (UPR), a mechanism to sense and respond to the accumulation of unfolded proteins in the endoplasmic reticulum (ER), has an important role in development and stress resistance from C. elegans to mammals. We asked if the UPR functions in C. elegans immune defense against the bacterial pathogen Pseudomonas aeruginosa. We found that the conserved IRE-1-XBP-1 branch of the UPR is required specifically for immunity during larval development. IRE-1 is an endoribonuclease that activates the transcription factor XBP-1 by splicing a short exon from its mRNA. Using quantitative PCR, we show that the relative amount of IRE-1-spliced xbp-1 transcript increases after pathogen exposure. Furthermore, a fluorescent reporter for IRE-1 activation is induced after exposure to Pseudomonas specifically at the site of infection - the intestine. We analyzed the relationship between the IRE-1 branch of the UPR and the PMK-1 pathway, which is known to promote C. elegans immunity, and found that IRE-1 activation in response to Pseudomonas is downstream of the PMK-1 pathway. The IRE-1-XBP-1 branch of the UPR has been recently shown to be required for cellular defense against pore-forming toxins, also functioning downstream of PMK-1 (Bischoff et al, 2008). Our data point to a more general role for the UPR in innate immunity against infection. Since PMK-1 pathway activates transcription of putative pathogen resistance proteins, we suggest that the IRE-1 branch of the UPR promotes pathogen resistance by accommodating a PMK-1-driven influx of pathogen resistance proteins to the secretory pathway. Bischof, L.J., Kao, C.-Y., Los, F.C.O., Gonzalez, M.R., Shen, Z., Briggs, S.P., van der Goot, F.G., Aroian, R.V. (2008) Activation of the unfolded protein response is required for defenses against bacterial pore-forming toxin in vivo. PLOS pathogens, 4, 1-11.

Richardson SJ et al. (2005) Ann N Y Acad Sci "Evolution of the thyroid hormone distributor protein transthyretin in microbes, C. elegans, and vertebrates."

Hennebry SC, Smith BJ, Wright HM, Richardson SJ

[Ann N Y Acad Sci, 2005]

Transthyretin (TTR) is an extracellular thyroid hormone distributor protein in vertebrates, whose structure has been highly conserved between fish and humans. However, the ligand preferentially bound by TTR has changed during evolution from 3'',3,5-l-triiodothyronine (T3) to 3'',5'',3,5-l-tetraiodothyronine (T4). We identified genes in the genomes of >50 species of nonvertebrates, which could code for TTR-like proteins. Molecular modeling suggested most would have similar 3D structures and electrostatic surface potentials to vertebrate TTRs. We amplified TTR-like genes from a C. elegans cDNA library, demonstrating that it is transcribed. We synthesized recombinant TTR-like proteins from S. dublin and C. elegans. These proteins form tetramers similarly to vertebrate TTRs, but their ligands remain elusive.