Feng H et al. (2013) Genesis "The Caenorhabditis elegans homeobox gene ceh-19 is required for MC motorneuron function."

Feng H, Hope IA

[Genesis, 2013]

Simplicity has made C. elegans pharyngeal development a particularly well-studied subject. Nevertheless, here we add the previously uncharacterized homeobox gene F20D12.6/ceh-19 to the set of transcription factor genes involved. GFP reporter assays revealed that ceh-19 is expressed in three pairs of neurons, the pharyngeal pace-maker neurons MC, the amphid neurons ADF and the phasmid neurons PHA. ceh-19(tm452) mutants are viable and fertile, but grow slightly slower, produce less progeny over a prolonged period, and live longer than the wild type. These phenotypes are likely due to the moderately reduced pharyngeal pumping speed arising from the impairment of MC activity. MC neurons are still born in the ceh-19 mutants but display various morphological defects. ceh-19 expression in MC is completely lost in progeny from animals subject to RNAi for pha-4, which encodes an organ-specifying forkhead transcription factor. CEH-19 is required for the activation in MCs of the excitatory FMRFamide-like neuropeptide-encoding gene flp-2. A regulatory pathway from pha-4 through ceh-19 to flp-2 is thereby defined. The resilience of MC identity in the absence of CEH-19 may reflect the buffering qualities of transcription factor regulatory networks.

Feng H et al. (2012) Methods Mol Biol "Expression pattern analysis of regulatory transcription factors in Caenorhabditis elegans."

Hope IA, Feng H, Craig HL

[Methods Mol Biol, 2012]

Expression pattern data are fundamental to understanding transcriptional regulatory networks and the biological significance of such networks. For Caenorhabditis elegans, expression pattern analysis of transcription factor genes, with cellular resolution, typically involves generation of transcription factor gene/reporter gene fusions. This is followed by the creation of C. elegans strains transgenic for, and determination of expression patterns driven by, these fusions. Physiologically relevant regulatory relationships between transcription factors are both inferred from their expression patterns, in combination with protein-DNA interaction data, and evidenced from alterations of expression patterns when networks are disturbed.

Feng H et al. (2012) Gene "A regulatory cascade of three transcription factors in a single specific neuron, DVC, in Caenorhabditis elegans."

Feng H, Walhout AJ, Reece-Hoyes JS, Hope IA

[Gene, 2012]

Homeobox proteins are critical regulators of developmental gene transcription and cell specification. Many insights into transcriptional regulation have been gained from studies in the nematode Caenorhabditis elegans. We investigated the expression and regulation of the C. elegans homeobox gene ceh-63, which encodes a single-homeodomain transcription factor of 152 amino acids. ceh-63 is expressed in the interneuron DVC in both sexes, from late embryogenesis through adulthood, and two pairs of uterine cells in reproductive hermaphrodites only. A reporter gene fusion, encoding GFP fused to the full-length CEH-63, also drove weak inconsistent expression in additional unidentified cells in the head and tail. A potential ceh-63 null mutant had no obvious abnormalities, except for a possible increase in subtle defects of the DVC axon projection. No behavioural responses were observed upon either laser ablation of DVC or activation of DVC through light stimulation of channelrhodopsin-2 specifically expressed in this neuron. The function of DVC therefore remains enigmatic. A transcriptional regulatory cascade operating in DVC was defined from the LIM-homeodomain protein CEH-14 through CEH-63 to the helix-turn-helix transcription factor MBR-1. Both CEH-14 and CEH-63 individually bound the mbr-1 promoter in a yeast one-hybrid assay. A model is proposed suggesting that CEH-14 activates ceh-63 and then along with CEH-63 co-ordinately activates mbr-1.

Feng H et al. (2006) J Biol Chem "Conserved domains subserve novel mechanisms and functions in DKF-1, a Caenorhabditis elegans protein kinase D."

Rubin CS, Ren M, Feng H

[J Biol Chem, 2006]

Protein kinase D (PKD) isoforms are effectors in signaling pathways controlled by diacylglycerol (DAG). PKDs contain conserved DAG binding (C1a, C1b), PH and S/T kinase domains. However, properties of conserved domains may vary within the context of distinct PKD polypeptides. Such functional/structural malleability (plasticity) was explored by studying C. elegans D kinase family-1 (DKF-1), a PKD that governs locomotion in vivo. Phorbol ester binding with C1b alone activates classical PKDs by relieving C1-mediated inhibition. In contrast, C1a avidly ligates PMA and anchors DKF-1 at plasma membrane. C1b binds PMA (moderate affinity) and co-operates with C1a in targeting DKF-1 to membranes. Mutations at a "Pro(11)" position in C1 domains are inactivating; kinase activity is minimal at PMA concentrations that stimulate wild type (WT) DKF-1 ~10-fold. DKF-1 mutants exhibited unchanged, maximum kinase activity after cells were incubated with high PMA concentrations. Titration in situ revealed that translocation and activation of WT and mutant DKF-1 are tightly and quantitatively linked at all PMA concentrations. C1 domains are positive regulators of phosphotransferase activity that dock DKF-1 with pools of activating lipid. A PH domain inhibits kinase activity in classical PKDs. DKF-1 PH module neither inhibits catalytic activity, nor binds phosphoinositides. The PH module is an obligatory, positive regulator of DKF-1 activity that is compromised by mutation of K(298) or W(396). Phosphorylation of T(588) switches on DKF-1 kinase activity. Persistent phosphorylation of T(588) (activation loop) promotes ubiquitinylation and proteasome-mediated degradation of DKF-1. Each DKF-1 domain displays novel properties indicative of functional malleability (plasticity).

Feng H et al. (1999) Nat Cell Biol "CUL-2 is required for the G1-to-S-phase transition and mitotic chromosome condensation in Caenorhabditis elegans."

Zhong W, Punkosdy G, Seabolt EK, Zhou L, Feng H, Gu S, Kipreos ET

[Nat Cell Biol, 1999]

The human cullin protein CUL-2 functions in a ubiquitin-ligase complex with the von Hippel-Lindau (VHL) tumour suppressor protein. Here we show that, in Caenorhabditis elegans, cul-2 is expressed in proliferating cells and is required at two distinct points in the cell cycle, the G1-to-S-phase transition and mitosis. cul-2 mutant germ cells undergo a G1-phase arrest that correlates with accumulation of CKI-1, a member of the CIP/KIP family of cyclin-dependent-kinase inhibitors. In cul-2 mutant embryos, mitotic chromosomes are unable to condense, leading to unequal DNA segregation, chromosome bridging and the formation of multiple nuclei.

Feng H et al. (2006) J Biol Chem "Characterization of a novel protein kinase D: Caenorhabditis elegans DKF-1 is activated by translocation-phosphorylation and regulates movement and growth in vivo."

Hall DH, Ren M, Rubin CS, Feng H, Wu SL

[J Biol Chem, 2006]

Protein kinase D (PKD) isoforms are protein kinase C (PKC) effectors in diacylglycerol (DAG)-regulated signaling pathways. Key physiological processes are placed under DAG control by the distinctive substrate specificity and intracellular distribution of PKDs. Comprehension of PKDs'' roles in homeostasis and signal transduction requires further knowledge of regulatory interplay among PKD and PKC isoforms, analysis of PKC-independent PKD activation and characterization of functions controlled by PKDs in vivo. C. elegans and mammals share conserved signaling mechanisms, molecules and pathways Thus, characterization of C. elegans PKDs could yield insights into regulation and function that apply to all eukaryotic PKDs. C. elegans DKF-1 (D Kinase Family-1) contains tandem, DAG binding (C1) modules, a PH domain and S/T protein kinase segment, which are homologous with domains in classical PKDs. DKF-1 and PKDs have similar substrate specificities. PMA switches on DKF-1 catalytic activity in situ by promoting phosphorylation of a single amino acid T(588), in the activation loop. DKF-1 phosphorylation and activation are unaffected when PKC activity is eliminated by inhibitors. Both phosphorylation and kinase activity of DKF-1 are extinguished by substituting A for T(588), Q for K(455) ("kinase dead") or incubating with protein phosphatase 2C. Thus, DKF-1 is a PMA-activated, PKC-independent D kinase. In vivo, dkf-1 gene promoter activity is evident in neurons. Both dkf-1 gene disruption (null phenotype) and RNAi-mediated depletion of DKF-1 protein cause lower body paralysis. Targeted DKF-1 expression corrected this locomotory defect in dkf-1 null animals. Supra-physiological expression of DKF-1 limited C. elegans growth to ~60% of normal length.

Feng H et al. (2007) J Biol Chem "Properties, regulation, and in vivo functions of a novel protein kinase D: Caenorhabditis elegans DKF-2 links diacylglycerol second messenger to the regulation of stress responses and life span."

Feng H, Ren M, Chen L, Rubin CS

[J Biol Chem, 2007]

Protein kinase D (PKD) isoforms are protein kinase C (PKC) effectors in signaling cascades controlled by diacylglycerol (DAG). All PKDs are regulated by DAG/PMA-binding C1 domains and an activation loop (A-loop). To understand how PKD isoforms diversify DAG signaling networks, it is essential to determine redundant and novel properties of their regulatory domains; characterize factors controlling PKD gene expression; and discover their in vivo physiological roles. Studies on a novel PKD, C. elegans DKF-2 (D kinase family-2), addressed these topics. The C1b domain mediates PMA-induced translocation and activation of DKF-2. However, when DAG is elevated, C1a and C1b contribute equally to targeting/activation of DKF-2. DKF-2 C1 domains do not inhibit catalytic activity; they mediate delivery of DKF-2 to a membrane where PKC phosphorylates S(925) and S(929) in the A-loop. This potently stimulates DKF-2 catalytic activity. Phosphorylation of S(925) alone switches on 70% of maximal kinase activity. Persistent phosphorylation of S(929) tags DKF-2 for proteasomal degradation; P-Ser(925) plays a minor role in DKF-2 degradation. GATA enhancer sequences govern DKF-2 expression in intestine in vivo. Adult lifespan increases 40% in animals lacking DKF-2. In thermally stressed WT animals, the DAF-16 transcription factor is segregated from nuclei of adult intestinal cells. In contrast, DAF-16 enters adult intestinal nuclei of DKF-2 deficient, thermally-stressed animals, where it can trigger gene transcription that protects against various insults. The results suggest a mechanism for increased longevity and show that a PKD links DAG signals to regulation of stress responses and lifespan.

Sun J et al. (2013) Exp Parasitol "Parasitism of secondary-stage juvenile of Heterodera glycines and four larva stages of Caenorhabditis elegans by Hirsutella spp."

Sun J, Xie H, Xiang M, Liu X, Qiu J

[Exp Parasitol, 2013]

The fungi Hirsutella rhossiliensis and Hirsutella minnesotensis generally parasitize only plant-parasitic nematodes in nature but parasitize the bacterivorous nematode Caenorhabditis elegans on agar plates. To establish a model system for studying the interaction between fungi and nematodes, we compared the parasitism of the first- to fourth-stage larvae (L1-L4) of C. elegans and second-stage juvenile (J2) of Heterodera glycines by twenty isolates of Hirsutella spp. Although parasitism differed substantially among isolates, both H. minnesotensis and H. rhossiliensis parasitized a higher percentage of H. glycines J2s than of C. elegans larvae. Parasitism of C. elegans L1s was correlated with parasitism of H. glycines J2s. Parasitism of C. elegans by H. rhossiliensis and H. minnesotensis was negatively correlated with larva size and motility, i.e., parasitism was higher for the younger stages. The C. elegans L1 is recommended for studying parasitism of nematodes by H. rhossiliensis and H. minnesotensis.

Fei YJ et al. (2000) J Biol Chem "A novel H(+)-coupled oligopeptide transporter (OPT3) from Caenorhabditis elegans with a predominant function as a H(+) channel and an exclusive expression in neurons."

Leibach FH, Romero MF, Krause MW, Huang W, Ganapathy V, Fei YJ, Liu JC

[J Biol Chem, 2000]

We have cloned and functionally characterized a novel, neuron-specific, H(+)-coupled oligopeptide transporter (OPT3) from Caenorhabditis elegans that functions predominantly as a H(+) channel. The opt3 gene is approximately 4.4 kilobases long and consists of 13 exons. The cDNA codes for a protein of 701 amino acids with 11 putative transmembrane domains. When expressed in mammalian cells and in Xenopus laevis oocytes, OPT3 cDNA induces H(+)-coupled transport of the dipeptide glycylsarcosine. Electrophysiological studies of the transport function of OPT3 in Xenopus oocytes show that this transporter, although capable of mediating H(+)-coupled peptide transport, functions predominantly as a H(+) channel. The H(+) channel activity of OPT3 is approximately 3-4-fold greater than the H(+)/peptide cotransport activity as determined by measurements of H(+) gradient-induced inward currents in the absence and presence of the dipeptide using the two-microelectrode voltage clamp technique. A downhill influx of H(+) was accompanied by a large intracellular acidification as evidenced from the changes in intracellular pH using an ion-selective microelectrode. The H(+) channel activity exhibits a K(0.5)(H) of 1.0 microM at a membrane potential of -50 mV. At the level of primary structure, OPT3 has moderate homology with OPT1 and OPT2, two other H(+)-coupled oligopeptide transporters previously cloned from C. elegans. Expression studies using the opt3::gfp fusion constructs in transgenic C. elegans demonstrate that opt3 gene is exclusively expressed in neurons. OPT3 may play an important physiological role as a pH balancer in the maintenance of H(+) homeostasis in C. elegans.

Wilson PA et al. (1982) Parasitology "Strongyloides ratti (homogonic): the time-course of early migration in the generalized host deduced from experiments in lactating rats."

Steven GE, Simpson NE, Wilson PA

[Parasitology, 1982]

Unsuckled mother rats given a 1 h suckling stimulus 3 h after subcutaneous injection of an exact dose of homogonic Strongyloides ratti allow fewer worms to develop in their intestines by day 9 than nulliparous rats (Wilson & Simpson, 1981). This effect is studied in more detail in terms of the length of time between weaning and stimulus (W leads to S) and injection and stimulus (I leads to S). It was observable with a W leads to S of 30 h but this and a period of 5 h were less effective than 24 h. With W leads to S constant at 24 h, significantly more worms developed in mothers when I leads to S was 24 h compared to 3 h and 10 h (P less than 0.005). The data, combined with those from nulliparous controls, are presented as a measure of the change with time of numbers of larvae in that compartment of the system which gives access to the stimulated mammary gland. It is argued that the particular compartment is the local lymph node draining the injection site and that the kinetics deduced are applicable to migration in the rat in general.