Edbauer D et al. (2004) J Biol Chem "Co-expression of nicastrin and presenilin rescues a loss of function mutant of APH-1."

Kaether C, Haass C, Edbauer D, Steiner H

[J Biol Chem, 2004]

gamma-Secretase is an intramembrane-cleaving aspartyl protease complex that mediates the final cleavage of beta-amyloid precursor protein (APP) to liberate the neurotoxic amyloid-beta peptide implicated in Alzheimers disease. The four proteins presenilin (PS), nicastrin (NCT), APH-1 and PEN-2 are sufficient to reconstitute gamma-secretase activity in yeast. While PS seems to contribute the catalytic core of the gamma-secretase complex, no distinct function could be attributed to the other components so far. In C. elegans mutation of a glycine to an aspartic acid within a conserved GxxxG motif in the fourth transmembrane domain of APH-1 causes a loss of function phenotype. Surprisingly, we now found that the human homologue APH-1a carrying the equivalent mutation G122D is fully active in yeast co-expressing PS1, NCT and PEN-2. To address this discrepancy we expressed APH-1a G122D in HEK293 cells. As previously reported, overexpressed APH-1a G122D was not incorporated into the gamma-secretase complex. Separate overexpression of PS1, NCT or PEN-2 together with APH-1a G122D allowed the formation of heterodimers lacking the other endogenous components. Only the combined overexpression of PS1 and NCT together with APH-1a G122D facilitated the formation of a fully active gamma-secretase complex. Under these conditions APH-1a G122D supported the production of normal amounts of Abeta. We conclude that cooperative effects may stabilize a trimeric complex of APH-1a G122D together with PS1 and NCT. Upon successful complex assembly the GxxxG motif becomes dispensable for gamma-secretase activity.

Koehnlein K et al. (2019) Redox Biol "A Caenorhabditis elegans ortholog of human selenium-binding protein 1 is a pro-aging factor protecting against selenite toxicity."

Klotz LO, Koehnlein K, Kaether C, Urbanek P, Steinbrenner H, Guerrero-Gomez D, Priebs J, Miranda-Vizuete A, Koch P, Urban N

[Redox Biol, 2019]

Human selenium-binding protein 1 (SELENBP1) was originally identified as a protein binding selenium, most likely as selenite. SELENBP1 is associated with cellular redox and thiol homeostasis in several respects, including its established role as a methanethiol oxidase that is involved in degradation of methanethiol, a methionine catabolite, generating hydrogen sulfide (H₂S) and hydrogen peroxide (H₂O₂). As both H₂S and reactive oxygen species (such as H₂O₂) are major regulators of Caenorhabditis elegans lifespan and stress resistance, we hypothesized that a SELENBP1 ortholog in C. elegans would likely be involved in regulating these aspects. Here we characterize Y37A1B.5, a putative selenium-binding protein 1 ortholog in C. elegans with 52% primary structure identity to human SELENBP1. While conferring resistance to toxic concentrations of selenite, Y37A1B.5 also attenuates resistance to oxidative stress and lowers C. elegans lifespan: knockdown of Y37A1B.5 using RNA interference resulted in an approx. 10% increase of C. elegans lifespan and an enhanced resistance against the redox cycler paraquat, as well as enhanced motility. Analyses of transgenic reporter strains suggest hypodermal expression and cytoplasmic localization of Y37A1B.5, whose expression decreases with worm age. We identify the transcriptional coregulator MDT-15 and transcription factor EGL-27 as regulators of Y37A1B.5 levels and show that the lifespan extending effect elicited by downregulation of Y37A1B.5 is independent of known MDT-15 interacting factors, such as DAF-16 and NHR-49. In summary, Y37A1B.5 is an ortholog of SELENBP1 that shortens C. elegans lifespan and lowers resistance against oxidative stress, while allowing for a better survival under toxic selenite concentrations.

Ridolfi, Verena Alexia et al. (2021) International Worm Meeting "Downregulation of SEMO-1, a novel hydrogen sulfide-generating C. elegans enzyme, enhances lifespan: role of AAK-1/-2"

Priebs, Josephine, Ridolfi, Verena Alexia, Philipp, Thilo Magnus, Kohnlein, Karl, Klotz, Lars-Oliver, Steinbrenner, Holger

[International Worm Meeting, 2021]

The C. elegans ortholog of human selenium-binding protein 1 (SELENBP1), Y37A1B.5, is a pro-aging factor that confers resistance to high doses of selenite (1). SELENBP1 was recently identified as a methanethiol oxidase (MTO), catalyzing the conversion of methanethiol to hydrogen sulfide (H2S), hydrogen peroxide (H2O2) and formaldehyde. Here, we tested whether Y37A1B.5 has MTO activity and whether the AMPK orthologs AAK-1/-2 are involved in the effects of the protein on C. elegans lifespan. We developed an MTO activity assay that is based on in situ-generation of methanethiol from methionine as catalyzed by a bacterial recombinant L-methionine gamma-lyase, followed by detection of two methanethiol oxidation products, H2S and H2O2. Using this assay, we demonstrate MTO activity of isolated recombinant Y37A1B.5, similar to recombinant human SELENBP1. Moreover, MTO activity was detected in lysates from wild-type nematodes but not in lysates from a newly generated Y37A1B.5-deficient mutant strain, suggesting that the Y37A1B.5 protein is the major C. elegans MTO. Thus, Y37A1B.5 was named SEMO-1 (SELENBP1 ortholog with MTO activity). It is a novel methanethiol oxidase and therefore a novel potential source of H2S and H2O2, two molecules known to affect lifespan in C. elegans. A Y37A1B.5/SEMO-1-deficient mutant strain showed an extended lifespan similar to the previously reported worms exposed to Y37A1B.5-specific RNAi (1). SEMO-1, therefore, is a factor apparently shortening C. elegans lifespan. Interestingly, lifespan extension following SEMO-1 depletion was abrogated in an AAK-deficient strain (NB245; deficient in both isoforms of the catalytic AAK subunit), and vice versa, SEMO-1 depletion through RNAi appeared to enhance AAK phosphorylation in wild-type worms. As AAK activity is known to be related to C. elegans lifespan, we propose that the extended lifespan of SEMO-1-depleted worms is caused by AAK activation. The mode of AAK activation following SEMO-1 depletion remains to be identified. (1) Kohnlein K, Urban N, Guerrero-Gomez D, Steinbrenner H, Urbánek P, Priebs J, Koch P, Kaether C, Miranda-Vizuete A, Klotz LO. Redox Biol. 28:101323 (2020).

Yamasaki A et al. (2006) J Neurosci "The GxGD motif of presenilin contributes to catalytic function and substrate identification of gamma-secretase."

Yamasaki A, Eimer S, Kaether C, Haass C, Baumeister R, Steiner H, Smialowska A, Okochi M

[J Neurosci, 2006]

Gamma-secretase is a multisubunit aspartyl protease complex that catalyzes intramembrane cleavage of beta-amyloid precursor protein (APP), a substrate key to Alzheimer''s disease pathogenesis, and of Notch, a substrate crucial for cell differentiation. How gamma-secretase recognizes and selects substrates is currently barely understood. Recent data suggest that its subunit nicastrin serves as an initial substrate receptor, which might subsequently forward substrates to the active site domain located in its catalytic subunit presenilin (PS), where an additional substrate binding site has been proposed. We now used an active site domain swapping approach of PS1 with its most distant homolog, spermatogenesis defective (SPE-4), to identify sequence determinants in this region. Strikingly, when the active site domain of PS1 was exchanged with that of SPE-4, the chimeric protein, PS1/SPE-4(6/7), supported APP but not Notch processing. In addition, PS1/SPE-4(6/7) was strongly impaired in Caenorhabditis elegans Notch signaling in vivo. Mapping experiments identified a single amino acid at position x of the GxGD motif, which contains one of the two active site aspartates, to be responsible for the observed defect in Notch processing and signaling. Our data thus implicate a role of the GxGD motif in catalytic function and substrate identification of gamma-secretase.

Zhao Y et al. (2007) BMC Genomics "Poly-G/poly-C tracts in the genomes of Caenorhabditis."

Zhao Y, O'Neil NJ, Rose AM

[BMC Genomics, 2007]

ABSTRACT: BACKGROUND: In the genome of Caenorhabditis elegans, homopolymeric poly-G/poly-C tracts (G/C tracts) exist at high frequency and are maintained by the activity of the DOG-1 protein. The frequency and distribution of G/C tracts in the genomes of C. elegans and the related nematode, C. briggsae were analyzed to investigate possible biological roles for G/C tracts. RESULTS: In C. elegans, G/C tracts are distributed along every chromosome in a non-random pattern. Most G/C tracts are within introns or are close to genes. Analysis of SAGE data showed that G/C tracts correlate with the levels of regional gene expression in C. elegans. G/C tracts are over-represented and dispersed across all chromosomes in another Caenorhabditis species, C. briggase. However, the positions and distribution of G/C tracts in C. briggsae differ from those in C. elegans. Furthermore, the C. briggsae dog-1 ortholog CBG19723 can rescue the mutator phenotype of C. elegans dog-1 mutants. CONCLUSIONS: The abundance and genomic distribution of G/C tracts in C. elegans, the effect of G/C tracts on regional transcription levels, and the lack of positional conservation of G/C tracts in C. briggsae suggest a role for G/C tracts in chromatin structure but not in the transcriptional regulation of specific genes.

Bhagwati P Gupta et al. (2002) West Coast Worm Meeting "Genetic analysis of the vulval mutants in C. briggsae"

Shahla Gharib, Bhagwati P Gupta, Paul W Sternberg, Jennifer X Li

[West Coast Worm Meeting, 2002]

To understand the evolution of developmental mechanisms, we are doing a comparative analysis of vulval patterning in C. elegans and C. briggsae. C. briggsae is closely related to C. elegans and has identical looking vulval morphology. However, recent studies have indicated subtle differences in the underlying mechanisms of development. The recent completion of C. briggsae genome sequence by the C. elegans Sequencing Consortium is extremely valuable in identifying the conserved genes between C. elegans and C. briggsae.

Antika TR et al. (2023) J Biol Chem "Sequence-specific targeting of C. elegans C-Ala to the D-loop of tRNAAla."

Horng JC, Hsu HL, Nazilah KR, Wang CC, Wang TL, Wang SC, Antika TR, Chuang TH, Chrestella DJ, Wang SW, Tseng YK, Pan HC

[J Biol Chem, 2023]

Alanyl-tRNA synthetase (AlaRS) retains a conserved prototype structure throughout its biology. Nevertheless, its C-terminal domain (C-Ala) is highly diverged and has been shown to play a role in either tRNA or DNA binding. Interestingly, we discovered that Caenorhabditis elegans cytoplasmic C-Ala (Ce-C-Ala_c) robustly binds both ligands. How Ce-C-Ala_c targets its cognate tRNA and whether a similar feature is conserved in its mitochondrial counterpart remain elusive. We show that the N- and C-terminal subdomains of Ce-C-Ala_c are responsible for DNA and tRNA binding, respectively. Ce-C-Ala_c specifically recognized the conserved invariant base G¹⁸ in the D-loop of tRNA^Ala through a highly conserved lysine residue, K934. Despite bearing little resemblance to other C-Ala domains, C. elegans mitochondrial C-Ala (Ce-C-Ala_m) robustly bound both tRNA^Ala and DNA and maintained targeting specificity for the D-loop of its cognate tRNA. This study uncovers the underlying mechanism of how C. elegans C-Ala specifically targets the D-loop of tRNA^Ala.

Blumenthal TE et al. (1994) Worm Breeder's Gazette "C. elegans U2AF 65."

Zorio DAR, Lea K, Blumenthal TE

[Worm Breeder's Gazette, 1994]

C. elegans U2AF65

Oomura, S. et al. (2019) International Worm Meeting "Early embryogenesis of C. inopinata, a sibling species of C.elegans."

Matsumura, Y., Haruta, N., Hoshi, Y., Sugimoto, A., Oomura, S.

[International Worm Meeting, 2019]

C. inopinata is a newly discovered sibling species of C. elegans. Despite their phylogenetic closeness, they have many differences in morphology and ecology. For example, while C. elegans is hermaphroditic, C. inopinata is gonochoristic; C. inopinata is nearly twice as long as C. elegans. A comparative analysis of C. elegans and C. inopinata enables us to study how genomic changes cause these phenotypic differences. In this study, we focused on early embryogenesis of C. inopinata. First, by the microparticle bombardment method we made a C. inopinata line that express GFP::histone in whole body, and compared the early embryogenesis with C. elegans by DIC and fluorescent live imaging. We found that the position of pronuclei and polar bodies were different between these two species. In C. elegans, the female and male pronuclei first become visible in anterior and posterior sides, respectively, then they meet at the center of embryo. On the other hand, the initial position of pronuclei were more closely located in C. inopinata. Also, the polar bodies usually appear in the anterior side of embryo in C. elegans, but they appeared at random positions in C. inopinata. Therefore, we infer that C. inopinata may have a different polarity formation mechanism from that in C. elegans. We are also analyzing temperature dependency of embryogenesis in C. inopinata, whose optimal temperature is ~7 degree higher than that in C. elegans.

Guven K (1995) Journal of Thermal Biology "Differential expression of hsp70 proteins in response to heat and cadmium in Caenorhabditis elegans."

Guven K

[Journal of Thermal Biology, 1995]

1. The patterns of HSP70 expression induced in Caenorhabditis elegans by mild (31 degrees C) or severe (34 degrees C) heat shock, and by cadmium ions at 31 degrees C, have been compared with those expressed constitutively ill 20 degrees C controls by 1- and a-dimensional immunoblotting. 2. The 2D spot patterns become more complex with increasing severity of stress (34 degrees C > 31 degrees C + Cd > 31 degrees C > 20 degrees C). 3. A stress-inducible transgene construct is minimally active at 31 degrees C, but is abundantly expressed in the presence of cadmium or at 34 degrees C. 4. Differing degrees or types of stress may differentially induce available hsp70