Regulation of Easter activity is required for shaping the Dorsal gradient in the<i>Drosophila</i>embryo

Chang, Andy J.; Morisato, Donald

doi:10.1242/dev.00161

Cited by 22 publications

(15 citation statements)

References 46 publications

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“…5A), probably due to the positive feedback regulation of the Toll pathway (30). As reported previously (36), Spaetzle precursors expressed in adults appeared as multiple bands on Western blots (Fig. 5A).…”

Section: Chmp2b Intron5supporting

confidence: 80%

Genetic screen identifies serpin5 as a regulator of the toll pathway and CHMP2B toxicity associated with frontotemporal dementia

Ahmad

Sweeney

Lee

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

104

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Frontotemporal dementia (FTD) is the most common form of dementia before 60 years of age. Rare pathogenic mutations in CHMP2B, which encodes a component of the endosomal sorting complex required for transport (ESCRT-III), are associated with FTD linked to chromosome 3 (FTD3). Animal models of FTD3 have not yet been reported, and what signaling pathways are misregulated by mutant CHMP2B in vivo is unknown. Here we report the establishment of a Drosophila model of FTD3 and show the genetic interactions between mutant CHMP2B and other components of ESCRT. Through an unbiased genome-wide screen, we identified 29 modifier loci and found that serpin5 (Spn5), a largely uncharacterized serine protease inhibitor, suppresses the melanization phenotype induced by mutant CHMP2B in the fly eye. We also found that Spn5 is a negative regulator of the Toll pathway and functions extracellularly, likely by blocking the proteolytic activation of Spaetzle, the Toll receptor ligand. Moreover, Spn5 inhibited activation of the Toll pathway by mutant CHMP2B. Our findings identify Spn5 as a regulator of the Toll pathway and CHMP2B toxicity and show that the Toll pathway is a major signaling pathway misregulated by mutant CHMP2B in vivo. This fly model will be useful to further dissect genetic pathways that are potentially relevant to the pathogenesis and treatment of FTD.Drosophila ͉ endosomal sorting complex required for transport (ESCRT) ͉ neurodegeneration ͉ modifier screen F rontotemporal dementia (FTD), a major clinical syndrome of frontotemporal lobar degeneration (FTLD), is a progressive neurodegenerative condition associated with focal atrophy of the frontal and/or temporal lobes (1, 2). Although FTD is the most common form of senile dementia in people under 60 years of age, the molecular pathogenesis remains poorly understood (3). In some FTD brains, tau neurofibrillary tangles are present in diseased neurons, and some tau mutations are indeed pathogenic (4, 5). Several new genes have been implicated in FTD with tau-negative pathology, including those encoding valosin-containing protein (VCP) (6), CHMP2B (7), progranulin (8, 9), and TDP-43 (10, 11). The molecular pathways affected by these mutations and how they contribute to disease progression remain unclear.Although dominantly inherited CHMP2B mutations associated with FTD linked to chromosome 3 (FTD3) are rare (7,12,13), studies of CHMP2B neurotoxicity in cell culture models have been informative. CHMP2B is the ortholog of the yeast protein Vps2, a component of the endosomal sorting complex required for transport (ESCRT-III), which is involved in the biogenesis of multivesicular bodies and other biological processes (14). In undifferentiated PC12 cells, ectopic overexpression of CHMP2B Intron5 , a mutant form of CHMP2B missing 35 aa at the C terminus, led to the accumulation of vesicular structures (7). In cultured rodent cortical neurons and other cell types, CHMP2B Intron5 caused dendritic retraction, autophagosome accumulation, and neuronal cell loss (15,16). At the mol...

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Section: Chmp2b Intron5supporting

confidence: 80%

Genetic screen identifies serpin5 as a regulator of the toll pathway and CHMP2B toxicity associated with frontotemporal dementia

Ahmad

Sweeney

Lee

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

104

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“…The P373Y (P225Y) mutant had significantly stronger ventralizing capacity than did P373S (P225S) and only rarely resulted in wild-type gastrulation or embryo hatching, even when titrated to a level (0.2 mg/ml) in which incomplete rescue was commonly seen together with weak ventralization. This behavior differs from that of previously described ventralizing easter alleles (24), which can be titrated to give a significant level of wild-type rescue, and suggests that this mutant enzyme may be less influenced by normal regulatory controls (43). A P373I (P225I) substitution resulted in a significant loss of activity with only weak partial rescue seen.…”

Section: Fig 5 Representative Cuticle Patterns Of Injected Embryoscontrasting

confidence: 72%

Three-dimensional Models of Proteases Involved in Patterning of the Drosophila Embryo

Rose¹,

LeMosy²,

Cantwell³

et al. 2003

Journal of Biological Chemistry

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Three-dimensional models of the catalytic domains of Nudel (Ndl), Gastrulation Defective (Gd), Snake (Snk), and Easter (Ea), and their complexes with substrate suggest a possible organization of the enzyme cascade controlling the dorsoventral fate of the fruit fly embryo. The models predict that Gd activates Snk, which in turn activates Ea. Gd can be activated either autoproteolytically or by Ndl. The three-dimensional models of each enzyme-substrate complex in the cascade rationalize existing mutagenesis data and the associated phenotypes. The models also predict unanticipated features like a Ca 2؉ binding site in Ea and a Na ؉ binding site in Ndl and Gd. These binding sites are likely to play a crucial role in vivo as suggested by mutant enzymes introduced into embryos as mRNAs. The mutations in Gd that eliminate Na ؉ binding cause an apparent increase in activity, whereas mutations in Ea that abrogate Ca 2؉ binding result in complete loss of activity. A mutation in Ea predicted to introduce Na ؉ binding results in apparently increased activity with ventralization of the embryo, an effect not observed with wild-type Ea mRNA.Several genes in the dorsal group (1) are involved in extracellular events that lead to dorsoventral polarization of the Drosophila melanogaster embryo. nudel, pipe, and windbeutel are expressed by somatic follicle cells during mid-oogenesis, whereas easter, gastrulation defective, snake, and spä tzle are expressed by the nurse cells and oocyte. These genes were identified in several large scale genetic screens for maternal effect mutations that cause homozygous mutant females to produce embryos with abnormal cell fates (2). Among the dorsal group genes, nudel, gastrulation defective, snake, and easter encode proteins containing serine protease domains of the trypsin family. Easter (Ea), 1

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“…First, the pro-domain does not interfere with the activation of Toll. Studies using Western blot analysis showed that pro-domain remains stable after cleavage by Easter and also presented evidence that it can act as a negative regulator of Toll signaling, either by directly antagonizing the receptor or by modulating the activity of the protease cascade (23,28). As isolated C106 and the pro-domain/C106 activate Toll with very similar characteristics, it appears that 7 A. Weber and P. Ligoxygakis, personal communication.…”

Section: Functions Of the Spätzle Pro-domain In Biosynthesis Andmentioning

confidence: 99%

Role of the Spätzle Pro-domain in the Generation of an Active Toll Receptor Ligand

Weber

Gangloff

Moncrieffe

et al. 2007

Journal of Biological Chemistry

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The cytokine Spätzle is the ligand for Drosophila Toll, the prototype of an important family of membrane receptors that function in embryonic patterning and innate immunity. A dimeric precursor of Spätzle is processed by an endoprotease to produce a form (C-106) that cross-links Toll receptor ectodomains and establishes signaling. Here we show that before processing the pro-domain of Spätzle is required for correct biosynthesis and secretion. We mapped two loss-of-function mutations of Spätzle to a discrete site in the pro-domain and showed that the phenotype arises because of a defect in biosynthesis rather than signaling. We also report that the pro-domain and C-106 remain associated after cleavage and that this processed complex signals with the same characteristics as the C-terminal fragment. These results suggest that before activation the determinants on C-106 that bind specifically to Toll are sequestered by the pro-domain and that proteolytic processing causes conformational rearrangements that expose these determinants and enables binding to Toll. Furthermore, we show that the pro-domain is released when the Toll extracellular domain binds to the complex, a finding that has implications for the generation of a signaling-competent Toll dimer.

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Regulation of Easter activity is required for shaping the Dorsal gradient in theDrosophilaembryo

Cited by 22 publications

References 46 publications

Genetic screen identifies serpin5 as a regulator of the toll pathway and CHMP2B toxicity associated with frontotemporal dementia

Genetic screen identifies serpin5 as a regulator of the toll pathway and CHMP2B toxicity associated with frontotemporal dementia

Three-dimensional Models of Proteases Involved in Patterning of the Drosophila Embryo

Role of the Spätzle Pro-domain in the Generation of an Active Toll Receptor Ligand

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