6 research outputs found
An Activating Mutation in sos-1 Identifies Its Dbl Domain as a Critical Inhibitor of the Epidermal Growth Factor Receptor Pathway during Caenorhabditis elegans Vulval Development
Proper regulation of receptor tyrosine kinase (RTK)-Ras-mitogen-activated protein kinase (MAPK) signaling pathways is critical for normal development and the prevention of cancer. SOS is a dual-function guanine nucleotide exchange factor (GEF) that catalyzes exchange on Ras and Rac. Although the physiologic role of SOS and its CDC25 domain in RTK-mediated Ras activation is well established, the in vivo function of its Dbl Rac GEF domain is less clear. We have identified a novel gain-of-function missense mutation in the Dbl domain of Caenorhabditis elegans SOS-1 that promotes epidermal growth factor receptor (EGFR) signaling in vivo. Our data indicate that a major developmental function of the Dbl domain is to inhibit EGF-dependent MAPK activation. The amount of inhibition conferred by the Dbl domain is equal to that of established trans-acting inhibitors of the EGFR pathway, including c-Cbl and RasGAP, and more than that of MAPK phosphatase. In conjunction with molecular modeling, our data suggest that the C. elegans mutation, as well as an equivalent mutation in human SOS1, activates the MAPK pathway by disrupting an autoinhibitory function of the Dbl domain on Ras activation. Our work suggests that functionally similar point mutations in humans could directly contribute to disease
Negative regulators of the let-23 EGF receptor in Caenorhabditis elegans vulval differentiation
Vulval induction in C. elegans is an example of the use of an EGF
(Epidermal Growth Factor) mediated signal transduction system. At least
five genes are involved in the negative regulation of vulval induction.
Mutations at the silent locus sli-1 (suppressor of lineage defect) are
sufficient to suppress all of the phenotypes associated with hypomorphic
alleles of let-23. sli-1 functions to modify the activity of let-23 but muations
at sli-1 do not bypass the requirement for let-23. Based on the phenotypes of
animals bearing mutations at sli-1 and other genes, sli-1 may function at or
near the let-23 or sem-5 step of vulval differentiation.
Null alleles of the pleiotropic locus unc-101 cause a number of mutant
phenotypes including neural defects and suppression of the vulval defects
associated with some weak let-23 mutations. These unc-101 mutations
interact with mutations in other genes required for proper vulval
differentiation but do not act as generalized suppressors. This locus has been
cloned and encodes the C. elegans homolog of the Golgi-associated clathrin
adaptor protein AP47.
Animals mutant for both unc-101 and sli-1 display excessive vulval
differentiation. Animals mutant at only one of these loci display no vulval
abnormalities. This excessive vulval differentiation requires the inductive
signal and functionallet-23, suggesting that sli-1 and unc-101 function to
negatively regulate the response to the inductive signal, rather than the
basal activity of let-23.
Rare mutant alleles at lin-2, lin-7, and let-23 result in excessive vulval
differentiation. These alleles are genetically similar to more common alleles
of these genes which result in the failure to differentiate vulval tissue. These
three genes apparently are required for the activation of both positive and negative regulators of vulval differentiation.
A number of negative regulators function to control the activity of let-23.
At least three pathaways of negative regulation have been genetically
identified. These negative regulators act to limit the response to a growth or
differentiation factor.</p
Similarity of sli-1, a regulator of vulval development in C. elegans, to the mammalian proto-oncogene c-cbl
Vulval induction during Caenorhabditis elegans development is mediated by LET-23, a homolog of the mammalian epidermal growth factor receptor tyrosine kinase. The sli-1 gene is a negative regulator of LET-23 and is shown here to encode a protein similar to c-Cbl, a mammalian proto-oncoprotein. SLI-1 and c-Cbl share approximately 55 percent amino acid identity over a stretch of 390 residues, which includes a C_3HC_4 zinc-binding motif known as the RING finger, and multiple consensus binding sites for Src homology 3 (SH3) domains. SLI-1 and c-Cbl may define a new class of proteins that modify receptor tyrosine kinase-mediated signal transduction
Auranofin inactivates Trichomonas vaginalis thioredoxin reductase and is effective against trichomonads in vitro and in vivo
Trichomoniasis, caused by the protozoan parasite Trichomonas vaginalis, is the most common, non-viral, sexually transmitted infection in the world, but only two closely related nitro drugs are approved for its treatment. New antimicrobials against trichomoniasis remain an urgent need. Several organic gold compounds were tested for activity against T. vaginalis thioredoxin reductase (TrxR) in cell-free systems as well as for activity against different trichomonads in vitro and in a murine infection model. The organic gold(I) compounds auranofin and chloro(diethylphenylphosphine)gold(I) inhibited TrxR in a concentration-dependent manner in assays with recombinant purified reductase and in cytoplasmic extracts of T. vaginalis transfected with a haemagglutinin epitope-tagged form of the reductase. Auranofin potently suppressed the growth of three independent clinical T. vaginalis isolates as well as several strains of another trichomonad (Tritrichomonas foetus) in a 24βh-assay, with 50% inhibitory concentrations of 0.7β2.5βΒ΅M and minimum lethal concentrations of 2β6βΒ΅M. The drug also compromised the ability of the parasite to overcome oxidant stress, supporting the notion that auranofin acts, in part, by inactivating TrxR-dependent antioxidant defences. Chloro(diethylphenylphosphine)gold(I) was 10-fold less effective against T. vaginalis in vitro than auranofin. Oral administration of auranofin for 4 days cleared the parasites in a murine model of vaginal T. foetus infection without displaying any apparent adverse effects. The approved human drug auranofin may be a promising agent as an alternative treatment of trichomoniasis in cases when standard nitro drug therapies have failed
Recommended from our members
Auranofin inactivates Trichomonas vaginalis thioredoxin reductase and is effective against trichomonads in vitro and in vivo
Trichomoniasis, caused by the protozoan parasite Trichomonas vaginalis, is the most common, non-viral, sexually transmitted infection in the world, but only two closely related nitro drugs are approved for its treatment. New antimicrobials against trichomoniasis remain an urgent need. Several organic gold compounds were tested for activity against T. vaginalis thioredoxin reductase (TrxR) in cell-free systems as well as for activity against different trichomonads in vitro and in a murine infection model. The organic gold(I) compounds auranofin and chloro(diethylphenylphosphine)gold(I) inhibited TrxR in a concentration-dependent manner in assays with recombinant purified reductase and in cytoplasmic extracts of T. vaginalis transfected with a haemagglutinin epitope-tagged form of the reductase. Auranofin potently suppressed the growth of three independent clinical T. vaginalis isolates as well as several strains of another trichomonad (Tritrichomonas foetus) in a 24βh-assay, with 50% inhibitory concentrations of 0.7-2.5βΒ΅M and minimum lethal concentrations of 2-6βΒ΅M. The drug also compromised the ability of the parasite to overcome oxidant stress, supporting the notion that auranofin acts, in part, by inactivating TrxR-dependent antioxidant defences. Chloro(diethylphenylphosphine)gold(I) was 10-fold less effective against T. vaginalis in vitro than auranofin. Oral administration of auranofin for 4 days cleared the parasites in a murine model of vaginal T. foetus infection without displaying any apparent adverse effects. The approved human drug auranofin may be a promising agent as an alternative treatment of trichomoniasis in cases when standard nitro drug therapies have failed
Auranofin inactivates Trichomonas vaginalis thioredoxin reductase and is effective against trichomonads in vitro and in vivo
Trichomoniasis, caused by the protozoan parasite Trichomonas vaginalis, is the most common, non-viral, sexually transmitted infection in the world, but only two closely related nitro drugs are approved for its treatment. New antimicrobials against trichomoniasis remain an urgent need. Several organic gold compounds were tested for activity against T. vaginalis thioredoxin reductase (TrxR) in cell-free systems as well as for activity against different trichomonads in vitro and in a murine infection model. The organic gold(I) compounds auranofin and chloro(diethylphenylphosphine)gold(I) inhibited TrxR in a concentration-dependent manner in assays with recombinant purified reductase and in cytoplasmic extracts of T. vaginalis transfected with a haemagglutinin epitope-tagged form of the reductase. Auranofin potently suppressed the growth of three independent clinical T. vaginalis isolates as well as several strains of another trichomonad (Tritrichomonas foetus) in a 24 h-assay, with 50% inhibitory concentrations of 0.7β2.5 Β΅M and minimum lethal concentrations of 2β6 Β΅M. The drug also compromised the ability of the parasite to overcome oxidant stress, supporting the notion that auranofin acts, in part, by inactivating TrxR-dependent antioxidant defences. Chloro(diethylphenylphosphine)gold(I) was 10-fold less effective against T. vaginalis in vitro than auranofin. Oral administration of auranofin for 4 days cleared the parasites in a murine model of vaginal T. foetus infection without displaying any apparent adverse effects. The approved human drug auranofin may be a promising agent as an alternative treatment of trichomoniasis in cases when standard nitro drug therapies have failed