3 research outputs found
Requirement For C-terminal Sequences in Regulation of Ect2 Guanine Nucleotide Exchange Specificity and Transformation
Ect2 was identified originally as a transforming protein and a member of the Dbl family of Rho guanine nucleotide exchange factors (GEFs). Like all Dbl family proteins, Ect2 contains a tandem Dbl homology (DH) and pleckstrin homology (PH) domain structure. Previous studies demonstrated that N-terminal deletion of sequences upstream of the DH domain created a constitutively activated, transforming variant of Ect2 (designated DeltaN-Ect2 DH/PH/C), indicating that the N terminus served as a negative regulator of DH domain function in vivo. The role of sequences C-terminal to the DH domain has not been established. Therefore, we assessed the consequences of mutation of C-terminal sequences on Ect2-transforming activity. Surprisingly, in contrast to observations with other Dbl family proteins, we found that mutation of the invariant tryptophan residue in the PH domain did not impair DeltaN-Ect2 DH/PH/C transforming activity. Furthermore, although the sequences C-terminal to the PH domain lack any known functional domains or motifs, deletion of these sequences (DeltaN-Ect2 DH/PH) resulted in a dramatic reduction in transforming activity. Whereas DeltaN-Ect2 caused formation of lamellipodia, DeltaN-Ect2 DH/PH enhanced actin stress fiber formation, suggesting that C-terminal sequences influenced Ect2 Rho GTPase specificity. Consistent with this possibility, we determined that DeltaN-Ect2 DH/PH activated RhoA, but not Rac1 or Cdc42, whereas DeltaN-Ect2 DH/PH/C activated all three Rho GTPases in vivo. Taken together, these observations suggest that regions of Ect2 C-terminal to the DH domain alter the profile of Rho GTPases activated in vivo and consequently may contribute to the enhanced transforming activity of DeltaN-Ect2 DH/PH/C
Recommended from our members
Effect of Ivermectin vs Placebo on Time to Sustained Recovery in Outpatients With Mild to Moderate COVID-19: A Randomized Clinical Trial
The effectiveness of ivermectin to shorten symptom duration or prevent hospitalization among outpatients in the US with mild to moderate symptomatic COVID-19 is unknown.
To evaluate the efficacy of ivermectin, 400 μg/kg, daily for 3 days compared with placebo for the treatment of early mild to moderate COVID-19.
ACTIV-6, an ongoing, decentralized, double-blind, randomized, placebo-controlled platform trial, was designed to evaluate repurposed therapies in outpatients with mild to moderate COVID-19. A total of 1591 participants aged 30 years and older with confirmed COVID-19, experiencing 2 or more symptoms of acute infection for 7 days or less, were enrolled from June 23, 2021, through February 4, 2022, with follow-up data through May 31, 2022, at 93 sites in the US.
Participants were randomized to receive ivermectin, 400 μg/kg (n = 817), daily for 3 days or placebo (n = 774).
Time to sustained recovery, defined as at least 3 consecutive days without symptoms. There were 7 secondary outcomes, including a composite of hospitalization or death by day 28.
Among 1800 participants who were randomized (mean [SD] age, 48 [12] years; 932 women [58.6%]; 753 [47.3%] reported receiving at least 2 doses of a SARS-CoV-2 vaccine), 1591 completed the trial. The hazard ratio (HR) for improvement in time to recovery was 1.07 (95% credible interval [CrI], 0.96-1.17; posterior P value [HR >1] = .91). The median time to recovery was 12 days (IQR, 11-13) in the ivermectin group and 13 days (IQR, 12-14) in the placebo group. There were 10 hospitalizations or deaths in the ivermectin group and 9 in the placebo group (1.2% vs 1.2%; HR, 1.1 [95% CrI, 0.4-2.6]). The most common serious adverse events were COVID-19 pneumonia (ivermectin [n = 5]; placebo [n = 7]) and venous thromboembolism (ivermectin [n = 1]; placebo [n = 5]).
Among outpatients with mild to moderate COVID-19, treatment with ivermectin, compared with placebo, did not significantly improve time to recovery. These findings do not support the use of ivermectin in patients with mild to moderate COVID-19.
ClinicalTrials.gov Identifier: NCT04885530
Recommended from our members
Effect of Montelukast vs Placebo on Time to Sustained Recovery in Outpatients with COVID-19: The ACTIV-6 Randomized Clinical Trial
The effect of montelukast in reducing symptom duration among outpatients with mild to moderate coronavirus disease 2019 (COVID-19) is uncertain.
To assess the effectiveness of montelukast compared with placebo in treating outpatients with mild to moderate COVID-19.
The ACTIV-6 platform randomized clinical trial aims to evaluate the effectiveness of repurposed medications in treating mild to moderate COVID-19. Between January 27, 2023, and June 23, 2023, 1250 participants ≥30 years of age with confirmed SARS-CoV-2 infection and ≥2 acute COVID-19 symptoms for ≤7 days, were included across 104 US sites to evaluate the use of montelukast.
Participants were randomized to receive montelukast 10 mg once daily or matched placebo for 14 days.
The primary outcome was time to sustained recovery (defined as at least 3 consecutive days without symptoms). Secondary outcomes included time to death; time to hospitalization or death; a composite of hospitalization, urgent care visit, emergency department visit, or death; COVID clinical progression scale; and difference in mean time unwell.
Among participants who were randomized and received study drug, the median age was 53 years (IQR 42-62), 60.2% were female, 64.6% identified as Hispanic/Latino, and 56.3% reported ≥2 doses of a SARS-CoV-2 vaccine. Among 628 participants who received montelukast and 622 who received placebo, differences in time to sustained recovery were not observed (adjusted hazard ratio [HR] 1.02; 95% credible interval [CrI] 0.92-1.12; P(efficacy) = 0.63]). Unadjusted median time to sustained recovery was 10 days (95% confidence interval 10-11) in both groups. No deaths were reported and 2 hospitalizations were reported in each group; 36 participants reported healthcare utilization events (a priori defined as death, hospitalization, emergency department/urgent care visit); 18 in the montelukast group compared with 18 in the placebo group (HR 1.01; 95% CrI 0.45-1.84; P(efficacy)=0.48). Five participants experienced serious adverse events (3 with montelukast and 2 with placebo).
Among outpatients with mild to moderate COVID-19, treatment with montelukast does not reduce duration of COVID-19 symptoms.
ClinicalTrials.gov ( NCT04885530 )