Worming to Complete the Insulin/IGF-1 Signaling Cascade: A Dissertation

The insulin/IGF-1 signaling (IIS) was initially identified in C. elegansto control a developmental phenotype called dauer. Subsequently, it was realized that lifespan was extended by mutations in this pathway and became an intense focus of study. The IIS pathway regulates growth, metabolism and longevity across phylogeny and plays important roles in human disease such as cancer and diabetes. Given the large number of cellular processes that this pathway controls, understanding the regulatory mechanisms that modulate insulin/IGF-1 signaling is of paramount importance. IIS signaling is a very well-studied kinase cascade but few phosphatases in the pathway are known. Identification of these phosphatases, especially those that counteract the activity of the kinases, would provide a better insight into the regulation of this critical pathway. Study of serine/threonine phosphatases is hampered by the lack of appropriate reagents. In Chapter II, we discuss the design and results of an RNAi screen of serine/threonine phosphatases performed in C. elegans using dauer formation as a phenotypic output. We identified several strong regulators of dauer formation and in Chapter III, proceed to characterize one of the top candidates of our screen, pptr-1. We show that pptr-1 regulates the IIS and thereby affects lifespan, development and metabolism in C .elegans. pptr-1gene encodes a protein with high homology to the mammalian B56 family of PP2A regulatory subunits. PP2A is a ubiquitously expressed phosphatase that is involved in multiple cellular processes whose specificity determined by its association with distinct regulatory subunits. Our studies using C. elegans provides mechanistic insight into how the PP2A regulatory subunit PPTR-1 specifically modulates AKT-1 activity by regulating its phosphorylation status in the context of a whole organism. Furthermore, we show that this mechanism of regulation is conserved in mammals

Treatment with Hydroxychloroquine vs Hydroxychloroquine + Nitazoxanide in COVID-19 patients with risk factors for poor prognosis: A structured summary of a study protocol for a randomised controlled trial.

Objectives: To determine the efficacy of Hydroxychloroquine vs. Hydroxychloroquine + Nitazoxanide in reducing the need for invasive mechanical ventilatory support for patients with COVID-19. Hydroxychloroquine is currently being used in multiple trials with varying doses in an attempt to treat COVID-19. Nitazoxanide has powerful antiviral effects and proven efficacy against a range of viruses including SARS and MERS. Dual therapy by combining appropriate doses of these two medications with diverse activities against COVID-19 is expected to be better than monotherapy with hydroxychloroquine. Trial design: This is a single centre, randomized, controlled, single blinded, 2 arm (ratio 1:1) parallel group trial

Treatment with hydroxychloroquine vs nitazoxanide in patients with COVID-19. Brief report

Introduction: coronavirus pandemic has led to 1.8 million deaths worldwide as of May 1st, 2021. Nitazoxanide (NTZ) is currently being studied in several ambulatory clinical trials to control viral infections including SARS-CoV-2. This study evaluates the effect of treatment with NTZ compared to Hydroxychloroquine (HCQ) in hospitalized patients. Methods: in this clinical study performed from May to August 2020, two groups of COVID-19 patients were compared: A) a control group treated with HCQ 200 mg PO twice a day for seven days and B) an experimental group treated with NTZ 500 mg PO every 6 hours for seven days. Student's t-test between the two groups and Relative Risk (RR) with a 95% confidence interval (CI), were calculated. In all cases a P<0.05 was considered statistically significant. Results: twenty-seven (27) patients (females 17, males 10) treated with HCQ and 17 patients (females 8, males 9) administered NTZ were included in the study (mean age 44.6 ± 14.4 years old). At the moment of hospital admission, the following variables were statistically significant: BMI (P=0.0225) and leucocyte counts (P=0.069). In the follow-up period, the statistically significant variables were hospital length of stay (P=0.003257) and Intensive Care Units (ICU) admission with a lower RR in the group taking NTZ vs HCQ of 0.4074 (95% CI: 0.2451 to 0.5927, attributable risk (P1 - P2): 0.5926, P≤0.0001, NNT: 1.688). Conclusion: in comparison to HCQ, NTZ significantly reduces the risk to be hospitalized in the ICU and this approach could be replicated easily in any hospital

Genome-wide co-occupancy of AML1-ETO and N-CoR defines the t(8;21) AML signature in leukemic cells

BACKGROUND: Many leukemias result from chromosomal rearrangements. The t(8;21) chromosomal translocation produces AML1-ETO, an oncogenic fusion protein that compromises the function of AML1, a transcription factor critical for myeloid cell differentiation. Because of the pressing need for new therapies in the treatment of acute myleoid leukemia, we investigated the genome-wide occupancy of AML1-ETO in leukemic cells to discover novel regulatory mechanisms involving AML-ETO bound genes. RESULTS: We report the co-localization of AML1-ETO with the N-CoR co-repressor to be primarily on genomic regions distal to transcriptional start sites (TSSs). These regions exhibit over-representation of the motif for PU.1, a key hematopoietic regulator and member of the ETS family of transcription factors. A significant discovery of our study is that genes co-occupied by AML1-ETO and N-CoR (e.g., TYROBP and LAPTM5) are associated with the leukemic phenotype, as determined by analyses of gene ontology and by the observation that these genes are predominantly up-regulated upon AML1-ETO depletion. In contrast, the AML1-ETO/p300 gene network is less responsive to AML1-ETO depletion and less associated with the differentiation block characteristic of leukemic cells. Furthermore, a substantial fraction of AML1-ETO/p300 co-localization occurs near TSSs in promoter regions associated with transcriptionally active loci. CONCLUSIONS: Our findings establish a novel and dominant t(8;21) AML leukemia signature characterized by occupancy of AML1-ETO/N-CoR at promoter-distal genomic regions enriched in motifs for myeloid differentiation factors, thus providing mechanistic insight into the leukemic phenotype

Nitazoxanide against COVID-19 in three explorative scenarios

to describe the results of treating COVID-19 positive patients with nitazoxanide in three clinical settings: pregnancy/puerperium, hospitalized patients in an Internal Medicine Service and in an ambulatory setting. Methodology: This was a prospective follow-up and report of COVID-19 cases in three different situations, pregnant women, hospitalized patients receiving medical attention in an Internal Medicine Service and ambulatory patients residing in Toluca City, and Mexico City. Results: The experience with a first group of 20 women, pregnant (17) or in immediate puerperium (3) was successful in 18 cases with two unfortunate deaths. The five cases treated in an Internal Medicine service showed a positive outcome with two patients weaned from mechanical ventilation. Of the remaining 16 patients treated in an ambulatory setting, all got cured. Nitazoxanide seems to be useful against SARS-CoV-2, not only in an early intervention but also in critical condition as well as in pregnancy without undesired effects for the babies. As an adjunctive therapy budesonide was used that seems to contribute to the clinical improvement. Conclusions: Nitazoxanide could be useful against COVID-19 as a safe and available regimen to be tested in a massive way immediately

PDP-1 Links the TGF-β and IIS Pathways to Regulate Longevity, Development, and Metabolism

The insulin/IGF-1 signaling (IIS) pathway is a conserved regulator of longevity, development, and metabolism. In Caenorhabditis elegans IIS involves activation of DAF-2 (insulin/IGF-1 receptor tyrosine kinase), AGE-1 (PI 3-kinase), and additional downstream serine/threonine kinases that ultimately phosphorylate and negatively regulate the single FOXO transcription factor homolog DAF-16. Phosphatases help to maintain cellular signaling homeostasis by counterbalancing kinase activity. However, few phosphatases have been identified that negatively regulate the IIS pathway. Here we identify and characterize pdp-1 as a novel negative modulator of the IIS pathway. We show that PDP-1 regulates multiple outputs of IIS such as longevity, fat storage, and dauer diapause. In addition, PDP-1 promotes DAF-16 nuclear localization and transcriptional activity. Interestingly, genetic epistasis analyses place PDP-1 in the DAF-7/TGF-β signaling pathway, at the level of the R-SMAD proteins DAF-14 and DAF-8. Further investigation into how a component of TGF-β signaling affects multiple outputs of IIS/DAF-16, revealed extensive crosstalk between these two well-conserved signaling pathways. We find that PDP-1 modulates the expression of several insulin genes that are likely to feed into the IIS pathway to regulate DAF-16 activity. Importantly, dysregulation of IIS and TGF-β signaling has been implicated in diseases such as Type 2 Diabetes, obesity, and cancer. Our results may provide a new perspective in understanding of the regulation of these pathways under normal conditions and in the context of disease

A PP2A regulatory subunit regulates C. elegans insulin/IGF-1 signaling by modulating AKT-1 phosphorylation.

The C. elegans insulin/IGF-1 signaling (IIS) cascade plays a central role in regulating life span, dauer, metabolism, and stress. The major regulatory control of IIS is through phosphorylation of its components by serine/threonine-specific protein kinases. An RNAi screen for serine/threonine protein phosphatases that counterbalance the effect of the kinases in the IIS pathway identified pptr-1, a B56 regulatory subunit of the PP2A holoenzyme. Modulation of pptr-1 affects IIS pathway-associated phenotypes including life span, dauer, stress resistance, and fat storage. We show that PPTR-1 functions by regulating worm AKT-1 phosphorylation at Thr 350. With striking conservation, mammalian B56beta regulates Akt phosphorylation at Thr 308 in 3T3-L1 adipocytes. In C. elegans, this ultimately leads to changes in subcellular localization and transcriptional activity of the forkhead transcription factor DAF-16. This study reveals a conserved role for the B56 regulatory subunit in regulating insulin signaling through AKT dephosphorylation, thereby having widespread implications in cancer and diabetes research

Oncogenic cooperation between PI3K/Akt signaling and transcription factor Runx2 promotes the invasive properties of metastatic breast cancer cells

The serine/threonine kinase Akt/PKB promotes cancer cell growth and invasion through several downstream targets. Identification of novel substrates may provide new avenues for therapeutic intervention. Our study shows that Akt phosphorylates the cancer-related transcription factor Runx2 resulting in stimulated DNA binding of the purified recombinant protein in vitro. Pharmacological inhibition of the PI3K/Akt pathway in breast cancer cells reduces DNA-binding activity of Runx2 with concomitant reduction in the expression of metastasis-related Runx2 target genes. Akt phosphorylates Runx2 at three critical residues within the runt DNA-binding domain to enhance its in vivo genomic interactions with a target gene promoter, MMP13. Mutation of these three phosphorylation sites reduces Runx2 DNA-binding activity. However, Akt signaling does not appear to interefere with CBFbeta-Runx2 interactions. Consequently, expression of multiple metastasis-related genes is decreased and Runx2-mediated cell invasion is supressed. Thus, our work identifies Runx2 as a novel and important downstream mediator of the PI3K/Akt pathway that is linked to metastatic properties of breast cancer cells