Uncovering a multitude of human glucocorticoid receptor variants: an expansive survey of a single gene.

BACKGROUND: Glucocorticoids are commonly used in the clinical setting for their potent anti-inflammatory effects; however, significant variations in response to treatment have been demonstrated. Although the underlying mechanisms have yet to be fully understood, this variable response may be a result of alterations in human glucocorticoid receptor (hGR) expression and function. In addition to hGRα, the biologically active isoform, a screening of current databases and publications revealed five alternative splice isoforms and hundreds of variants that have been reported to date. Many of these changes in the hGR-coding gene, NR3C1, have been linked to pathophysiology. However, many studies focus on evaluating hGR expression in vitro or detecting previously reported variants. RESULTS: In this study, blood from healthy volunteers, burn and asthma patients, as well as from peripheral blood mononuclear cells isolated from leukoreduced donor whole blood, were screened for NR3C1 isoforms. We identified more than 1500 variants, including an additional 21 unique splice isoforms which contain 15 new cryptic exons. A dynamic database, named the Universal hGR (UhGR), was created to annotate and visualize the variants. CONCLUSION: This identification of naturally occurring and stress-induced hGR isoforms, as well as the establishment of an hGR-specific database, may reveal new patterns or suggest areas of interest that will lead to the improved understanding of the human stress response system.

Expanded profiling of Remdesivir as a broad-spectrum antiviral and low potential for interaction with other medications in vitro.

Remdesivir (GS-5734; VEKLURY) is a single diastereomer monophosphoramidate prodrug of an adenosine analog (GS-441524). Remdesivir is taken up by target cells and metabolized in multiple steps to form the active nucleoside triphosphate (GS-443902), which acts as a potent inhibitor of viral RNA-dependent RNA polymerases. Remdesivir and GS-441524 have antiviral activity against multiple RNA viruses. Here, we expand the evaluation of remdesivir's antiviral activity to members of the families Flaviviridae, Picornaviridae, Filoviridae, Orthomyxoviridae, and Hepadnaviridae. Using cell-based assays, we show that remdesivir can inhibit infection of flaviviruses (such as dengue 1-4, West Nile, yellow fever, Zika viruses), picornaviruses (such as enterovirus and rhinovirus), and filoviruses (such as various Ebola, Marburg, and Sudan virus isolates, including novel geographic isolates), but is ineffective or is significantly less effective against orthomyxoviruses (influenza A and B viruses), or hepadnaviruses B, D, and E. In addition, remdesivir shows no antagonistic effect when combined with favipiravir, another broadly acting antiviral nucleoside analog, and has minimal interaction with a panel of concomitant medications. Our data further support remdesivir as a broad-spectrum antiviral agent that has the potential to address multiple unmet medical needs, including those related to antiviral pandemic preparedness.

Lipopolysaccharide Stress Induces Cryptic Exon Splice Variants of the Human Glucocorticoid Receptor.

Glucocorticoids are widely used in the treatment of numerous inflammatory conditions, including sepsis. Unfortunately, patient response to glucocorticoid therapy can be inconsistent. Variations in the human glucocorticoid receptor (hGR) may contribute to the differential patient response. We screened for hGR variants in the buffy coats of burn patients and peripheral blood mononuclear cells (PBMCs) treated with lipopolysaccharide. Three novel splice variants containing cryptic exons were upregulated in the PBMCs after lipopolysaccharide exposure at 3 and 13 h with the greatest observed expression at 3 h. Luciferase assays revealed that two of the isoforms had no significant activity in comparison with the reference hGR when stimulated with hydrocortisone. The third isoform had an augmented response that was greater than the reference hGR at a high cortisol dose. This shows that PBMCs are able to produce variant hGR isoforms in response to stress. Furthermore, lipopolysaccharide stress appears to induce these hGR variants, potentially by influencing mRNA splicing. In the future, identifying hGR expression profiles may be a key component in individually tailoring a patient's treatment to sepsis and injury.

A novel human glucocorticoid receptor SNP results in increased transactivation potential.

Glucocorticoids are one of the most widely used therapeutics in the treatment of a variety of inflammatory disorders. However, it is known that there are variable patient responses to glucocorticoid treatment; there are responders and non-responders, or those that need higher dosages. Polymorphisms in the glucocorticoid receptor (GR) have been implicated in this variability. In this study, ninety-seven volunteers were surveyed for polymorphisms in the human GR-alpha (hGRα), the accepted biologically active reference isoform. One isoform identified in our survey, named hGR DL-2, had four single nucleotide polymorphisms (SNPs), one synonymous and three non-synonymous, and a four base pair deletion resulting in a frame shift and early termination to produce a 743 amino acid putative protein. hGR DL-2 had a decrease in transactivation potential of more than 90%. Upon further analysis of the individual SNPs and deletion, one SNP, A829G, which results in a lysine to glutamic acid amino acid change at position 277, was found to increase the transactivation potential of hGR more than eight times the full-length reference. Furthermore, the hGRα-A829G isoform had a differential hyperactive response to various exogenous steroids. Increasing our knowledge as to how various SNPs affect hGR activity may help in understanding the unpredictable patient response to steroid treatment, and is a step towards personalizing patient care.

A Tri-Nucleotide Pattern in a 3' UTR Segment Affects The Activity of a Human Glucocorticoid Receptor Isoform.

We previously identified a truncated human glucocorticoid receptor (hGR) isoform of 118 amino acids, hGR-S1(-349A), that despite lacking the major functional domains, was more hyperactive after glucocorticoid treatment than the full-length receptor. Furthermore, its 3' untranslated region (UTR) was required. To dissect the underlying mechanisms for hyperactivity, a series of hGR isoforms with consecutive deletions in the 3' UTR were created to test their transactivation potential using reporter assays. The hGR-S1(-349A) isoform retaining 1303 bp of 3' UTR displayed unusually high activity with or without glucocorticoid stimulation. Unexpectedly, a complete loss of significant activity was observed with isoforms retaining 1293 bp or 1263 bp of 3' UTR. Analysis of the 20 bp region neighboring the 1293 bp site showed a pattern: 3'UTR termination at every third base pair in this region resulted in a loss of transactivation potential while the other sites retained hyperactivity with or without glucocorticoid stimulation. Variations in the activity of an hGR isoform, due to changes in the 3' UTR sequence configuration, may provide an important link in explaining inconsistent responses to glucocorticoid treatment in individuals and ultimately enable tailored, patient-specific care. Furthermore, understanding the mechanisms underlying the cyclic hyperactivity/loss of activity phenomenon may be a step toward identifying a novel mechanism of gene regulation.

Hyperactive Human Glucocorticoid Receptor Isoforms and their Implications for the Stress Response.

Glucocorticoids are indispensable therapeutic agents in diseases of inflammation, but their effectiveness in treating advanced septic shock has been inconsistent. Our understanding of the mechanisms causing this variability to steroid therapy remains limited. Previous studies in our laboratory have implicated human glucocorticoid receptor (hGR) polymorphisms as one of the likely reasons for this variability. We examined the effect of two single-nucleotide polymorphisms (SNPs) on the transactivation potential of the hGR in the absence and presence of exogenous steroids. An isoform containing a novel naturally occurring human SNP, T1463C, was found to have a hyperactive response with treatment of all three steroids examined while maintaining low activity in the absence of steroids, relative to reference hGR. In comparison, another hGR isoform with the A2297G SNP, previously identified in our laboratory, demonstrated hyperactive transactivational response in the absence of steroids; however, it had a significant increase in activity after treatment with only one of the glucocorticoids (hydrocortisone) tested. These results offer a possible explanation for the clinical variability seen among individuals in response to stress or shock.