The general focus of our group is on the transcriptional and epigenomic control of inflammation, and especially on the molecular mechanisms of the anti-inflammatory actions of glucocorticoids (GC) – steroid compounds that remain the most commonly prescribed class of drugs for a majority of inflammatory and autoimmune diseases. Despite their clinical efficacy, GC are prone to causing serious side effects, especially on the bone and metabolism. The design of more specific ‘new generation’ GC-like medications requires a better understanding of how conventional GC function. We have been studying the transcriptional cofactors of the GC receptor (GR) and, more broadly, inflammation-relevant transcription regulators that control gene expression programs in macrophages – a central cell type to mediate protective as well as pathogenic inflammatory pathways. We rely on molecular biology, biochemistry and genomics to understand the transcriptional and chromatin networks that govern macrophage identity and gene expression, we engineer mouse strains lacking key components of suspect pathways and evaluate these mice in animal models of disease. By doing so, we have been able to identify novel critical players that regulate inflammation in vitro and in vivo that can be tested in future translational studies that will help understand mechanisms of disease pathogenesis in humans and ultimately improve patient care.
1. Transcriptional control of inflammatory gene expression during early elongation
Historically, the recruitment of RNA Polymerase II (Pol II) to target promoters was considered the rate-limiting step for gene activation, yet in recent years, a different view has emerged. Many signal-induced genes are occupied by Pol II even prior to stimulation; Pol II initiates transcription but pauses at the promoter-proximal region bound by the Negative Elongation Factor (NELF) complex until signal-dependent phosphorylation by positive transcription elongation factor (PTEFb) enables NELF dissociation and productive Pol II elongation. We discovered that this pause-release checkpoint serves as a rate-limiting step for activation of the majority of genes encoding mediators of inflammation in macrophages (Adelman et al, Proc Natl Acad Sci USA 2009; Gupte et al, Proc Natl Acad Sci USA 2013; Sacta et al, eLife 2018). Several projects in the lab use mouse models of inflammatory diseases to understand how interfering with Pol II pausing through genetic and pharmacological approaches affects inflammation control.
2. GRIP1 coregulator, GR-mediated repression of genes in distinct transcriptional classes and anti-inflammatory actions of GCs
In addition to activating transcription by binding directly to DNA palindromic GC response elements (GREs), GR can ‘tether’ to other DNA-bound transcription factors, notably AP1 and NFkB, and repress their activity - a key component of the anti-inflammatory and immunosuppressive actions of GCs, however the underlying mechanisms remain obscure. Unexpectedly, GRIP1 (NCoA2), an established coactivator for GR at palindromic GREs, is also recruited to GR ‘tethering’ sites as an atypical corepressor. We generated mouse strains lacking GRIP1 in myeloid cells. Transcriptome analysis of GRIP1-deficient macrophages revealed broad attenuation of GC repression of inflammatory genes which in vivo led to an exaggerated response of the GRIP1 KO mice to inflammatory triggers (Chinenov, Gupte et al, Proc Natl Acad Sci USA 2012; Rollins et al, Nature Communications 2017). The specific molecular mechanism underlying repression is under investigation, however GR/GRIP1 repress both paused ‘elongation-controlled’ and non-paused ‘initiation-controlled’ genes by targeting distinct components of chromatin and transcriptional machinery (Gupte et al, Proc Natl Acad Sci USA 2013; Sacta et al, eLife 2018).
3. GR and GRIP1 in macrophage polarization and metabolic homeostasis
Macrophages are a cell type of great plasticity encompassing distinct populations that differ in their developmental origin and perform distinct, even opposing functions. Importantly, a disrupted balance of these populations leads to numerous human pathologies including metabolic syndrome and type II diabetes, cardiovascular disease and even cancer. For example, in obese adipose tissue, activated inflammatory macrophages (aka ‘M1’) promote chronic inflammation and insulin resistance, whereas homeostatic tissue-repair (M2) macrophages that normally reside in ‘lean’ adipose tissue are anti-inflammatory and antagonize metabolic dysfunction. GCs are known for their diabetogenic systemic side effects, however in macrophages, they both suppress inflammatory gene expression in M1 and promote M2 polarization. Interestingly, GRIP1 cofactor participates in both processes, not only by facilitating actions of GR but unexpectedly, by serving as a coactivator for KLF4 (Coppo et al, Nature Communications 2016) – a master-regulator of M2 polarization. Consistently, mice lacking GRIP1 in macrophages are sensitized to obesity-induced metabolic inflammation and insulin resistance, and their adipose tissue-derived macrophages display a general transcriptomic shift toward the inflammatory M1-like phenotype. We are investigating the genomic and molecular basis of homeostatic macrophage polarization in response to different cytokine and hormonal stimuli and the role of GRIP1 in their functional convergence.
4. Regulation of GRIP1 by phosphorylation
GRIP1 is a multi-functional coregulator that can elicit opposite transcriptional responses or engage in complexes with physiologically varied or even antagonistic functions, such as immunosuppression in conjunction with GR, M2 macrophage polarization by cooperating with KLF4 or innate immune response when bound by IRFs. What enables this regulatory diversity is unknown. We discovered that in response to GCs, GRIP1 is phosphorylated on multiple sites in a GR interaction-dependent manner and that distinct GRIP1 phospho-isoforms are recruited to individual GR genomic binding sites (Dobrovolna et al, Mol Cell Biol 2011; Rollins et al, Nature Communications 2017). Moreover, GRIP1 phosphorylation facilitated GR-mediated gene activation at palindromic GREs but not repression at the tethering sites suggesting that it serves as a code to drive both selective recruitment and function of GRIP1. We envision that other posttranslational modifications may occur in response to signals that activate non-GR GRIP1 partners (e.g., IRFs or KLF4) as a potential mechanism to direct GRIP1 to specific pathways.
5. The role of GRIP1 in neuroinflammation
Macrophages and microglia are critical in the pathogenesis of multiple sclerosis (MS) – an autoimmune demyelinating disease of the central nervous system (CNS) and its mouse model, experimental autoimmune encephalomyelitis (EAE). GCs and interferon (IFN)β are front-line treatments for MS, and disrupting each pathway in mice aggravates EAE. Because GRIP1 facilitates both GC and IFNβ transcriptional actions, we anticipated loss of GRIP1 to aggravate disease. Surprisingly, myeloid cell-specific GRIP1 deletion dramatically reduced EAE severity, yet, also blunted therapeutic properties of IFNβ. We are using genetic and transcriptomic approaches to understand the molecular basis for the unexpected permissive GRIP1 function in microglia and/or CNS-infiltrating macrophages during neuroinflammation.
Senior Scientist, Hospital for Special Surgery
Professor, Department of Microbiology and Immunology, Weill Medical College of Cornell University
Member, Graduate Program in Immunology and Microbial Pathogenesis, Weill-Cornell
Member, Allied Graduate Program in Biochemistry, Cell and Molecular Biology (BCMB), Weill-Cornell
Chinenov Y., Sacta M.A., Cruz A.R., Rogatsky I. (2008) GRIP1-associated SET-domain methyltransferase in glucocorticoid receptor target gene expression. Proc. Natl. Acad. Sci. USA 105: 20185-90.
Adelman K., Kennedy M.A., Nechaev S., Gilchrist D.A., Muse G.W.,Chinenov Y., Rogatsky I. (2009) Immediate mediators of the inflammatory response are poised for gene activation through RNA polymerase II stalling. Proc. Natl. Acad. Sci. USA 106:18207-12.
Flammer J.R., Dobrovolna J., Kennedy M.A., Chinenov Y., Glass C.K., Ivashkiv L.B., Rogatsky I. (2010) Type I interferon signaling pathway is a target for glucocorticoid inhibition. Mol. Cell. Biol. 30: 4564-4574 Supplementary Material
Dobrovolna J., Chinenov Y., Kennedy M.A., Liu B. and Rogatsky I. (2012) Glucocorticoid-dependent phosphorylation of the transcriptional coregulator GRIP1. Mol. Cell. Biol. 32:730-9
Chinenov Y., Gupte R., Dobrovolna J., Flammer J.R., Liu B., Michelassi F.E. and Rogatsky I. (2012) The role of transcriptional coregulator GRIP1 in the anti-inflammatory actions of glucocorticoids. Proc. Natl. Acad. Sci. USA 109:11776-81
Gupte R., Muse G.W., Chinenov Y., Adelman K. and Rogatsky I. (2013) Glucocorticoid receptor represses pro-inflammatory genes at distinct steps of the transcription cycle. Proc. Natl. Acad. Sci. USA 110:14616-21
Rogatsky I. and Adelman K. (2014) Preparing the first responders: Building the inflammatory transcriptome from the ground up. Molecular Cell 54:245-54
Chinenov Y., Coppo M., Gupte R., Sacta M.A. and Rogatsky I. (2014) Glucocorticoid receptor coordinates transcription factor-dominated regulatory network in macrophages. BMC Genomics 15:656
Sacta M.A., Chinenov Y. and Rogatsky I. (2016) Glucocorticoid signaling: An update from a genomic perspective. Annu Rev Physiol. 78:155-80
Shang Y., Coppo M., Ning F., Yu L., Kang L., Zhang B., Ju C., Qiao Y., Zhao B., Gessler M., He T., Rogatsky I. and Hu X. (2016) Hairy and enhancer of split 1 attenuates inflammation via regulating transcriptional elongation. Nature Immunology 17:930-7
Coppo M., Chinenov Y., Sacta M.A. and Rogatsky I. (2016) Transcriptional coregulator GRIP1 controls macrophage polarization and metabolic homeostasis. Nature Communications 7:12254
Rollins DA, Kharlyngdoh JB, Coppo M, Tharmalingam B, Mimouna S, Guo Z, Sacta MA, Pufall AM, Fisher RP, Hu X, Chinenov Y and Rogatsky I (2017) Glucocorticoid-induced phosphorylation by CDK9 modulates the coactivator functions of transcriptional cofactor GRIP1 in macrophages. Nature Communications 8:1739
Sacta MA, Tharmalingam B, Coppo M, Rollins DA, Deochand DK, Benjamin B, Yu L, Zhang B, Hu X, Li R, Chinenov Y, Rogatsky I (2018) Gene-specific mechanisms direct glucocorticoid-receptor-driven repression of inflammatory response genes in macrophages. Elife. 2018 Feb 9;7. pii: e34864.
For more publications, please see the PubMed listing.
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As of April 27, 2020, Dr. Rogatsky reported no relationships with healthcare industry.
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