Patent Publication Number: US-2022220168-A1

Title: Interferon regulatory factor 5 inhibitors and uses thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/844,894, filed on May 8, 2019, the contents of which are herein incorporated by reference into the subject application. 
    
    
     STATEMENT OF GOVERNMENT SUPPORT 
     This invention was made with government support under grant numbers AR065959 and RR033072 awarded by the National Institutes of Health and grant number W81XWH-18-1-0674 awarded by the Department of Defense. The government has certain rights in the invention. 
    
    
     BACKGROUND OF THE INVENTION 
     Throughout this application various publications are referred to in parentheses. Full citations for these references may be found at the end of the specification immediately preceding the claims. The disclosures of these publications are hereby incorporated by reference in their entireties into the subject application to more fully describe the art to which the subject application pertains. 
     Systemic lupus erythematosus (SLE) is a debilitating systemic autoimmune disease characterized by elevated levels of circulating anti-nuclear autoantibodies (ANA) that are thought to be caused by immune dysregulation. Immune dysregulation may be conferred by genetic susceptibility and/or environmental triggers. In the past 50 years, only one new drug has been approved for the treatment of SLE—the monoclonal antibody Belimumab. Unfortunately, global immunosuppression to control disease activity remains the standard of care treatment. Thus, extensive efforts are underway to develop drugs against targets involved in disease progression. One such new target is interferon regulatory factor 5 (IRF5), a member of the IRF family of transcription factors. IRF5 was originally identified as a regulator of type I interferons (IFNs) and IFN-stimulated genes (ISGs) in response to virus infection (1-3). Subsequent studies revealed important roles for IRF5 in both innate and adaptive immunity, macrophage polarization, cell growth regulation, and apoptosis (4,5). IRF5 was later identified as an autoimmune susceptibility gene. IRF5 polymorphisms associate with autoimmune and inflammatory conditions, including inflammatory bowel disease, primary biliary cirrhosis, rheumatoid arthritis, systemic lupus erythematosus (SLE), and systemic sclerosis (6-11). Most well-studied is the role of IRF5 in SLE pathogenesis and a common characteristic amongst SLE patients is increased expression of inflammatory cytokines and type I IFNs that contribute to sustained and persistent autoimmunity (12-17). IRF5 expression is significantly elevated in peripheral blood mononuclear cells (PBMC) from SLE patients as compared to age-matched healthy donors (18), and IRF5 is found to be constitutively activated, i.e. nuclear-localized, in SLE monocytes (19). These findings, which implicate IRF5 dysfunction in SLE pathogenesis, are supported by data from multiple models of murine lupus showing that mice lacking Irf5 (i.e., having an Irf5 −/−  genotype) are protected from disease onset and severity (11,20-22). Equally important and relevant to the therapeutic potential of IRF5 is the finding that lupus disease onset is abrogated in Irf5 +/−  mice indicating that a reduction in IRF5 expression and/or activity by only half is sufficient for therapeutic effect (23-25). 
     Although the mechanism(s) by which IRF5 contributes to disease pathogenesis remains unclear, much of the data point to its role in regulating the expression of pro-inflammatory cytokines such as IFNa, interleukin (IL) 6, tumor necrosis factor (TNF) α, and IL12 (3,11,26). Dysregulation of many of these cytokines is associated with disease pathogenesis and IRF5 is predominantly expressed in immune cells (monocytes, dendritic cells and B cells) responsible for their production (26). In an unstimulated cell, IRF5 is localized in the cytoplasm as an inactive monomer (27). While in the inactive conformation, the C-terminal autoinhibitory domain (AID) of IRF5 is thought to either mask the N-terminal DNA binding domain (DBD) and/or the C-terminal protein interaction domain (IAD) that is required for homo/heterodimerization (27,28). Upon activation by post-translational modification events downstream of Toll-like receptors (TLRs), DNA damage, or other antigenic signaling cascades, IRF5 undergoes a conformational change that exposes the IAD for dimerization, and nuclear localization signals (NLS) for translocation (1,27-29). While a significant body of in vitro work suggests this conformational shift is dependent on phosphorylation of C-terminal Serine (Ser) residues by activating kinases (30-32), nuclear translocation remains the essential regulatory step mediating IRF5 transcriptional activity (1,27). 
     Identification of IRF5 as a global risk factor for autoimmune and inflammatory diseases (11,20-22,33-36), coupled with its increased activation in SLE patient blood, make IRF5 an attractive target for therapeutic inhibition. While C-terminal phosphorylation and dimerization represent steps amenable to inhibition, neither has been definitively shown as an absolute requirement for nuclear translocation (32). An alternate approach to inhibit IRF5 stems from the finding that either N- or C-terminal regions of IRFs can act as dominant negative (DN) mutants to block transactivation ability (2,26,37-41). Though the mechanism(s) by which DN mutants inhibit IRFs remain unclear, their activity suggests that IRF peptide mimetics may be an effective approach for blocking function. Previous studies have described inhibitors of IRF5 nuclear localization and methods of using the inhibitors to treat autoimmune diseases such as SLE (59). The present invention addresses the continuing need for new therapeutics to treat diseases such as autoimmune and inflammatory diseases by inhibiting IRF5. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to polypeptides comprising a cell penetrating amino acid sequence and an interferon regulatory factor 5 (IRF5) targeting amino acid sequence, where the IRF5 targeting amino acid sequence is one or more of RHATRHG (SEQ ID NO:1), KSRDFRL (SEQ ID NO:2) and GPRDMPP (SEQ ID NO:3), and to methods of using these polypeptides to treat diseases, such as autoimmune diseases and inflammatory diseases. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention provides a polypeptide comprising a cell penetrating amino acid sequence and an interferon regulatory factor 5 (IRF5) targeting amino acid sequence, where the IRF5 targeting amino acid sequence is one or more of RHATRHG (SEQ ID NO:1), KSRDFRL (SEQ ID NO:2) and GPRDMPP (SEQ ID NO:3). 
     In one embodiment, the polypeptide consists essentially of the cell penetrating amino acid sequence and the IRF5 targeting amino acid sequence, wherein addition of any element to the polypeptide does not negatively affect the cell penetrating function of the polypeptide and does not negatively affect the IRF5 targeting function of the polypeptide. In one embodiment, the polypeptide consists of the cell penetrating amino acid sequence and the IRF5 targeting amino acid sequence. 
     In different embodiments, the cell penetrating amino acid sequence comprises a sequence at least 90% identical to DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the cell penetrating amino acid sequence comprises DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the cell penetrating amino acid sequence consists essentially of a sequence at least 90% identical to DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the cell penetrating amino acid sequence consists essentially of DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the cell penetrating amino acid sequence consists of a sequence at least 90% identical to DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the cell penetrating amino acid sequence consists of DRQIKIWFQNRRMKWKK (SEQ ID NO:4), AAVALLPAVLLALLAP (SEQ ID NO:5), GRKKRRQRRRPPQ (SEQ ID NO:6), CSIPPEVKFNKPFVYLI (SEQ ID NO:7), KKWKMRRNQFWVKVQRG (SEQ ID NO:8), KLLKLLLKLWLKLLKLLL (SEQ ID NO:9), INLKALAALAKKIL (SEQ ID NO:10), RQIKIWFQNRRMKWKKGG (SEQ ID NO:11), GWTLNSAGYLLGKINLKALAALAKKIL (SEQ ID NO:12), YLKFIPLKRAIWLIK (SEQ ID NO:13), MANLGYWLLALFVTMWTDVGLCKKRPKP (SEQ ID NO:14), RQIKIWFQNRRMKWKK (SEQ ID NO:15) or LCLRPVG (SEQ ID NO:16). 
     In different embodiments, the polypeptide comprises an amino acid sequence at least 90% identical to DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWFQNRRMKWKKKSRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     In different embodiments, the polypeptide comprises amino acid sequence DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWFQNRRMKWKKKSRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     In different embodiments, the polypeptide consists essentially of an amino acid sequence at least 90% identical to DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWFQNRRMKWKKKSRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     In different embodiments, the polypeptide consists essentially of amino acid sequence DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWFQNRRMKWKKKSRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     In different embodiments, the polypeptide consists of an amino acid sequence at least 90% identical to DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWF QNRRMKWKKK SRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     In different embodiments, the polypeptide consists of amino acid sequence DRQIKIWFQNRRMKWKKRHATRHG (SEQ ID NO:17), DRQIKIWFQNRRMKWKKK SRDFRL (SEQ ID NO:18) or DRQIKIWFQNRRMKWKKGPRDMPP (SEQ ID NO:19). 
     The invention provides an inhibitor of interferon regulatory factor 5 (IRF5) comprising one or more of any of the polypeptides disclosed herein. The invention provides an inhibitor of interferon regulatory factor 5 (IRF5) nuclear translocation comprising one or more of any of the polypeptides disclosed herein. The invention provides polypeptides that bind directly to IRF5 to inhibit IRF5 nuclear translocation. 
     The invention provides a nucleic acid sequence encoding any of the polypeptides disclosed herein. 
     The invention provides a pharmaceutical composition comprising one or more of any of the polypeptides disclosed herein and a pharmaceutically acceptable carrier. Examples of acceptable pharmaceutical carriers include, but are not limited to, additive solution-3 (AS-3), saline, phosphate buffered saline, Ringer&#39;s solution, lactated Ringer&#39;s solution, Locke-Ringer&#39;s solution, Krebs Ringer&#39;s solution, Hartmann&#39;s balanced saline solution, and heparinized sodium citrate acid dextrose solution. 
     The invention provides a method of inhibiting interferon regulatory factor 5 (IRF5) comprising contacting IRF5 with one or more of any of the polypeptides disclosed herein in an amount effective to inhibit IRF5. 
     The invention provides a method of inhibiting interferon regulatory factor 5 (IRF5) in a patient in need thereof, comprising administering to the patient one or more of any of the polypeptides disclosed herein in an amount effective to inhibit IRF5 in a patient. 
     The invention provides a method of inhibiting interferon regulatory factor 5 (IRF5) nuclear translocation in a patient in need thereof, comprising administering to the patient one or more of any of the polypeptides disclosed herein in an amount effective to inhibit IRF5 nuclear translocation in a patient. The invention provides polypeptides that bind directly to IRF5 to inhibit IRF5 nuclear translocation. 
     In the methods disclosed herein, the patient can have an autoimmune disease. 
     The invention provides a method for treating an autoimmune disease in a patient in need of such treatment, comprising administering to the patient one or more of any of the polypeptides disclosed herein in an amount effective to inhibit IRF5 in a patient. 
     The autoimmune disease can be, for example, any one or more of systemic lupus erythematosus (SLE), systemic sclerosis (scleroderma), polymyositis/dermatomyositis, Crohn&#39;s disease, rheumatoid arthritis, periodontitis, SLE-associated atherosclerosis, Sjögren&#39;s syndrome, autoimmune encephalomyelitis, sarcoidosis, Behçet&#39;s disease, myasthenia gravis, lupus nephritis, inflammatory bowel disease, ankylosing spondylitis, primary biliary cirrhosis, colitis, juvenile idiopathic arthritis, pulmonary fibrosis, antiphospholipid syndrome and psoriasis. 
     In the methods disclosed herein, the patient can have classical Hodgkin lymphoma, atherosclerosis, cardiovascular disease, neuropathic pain, leukemia (e.g., T cell large granular lymphocyte leukemia) or lymphoma. 
     The invention provides a method for treating a patient having classical Hodgkin lymphoma, atherosclerosis, cardiovascular disease, neuropathic pain, leukemia (e.g., T cell large granular lymphocyte leukemia) or lymphoma, comprising administering to the patient one or more of any of the polypeptides disclosed herein in an amount effective to inhibit IRF5 in a patient. 
     Any of the treatment methods disclosed herein can further comprise administering a second therapeutic agent to the patient. 
     The invention provides one or more of any of the polypeptides disclosed herein for use in medical treatment or diagnosis or for preparation of a medicament for inhibiting interferon regulatory factor 5 (IRF5). 
     The invention provides a research agent for studying interferon regulatory factor 5 (IRF5) comprising one or more of any of the polypeptides disclosed herein. 
     The invention provides a kit comprising one or more of any of the polypeptides disclosed herein, at least one other therapeutic agent, and instructions for administering the polypeptide and the other therapeutic agent(s) to a patient to treat an autoimmune disease, classical Hodgkin lymphoma, atherosclerosis, cardiovascular disease, neuropathic pain, leukemia (e.g., T cell large granular lymphocyte leukemia) or lymphoma. 
     The patient can be any mammal. Preferably, the patient is a human. 
     “And/or” as used herein, for example, with option A and/or option B, encompasses the embodiments of (i) option A, (ii) option B, and (iii) option A plus option B. 
     All combinations of the various elements described herein are within the scope of the invention unless otherwise indicated herein or otherwise clearly contradicted by context. 
     This invention will be better understood from the Experimental Details, which follow. However, one skilled in the art will readily appreciate that the specific methods and results discussed are merely illustrative of the invention as described more fully in the claims that follow thereafter. 
     EXPERIMENTAL DETAILS 
     Materials and Methods 
     Study Design and Methods. The main objectives of this program were to design a small library of cell permeable peptide mimetics that directly bind to and inhibit IRF5 activation as therapeutic candidates against SLE and other disease conditions in which IRF5 activation contributes to pathogenesis. 
     Synthesis of IRF5 Peptide inhibitors. Peptides were synthesized by LifeTein, LLC and purity confirmed by HPLC and mass spectrometry (Table 1). A peptide consisting of the cell permeable sequence alone, designated Cell Penetrating Peptide 1 (CPP1) (SEQ ID NO:4), was used as a negative control. Peptides 1-5 (N5-1 (SEQ ID NO:20), N5-2 (SEQ ID NO:17), N5-3 (SEQ ID NO:18), N5-4 (SEQ ID NO:19), N5-5 (SEQ ID NO:21)) correspond to N-terminal sequences of IRF5; C5-2 (SEQ ID NO:22) corresponds to a C-terminal sequence of IRF5. Individual peptides conjugated to FITC were also synthesized for uptake experiments. 
     Surface Plasmon Resonance (SPR) Analysis. The Biacore T200 (GE Healthcare, UK) was used for real-time binding interaction studies. Full-length recombinant IRF5 protein (ab173024, Abcam) was immobilized onto a CMS series chip (GE Healthcare) by diluting to a concentration of 20 μg/mL in 10 mM acetate buffer (pH=5.0). A 1:1 mixture of N-hyrdoxysuccinimide and N-ethyl-N-(dimethyaminopropyl)carbodiimide was used to activate 2 flow-cells of the CMS chip. One flow-cell was used as a reference and thus immediately blocked upon activation by 1 M ethanolamine (pH=8.5). The sample flow-cell was injected with the diluted IRF5 at a flow rate of 10 μL/min by manual injection. The IRF5 injection was stopped when the SPR reached ˜490 RU. For binding of peptides to IRF5, the analytes (peptides) were diluted to 1 μM in 1×PBS+0.05% Tween20 buffer, filtered (0.22 μm) and injected over the IRF5 immobilized chip at a flow rate of 30 μL/min for 60 s at 25° C. with a dissociation time set for 1 min. Binding experiments were conducted in 1×PBS+0.05% Tween20 as the running buffer; at least 3 independent experiments were performed. 
     Imaging Flow Cytometry. Imaging flow was performed as previously described on the Amnis Imagestream (19). Briefly, PBMCs from healthy donors were isolated and treated with inhibitor for 1 h, subsequently stimulated with R848 (500 ng/mL) or 2% SLE serum for 2 h, followed by staining for CD19 and CD14. PBMC were then fixed overnight in 1% paraformaldehyde and then permeabilized (19). Permeabilized cells were blocked in 5% BSA solution and stained for intracellular IRF5 (Abcam Catalog #: ab193245) or phospho(pSer462)IRF5 and FITC-conjugated secondary antibody (Abcam Catalog #: ab6896). Prior to acquisition, DRAQS dye was added at a 1:50 dilution. PBMC from SLE patients were only surface-stained and permeabilzed for intracellular IRF5 and DRAQS staining. Murine PBMC were stained similarly for intracellular IRF5 (Abcam Catolog #: 181553) (58) and APC-conjugated secondary antibody (BioLegend). Images were acquired on the ImageStream using the 40× objective. Nuclear translocation was quantified in the Amnis IDEAS software suite. Briefly, cells were first filtered through the brightfield area vs. brightfield aspect ratio gate to exclude non-viable and doublet events. Following which a similar gate of the DRAQS nuclear channel was used. This added an extra measure of stringency for cell viability. Images were gated on either CD14 + IRF5 + , CD19 + IRF5 + , or CD123 + BDCA2 + IRF5 +  events, followed by gating on images with a Gradient RMS of greater than 20 on the DRAQS channel. This was done to select images with a high level of clarity. Finally, IRF5 nuclear translocation was determined through use of the similarity score feature contrasting IRF5 staining with DRAQS staining. A similarity score &gt;2 was considered a translocation event. 
     Results 
     Design of peptide mimetics that specifically bind to IRF5. Given that IRF5 is hyper-activated in immune cells from SLE patients and NZB/W F1 lupus mice, we designed a series of inhibitors that would potentially bind to and target IRF5 activation. We used data from IRF crystal structures and IRF5 DN mutants (2,26,28,37) to generate a series of peptide mimetics that correspond to the N-terminus of IRF5 with the intent to stabilize or maintain the inactive IRF5 monomer, thus inhibiting IRF5 nuclear translocation. Since a crystal structure containing the IRF5 N-terminus has yet to be resolved (28), and the DNA binding domain (DBD) of IRFs is highly homologous, we used coordinates from the resolved IRF3 DBD to build an N-terminal homology model of IRF5 (42). This model was used to predict amino acid sequences with different characteristics to promote interaction with the IRF5 C-terminus. Sequence predictions were based on solvent accessible surface, charge, and hydrophobicity (Table 1). In order for the peptides to transduce the cell membrane, IRF5 sequences were combined with a protein transduction domain, in this case CPP1 (SEQ ID NO:4). CPP1 (SEQ ID NO:4) has been previously shown to facilitate cell permeability of small peptides (43). 
     Peptides (1 μM) were tested for their ability to directly interact with human full-length recombinant IRF5 variant 5 (isoform V5) by surface plasmon resonance (SPR) analysis. DWEYS (SEQ ID NO:23) peptide served as a non-targeted control and CPP1 (SEQ ID NO:4) as a control for the cell permeable sequence. As expected, DWEYS (SEQ ID NO:23) showed no affinity for IRF5 and CPP1 (SEQ ID NO:4) had minimal binding affinity. N5-1 (SEQ ID NO:20) and N5-2 (SEQ ID NO:17) showed the strongest binding affinity for IRF5, with N5-3 (SEQ ID NO:18) binding to a slightly lesser extent; N5-5 (SEQ ID NO:21) showed no affinity for IRF5 (binding affinity for IRF5: N5-1 (SEQ ID NO:20)≥N5-2 (SEQ ID NO:17)&gt;N5-3 (SEQ ID NO:18)&gt;N5-4 (SEQ ID NO:19)&gt;CPP1 (SEQ ID NO:4)&gt;N5-5 (SEQ ID NO:21)). A shared similarity between N5-1 (SEQ ID NO:20) and N5-2 (SEQ ID NO:17) is their relatively stronger positive charge, as compared to the others (Table 1). 
     Human IRF5 contains two nuclear localization signals (NLS), one in the N-terminus and one in the C-terminus (27). N5-1 (SEQ ID NO:20) corresponds to the N-terminal NLS (PRRVRLK) (SEQ ID NO:24). To test whether any NLS is capable of binding to IRF5, we generated C5-2 (SEQ ID NO:22) that corresponds to the C-terminal NLS of IRF5 (PREKKLI) (SEQ ID NO:25) and examined binding by SPR. C5-2 (SEQ ID NO:22) and CPP1 (SEQ ID NO:4) bound with similar low affinities. We have thus identified first generation peptide mimetics N5-1 (SEQ ID NO:20), N5-2 (SEQ ID NO:17) and N5-3 (SEQ ID NO:18) that directly bind to the full-length inactive IRF5 monomer. The observed difference in function between N5-1 (SEQ ID NO:20) and C5-2 (SEQ ID NO:22) supports that the NLS is not the driver of inhibitor activity and instead, peptide mimetics showing the strongest binding affinity for IRF5, N5-1 (SEQ ID NO:20) and N5-2 (SEQ ID NO:17) are those positively charged and relatively surface accessible. 
     Peptide mimetics inhibit TLR7-induced IRF5 nuclear translocation. We next sought to determine whether in vitro binding data would translate into IRF5 cellular inhibition. IRF5 is a key downstream mediator of TLR7-induced cytokine expression and TLR7 signaling has been implicated in SLE pathogenesis (2,44-47). We examined the ability of IRF5 peptide mimetics to inhibit IRF5 nuclear translocation following stimulation of PBMC with R848. We focused on peptides that showed binding to IRF5 by SPR analysis and included CPP1 (SEQ ID NO:4) and C5-2 (SEQ ID NO:22) as negative controls. For the initial screening, isolated PBMC from healthy donors were pre-incubated in the presence of mock (PBS), or 10 μM CPP1 (SEQ ID NO:4), N5-1 (SEQ ID NO:20), N5-2 (SEQ ID NO:17), N5-3 (SEQ ID NO:18) or C5-2 (SEQ ID NO:22) inhibitor for 1 h followed by stimulation with 500 ng/mL of R848 for 2 h. Cells were surface-stained with anti-CD14 (monocytes or Mo) and anti-CD19 (B cells) antibodies, then permeabilized and stained for intracellular IRF5 and DRAQ5. As expected, R848 induced significant IRF5 nuclear translocation in mock-incubated Mo (2) and B cells. While pre-incubation with CPP1 (SEQ ID NO:4) had no significant effect on R848-induced IRF5 nuclear translocation in either cell type, N5-1 (SEQ ID NO:20), N5-2 (SEQ ID NO:17) and N5-3 (SEQ ID NO:18) provided a significant reduction in R848-induced nuclear translocation in Mo. 
     Discussion 
     Signaling pathways have emerged as key targets for the development of small molecule inhibitors, with the primary targets being protein kinases and phosphatases (48,49). A caveat to this type of therapeutic targeting, however, is that it requires a priori knowledge of the signaling molecules leading to activation. Second, kinase inhibitors are generally not specific to one kinase, one signaling pathway, nor one downstream target protein. In the case of IRF5, it is well-documented that IRF5 becomes activated in a cell type- and stimuli-dependent manner (1,26,30-32,50-52). Regulation of IFN and inflammatory cytokine production by IRF5 requires nuclear translocation whereby it transcriptionally modulates target gene expression. Previous work suggested a requirement for ubiquitination and/or acetylation before phosphorylation and homo/heterodimerization, which may or may not ultimately lead to nuclear translocation to occur (32,53,54). Further, IRF5 phosphorylation occurs at multiple sites, which is dependent on the pathway of activation (27-32). Thus, in order to bypass the ambiguity of post-translational modifications and dimerization, we developed peptide mimetics that directly bind to and inhibit IRF5 activation (nuclear translocation) independent of the initiating pathway. We report selective IRF5 inhibitors that directly bind to endogenous, intracellular IRF5 to inhibit nuclear translocation (55,56). This identifies these fusion peptides as inhibitors of IRF5 with therapeutic potential in inflammatory and autoimmune diseases where IRF5 activation contributes to pathogenesis, such as lupus. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 IRF5 peptide inhibitor sequences, charge 
               
               
                 distribution and hydrophobicity. 
               
            
           
           
               
               
               
               
            
               
                   
                 Peptide Inhibitor 
                 Sequence 
                 Charge 
               
               
                   
                   
               
               
                   
                 Cell Penetrating 
                 DRQIKIWFQNRRMK 
                 positive 
               
               
                   
                 Peptide 1 (CPP1) 
                 WKK 
                   
               
               
                   
                 SEQ ID NO: 4 
                   
                   
               
               
                   
                   
               
               
                   
                 N5-1 
                 DRQIKIWFQNRRMK 
                 positive 
               
               
                   
                 (SEQ ID NO: 20) 
                 WKKPRRVRLK 
                   
               
               
                   
                   
               
               
                   
                 N5-2 
                 DRQIKIWFQNRRMK 
                 positive 
               
               
                   
                 SEQ ID NO: 17 
                 WKKRHATRHG 
                   
               
               
                   
                   
               
               
                   
                 N5-3 
                 DRQIKIWFQNRRMK 
                 +/− 
               
               
                   
                 SEQ ID NO: 18 
                 WKKKSRDFRL 
                   
               
               
                   
                   
               
               
                   
                 N5-4 
                 DRQIKIWFQNRRMK 
                 hydrophobic 
               
               
                   
                 SEQ ID NO: 19 
                 WKKGPRDMPP 
                   
               
               
                   
                   
               
               
                   
                 N5-5 
                 DRQIKIWFQNRRMK 
                 negative 
               
               
                   
                 (SEQ ID NO: 21) 
                 WKKEGVDEAD 
                   
               
               
                   
                   
               
               
                   
                 C5-2 
                 DRQIKIWFQNRRMK 
                 +/− 
               
               
                   
                 (SEQ ID NO: 22) 
                 WKKPREKKLI 
                   
               
               
                   
                   
               
               
                   
                 FITC-CPP1 
                 FITC- 
                 SAA 
               
               
                   
                 (SEQ ID NO: 4) 
                 DRQIKIWFQNRR 
                   
               
               
                   
                   
                 MKWKK 
                   
               
               
                   
                   
               
               
                   
                 FITC-N5-1 
                 FITC- 
                 SAA 
               
               
                   
                 (SEQ ID NO: 20) 
                 DRQIKIWFQNRR 
                   
               
               
                   
                   
                 MKWKKPRRVRLK 
                   
               
               
                   
                   
               
               
                   
                 FITC-C5-2 
                 FITC- 
                 SAA 
               
               
                   
                 (SEQ ID NO: 22) 
                 DRQIKIWFQNRR 
                   
               
               
                   
                   
                 MKWKKPREKKLI 
                   
               
               
                   
                   
               
               
                   
                 Non-specific 
                 DWEYS 
                 negative 
               
               
                   
                 control 
                   
                   
               
               
                   
                 (SEQ ID NO: 23) 
               
               
                   
                   
               
               
                   
                 SAA-same as above. 
               
            
           
         
       
     
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