Structural insights into the multifunctionality of rabies virus P3 protein.

Viruses form extensive interfaces with host proteins to modulate the biology of the infected cell, frequently via multifunctional viral proteins. These proteins are conventionally considered as assemblies of independent functional modules, where the presence or absence of modules determines the overall composite phenotype. However, this model cannot account for functions observed in specific viral proteins. For example, rabies virus (RABV) P3 protein is a truncated form of the pathogenicity factor P protein, but displays a unique phenotype with functions not seen in longer isoforms, indicating that changes beyond the simple complement of functional modules define the functions of P3. Here, we report structural and cellular analyses of P3 derived from the pathogenic RABV strain Nishigahara (Nish) and an attenuated derivative strain (Ni-CE). We identify a network of intraprotomer interactions involving the globular C-terminal domain and intrinsically disordered regions (IDRs) of the N-terminal region that characterize the fully functional Nish P3 to fluctuate between open and closed states, whereas the defective Ni-CE P3 is predominantly open. This conformational difference appears to be due to the single mutation N226H in Ni-CE P3. We find that Nish P3, but not Ni-CE or N226H P3, undergoes liquid-liquid phase separation and this property correlates with the capacity of P3 to interact with different cellular membrane-less organelles, including those associated with immune evasion and pathogenesis. Our analyses propose that discrete functions of a critical multifunctional viral protein depend on the conformational arrangements of distant individual domains and IDRs, in addition to their independent functions.

Noncovalent Peptide Stapling Using Alpha-Methyl-l-Phenylalanine for α-Helical Peptidomimetics.

Peptides and peptidomimetics are attractive drug candidates because of their high target specificity and low-toxicity profiles. Developing peptidomimetics using hydrocarbon (HC)-stapling or other stapling strategies has gained momentum because of their high stability and resistance to proteases; however, they have limitations. Here, we take advantage of the α-methyl group and an aromatic phenyl ring in a unique unnatural amino acid, α-methyl-l-phenylalanine (αF), and propose a novel, noncovalent stapling strategy to stabilize peptides. We utilized this strategy to create an α-helical B-chain mimetic of a complex insulin-like peptide, human relaxin-3 (H3 relaxin). Our comprehensive data set (in vitro, ex vivo, and in vivo) confirmed that the new high-yielding B-chain mimetic, H3B10-27(13/17αF), is remarkably stable in serum and fully mimics the biological function of H3 relaxin. H3B10-27(13/17αF) is an excellent scaffold for further development as a drug lead and an important tool to decipher the physiological functions of the neuropeptide G protein-coupled receptor, RXFP3.

Molecular Basis of Functional Effects of Phosphorylation of the C-Terminal Domain of the Rabies Virus P Protein.

The rabies virus (RABV) phosphoprotein (P protein) is expressed as several isoforms, which differ in nucleocytoplasmic localization and microtubule (MT) association, mediated by several sequences, including nuclear localization (NLS) and export (NES) sequences. This appears to underpin a functional diversity enabling multiple functions in viral replication and modulation of host biology. Mechanisms regulating trafficking are poorly defined, but phosphorylation by protein kinase C (PKC) in the P protein C-terminal domain (PCTD) regulates nuclear trafficking, mediated by PCTD-localized NLS/NES sequences, indicating that phosphorylation contributes to functional diversity. The molecular mechanism underlying the effects of PKC, and potential roles in regulating other host-cell interactions are unresolved. Here, we assess effects of phosphorylation on the P3 isoform, which differs from longer isoforms through an ability to localize to the nucleus and associate with MTs, which are associated with antagonism of interferon (IFN) signaling. We find that phosphomimetic mutation of the PKC site S210 inhibits nuclear accumulation and MT association/bundling. Structural analysis indicated that phosphomimetic mutation induces no significant structural change to the NLS/NES but results in the side chain of N226 switching its interactions from E228, within the NES, to E210. Intriguingly, N226 is the sole substituted residue between the PCTD of the pathogenic IFN-resistant RABV strain Nishigahara and a derivative attenuated IFN-sensitive strain Ni-CE, inhibiting P3 nuclear localization and MT association. Thus, S210 phosphorylation appears to impact on N226/E228 to regulate P protein localization, with N226 mutation in Ni-CE mimicking a constitutively phosphorylated state resulting in IFN sensitivity and attenuation. IMPORTANCE Rabies virus P protein is a multifunctional protein with critical roles in replication and manipulation of host-cell processes, including subversion of immunity. This functional diversity involves interactions of several P protein isoforms with the cell nucleus and microtubules. Previous studies showed that phosphorylation of the P protein C-terminal domain (PCTD) at S210, near nuclear trafficking sequences, regulates nucleocytoplasmic localization, indicating key roles in functional diversity. The molecular mechanisms of this regulation have remained unknown. Here, we show that phosphomimetic mutation of S210 regulates nuclear localization and MT association. This regulation does not appear to result from disrupted PCTD structure, but rather from a switch of specific side chain interactions of N226. Intriguingly, N226 was previously implicated in P protein nuclear localization/MT association, immune evasion, and RABV pathogenesis, through undefined mechanisms. Our data indicate that the S210-N226 interface is a key regulator of virus-host interactions, which is significant for pathogenesis.

Definition of the immune evasion-replication interface of rabies virus P protein.

Rabies virus phosphoprotein (P protein) is a multifunctional protein that plays key roles in replication as the polymerase cofactor that binds to the complex of viral genomic RNA and the nucleoprotein (N protein), and in evading the innate immune response by binding to STAT transcription factors. These interactions are mediated by the C-terminal domain of P (PCTD). The colocation of these binding sites in the small globular PCTD raises the question of how these interactions underlying replication and immune evasion, central to viral infection, are coordinated and, potentially, coregulated. While direct data on the binding interface of the PCTD for STAT1 is available, the lack of direct structural data on the sites that bind N protein limits our understanding of this interaction hub. The PCTD was proposed to bind via two sites to a flexible loop of N protein (Npep) that is not visible in crystal structures, but no direct analysis of this interaction has been reported. Here we use Nuclear Magnetic Resonance, and molecular modelling to show N protein residues, Leu381, Asp383, Asp384 and phosphor-Ser389, are likely to bind to a 'positive patch' of the PCTD formed by Lys211, Lys214 and Arg260. Furthermore, in contrast to previous predictions we identify a single site of interaction on the PCTD by this Npep. Intriguingly, this site is proximal to the defined STAT1 binding site that includes Ile201 to Phe209. However, cell-based assays indicate that STAT1 and N protein do not compete for P protein. Thus, it appears that interactions critical to replication and immune evasion can occur simultaneously with the same molecules of P protein so that the binding of P protein to activated STAT1 can potentially occur without interrupting interactions involved in replication. These data suggest that replication complexes might be directly involved in STAT1 antagonism.

Measuring translational diffusion of 15N-enriched biomolecules in complex solutions with a simplified 1H-15N HMQC-filtered BEST sequence.

Pulsed-field gradient nuclear magnetic resonance has seen an increase in applications spanning a broad range of disciplines where molecular translational diffusion properties are of interest. The current study introduces and experimentally evaluates the measurement of translational diffusion coefficients of 15N-enriched biomolecules using a 1H-15N HMQC-filtered band-selective excitation short transient (BEST) sequence as an alternative to the previously described SOFAST-XSTE sequence. The results demonstrate that accurate translational diffusion coefficients of 15N-labelled peptides and proteins can be obtained using this alternative 1H-15N HMQC-filtered BEST sequence which is implementable on NMR spectrometers equipped with probes fitted with a single-axis field gradient, including most cryoprobes dedicated to bio-NMR. The sequence is of potential use for direct quantification of protein or peptide translational diffusion within complex systems, such as in mixtures of macromolecules, crowded solutions, membrane-mimicking media and in bicontinuous cubic phases, where conventional sequences may not be readily applicable due to the presence of intense signals arising from sources other than the protein or peptide under investigation.

Native Chemical Ligation to Minimize Aspartimide Formation during Chemical Synthesis of Small LDLa Protein.

The inhibition of the G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), by a small LDLa protein may be a potential approach for prostate cancer treatment. However, it is a significant challenge to chemically produce the 41-residue and three-disulfide cross-bridged LDLa module which is highly prone to aspartimide formation due to the presence of several aspartic acid residues. Known palliative measures, including addition of HOBt to piperidine for N(α) -deprotection, failed to completely overcome this side reaction. For this reason, an elegant native chemical ligation approach was employed in which two segments were assembled for generating the linear LDLa protein. Acquisition of correct folding was achieved by using either a regioselective disulfide bond formation or global oxidation strategies. The final synthetic LDLa protein obtained was characterized by NMR spectroscopic structural analysis after chelation with a Ca(2+) ion and confirmed to be equivalent to the same protein obtained by recombinant DNA production.

RNA Binding Properties of SOX Family Members.

SOX proteins are a family of transcription factors (TFs) that play critical functions in sex determination, neurogenesis, and chondrocyte differentiation, as well as cardiac, vascular, and lymphatic development. There are 20 SOX family members in humans, each sharing a 79-residue L-shaped high mobility group (HMG)-box domain that is responsible for DNA binding. SOX2 was recently shown to interact with long non-coding RNA and large-intergenic non-coding RNA to regulate embryonic stem cell and neuronal differentiation. The RNA binding region was shown to reside within the HMG-box domain; however, the structural details of this binding remain unclear. Here, we show that all SOX family members, except group H, interact with RNA. Our mutational experiments demonstrate that the disordered C-terminal region of the HMG-box domain plays an important role in RNA binding. Further, by determining a high-resolution structure of the HMG-box domain of the group H family member SOX30, we show that despite differences in RNA binding ability, SOX30 shares a very similar secondary structure with other SOX protein HMG-box domains. Together, our study provides insight into the interaction of SOX TFs with RNA.

Evaluating the tightness of proximal contact between natural tooth and adjacent implant supported prosthesis.

The changes in interproximal contact between implant supported prosthesis (ISP) and adjacent natural tooth is of interest to dentists. Hence, we evaluated the tightness of proximal contact (PCT) between adjacent natural tooth and ISP by applying a digital force gauge spanning over a period of 1.5 year with a regular follow-up of 3, 6, and 12 months.80 patients who received ISP were included in this study. In order to measure the PCT, every patient seated in the identical upright position in the dentist chair. The digital force gauge was used to take measurements for mesial PCT and distal PCT. The mesial as well as distal interproximal contacts was more tight as in case of natural tooth adjacent to other natural tooth as compared to interproximal contacts between ISP and adjacent natural tooth. It was also observed that as the time progressed there was decrease in PCT values in both categories. After 12 month follow up 30.6% cases in category 2 while 21.2% cases in category 1 showed complete loss of interproximal contact. There is significant change in proximal contact tightness in interproximal area between implant supported prosthesis and adjacent natural tooth over a period of time and necessary measures should be taken to prevent or reduce it.

Malignant Portal Vein Thrombosis with No Obvious Liver Parenchymal Mass on Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

The presence of portal vein thrombosis (PVTT) in hepatocellular carcinoma (HCC) is associated with adverse prognosis with dismal survival. Malignant portal vein thrombosis usually develops as a contiguous extension of the liver tumour into portal vein or its branches. Here we present an interesting FDG PET-CT image of a patient with chronic hepatitis B infection having isolated malignant portal vein thrombosis without any obvious liver mass.

Molecular Mechanisms Driving and Regulating the AAA+ ATPase VCP/p97, an Important Therapeutic Target for Treating Cancer, Neurological and Infectious Diseases.

p97/VCP, a highly conserved type II ATPase associated with diverse cellular activities (AAA+ ATPase), is an important therapeutic target in the treatment of neurodegenerative diseases and cancer. p97 performs a variety of functions in the cell and facilitates virus replication. It is a mechanochemical enzyme that generates mechanical force from ATP-binding and hydrolysis to perform several functions, including unfolding of protein substrates. Several dozens of cofactors/adaptors interact with p97 and define the multifunctionality of p97. This review presents the current understanding of the molecular mechanism of p97 during the ATPase cycle and its regulation by cofactors and small-molecule inhibitors. We compare detailed structural information obtained in different nucleotide states in the presence and absence of substrates and inhibitors. We also review how pathogenic gain-of-function mutations modify the conformational changes of p97 during the ATPase cycle. Overall, the review highlights how the mechanistic knowledge of p97 helps in designing pathway-specific modulators and inhibitors.

The AAA+ ATPase p97 as a novel parasite and tuberculosis drug target.

The multifunctional AAA+ ATPase p97 is an unfoldase/segregase involved in various cellular processes and present in all kingdoms of life. In mammals and yeast, p97 functions upstream of the proteasome. Interestingly, proteasome inhibitors targeting pathogenic microorganisms display efficacy in overcoming drug-resistant strains. Homologues of p97 have been found in disease-causing parasites and mycobacteria. Here, we review the current knowledge on the structure, function, and conservation of p97 in pathogens. We discuss the potential of parasite and mycobacterial p97 as a drug target against these pathogens and explore strategies in designing novel inhibitors. A successful strategy for inhibiting pathogenic p97 should lead to effectively killing the pathogen, minimising toxic and off-target effects, and providing specificity to avoid interfering with human p97.

Membrane permeabilization is mediated by distinct epitopes in mouse and human orthologs of the necroptosis effector, MLKL.

Necroptosis is a lytic programmed cell death pathway with origins in innate immunity that is frequently dysregulated in inflammatory diseases. The terminal effector of the pathway, MLKL, is licensed to kill following phosphorylation of its pseudokinase domain by the upstream regulator, RIPK3 kinase. Phosphorylation provokes the unleashing of MLKL's N-terminal four-helix bundle (4HB or HeLo) domain, which binds and permeabilizes the plasma membrane to cause cell death. The precise mechanism by which the 4HB domain permeabilizes membranes, and how the mechanism differs between species, remains unclear. Here, we identify the membrane binding epitope of mouse MLKL using NMR spectroscopy. Using liposome permeabilization and cell death assays, we validate K69 in the α3 helix, W108 in the α4 helix, and R137/Q138 in the first brace helix as crucial residues for necroptotic signaling. This epitope differs from the phospholipid binding site reported for human MLKL, which comprises basic residues primarily located in the α1 and α2 helices. In further contrast to human and plant MLKL orthologs, in which the α3-α4 loop forms a helix, this loop is unstructured in mouse MLKL in solution. Together, these findings illustrate the versatility of the 4HB domain fold, whose lytic function can be mediated by distinct epitopes in different orthologs.

Broad and ultra-potent cross-clade neutralization of HIV-1 by a vaccine-induced CD4 binding site bovine antibody.

Human immunodeficiency virus type 1 (HIV-1) vaccination of cows has elicited broadly neutralizing antibodies (bNAbs). In this study, monoclonal antibodies (mAbs) are isolated from a clade A (KNH1144 and BG505) vaccinated cow using a heterologous clade B antigen (AD8). CD4 binding site (CD4bs) bNAb (MEL-1872) is more potent than a majority of CD4bs bNAbs isolated so far. MEL-1872 mAb with CDRH3 of 57 amino acids shows more potency (geometric mean half-maximal inhibitory concentration [IC50]: 0.009 µg/mL; breadth: 66%) than VRC01 against clade B viruses (29-fold) and than CHO1-31 against tested clade A viruses (21-fold). It also shows more breadth and potency than NC-Cow1, the only other reported anti-HIV-1 bovine bNAb, which has 60% breadth with geometric mean IC50 of 0.090 µg/mL in this study. Using successive different stable-structured SOSIP trimers in bovines can elicit bNAbs focusing on epitopes ubiquitous across subtypes. Furthermore, the cross-clade selection strategy also results in ultra-potent bNAbs.

Concurrent Chemoradiation With 5-Fluorouracil and Mitomycin in Squamous Cell Carcinoma of the Rectum.

Rectal carcinoma-squamous type is infrequently seen. Etiopathogenesis, prognosis, and therapeutic management of rectal squamous cell carcinoma (SCC) are not clearly defined. Rectal SCC is now approached with definitive upfront chemoradiotherapy (CRT), with 5-fluorouracil (5-FU) and mitomycin with a goal to avoid surgery. However, its management is planned based on histology features regardless of the localization of SCC rectal cancer. We present a case of a 47-year-old Caucasian female with rectal SCC who is under remission for two years after being treated with upfront chemoradiation with mitomycin and 5-fluorouracil (5-FU).

A Patient With Regressed Diffuse Large B-Cell Lymphoma and Aggressive Follicular Lymphoma.

Diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL) are the two most aggressive forms of non-Hodgkin lymphomas (NHLs). Spontaneous remission of DLBCL is a rare phenomenon. Immune system activation has been observed to play a significant role in the regression of untreated disease on some occasions. We present a case of DLBCL in a 75-year-old male patient who has been free of disease for two months without any treatment due to possible immune-related mechanism, but later he presented with FL.

Atypical Hemolytic Uremic Syndrome: Cancer-Induced or Chemotherapy-Induced?

Atypical hemolytic uremic syndrome (aHUS) is an atypical type of thrombotic microangiopathy (TMA), which is characterized by microangiopathic hemolytic anemia (MAHA), thrombocytopenia, and thrombi in small blood vessels, leading to end-organ damage. aHUS causes an over-activation of the complement pathway. There are many etiologies of aHUS, including inherited and acquired. This condition has a high mortality rate, as it is often detected late in the disease course. Eculizumab, an inhibitor of the terminal complement pathway, needs to be prescribed as soon as the diagnosis is confirmed. There is limited evidence, however, regarding the duration of treatment. Therefore, it is vital to conduct further analysis on other alternatives and pharmacokinetics with this type of complement inhibitor.

Pembrolizumab-Induced Lichenoid Dermatitis in a Patient With Metastatic Cancer of Unknown Primary.

Pembrolizumab is an immune checkpoint inhibitor approved for use in many cancer types such as non-small cell lung cancer (NSCLC), metastatic melanoma, head and neck cancers, hepatocellular carcinoma, and renal cell carcinoma. There are many reported cases of patients on immunotherapy who have discontinued treatment due to the development of immune-related adverse effects (irAE). Recognition of the histopathologic patterns of dermatologic toxicities due to immunotherapy will become increasingly important for ensuring appropriate management and optimal patient care. Here, we present a case of a 72-year-old man with metastatic carcinoma of unknown primary origin treated with pembrolizumab who developed an immune-related cutaneous adverse event (ircAE) in the form of lichenoid dermatitis.

Epidemiology and Retrospective Analysis in Extrapulmonary Neuroendocrine Carcinoma.

OBJECTIVES: We conducted a retrospective analysis of patients with extrapulmonary neuroendocrine carcinomas (EPNECs) to explore the distribution and overall outcomes by different regimens and their primary sites. SETTING: We reviewed the outcomes of one of the largest data sets of patients with extrapulmonary small cell carcinomas (EPSCCs) identified at Allegheny General Hospital located in Pittsburgh, Pennsylvania, USA. PARTICIPANTS: Patients diagnosed with grade 3 EPNECs were retrospectively identified. Primary endpoint and epidemiology: Overall survival (OS) with different treatment regimens was the primary endpoint. Also, epidemiological factors such as risk factors, race, family history of cancer, and associated comorbidities were recorded. RESULTS: OS was 16 months in seven patients who received cisplatin/etoposide chemotherapy and 8.5 months in seven patients with carboplatin/etoposide chemotherapy. The commonest primary site was the gastrointestinal tract (GIT). Smoking history association was observed to be 50%. Merkel cell carcinoma (MCC) patients had significantly better OS. Simultaneously, an extensive form of disease pattern was also noticed in 94.4% of the patients. Significantly, neutropenic sepsis was observed in 71.4% of the patients who were treated with cisplatin/etoposide combination. CONCLUSION: EPNECs demonstrated a low response rate to chemotherapy and high rates of distant metastases. Conclusively, brain metastases were rare.

Association of Celiac Disease With Pembrolizumab.

Immune checkpoint inhibitors (ICIs) in the recent times have transformed the landscape of the management of many solid tumors. Unfortunately, many immune-related adverse effects are associated with ICIs, which lead to a negative outcome in cancer treatment. We present a case of a 63-year-old female with metastatic adenocarcinoma of unknown origin, who developed celiac disease during the course of treatment with pembrolizumab. Association of celiac disease with this form of immunotherapy has never been documented before.

A Retrospective Analysis of Factors Affecting Palliative Care Consults in Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy.

Purpose This study was conducted to determine factors that influence palliative care (PC) consultation in patients receiving cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC). Patient and methods We queried our Electronic Medical Record EPIC for a list of patients who underwent cytoreductive surgery with HIPEC or hyperthermic intrathoracic chemotherapy (HITEC) in the hospital from April 2016-April 2019. Data was manually extracted and patients who did not meet our criteria were excluded. Patients were divided on the basis of palliative care consults and differences between the groups were analyzed. Odds ratios (OR) with p-value of 0.05 and confidence interval of (CI) 95% were calculated. Results We identified 55 patients of whom 34 met our inclusion criteria: 11 males and 23 females with an average age of 56 years at the time of diagnosis. Eight patients (23%) had PC, with six having commercial insurance, seven married, and six with more than one comorbid medical issue. Comorbidities >1 (OR: 0.12; CI: 0.02-0.76; p: 0.02) and age >40 (OR: 0.015; CI: 0.0007-0.3029; P: 0.006) were associated with a higher likelihood of PC. Gender, insurance type, and marital status did not have a significant association with PC. Mean age between PC consulted patients versus non-PC consulted patients was 58.5 vs. 55.9 and median age between the two groups was 60.5 vs. 60 which also showed a trend towards higher rates of PC in the older population. Conclusion Approximately one quarter of patients who underwent CRS with HIPEC had a concurrent PC consult. Though this is better than the national average of 11-16%, it continues to be a very small number. Efforts must be made to engage PC early in the course of treatment and recognize it as an integral part of cancer care. PC is not only an end-of-life service, in fact, studies have shown that early consultations lead to higher patient satisfaction, improved quality of life, and better communication.