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The Cdk8 kinase module (CKM) in Mediator, comprising Med13, Med12, CycC, and Cdk8, regulates RNA polymerase II transcription through kinase-dependent and -independent functions. Numerous pathogenic mutations causative for neurodevelopmental disorders and cancer congregate in CKM subunits. However, the structure of the intact CKM and the mechanism by which Cdk8 is non-canonically activated and functionally affected by oncogenic CKM alterations are poorly understood. Here, we report a cryo-electron microscopy structure of Saccharomyces cerevisiae CKM that redefines prior CKM structural models and explains the mechanism of Med12-dependent Cdk8 activation. Med12 interacts extensively with CycC and activates Cdk8 by stabilizing its activation (T-)loop through conserved Med12 residues recurrently mutated in human tumors. Unexpectedly, Med13 has a characteristic Argonaute-like bi-lobal architecture. These findings not only provide a structural basis for understanding CKM function and pathological dysfunction, but also further impute a previously unknown regulatory mechanism of Mediator in transcriptional modulation through its Med13 Argonaute-like features.

Uridylate kinase (UMPK; EC 2.7.4.22) transfers the γ-phosphate of ATP to UMP, forming UDP. It is allosterically regulated by GTP. Structures of Helicobacter pylori UMPK ( HpUMPK) complexed with GTP ( HpUMPK-GTP) and with UDP ( HpUMPK-UDP) were determined at 1.8 and 2.5 Å resolution, respectively. As expected, HpUMPK-GTP forms a hexamer with six GTP molecules at its centre. Interactions between HpUMPK and GTP are made by the β3 strand of the sheet, loop β3α4 and the α4 helix. In HpUMPK-UDP, the hexameric symmetry typical of UMPKs is absent. Only four of the HpUMPK molecules bind UDP; the other two HpUMPK molecules are in the UDP-free state. The asymmetric hexamer of HpUMPK-UDP, which has an exposed dimer interface, may assist in UDP release. Furthermore, the flexibility of the α2 helix, which interacts with UDP, is found to increase when UDP is absent in HpUMPK-UDP. In HpUMPK-GTP, the α2 helix is too flexible to be observed. This suggests that GTP binding may affect the conformation of the α2 helix, thereby promoting UDP release. [ABSTRACT FROM AUTHOR]

Protein kinase C delta (PKCδ) is prominently expressed in the nuclei of EGFR-mutant lung cancer cells, and its presence correlates with poor survival of the patients undergoing EGFR inhibitor treatment. The inhibition of PKCδ has emerged as a viable approach to overcoming resistance to EGFR inhibitors. However, clinical-grade PKCδ inhibitors are not available, highlighting the urgent needs for the development of effective drugs that target PKCδ. In this study, we designed and synthesized a series of inhibitors based on the chemical structure of a pan PKC inhibitor sotrastaurin. This was achieved by incorporating a triazole ring group into the original sotrastaurin configuration. Our findings revealed that the sotrastaurin derivative CMU-0101 exhibited an elevated affinity for binding to the ATP-binding site of PKCδ and effectively suppressed nuclear PKCδ in resistant cells in comparison to sotrastaurin. Furthermore, we demonstrated that CMU-0101 synergistically enhanced EGFR TKI gefitinib sensitivity in resistant cells. Altogether, our study provides a promising strategy for designing and synthesizing PKCδ inhibitors with improved efficacy, and suggests CMU-0101 as a potential lead compound to inhibit PKCδ and overcome TKI resistance in lung cancers., Competing Interests: None., (AJCR Copyright © 2023.)

It has been shown that several ribonuclease (RNase) A superfamily proteins serve as ligands of receptor tyrosine kinases (RTKs), representing a new concept for ligand/receptor interaction. Moreover, recent studies indicate high clinical values for this type of ligand/RTK interactions. However, there is no structural report for this new family of ligand/receptor. In an attempt to understand how RNase and RTK may interact, we focused on the RNase1/ephrin type-A receptor 4 (EphA4) complex and predicted their structure by using the state-of-the-art machine learning method, AlphaFold and its derivative method, AF2Complex. In this model, electrostatic force plays an essential role for the specific ligand/receptor interaction. We found the R39 of RNase1 is the key residue for EphA4-binding and activation. Mutation on this residue causes disruption of an essential basic patch, resulting in weaker ligand-receptor association and leading to the loss of activation. By comparing the surface charge distribution of the RNase A superfamily, we found the positively charged residues on the RNase1 surface is more accessible for EphA4 forming salt bridges than other RNases. Furthermore, RNase1 binds to the ligand-binding domain (LBD) of EphA4, which is responsible for the traditional ligand ephrin-binding. Our model reveals the location of RNase1 on EphA4 partially overlaps with that of ephrin-A5, a traditional ligand of EphA4, suggesting steric hindrance as the basis by which the ephrin-A5 precludes interactions of RNase1 with EphA4. Together, our discovery of RNase1/EphA4 interface provides a potential treatment strategy by blocking the RNase1-EphA4 axis., Competing Interests: None., (AJCR Copyright © 2022.)

Objective: To observe the effect of Tetramethyl pyrazine (TMP) on the cytokines and inflammatory mediators in the serum and the synovial fluid of collagen-induced arthritis (CIA)rats, and further to investigate its possible mechanisms for treating rheumatoid arthritis (RA)., Methods: Type II CIA rat model was established. Rats in the TMP group were administered with TMP at 50 mg/kg and 100 mg/kg, once daily. Dexamethasone at 2.0 mg/kg was intramuscularly injected to those in the Dexamethasone treated group, once daily. Normal saline at 2 mL/kg was given to those in the normal control group and the model group, once daily. All medication was started from the 7th day, lasting to the 35th day. CIA rats' foot swelling degree was observed. Contents of serum IL-1, IL-6, IL-2, NO and PGE2in the synovial fluid were detected by radioimmunoassay and nitrate reduction method., Results: Compared with the normal group, the foot swelling obviously increased, contents of NO and PGE2 in the synovial fluid were obviously elevated in the model group (P < 0.01). Compared with the model group, the foot swelling could be obviously inhibited by 100 mg/kg TMP and Dexamethasone; serum levels of IL-1 and IL-6 obviously decreased, serum IL-2 level obviously increased, contents of NO and PGE, decreased (P < 0.01). TMP 50 mg/kg could obviously inhibit the foot swelling of CIA rats (P < 0.01). There was no statistical difference in other indices (P > 0.05)., Conclusions: TMP at 100 mg/kg showed obvious inhibition on CIA rats. Its inhibitory effect might be correlated to inhibiting activities of endogenous cytokines and the generation of inflammatory mediators in inflammation local regions, improving contents of anti-inflammation cytokines, and inducing the balance of the inflammatory cytokine network.

Aim: To explore effects of total glucosides of paeonia (TGP)on the NF-κB/p65 protein expression in paws of rheumatoid arthritis (RA) rats, and the contents of serum TNF-α, IL-1β and IL-10 in RA rats serum., Methods: Type II collagen-induced arthritis model in SD rats was established. The expression of NF-κB/p65 proteins in rat, s paw tissues was detected by immunohistochemical staining. The contents of serum TNF-α, IL-1β and IL-10 in RA rats were detected by ELISA., Results: TGP could down-regulate the expression of NF-κB/ p65 protein and contents of TNF-α, IL-1β and IL-10 in RA rats., Conclusion: The inhibitory effect of TGP on anti-inflammation maybe related to decreasing the expression of NF-κB/p65 protein and suppressing the production of TNF-α and IL-1β in RA rats.

Sodium-hydrogen exchanger as a channel for regulation of intracellular pH might be a crucial modulator of sperm capacitation and motility. Three members of this family have been identified in spermatozoa. A novel protein testis-specific sodium-hydrogen exchanger named mtsNHE was cloned in the present study. The mtsNHE localizing on principle piece of sperm flagellum contained 12 predicted transmembrane regions without cytoplasmic fragment at carboxyl terminus. Hydrophilic region was common in the sodium-hydrogen exchanger family members. Polyclonal antibodies to trans-membrane region significantly reduced sperm motility, acrosome reaction and ratio of in vitro fertilization. By in-pouring the antibodies in sperm solution, intracellular pH and calcium concentration were decreased. Muscle injection of female mice with the specific gene vaccine of mtsNHE, significantly stepped down fertility rate. Considering its specific expression and involvement in the regulation of fertility, the mtsNHE might be a potential target molecule for developing a new male contraceptive.