Molecular basis for C-degron recognition by CRL2APPBP2 ubiquitin ligase.

E3 ubiquitin ligases determine the specificity of eukaryotic protein degradation by selective binding to destabilizing protein motifs, termed degrons, in substrates for ubiquitin-mediated proteolysis. The exposed C-terminal residues of proteins can act as C-degrons that are recognized by distinct substrate receptors (SRs) as part of dedicated cullin-RING E3 ubiquitin ligase (CRL) complexes. APPBP2, an SR of Cullin 2-RING ligase (CRL2), has been shown to recognize R-x-x-G/C-degron; however, the molecular mechanism of recognition remains elusive. By solving several cryogenic electron microscopy structures of active CRL2APPBP2 bound with different R-x-x-G/C-degrons, we unveiled the molecular mechanisms underlying the assembly of the CRL2APPBP2 dimer and tetramer, as well as C-degron recognition. The structural study, complemented by binding experiments and cell-based assays, demonstrates that APPBP2 specifically recognizes the R-x-x-G/C-degron via a bipartite mechanism; arginine and glycine, which play critical roles in C-degron recognition, accommodate distinct pockets that are spaced by two residues. In addition, the binding pocket is deep enough to enable the interaction of APPBP2 with the motif placed at or up to three residues upstream of the C-end. Overall, our study not only provides structural insight into CRL2APPBP2-mediated protein turnover but also serves as the basis for future structure-based chemical probe design.

Structural studies of SALL family protein zinc finger cluster domains in complex with DNA reveal preferential binding to an AATA tetranucleotide motif.

The Spalt-like 4 transcription factor (SALL4) plays an essential role in controlling the pluripotent property of embryonic stem cells via binding to AT-rich regions of genomic DNA, but structural details on this binding interaction have not been fully characterized. Here, we present crystal structures of the zinc finger cluster 4 (ZFC4) domain of SALL4 (SALL4ZFC4) bound with different dsDNAs containing a conserved AT-rich motif. In the structures, two zinc fingers of SALL4ZFC4 recognize an AATA tetranucleotide. We also solved the DNA-bound structures of SALL3ZFC4 and SALL4ZFC1. These structures illuminate a common preference for the AATA tetranucleotide shared by ZFC4 of SALL1, SALL3, and SALL4. Furthermore, our cell biology experiments demonstrate that the DNA-binding activity is essential for SALL4 function as DNA-binding defective mutants of mouse Sall4 failed to repress aberrant gene expression in Sall4-/- mESCs. Thus, these analyses provide new insights into the mechanisms of action underlying SALL family proteins in controlling cell fate via preferential targeting to AT-rich sites within genomic DNA during cell differentiation.

Structural insights into SMCR8 C-degron recognition by FEM1B.

C-degrons play critical roles in targeting the receptor proteins of Cullin-RING E3 ligase complexes to initiate protein degradation. FEM1 proteins, including FEM1A, FEM1B, and FEM1C, act as the receptors to specifically recognize Arg/C-degrons to enable CRL2-mediated protein turnover. Very few substrates have been identified for FEM1B, except CDK5R1. We found that CRL2FEM1B also recognizes the C-degron of an SMCR8 isoform, and uncovered the recognition of SMCR8 by FEM1B through presenting the structure of FEM1B bound to SMCR8. Our work provides insights into the role of CRL2FEM1B in regulating the lifetime of SMCR8, a critical autophagy regulator.

Ovarian failure-resistant effects of catalpol in aged female rats.

Catalpol, an iridoid glycoside obtained from various natural sources, has many biological functions. However, its ovarian failure-resistant effect has scarcely been studied. The present study used senile 14-month-old Sprague-Dawley female rats to examine the in vivo ovarian failure-resistant activity of catalpol. Daily oral graded doses of catalpol (1, 3, or 5 mg/kg/d) for 4 weeks significantly increased the levels of serum 17ß-estradiol (E2) and progesterone (P4) but reduced follicle-stimulating hormone and luteinizing hormone levels. Electron microscopic analysis and flow cytometry showed that catalpol significantly retarded apoptosis of the ovarian granulocytes of the rats. These findings suggest that catalpol works on the sex organs by nourishing ovarian tissues and improving both the quality and quantity of follicles, thus leading to rebalanced E2 and P4 levels in aged rats so that catalpol has a direct in vivo antiaging effect on the rat ovarian system.

[Study on serum fingerprint of menoprogen].

OBJECTIVE: To establish chromatographic fingerprint of components of Menoprogen absorbed into blood by RP-HPLC. METHODS: Kromasil C18 column was used, with of 0.1% phosphoric acid and acetonitrile as mobile phase in a gradient elution. The flow rate was 1.0 mL/min, the column temperature was 30 degrees C, the detection wavelength was 205 nm. 10 SD rats were administered 10 different batches of Menoprogen respectively. RESULTS: The fingerprint of Menoprogen was established. 18 common peaks were identified, the similarities were over 0. 95. By comparison drug and blank serum wiith contained drug serum, identified eight prototype components aborbed into blood directly and 10 metabolic components. CONCLUSION: The serum fingerprint of Menoprogen is established for the first time. 18 components are identifided in blood,one of them is hyperoside. It can reveal the change of chemical constituents after ingestion, and provide some data on material basis study in vivo for Menoprogen.

Association between serum NPTX2 and cognitive function in patients with vascular dementia.

OBJECTIVE: Neuronal Pentraxin 2 (NPTX2) has recently been widely reported as a novel biomarker for Alzheimer's disease (AD), but its correlation with vascular dementia (VaD) has not been elucidated. This study aimed to explore the correlation between NPTX2 and the cognitive function of VaD patients. METHODS: 112 VaD patients and 76 healthy controls were included in the study. Upon admission, clinical baseline data for all subjects were collected. Serum NPTX2 levels were determined using enzyme-linked immunosorbent assay (ELISA). At the same time, the Montreal cognitive assessment (MoCA) scale was used to measure cognitive function. Multivariate regression analysis was used to determine the relationship between serum NPTX2 level and the cognitive function of VaD patients. RESULTS: Compared with healthy controls, VaD patients had lower serum NPTX2 levels (p < .001). The results of Spearman's correlation analysis showed that serum NPTX2 levels in VaD patients were positively correlated with MoCA scores (r = .347, p = .042). The results of multivariate regression analysis showed that after adjusting for common risk factors, serum NPTX2 levels in VaD patients were still significantly associated with MoCA scores (ß = 0.346, p = .039). CONCLUSIONS: Serum NPTX2 level was independently associated with cognitive function in patients with VaD. Serum NPTX2 level may be a novel predictor for cognitive function in VaD.

Chemical constituents and bioactivities of Panax ginseng (C. A. Mey.).

Ginseng, Panax ginseng (C. A. Mey.), is a well-known Chinese traditional medicine in the Far East and has gained popularity in the West during the last decade. There is extensive literature on the chemical constituents and bioactivities of ginseng. In this paper we compiled the chemical constituents isolated and detected from ginseng including polysaccharides, ginsenosides, peptides, polyacetylenic alcohols, fatty acids, etc. Meanwhile we summarized the biological activities of ginseng, which have been reported over the past few decades, including: anti-aging activity, anti-diabetic activity, immunoregulatory activity, anti-cancer activity, neuroregulation activity, wound and ulcer healing activity, etc. Nevertheless, further studies to exploit other kinds of constituents and new biological activities of ginseng are still necessary to facilitate research and development in the future.

Chemical constituents and bioactivities of Colla corii asini.

In China, Colla corii asini is a health-care food and traditional Chinese medicine widely used in life-nourishing and clinical hematic antanemic therapy for more than 2,000 years. In this paper we compiled the chemical constituents isolated and detected from Colla corii asini including amino acids, proteins/gelatins, polysaccharides, volatile substances, inorganic substances, etc. Meanwhile we investigated the biological activities of Colla corii asini, which have been reported over the past few decades, including, hematologic diseases inhibitory activities, anti-aging activity, antitumor activity, immunomodulatory activity, bone repair activity, anti-inflammatory activity, antifatigue activity, etc. However, few reports on the relationships between the chemical constituents and bioactivities have been found, further studies of Colla corii asini are still necessary to facilitate research and development in the future.