Assembly of the eIF4E/eIF4G complex has a central role in the regulation of gene expression at the level of translation initiation. This complex is regulated by the 4E-BPs, which compete with eIF4G ...for binding to eIF4E and which have tumor-suppressor activity. To pharmacologically mimic 4E-BP function we developed a high-throughput screening assay for identifying small-molecule inhibitors of the eIF4E/eIF4G interaction. The most potent compound identified, 4EGI-1, binds eIF4E, disrupts eIF4E/eIF4G association, and inhibits cap-dependent translation but not initiation factor-independent translation. While 4EGI-1 displaces eIF4G from eIF4E, it effectively enhances 4E-BP1 association both in vitro and in cells. 4EGI-1 inhibits cellular expression of oncogenic proteins encoded by weak mRNAs, exhibits activity against multiple cancer cell lines, and appears to have a preferential effect on transformed versus nontransformed cells. The identification of this compound provides a new tool for studying translational control and establishes a possible new strategy for cancer therapy.
Plasma glycated CD59 (pGCD59) is an emerging biomarker in diabetes. We assessed whether pGCD59 could predict the following: the results of the glucose challenge test (GCT) for screening of ...gestational diabetes mellitus (GDM) (primary analysis); and the diagnosis of GDM and prevalence of large for gestational age (LGA) newborns (secondary analyses).
Case-control study of 1,000 plasma samples from women receiving standard prenatal care, 500 women having a normal GCT (control subjects) and 500 women with a failed GCT and a subsequent oral glucose tolerance test (case patients).
Compared with control subjects, the median (interquartile range) pGCD59 value was 8.5-fold higher in case patients and 10-fold higher in GDM patients, as follows: control subjects 0.33 (0.19); case patients 2.79 (1.4); GDM patients 3.23 (1.43) (
< 0.001); area under the receiver operating characteristic curve 0.92. LGA prevalence was 4.3% in the lowest quartile and 13.5% in the highest quartile of pGCD59.
One pGCD59 measurement during weeks 24-28 identifies pregnancy-induced glucose intolerance with high sensitivity and specificity and can potentially identify the risk for LGA.
The interaction of the eukaryotic translation initiation factor eIF4E with the initiation factor eIF4G recruits the 40S ribosomal particle to the 5′ end of mRNAs, facilitates scanning to the AUG ...start codon, and is crucial for eukaryotic translation of nearly all genes. Efficient recruitment of the 40S particle is particularly important for translation of mRNAs encoding oncoproteins and growth-promoting factors, which often harbor complex 5′ UTRs and require efficient initiation. Thus, inhibiting the eIF4E/eIF4G interaction has emerged as a previously unpursued route for developing anticancer agents. Indeed, we discovered small-molecule inhibitors of this eIF4E/eIF4G interaction (4EGIs) that inhibit translation initiation both in vitro and in vivo and were used successfully in numerous cancer–biology and neurobiology studies. However, their detailed molecular mechanism of action has remained elusive. Here, we show that the eIF4E/eIF4G inhibitor 4EGI-1 acts allosterically by binding to a site on eIF4E distant from the eIF4G binding epitope. Data from NMR mapping and high-resolution crystal structures are congruent with this mechanism, where 4EGI-1 attaches to a hydrophobic pocket of eIF4E between β-sheet ₂ (L ₆₀-T ₆₈) and α-helix ₁ (E ₆₉-N ₇₇), causing localized conformational changes mainly in the H ₇₈-L ₈₅ region. It acts by unfolding a short 3 ₁₀-helix (S ₈₂-L ₈₅) while extending α-helix ₁ by one turn (H ₇₈-S ₈₂). This unusual helix rearrangement has not been seen in any previous eIF4E structure and reveals elements of an allosteric inhibition mechanism leading to the dislocation of eIF4G from eIF4E.
Oxytocin (OT) is a neurohypophyseal peptide hormone containing a disulphide-bridged pseudocyclic conformation. The biomedical use of OT peptides is limited amongst others by disadvantageous ...pharmacokinetic parameters. To increase the stability of OT by replacing the disulphide bridge with the stable and more rigid 1,2,3triazol-1-yl moiety, we employed the Cu2+-catalysed side chain-to-side chain azide-alkyne 1,3-cycloaddition. Here we report the design, synthesis, conformational analysis, and in vitro pharmacological activity of a homologous series of Cα1-to-Cα6 side chain-to-side chain 1,2,3triazol-1-yl-containing OT analogues differing in the length of the bridge, location, and orientation of the linking moiety. Exploiting this macrocyclisation approach, it was possible to generate a systematic series of compounds providing interesting insight into the structure-conformation-function relationship of OT. Most analogues were able to adopt similar conformation to endogenous OT in water, namely, a type I β-turn. This approach may in the future generate stabilised pharmacological peptide tools to advance understanding of OT physiology.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Context:
Human CD59, an inhibitor of the membrane attack complex of complement, is inactivated by glycation. Glycation inactivation of CD59 enhances complement-mediated injury in target organs of ...diabetes complications.
Objective:
We hypothesized that circulating soluble glycated CD59 (GCD59) represents a novel biomarker of blood glucose handling and aimed to conduct human study protocols to test this hypothesis.
Design, Setting, Participants, and Outcome Measures:
Using a newly developed ELISA, we measured circulating soluble GCD59 in samples from 3 separate human studies evaluating acute and chronic glucose handling and glucose responses to insulin therapy. Study 1 (normal vs diabetic subjects) evaluated the cross-sectional association between GCD59 and glycated hemoglobin (HbA1c) in 400 subjects with and without type 2 diabetes. Study 2 (oral glucose tolerance test OGTT in nondiabetics) evaluated whether fasting GCD59 independently predicted the 2-hour glucose response to an OGTT in 109 subjects without a diagnosis of diabetes. Study 3 (intensified insulin treatment) evaluated the effect of intensification of glycemic control with insulin on GCD59 in 21 poorly controlled individuals with diabetes.
Results:
In study 1 (normal vs diabetic subjects), GCD59 was independently and positively associated with HbA1c in individuals with and without diabetes (β = 1.1, P < .0001 and β = 1.1 P < .001, respectively). In study 2 (OGTT in nondiabetics), a single GCD59 measurement independently predicted the results of the 2-hour OGTT (β = 19.8, P < .05) after multivariate modeling. In study 3 (intensified insulin treatment), intensification of glucose control with insulin resulted in a concomitant and parallel reduction of average weekly glucose and GCD59 within 2 weeks.
Conclusions:
We observed robust relationships between a single measurement of blood levels of GCD59 and both acute (2-hour OGTT) and chronic (HbA1c) measures of glucose handling. Lowering of GCD59 levels closely reflected lowering of average weekly glucose within 2 weeks. The role of GCD59 in the diagnosis, management, and vascular risk stratification in diabetes warrants further investigation.
Intramolecular side-chain to side-chain cyclization is an established approach to achieve stabilization of specific conformations and a recognized strategy to improve resistance toward proteolytic ...degradation. To this end, cyclizations, which are bioisosteric to the lactam-type side-chain to side-chain modification and do not require orthogonal protection schemes, are of great interest. Herein, we report the employment of CuI-catalyzed 1,3-dipolar cycloaddition of side chains modified with azido and alkynyl functions and explore alternative synthetic routes to efficiently generate 1,4-disubstituted 1,2,3triazolyl-containing cyclopeptides. The solid-phase assembly of the linear precursor including ϵ-azido norleucine and the propargylglycine (Pra) in positions i and i+4, respectively, was accomplished by either subjecting the resin-bound peptide to selective on-resin diazo transformation of a Lys into the Nle(ϵ-N3) or the incorporation of Fmoc-Nle(ϵ-N3)-OH during the stepwise build-up of the resin-bound peptide 1b. Solution-phase CuI-catalyzed 1,3-dipolar cycloaddition converts the linear precursor Ac-Lys-Gly-Nle(ϵ-N3)-Ser-Ile-Gln-Pra-Leu-Arg-NH2 (2) into the 1,4-disubstituted 1,2,3triazolyl-containing cyclopeptide Ac-Lys-Gly-Xaa(&1)-Ser-Ile-Gln-Yaa(&2)-Leu-Arg-NH2(&1(CH2)4-1,4-1,2,3triazolyl-CH2&2) (3). The conformational preferences of the model cyclopeptide 3 (III), which is derived from the sequence of a highly helical and potent i to i+4 side-chain to side-chain lactam-containing antagonist of parathyroid hormone-related peptide (PTHrP), are compared to the corresponding lactam analogue AcLys13(&1),Asp17(&2)hPTHrP(11−19)NH2 (II). CD and NMR studies of 3 and II in water/hexafluoroacetone (HFA) (50:50, v/v) revealed a high prevalence of turn-helical structures involving in particular the cyclic regions of the molecule. Despite a slight difference of the backbone arrangement, the side-chains of Ser, Gln, and Ile located at the i+1 to i+3 of the ring-forming sequences share the same spatial orientation. Both cyclopeptides differ regarding the location of the turn-helical segment, which in II involves noncyclized residues while in 3 it overlaps with residues involved in the cyclic structure. Therefore, the synthetic accessibility and conformational similarity of i to i+4 side-chain to side-chain cyclopeptide containing the 1,4-disubstituted 1,2,3triazolyl moiety to the lactam-type one may result in similar bioactivities.
Rituximab efficacy in cancer therapy depends in part on induction of complement-dependent cytotoxicity (CDC). Human CD59 (hCD59) is a key complement regulatory protein that restricts the formation of ...the membrane attack complex, thereby inhibiting induction of CDC. hCD59 is highly expressed in B-cell non-Hodgkin's lymphoma (NHL), and upregulation of hCD59 is an important determinant of the sensitivity of NHL cells to rituximab treatment. Here, we report that the potent hCD59 inhibitor rILYd4 enhances CDC in vitro and in vivo, thereby sensitizing rituximab-resistant lymphoma cells and primary chronic lymphocytic leukemia cells (CLL) to rituximab treatment. By defining pharmcokinetic/pharmacodynamic profiles of rILYd4 in mice, we showed that by itself rILYd4 does not adversely mediate in vivo hemolysis of hCD59-expressing erythrocytes. Increasing expression levels of the complement regulators CD59 and CD55 in rituximab-resistant cells occur due to selection of preexisting clones rather than de novo induction of these proteins. Moreover, lymphoma cells overexpressing CD59 were directly responsible for the resistance to rituximab-mediated CDC therapy. Our results rationalize the use of rILYd4 as a therapeutic adjuvant for rituximab treatment of rituximab-resistant lymphoma and CLL. Furthermore, they suggest that preemptive elimination of CD59-overexpressing subpopulations along with rituximab treatment may be a useful approach to ablate or conquer rituximab resistance.
Considerable evidence indicates that the general blockade of protein synthesis prevents both the initial consolidation and the postretrieval reconsolidation of long-term memories. These findings come ...largely from studies of drugs that block ribosomal function, so as to globally interfere with both cap-dependent and -independent forms of translation. Here we show that intra-amygdala microinfusions of 4EGI-1, a small molecule inhibitor of cap-dependent translation that selectively disrupts the interaction between eukaryotic initiation factors (eIF) 4E and 4G, attenuates fear memory consolidation but not reconsolidation. Using a combination of behavioral and biochemical techniques, we provide both in vitro and in vivo evidence that the eIF4E-eIF4G complex is more stringently required for plasticity induced by initial learning than for that triggered by reactivation of an existing memory.
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