Proteasome inhibitors activate autophagy as a cytoprotective response in human prostate cancer cells

The ubiquitin-proteasome and lysosome-autophagy pathways are the two major intracellular protein degradation systems that work cooperatively to maintain homeostasis. Proteasome inhibitors (PIs) have clinical activity in hematological tumors, and inhibitors of autophagy are also being evaluated as potential antitumor therapies. In this study, we found that chemical PIs and small interfering RNA-mediated knockdown of the proteasome's enzymatic subunits promoted autophagosome formation, stimulated autophagic flux, and upregulated expression of the autophagy-specific genes (ATGs) (ATG5 and ATG7) in some human prostate cancer cells and immortalized mouse embryonic fibroblasts (MEFs). Upregulation of ATG5 and ATG7 only occurred in cells displaying PI-induced phosphorylation of the eukaryotic translation initiation factor 2 alpha (eIF2alpha), an important component of the unfolded protein responses. Furthermore, PIs did not induce autophagy or upregulate ATG5 in MEFs expressing a phosphorylation-deficient mutant form of eIF2alpha. Combined inhibition of autophagy and the proteasome induced an accumulation of intracellular protein aggregates reminiscent of neuronal inclusion bodies and caused more cancer cell death than blocking either degradation pathway alone. Overall, our data show that proteasome inhibition activates autophagy through a phospho-eIF2alpha-dependent mechanism to eliminate protein aggregates and alleviate proteotoxic stress.

Lysophosphatidylcholine as a ligand for the immunoregulatory receptor G2A

Although the biological actions of the cell membrane and serum lipid lysophosphatidylcholine (LPC) in atherosclerosis and systemic autoimmune disease are well recognized, LPC has not been linked to a specific cell-surface receptor. We show that LPC is a high-affinity ligand for G2A, a lymphocyte-expressed G protein-coupled receptor whose genetic ablation results in the development of autoimmunity. Activation of G2A by LPC increased intracellular calcium concentration, induced receptor internalization, activated ERK mitogen-activated protein kinase, and modified migratory responses of Jurkat T lymphocytes. This finding implicates a role for LPC-G2A interaction in the etiology of inflammatory autoimmune disease and atherosclerosis.

Sphingosylphosphorylcholine is a ligand for ovarian cancer G-protein-coupled receptor 1

Sphingosylphosphorylcholine (SPC) is a bioactive lipid that acts as an intracellular and extracellular signalling molecule in numerous biological processes. Many of the cellular actions of SPC are believed to be mediated by the activation of unidentified G-protein-coupled receptors. Here we show that SPC is a high-affinity ligand for an orphan receptor, ovarian cancer G-protein-coupled receptor 1 (OGR1). In OGR1-transfected cells, SPC binds to OGR1 with high affinity (Kd = 33.3 nM) and high specificity and transiently increases intracellular calcium. The specific binding of SPC to OGR1 also activates p42/44 mitogen-activated protein kinases (MAP kinases) and inhibits cell proliferation. In addition, SPC causes internalization of OGR1 in a structurally specific manner.

Sphingosylphosphorylcholine and lysophosphatidylcholine are ligands for the G protein-coupled receptor GPR4

Sphingosylphosphorylcholine (SPC) and lysophosphatidylcholine (LPC) are bioactive lipid molecules involved in numerous biological processes. We have recently identified ovarian cancer G protein-coupled receptor 1 (OGR1) as a specific and high affinity receptor for SPC, and G2A as a receptor with high affinity for LPC, but low affinity for SPC. Among G protein-coupled receptors, GPR4 shares highest sequence homology with OGR1 (51%). In this work, we have identified GPR4 as not only another high affinity receptor for SPC, but also a receptor for LPC, albeit of lower affinity. Both SPC and LPC induce increases in intracellular calcium concentration in GPR4-, but not vector-transfected MCF10A cells. These effects are insensitive to treatment with BN52021, WEB-2170, and WEB-2086 (specific platelet activating factor (PAF) receptor antagonists), suggesting that they are not mediated through an endogenous PAF receptor. SPC and LPC bind to GPR4 in GPR4-transfected CHO cells with K(d)/SPC = 36 nm, and K(d)/LPC = 159 nm, respectively. Competitive binding is elicited only by SPC and LPC. Both SPC and LPC activate GPR4-dependent activation of serum response element reporter and receptor internalization. Swiss 3T3 cells expressing GPR4 respond to both SPC and LPC, but not sphingosine 1-phosphate (S1P), PAF, psychosine (Psy), glucosyl-beta1'1-sphingosine (Glu-Sph), galactosyl-beta1'1-ceramide (Gal-Cer), or lactosyl-beta1'1-ceramide (Lac-Cer) to activate extracellular signal-regulated kinase mitogen-activated protein kinase in a concentration- and time-dependent manner. SPC and LPC stimulate DNA synthesis in GPR4-expressing Swiss 3T3 cells. Both extracellular signal-regulated kinase activation and DNA synthesis stimulated by SPC and LPC are pertussis toxin-sensitive, suggesting the involvement of a G(i)-heterotrimeric G protein. In addition, GPR4 expression confers chemotactic responses to both SPC and LPC in Swiss 3T3 cells. Taken together, our data indicate that GPR4 is a receptor with high affinity to SPC and low affinity to LPC, and that multiple cellular functions can be transduced via this receptor.

Comparison of QCT-derived and DXA-derived areal bone mineral density and T scores

Two-dimensional areal bone mineral density (aBMD) of the proximal femur measured by three-dimensional quantitative computed tomography (QCT) in 91 elderly women was compared to dual-energy X-ray absorptiometry (DXA) aBMD results measured in the same patients. The measurements were highly correlated, though QCT aBMD values were marginally lower in absolute units. Transformation of the QCT aBMD values to T score values using National Health and Nutrition Examination Survey (NHANES) DXA-derived reference data improved agreement and clinical utility.

INTRODUCTION

World Health Organization guidelines promulgate aBMD (g cm(-2)) measurement of the proximal femur for the diagnosis of bone fragility. In recent years, there has been increasing interest in QCT to facilitate understanding of three-dimensional bone structure and strength.

OBJECTIVE

To assist in comparison of QCT-derived data with DXA aBMD results, a technique for deriving aBMD from QCT measurements has been developed.

METHODS

To test the validity of the QCT method, 91 elderly females were scanned on both DXA and CT scanners. QCT-derived DXA equivalent aBMD (QCT(DXA) aBMD) was calculated using CTXA Hip software (Mindways Software Inc., Austin, TX, USA) and compared to DXA-derived aBMD results.

RESULTS

Test retest analysis indicated lower root mean square (RMS) errors for CTXA; F test between CTXA and DXA was significantly different at femoral neck (FN) and trochanter (TR) (p < 0.05). QCT underestimates DXA values by 0.02 +/- 0.05 g cm(-2) (total hip, TH), 0.01 +/- 0.04 g cm(-2) (FN), 0.03 +/- 0.07 g cm(-2) (inter-trochanter, IT), and 0.02 +/- 0.05 g cm(-2) (TR). The RMS errors (standard error of estimate) between QCT and DXA T scores for TH, FN, IT, and TR were 0.36, 0.40, 0.39, and 0.49, respectively.

CONCLUSIONS

This study shows that results from QCT aBMD appropriately adjusted can be evaluated against NHANES reference data to diagnose osteoporosis.

Structure and mutagenesis of the Dbl homology domain

Guanine nucleotide exchange factors in the Dbl family activate Rho GTPases by accelerating dissociation of bound GDP, promoting acquisition of the GTP-bound state. Dbl proteins possess a approximately 200 residue catalytic Dbl-homology (DH) domain, that is arranged in tandem with a C-terminal pleckstrin homology (PH) domain in nearly all cases. Here we report the solution structure of the DH domain of human PAK-interacting exchange protein (betaPIX). The domain is composed of 11 alpha-helices that form a flattened, elongated bundle. The structure explains a large body of mutagenesis data, which, along with sequence comparisons, identify the GTPase interaction site as a surface formed by three conserved helices near the center of one face of the domain. Proximity of the site to the DH C-terminus suggests a means by which PH-ligand interactions may be coupled to DH-GTPase interactions to regulate signaling through the Dbl proteins in vivo.

Risk factors for preeclampsia in twin pregnancies: a population-based cohort study

OBJECTIVE

To evaluate in twin pregnancies the characteristics parity, race, smoking, and age, known to be risk factors for preeclampsia in non-twin pregnancies.

METHODS

All twin pregnancies (3407) and approximately twice as many singletons (8287) were assembled using Washington state birth certificates from the period 1984-1988.

RESULTS

In singleton pregnancies, preeclampsia was more common in women who were younger, black, poor, nulliparous, and nonsmokers. In twin pregnancies, similar associations were found, but were only statistically significant for age, race, and parity. There were no significant differences in the risk factors between twin and singleton women. Logistic regression showed that twin pregnancy carries a relative risk (RR) of 3.5 (95% confidence interval [CI] 3.0-4.2), nulliparity an RR of 4.0 (95% CI 3.3-4.8), and black race an RR of 1.8 (95% CI 1.2-2.6) for preeclampsia. In each case, this risk is independent of the other risk factors.

CONCLUSION

Twin pregnancy carries nearly a fourfold increased risk of preeclampsia, independent of race and parity, and the risk of a nulliparous twin pregnancy is 14 times that of a parous singleton pregnancy. Risk factors in a singleton pregnancy act similarly in a twin pregnancy. Thus, any pathophysiologic model for preeclampsia needs to account for the risk twin pregnancy poses as well as other risk factors, such as parity and race.

Partial splenic embolization for hypersplenism in cirrhosis: a long-term outcome in 62 patients

BACKGROUND

Although partial splenic embolization (PSE) has been widely used for treatment of leucocytopaenia and thrombocytopaenia in cirrhosis, only few studies on the correlation between splenic infarction rate and long-term outcome of partial splenic embolization have been reported so far.

AIM

To evaluate long-term results of partial splenic embolization with different infarction rates in cirrhotic patients with hypersplenism.

METHODS

Sixty-two consecutive patients with hypersplenism in cirrhosis received partial splenic embolization. According to the splenic infarction rate after partial splenic embolization, the patients were divided into three groups: more than 70% in group A (n=12), 50-70% in group B (n=34), and less than 50% in group C (n=16). The post-partial splenic embolization following-up time was 5 years.

RESULTS

Before partial splenic embolization, there were no significant differences among the three groups with respect to sex, age, splenic volume, Child-Pugh class, oesophageal varices, and peripheral blood cell counts. After partial splenic embolization, the short- and long-term outcomes of leucocyte and platelet counts showed significant difference among the three groups (P<0.001). In groups A and B, the leucocyte and platelet counts after partial splenic embolization remained significantly higher than those before partial splenic embolization for 2 weeks to 5 years (P<0.05), the post-partial splenic embolization leucocyte and platelet counts was even higher in group A than in group B; while in group C, leucocyte and platelet count improvement only lasted for 6 months after partial splenic embolization. No significant changes were observed concerning blood red cell counts and liver function parameters after partial splenic embolization among the three groups. Severe complications occurred in six patients (50%) in group A and three patients (8.8%) in group B (P<0.05), while in group C, no severe complications developed.

CONCLUSIONS

In partial splenic embolization, the splenic infarction rate should be limited to 50%-70% in order to ensure the long-term efficacy in alleviating hypersplenism and reduce complications.

Differential regulation of cellular target genes by p53 devoid of the PXXP motifs with impaired apoptotic activity

Activation of the p53 tumor suppressor protein can lead to either cell cycle arrest or apoptosis. Several functional domains necessary for mediating cell cycle arrest and apoptosis in p53 have been mapped, e.g., the proline-rich domain. The proline-rich domain is located within residues 60-90, which comprise five PXXP motifs (where P represents proline and X any amino acid). To further delineate the function of the proline-rich domain and its potential role in transactivation, we generated several groups of cell lines that inducibly express various p53 mutants using a tetracycline-regulated expression system. We found that p53(delta62-91), which lacks all five PXXP motifs in human p53, is capable of inducing cell cycle arrest but not apoptosis, while p53(gln22-ser23/delta62-91), which contains a double point mutation in the activation domain as well as deletion of the proline-rich domain, completely loses its activity. However, p53(delta74-91), which contains only one PXXP motif at its N-terminus, is not only capable of inducing cell cycle arrest but also retains a partial apoptotic activity. Furthermore, we found that deletion of the proline-rich region has no or very mild effects on activation of several transiently transfected p53 target gene promoters, i.e., the p21, MDM2, BAX, and GADD45 promoters. However, such deletion differentially affects p53 induction of endogenous target genes, i.e., induction of p21, MDM2, BTG2, p85, PIG3, PIG6 and PIG11 was reduced or abrogated but induction of BAX, KILLER/DR5, PIG2, PIG7 and PIG8 was not substantially affected. Interestingly, induction of GADD45 was enhanced. These results suggest that the proline-rich region may play a role in chromatin remodeling, which counteracts chromatin-mediated repression for some of the endogenous p53 target genes.

Inhibition of dendritic cell differentiation by fumaric acid esters

Fumaric acid esters have proved to be effective for the systemic treatment of severe psoriasis vulgaris. These compounds have been shown to induce a Th2-like cytokine secretion pattern in T cells and to reduce keratinocyte proliferation in vitro. Dendritic cells seem to be of major importance as regulatory cells driving the psoriatic tissue reaction. Monocytes or CD34-positive myeloid progenitor cells are precursors of dendritic cells that can be generated in vitro by culture with granulocyte-macrophage colony-stimulating factor and interleukin-4. Using this model the effect of fumaric acid esters on granulocyte-macrophage colony-stimulating factor/interleukin-4-induced differentiation of monocyte-derived dendritic cells was investigated. The results of this study show that dimethylfumarate as well as methylhydrogenfumarate-calcium-salt (0.01-100 microg per ml) concentration-dependently inhibit monocyte-derived dendritic cell differentiation. This was reflected by an inhibition of CD1a, CD40, CD80, CD86, and HLA-DR expression as well as by a reduced capacity of dimethylfumarate-treated monocyte-derived dendritic cells to stimulate lymphocytes in the allogeneic mixed lymphocyte reaction. Other fumaric acid esters showed no effect on monocyte-derived dendritic cell-differentiation. At higher concentrations (30-100 microg per ml) dimethylfumarate, but not methylhydrogenfumarate calcium-salt induced apoptosis in monocyte-derived dendritic cells as measured by expression of Apo 2.7 and DNA fragmentation (TUNEL assay). These data point to a high susceptibility of the monocyte/dendritic cell system to dimethylfumarate and its main metabolite methylhydrogenfumarate. Other fumaric acid esters investigated were without effect. As the effects of fumarates on monocyte-derived dendritic cells observed occur at concentrations 20-fold lower compared with lymphocytes, our data seem to be of relevance in explaining the possible mode of action of these compounds in psoriasis.

Relationship between vitamin D status, body composition and physical exercise of adolescent girls in Beijing

Little is known about the prevalence of actual vitamin D deficiency in healthy school-aged adolescents, particularly in China. The aim of this study was to examine the prevalence of hypovitaminosis D and to identify whether there was any association between vitamin D status, body composition and physical exercise in 323 Chinese adolescent girls in Beijing, China (40 degrees N).

INTRODUCTION

It is well recognized that persistent severe vitamin D deficiency is associated with the bone abnormalities of rickets and osteomalacia. However, there is now evidence suggesting that low vitamin D status, not previously considered to be a state of deficiency is associated with secondary hyperparathyroidism, increased bone remodelling and other clinical signs thought only to be found in severe vitamin D deficiency. Hypovitaminosis D in healthy children and adolescents has been reported frequently in many countries, especially in winter.

METHODS

We performed a cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter. Mean age of the subjects was 15.0 (+/-0.4) years. About 32.8%, 68.4% and 89.2% of the subjects were at risk of vitamin D deficiency when defined as plasma concentrations of 25OHD of 25, 37.5 or 50 nmol/L, respectively.

RESULTS

This cross-sectional analysis of 323 Chinese adolescent girls in Beijing in winter showed that hypovitaminosis D was common in these subjects. In addition, body mass index, milk intake, participation in organized sports and total physical activity were all significant independent determinants of vitamin D status. An inverse association was found between plasma 25OHD and intact-parathyroid hormone (iPTH) concentration. Body mass index (BMI), milk intake, participation in organized sports and total physical activity all emerged as major independent determinants of vitamin D status as assessed by plasma 25OHD concentration. Vitamin D status was positively associated with lean body mass (LBM), but there was no association with the degree of body adiposity. Regardless of the concentration of 25OHD in blood used to define vitamin D deficiency, hypovitaminosis D was common in these subjects.

CONCLUSION

It is recommended that policies be developed to prevent vitamin D deficiency in adolescent girls. Further studies are needed to identify the mechanisms whereby vitamin D status is related to exercise and to body composition during growth.

p53 induces TAP1 and enhances the transport of MHC class I peptides

The transporter associated with antigen processing (TAP) 1 is required for the major histocompatibility complex (MHC) class I antigen presentation pathway, which plays a key role in host tumor surveillance. Since more than 50% of tumors have a dysfunctional p53, evasion of tumor surveillance by tumor cells may be linked to loss of p53 function. Here we found that TAP1 is strongly induced by p53 and DNA-damaging agents through a p53-responsive element. We also found that p73, which is homologous to p53, is capable of inducing TAP1 and cooperates with p53 to activate TAP1. Furthermore, we found that by inducing TAP1, p53 enhances the transport of MHC class I peptides and expression of surface MHC-peptide complexes, and cooperates with interferon gamma to activate the MHC class I pathway. These results suggest that tumor surveillance may be a mechanism by which p53 and/or p73 function as tumor suppressors.

Resonance Raman and Raman Spectroscopy for Breast Cancer Detection

Raman spectroscopy is a sensitive method to detect early changes of molecular composition and structure that occur in lesions during carcinogenesis. The Raman spectra of normal, benign and cancerous breast tissues were investigated in vitro using a near-infrared (NIR) Raman system of 785 nm excitation and confocal micro resonance Raman system of 532 nm excitation. A total number of 491 Raman spectra were acquired from normal, benign and cancerous breast tissues taken from 15 patients. When the 785 nm excitation was used, the dominant peaks in the spectra were characteristic of the vibrations of proteins and lipids. The differences between the normal and cancerous breast tissues were observed in both the peak positions and the intensity ratios of the characteristic Raman peaks in the spectral region of 700–1800 cm−1. With 532 nm excitation, the resonance Raman (RR) spectra exhibited a robust pattern of peaks within the region of 500–4000 cm−1. The intensities of four distinct peaks at 1156, 1521, 2854 and 3013 cm−1 detected in the spectra collected from normal breast tissue were found to be stronger in comparison with those collected from cancerous breast tissue. The twelve dramatically enhanced characteristic peaks, including the enhanced amide II peak at 1548 cm−1 in the spectra collected from cancerous breast tissue, distinguished the cancerous tissue from the normal tissue. Principal component analysis (PCA) combined with support vector machine (SVM) analysis of the Raman and RR spectral data yielded a high performance in the classification of cancerous and benign lesions from normal breast tissue.

Involvement of endoplasmic reticulum stress in the necroptosis of microglia/macrophages after spinal cord injury

Microglia/macrophages play a crucial role in inflammation after spinal cord injury (SCI). Although extensive studies have been performed on the mechanisms of microglia/macrophage activation and recruitment, how microglia/macrophages are eliminated remains unclear. In the present study, we observed a high-level expression of mixed lineage kinase domain-like protein (MLKL), a key molecule in the execution of necroptosis, in microglia/macrophages after SCI in mice. In vivo PI-labeling and Necrostatin-1 treatment confirmed the necroptosis of microglia/macrophages. Interestingly, our electronic microscopic (EM) study revealed that MLKL localized not only at the membrane but also on the endoplasmic reticulum (ER) of necroptotic microglia/macrophages. Furthermore, receptor-interacting protein 3 (RIP3), another necrosome component, was also found on the ER of necroptotic microglia/macrophages. And Glucose-regulated protein 78 (GRP78), an ER stress sensor, was up-regulated in MLKL-positive microglia/macrophages after SCI, suggesting a possible link between necroptosis and ER stress. In vitro, oxygen-glucose deprivation (OGD) stress induced ER stress and necroptosis in microglia. Inhibiting ER stress by 4-phenylbutyrate (4-PBA) significantly blocked the OGD-induced necroptosis of microglia. In the end, our data showed that, GRP78 and phosphorylated MLKL were co-expressed by the microglia/macrophages in the injured human spinal cord. Taken together, these results suggested that microglia/macrophages undergo an ER-stress involved necroptosis after SCI, implying that ER stress and necroptosis could be manipulated for modulating inflammation post-SCI.

Comparison of self-report data and medical records data: results from a case-control study on prostate cancer

BACKGROUND

Self-report and review of medical records are the most common methods for the assessment of past exposures. However, information obtained from self-reports and medical records may not be consistent. This study compared information provided in a self-administered questionnaire with medical records data.

METHODS

Self-report and medical records data came from a case-control study on prostate cancer. Cases were 181 patients with primary prostate cancer and controls were 297 men without the disease, enrolled in Group Health Cooperative (GHC) in Seattle. The consistencies between the two data sources were examined.

RESULTS

In general, agreement between the two data sources was almost perfect for demographic and anthropometric variables, substantial for the history of inguinal hernia and kidney stones, and moderate for vasectomy, family history of prostate cancer, smoking and alcohol consumption. However, the two data sources generally were poorly concordant for prior genitourinary diseases that have less explicit diagnostic criteria such as benign prostatic hyperplasia and prostatitis. Analyses of discordant data showed that men were more likely to report an exposure or medical condition that could not be verified from medical records. No discernible patterns in the difference of agreement were found according to age, GHC membership length or case-control status.

CONCLUSIONS

This study suggests that agreement between self-reported data and medical records data varies depending upon the study variables. While both data sources are subject to some problems, self-report may provide more complete and comparable information, at least for variables unrelated to diagnosis.

The Impact of Dietary Protein or Amino Acid Supplementation on Muscle Mass and Strength in Elderly People: Individual Participant Data and Meta-Analysis of RCT's

OBJECTIVES

Increasing protein or amino acid intake has been promoted as a promising strategy to increase muscle mass and strength in elderly people, however, long-term intervention studies show inconsistent findings. Therefore, we aim to determine the impact of protein or amino acid supplementation compared to placebo on muscle mass and strength in older adults by combining the results from published trials in a meta-analysis and pooled individual participant data analysis.

DESIGN

We searched Medline and Cochrane databases and performed a meta-analysis on eight available trials on the effect of protein or amino acid supplementation on muscle mass and strength in older adults. Furthermore, we pooled individual data of six of these randomized double-blind placebo-controlled trials. The main outcomes were change in lean body mass and change in muscle strength for both the meta-analysis and the pooled analysis.

RESULTS

The meta-analysis of eight studies (n=557) showed no significant positive effects of protein or amino acid supplementation on lean body mass (mean difference: 0.014 kg: 95% CI -0.152; 0.18), leg press strength (mean difference: 2.26 kg: 95% CI -0.56; 5.08), leg extension strength (mean difference: 0.75 kg: 95% CI: -1.96, 3.47) or handgrip strength (mean difference: -0.002 kg: 95% CI -0.182; 0.179). Likewise, the pooled analysis showed no significant difference between protein and placebo treatment on lean body mass (n=412: p=0.78), leg press strength (n=121: p=0.50), leg extension strength (n=121: p=0.16) and handgrip strength (n=318: p=0.37).

CONCLUSIONS

There is currently no evidence to suggest that protein or amino acid supplementation without concomitant nutritional or exercise interventions increases muscle mass or strength in predominantly healthy elderly people.

Detergent-induced conformational changes of Humicola lanuginosa lipase studied by fluorescence spectroscopy

Detergent (pentaoxyethylene octyl ether, C(8)E(5))-induced conformational changes of Humicola lanuginosa lipase (HLL) were investigated by stationary and time-resolved fluorescence intensity and anisotropy measurements. Activation of HLL is characterized by opening of a surface loop (the "lid") residing directly over the enzyme active site. The interaction of HLL with C(8)E(5) increases fluorescence intensities, prolongs fluorescence lifetimes, and decreases the values of steady-state anisotropy, residual anisotropy, and the short rotational correlation time. Based on these data, we propose the following model. Already below critical micellar concentration (CMC) the detergent can intercalate into the active site accommodating cleft, while the lid remains closed. Occupation of the cleft by C(8)E(5) also blocks the entry of the monomeric substrate, and inhibition of catalytic activity at [C(8)E(5)] less than or equal to CMC is evident. At a threshold concentration close to CMC the cooperativity of the hydrophobicity-driven binding of C(8)E(5) to the lipase increases because of an increase in the number of C(8)E(5) molecules present in the premicellar nucleates on the hydrophobic surface of HLL. These aggregates contacting the lipase should have long enough residence times to allow the lid to open completely and expose the hydrophobic cleft. Concomitantly, the cleft becomes filled with C(8)E(5) and the "open" conformation of HLL becomes stable.

Higher PD-1 expression concurrent with exhausted CD8+ T cells in patients with de novo acute myeloid leukemia

Objective

To investigate the association between the T cell inhibitory receptor programmed death 1 (PD-1) and T cell exhaustion status in T cells from patients with de novo acute myeloid leukemia (AML) and AML in complete remission (CR).

Methods

Surface expression of PD-1 and the exhaustion and immunosenescence markers CD244 and CD57 on CD3+, CD4+ and CD8+ T cells from peripheral blood samples from 20 newly diagnosed, untreated AML patients and 10 cases with AML in CR was analyzed by flow cytometry. Twenty-three healthy individuals served as control.

Results

A significantly higher percentage of PD-1+ cells were found for CD3+ T cells in the de novo AML group compared with healthy controls. In addition, an increased level of PD-1+CD8+ T cells, but not PD-1+CD4+, was found for CD3+ T cells in the de novo AML and AML-CR samples. A higher percentage of CD244+CD4+, CD244+CD8+, CD57+CD4+ and CD57+CD8+ T cells was found in CD3+ T cells in samples from those with de novo AML compared with those from healthy controls. Strong increased PD-1+CD244+ and PD-1+CD57+ co-expression was found for CD4+ and CD8+ T cells in the de novo AML group compared with healthy controls.

Conclusions

We characterized the major T cell defects, including co-expression of PD-1 and CD244, CD57-exhausted T cells in patients with de novo AML, and found a particular influence on CD8+ T cells, suggesting a poor anti-leukemia immune response in these patients.

Autoinhibition mechanism of proto-Dbl

The dbl oncogene encodes a prototype member of the Rho GTPase guanine nucleotide exchange factor (GEF) family. Oncogenic activation of proto-Dbl occurs through truncation of the N-terminal 497 residues. The C-terminal half of proto-Dbl includes residues 498 to 680 and 710 to 815, which fold into the Dbl homology (DH) domain and the pleckstrin homology (PH) domain, respectively, both of which are essential for cell transformation via the Rho GEF activity or cytoskeletal targeting function. Here we have investigated the mechanism of the apparent negative regulation of proto-Dbl imposed by the N-terminal sequences. Deletion of the N-terminal 285 or C-terminal 100 residues of proto-Dbl did not significantly affect either its transforming activity or GEF activity, while removal of the N-terminal 348 amino acids resulted in a significant increase in both transformation and GEF potential. Proto-Dbl displayed a mostly perinuclear distribution pattern, similar to a polypeptide derived from its N-terminal sequences, whereas onco-Dbl colocalized with actin stress fibers, like the PH domain. Coexpression of the N-terminal 482 residues with onco-Dbl resulted in disruption of its cytoskeletal localization and led to inhibition of onco-Dbl transforming activity. The apparent interference with the DH and PH functions by the N-terminal sequences can be rationalized by the observation that the N-terminal 482 residues or a fragment containing residues 286 to 482 binds specifically to the PH domain, limiting the access of Rho GTPases to the catalytic DH domain and masking the intracellular targeting function of the PH domain. Taken together, our findings unveiled an autoinhibitory mode of regulation of proto-Dbl that is mediated by the intramolecular interaction between its N-terminal sequences and PH domain, directly impacting both the GEF function and intracellular distribution.

Irreversible inhibition of human immunodeficiency virus type 1 integrase by dicaffeoylquinic acids

Human immunodeficiency virus type 1 (HIV-1) and other retroviruses require integration of a double-stranded DNA copy of the RNA genome into the host cell chromosome for productive infection. The viral enzyme, integrase, catalyzes the integration of retroviral DNA and represents an attractive target for developing antiretroviral agents. We identified several derivatives of dicaffeoylquinic acids (DCQAs) that inhibit HIV-1 replication in tissue culture and catalytic activities of HIV-1 integrase in vitro. The specific step at which DCQAs inhibit the integration in vitro and the mechanism of inhibition were examined in the present study. Titration experiments with different concentrations of HIV-1 integrase or DNA substrate found that the effect of DCQAs was exerted on the enzyme and not the DNA. In addition to HIV-1, DCQAs also inhibited the in vitro activities of MLV integrase and truncated variants of feline immunodeficiency virus integrase, suggesting that these compounds interacted with the central core domain of integrase. The inhibition on retroviral integrases was relatively specific, and DCQAs had no effect on several other DNA-modifying enzymes and phosphoryltransferases. Kinetic analysis and dialysis experiments showed that the inhibition of integrase by DCQAs was irreversible. The inhibition did not require the presence of a divalent cation and was unaffected by preassembling integrase onto viral DNA. The results suggest that the irreversible inhibition by DCQAs on integrase is directed toward conserved amino acid residues in the central core domain during catalysis.