Promising properties of cytochrome P450 BM3 reconstituted from separate domains by split intein.

Recombinant cytochrome P450 monooxygenases possess significant potential as biocatalysts, and efforts to improve heme content, electron coupling efficiency, and catalytic activity and stability are ongoing. Domain swapping between heme and reductase domains, whether natural or engineered, has thus received increasing attention. Here, we successfully achieved split intein-mediated reconstitution (IMR) of the heme and reductase domains of P450 BM3 both in vitro and in vivo. Intriguingly, the reconstituted enzymes displayed promising properties for practical use. IMR BM3 exhibited a higher heme content (>50 %) and a greater tendency for oligomerization compared to the wild-type enzyme. Moreover, these reconstituted enzymes exhibited a distinct increase in activity ranging from 165 % to 430 % even under the same heme concentrations. The reproducibility of our results strongly suggests that the proposed reconstitution approach could pave a new path for enhancing the catalytic efficiency of related enzymes.

Long-term prediction of algal chlorophyll based on empirical models and the machine learning approach in relation to trophic variation in Juam Reservoir, Korea.

This study analyzed spatiotemporal variation and long-term trends in water quality indicators and trophic state conditions in an Asian temperate reservoir, Juam Reservoir (JR), and developed models that forecast algal chlorophyll (CHL-a) over a period of 30 years, 1993-2022. The analysis revealed that there were longitudinal gradients in water quality indicators along the reservoir, with notable influences from tributaries and seasonal variations in nutrient regimes and suspended solids. The empirical model showed phosphorus was found to be the key determinant of algal biomass, while suspended solids played a significant role in regulating water transparency. The trophic state indices indicated varying levels of trophic status, ranging from mesotrophic to eutrophic. Eutrophic states were particularly observed in zones after the summer monsoons, indicating a heightened risk of algal blooms, which were more prevalent in flood years. The analysis of trophic state index deviation suggested that phosphorus availability strongly influences the reservoir trophic status, with several episodes of non-algal turbidity at each site during Mon. Increases in non-algal turbidity were more prevalent during the monsoon in flood years. This study also highlighted overall long-term trends in certain water quality parameters, albeit with indications of shifting pollution sources towards non-biodegradable organic matter. According to the machine learning tests, a random forest (RF) model strongly predicted CHL-a (R2 = 0.72, p < 0.01), except for algal biomass peaks (>60 µg/L), compared to all other models. Overall, our research suggests that CHL-a and trophic variation are primarily regulated by the monsoon intensity and predicted well by the machine learning RF model.

Plasma Leptin and Alzheimer Protein Pathologies Among Older Adults.

Importance: Many epidemiologic studies have suggested that low levels of plasma leptin, a major adipokine, are associated with increased risk of Alzheimer disease (AD) dementia and cognitive decline. Nevertheless, the mechanistic pathway linking plasma leptin and AD-related cognitive decline is not yet fully understood. Objective: To examine the association of plasma leptin levels with in vivo AD pathologies, including amyloid-beta (Aß) and tau deposition, through both cross-sectional and longitudinal approaches among cognitively unimpaired older adults. Design, Setting, and Participants: This was a longitudinal cohort study from the Korean Brain Aging Study for Early Diagnosis and Prediction of Alzheimer Disease. Data were collected from January 1, 2014, to December 31, 2020, and data were analyzed from July 11 to September 6, 2022. The study included a total of 208 cognitively unimpaired participants who underwent baseline positron emission tomography (PET) scans for brain Aß deposition. For longitudinal analyses, 192 participants who completed both baseline and 2-year follow-up PET scans for brain Aß deposition were included. Exposure: Plasma leptin levels as assessed by enzyme-linked immunosorbent assay. Main Outcomes and Measures: Baseline levels and longitudinal changes of global Aß and AD-signature region tau deposition measured by PET scans. Results: Among the 208 participants, the mean (SD) age was 66.0 (11.3) years, 114 were women (54.8%), and 37 were apolipoprotein E ε4 carriers (17.8%). Lower plasma leptin levels had a significant cross-sectional association with greater brain Aß deposition (ß = -0.04; 95% CI, -0.09 to 0.00; P = .046), while there was no significant association between plasma leptin levels and tau deposition (ß = -0.02; 95% CI, -0.05 to 0.02; P = .41). In contrast, longitudinal analyses revealed that there was a significant association between lower baseline leptin levels and greater increase of tau deposition over 2 years (ß = -0.06; 95% CI, -0.11 to -0.01; P = .03), whereas plasma leptin levels did not have a significant association with longitudinal change of Aß deposition (ß = 0.006; 95% CI, 0.00-0.02; P = .27). Conclusions and Relevance: The present findings suggest that plasma leptin may be protective for the development or progression of AD pathology, including both Aß and tau deposition.

Construction and characterization of a functional variant hFGF7 with enhanced properties by circular permutation.

Human fibroblast growth factor 7 (hFGF7) is a member of the paracrine-acting FGF family and mediates various reactions such as wound healing, tissue homeostasis, and liver regeneration. These activities make it a plausible candidate for pharmaceutical applications as a drug. However, the low expression level and stability of the recombinant hFGF7 were known to be major hurdles for further applications. Here, the expression level and stability of hFGF7 were attempted to improve by changing the order of amino acids through circular permutation (CP), thereby expecting an alternative fate according to the N-end rule. CP-hFGF7 variants were constructed systematically by using putative amino acid residues in the loop region that avoided the disruption of the structural integrity especially in the functional motif. Among them, cp-hFGF7115-114 revealed a relatively higher expression level in the soluble fraction than the wild-type hFGF7 and was efficiently purified (7 mg L-1) to apparent homogeneity. The activity and stability of the purified variant cp-hFGF7115-114 were comparable or superior to that of the wild-type hFGF7, thereby strongly suggesting that CP could be an alternative tool for the functional expression of hFGF7 in Escherichia coli.

Association between brain amyloid deposition and longitudinal changes of white matter hyperintensities.

BACKGROUND: Growing evidence suggests that not only cerebrovascular disease but also Alzheimer's disease (AD) pathological process itself cause cerebral white matter degeneration, resulting in white matter hyperintensities (WMHs). Some preclinical evidence also indicates that white matter degeneration may precede or affect the development of AD pathology. This study aimed to clarify the direction of influence between in vivo AD pathologies, particularly beta-amyloid (Aß) and tau deposition, and WMHs through longitudinal approach. METHODS: Total 282 older adults including cognitively normal and cognitively impaired individuals were recruited from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease (KBASE) cohort. The participants underwent comprehensive clinical and neuropsychological assessment, [11C] Pittsburgh Compound B PET for measuring Aß deposition, [18F] AV-1451 PET for measuring tau deposition, and MRI scans with fluid-attenuated inversion recovery image for measuring WMH volume. The relationships between Aß or tau deposition and WMH volume were examined using multiple linear regression analysis. In this analysis, baseline Aß or tau were used as independent variables, and change of WMH volume over 2 years was used as dependent variable to examine the effect of AD pathology on increase of WMH volume. Additionally, we set baseline WMH volume as independent variable and longitudinal change of Aß or tau deposition for 2 years as dependent variables to investigate whether WMH volume could precede AD pathologies. RESULTS: Baseline Aß deposition, but not tau deposition, had significant positive association with longitudinal change of WMH volume over 2 years. Baseline WMH volume was not related with any of longitudinal change of Aß or tau deposition for 2 years. We also found a significant interaction effect between baseline Aß deposition and sex on longitudinal change of WMH volume. Subsequent subgroup analyses showed that high baseline Aß deposition was associated with increase of WMH volume over 2 years in female, but not in male. CONCLUSIONS: Our findings suggest that Aß deposition accelerates cerebral WMHs, particularly in female, whereas white matter degeneration appears not influence on longitudinal Aß increase. The results also did not support any direction of influence between tau deposition and WMHs.

Development of a Cognitive Composite for Preclinical Alzheimer's Disease in Korean Older Adults.

BACKGROUND: As tracking subtle cognitive declines in the preclinical stage of Alzheimer's disease (AD) is difficult with traditional individual outcome measures, need for cognitive composite for preclinical AD is widely recognized. OBJECTIVE: We aimed to develop culturally appropriate cognitive composite that sensitively identifies subtle cognitive decline of preclinical AD in Korean older adults. METHODS: A total 225 cognitively normal elderly individuals from the Korean Brain Aging Study for the Early Diagnosis and Prediction of Alzheimer's Disease, were included. Tests of episodic memory, orientation, and executive function were carefully selected through review of previously established composites. Three candidate composites including Consortium to Establish a Registry for Alzheimer's Disease Word list recall (WLR), Logical memory (LM) II, and Mini-Mental status examination (MMSE) in common, and Letter fluency test (LF), category fluency test, or Stroop color and word test, were selected. RESULTS: Student t-tests demonstrated that only the composite composed of WLR, LM II, MMSE, and LF (Composite 1) showed a significant difference in score decline over two-year follow-up period between Aß positive and negative group (p = 0.03). Linear mixed model analyses also showed that the Aß x time interaction effect was significant only for Composite 1 (p = 0.025). Based on the results, Composite 1 was chosen as the final cognitive composite for preclinical Alzheimer's disease (CPAD). CONCLUSIONS: CPAD can be used to assess subtle cognitive decline of preclinical AD in clinical research settings, especially in Korean older adults. It also may be used for monitoring progression or treatment benefits in clinical practices.

One-step metal affinity purification of recombinant hFGF19 without using tags.

Human fibroblast growth factor 19 (hFGF19) belongs to the endocrine FGF19 superfamily and is considered a potential agent to treat severe or relapsing nonalcoholic fatty liver disease. Numerous studies have confirmed the beneficial effects of this hormone on the related symptoms of the disease and attempts at producing recombinant proteins in various hosts are steadily proliferating. Recently, we reported that authentic hFGF19 can be solubly expressed through combining synonymous codon substitutions and co-expression with disulfide-bond isomerase (DsbC) in Escherichia coli. However, during purification, hFGF19 without the His-tag occasionally co-eluted with His-tagged DsbC when using metal affinity chromatography, thereby requiring auxiliary purification steps to achieve apparent homogeneity. This phenomenon provides evidence that hFGF19 specifically interacts with immobilized Ni2+, which can thus be used as an alternative tool for the purification of hFGF19. Consequently, we could simply and reproducibly purify hFGF19 from cell lysates by using Ni2+-immobilized metal affinity chromatography and stepwise gradient elution with imidazole.

Enhanced Light Absorption and Efficient Carrier Collection in MoS2 Monolayers on Au Nanopillars.

We fabricated hybrid nanostructures consisting of MoS2 monolayers and Au nanopillar (Au-NP) arrays. The surface morphology and Raman spectra showed that the MoS2 flakes transferred onto the Au-NPs were very flat and nonstrained. The Raman and photoluminescence intensities of MoS2/Au-NP were 3- and 20-fold larger than those of MoS2 flakes on a flat Au thin film, respectively. The finite-difference time-domain calculations showed that the Au-NPs significantly concentrated the incident light near their surfaces, leading to broadband absorption enhancement in the MoS2 flakes. Compared with a flat Au thin film, the Au-NPs enabled a 6-fold increase in the absorption in the MoS2 monolayer at a wavelength of 615 nm. The contact potential difference mapping showed that the electric potential at the MoS2/Au contact region was higher than that of the suspended MoS2 region by 85 mV. Such potential modulation enabled the Au-NPs to efficiently collect photogenerated electrons from the MoS2 flakes, as revealed by the uniform positive surface photovoltage signals throughout the MoS2 surface.

Mental Health and Quality of Life for Healthcare Workers in a University Hospital Under COVID-19.

OBJECTIVE: The aim of this study was to assess the psychosocial characteristics of the employees working at a university hospital and investigated the factors affecting their quality of life (QOL) under COVID-19. METHODS: This study enrolled 1,191 healthcare workers from a university hospital, including doctors, nurses, administrative officer and technicians. Besides demographic information, depression, anxiety, somatization, insomnia, resilience, and QOL were assessed. RESULTS: The nurses presented significantly higher scores for anxiety, depression and showed significantly higher insomnia scores and significantly lower resilience scores. The occupations showed significant differences in the QOL and sub-groups, including the overall quality of life and general health (F=4.774, p<0.001), psychological domain (F=6.230, p<0.001), and environment domain (F=5.254, p<0.001). There was a positive correlation between the QOL and resilience (r=0.608, p<0.01). However, depression (r=-0.502, p<0.01), anxiety (r=-0.425, p<0.01), somatization (r=-0.364, p<0.01), and insomnia (r=-0.385, p<0.01) showed negative correlations with the QOL. Resilience was the most important factor influencing the QOL. CONCLUSION: The results of this study showed that low resilience adversely affected the QOL and the mental health of the healthcare workers, which consequently had a direct effect on the quality of medical care given to patients.

A designed fusion tag for soluble expression and selective separation of extracellular domains of fibroblast growth factor receptors.

Fibroblast growth factor receptors (FGFRs) generate various transduction signals by interaction with fibroblast growth factors (FGFs) and are involved in various biological functions such as cell proliferation, migration, and differentiation. Malfunction of these proteins may lead to the development of various diseases, including cancer. Accordingly, FGFRs are considered an alternative therapeutic target for protein and/or gene therapy. However, the screening of antagonists or agonists of FGFRs is challenging due to their complex structural features associated with protein expression. Herein, we conducted the development of a protease-free cleavable tag (PFCT) for enhancing the solubility of difficult-to express protein by combining maltose-binding protein (MBP) and the C-terminal region of Npu intein. To validate the availability of the resulting tag for the functional production of extracellular domains of FGFRs (Ec_FGFRs), we performed fusion of PFCT with the N-terminus of Ec_FGFRs and analyzed the expression patterns. Almost all PFCT-Ec_FGFR fusion proteins were mainly detected in the soluble fraction except for Ec_FGFR4. Upon addition of the N-terminal region of Npu intein, approximately 85% of the PFCT-Ec_FGFRs was separated into PFCT and Ec_FGFR via intein-mediated cleavage. Additionally, the structural integrity of Ec_FGFR was confirmed by affinity purification using heparin column. Taken together, our study demonstrated that the PFCT could be used for soluble expression and selective separation of Ec_FGFRs.

The Korean Version of Fear of COVID-19 Scale: Psychometric Validation in the Korean Population.

OBJECTIVE: Coronavirus disease 2019 (COVID-19) has psychological effects such as anxiety and depression as well as direct infection in people. The Fear of COVID-19 scale is a scale that can measure anxiety related to COVID-19 in a short time. The purpose of this study was to verify the reliability and validity the Korean version of Fear of COVID-19 scale (KF-COVID-19S). METHODS: The data of total 186 normal adults and 17 patients were finally used for the statistical analysis. For internal consistency, Cronbach's α was calculated. For concurrent and discriminant validity, the correlations with the Hospital Anxiety and Depression scale (HADS), Patient Health Questionnaire-15 (PHQ-15), World Health Organization Quality of Life Assessment Instrument Brief Form (WHOQOLBREF) were analyzed. For construct validity, exploratory and confirmatory factor analysis were conducted. RESULTS: Cronbach alpha was 0.88. The two-factor model (factor 1: Physical fear, factor 2: Emotional fear) showed significantly positive correlations and appeared to be "good" fitness (CFI=0.906, IFI=0.907, NFI=0.902). CONCLUSION: The KF-COVID-19S can be a useful scale that can measure the physical and emotional fears associated with COVID-19 in a short time. Because the psychiatric patients are a more vulnerable group to the fear, it is thought that the KF-COVID-19S will help to determine the patient's level of anxiety and make a therapeutic plan for the underlying mental disorder.

Enhanced optical absorption in conformally grown MoS2 layers on SiO2/Si substrates with SiO2 nanopillars with a height of 50 nm.

The integration of transition metal dichalcogenide (TMDC) layers on nanostructures has attracted growing attention as a means to improve the physical properties of the ultrathin TMDC materials. In this work, the influence of SiO2 nanopillars (NPs) with a height of 50 nm on the optical characteristics of MoS2 layers is investigated. Using a metal organic chemical vapor deposition technique, a few layers of MoS2 were conformally grown on the NP-patterned SiO2/Si substrates without notable strain. The photoluminescence and Raman intensities of the MoS2 layers on the SiO2 NPs were larger than those observed from a flat SiO2 surface. For 100 nm-SiO2/Si wafers, the 50 nm-NP patterning enabled improved absorption in the MoS2 layers over the whole visible wavelength range. Optical simulations showed that a strong electric-field could be formed at the NP surface, which led to the enhanced absorption in the MoS2 layers. These results suggest a versatile strategy to realize high-efficiency TMDC-based optoelectronic devices.

Soluble Expression of hFGF19 without Fusion Protein through Synonymous Codon Substitutions and DsbC Co-Expression in E. coli.

Human fibroblast growth factor 19 (hFGF19) is a difficult-to-express protein that is frequently fused with another protein for soluble expression. However, residual amino acids after cleavage with protease represent one of the major problems in therapeutic protein development. Here, we introduced synonymous codon substitutions in the N-terminal region encoding sequence of hFGF19 and co-expressed disulfide bond isomerase (ΔssDsbC) to functionally express hFGF19 without any fusion protein. Synonymous codon substitution significantly increased hFGF19 expression. Subsequent co-expression of ΔssDsbC with a selected variant of hFGF19 (scvhFGF19) further increased the proportion of soluble hFGF19 expression in Escherichia coli XL1-Blue. Both total and soluble scvhFGF19 expression increased remarkably in the alternative host, E. coli Origami 2 with mutated thioredoxin reductase and glutathione reductase. scvhFGF19 purification by anion exchange and heparin affinity chromatography resulted in a yield of 6.5 mg/L under normal induction conditions in flask culture. As such, a high cell density culture is expected to achieve an even higher yield. The biological activities of purified scvhFGF19 were assessed based on its ability to activate ERK1/2 signaling pathway in HepG2 hepatocarcinoma cells. In conclusion, the strategy described here may represent an efficient alternative process for the production of hFGF19 and/or related proteins.

Soluble overexpression of a flagellin derivative from Salmonella enterica using synonymous codon substitutions of 5'-coding region in Escherichia coli.

OBJECTIVE: To obtain a recombinant flagellin derivative CBLB502, expressed in functionally soluble form, the technology of library construction and screening of synonymous codon variants was employed, and its expression, solubility, and activity were assessed. RESULTS: We screened several synonymous codon variants scvCBLB502s with the enhanced solubility from the constructed library, harboring the random substitutions of the first ten amino acid residues of the parental CBLB502 with synonymous codons. Among them, scvCBLB502-5 was purified (> 8.4 mg/l) by single step procedure using an affinity chromatography without any ancillary treatment with protease inhibitor cocktail solution and/or boiling at 90 °C. Subsequent study showed that the recombinant protein scvCBLB502-5 distinctly induced the TLR5 (Toll-Like Receptor 5)-mediated NF-κB activation and also IL-8 production in HEK293-hTLR5 cells. CONCLUSION: Results showed that scvCBLB502-5, engineered through the synonymous codon substitutions, was easily expressed in functionally soluble form and maintained the proper folding to be recognized by TLR5, as an inducer for pathogen-associated molecular pattern (PAMP).

Engineering of Immunoglobulin Fc Heterodimers Using Yeast Surface-Displayed Combinatorial Fc Library Screening.

Immunoglobulin Fc heterodimers, which are useful scaffolds for the generation of bispecific antibodies, have been mostly generated through structure-based rational design methods that introduce asymmetric mutations into the CH3 homodimeric interface to favor heterodimeric Fc formation. Here, we report an approach to generate heterodimeric Fc variants through directed evolution combined with yeast surface display. We developed a combinatorial heterodimeric Fc library display system by mating two haploid yeast cell lines, one haploid cell line displayed an Fc chain library (displayed FcCH3A) with mutations in one CH3 domain (CH3A) on the yeast cell surface, and the other cell line secreted an Fc chain library (secreted FcCH3B) with mutations in the other CH3 domain (CH3B). In the mated cells, secreted FcCH3B is displayed on the cell surface through heterodimerization with the displayed FcCH3A, the detection of which enabled us to screen the library for heterodimeric Fc variants. We constructed combinatorial heterodimeric Fc libraries with simultaneous mutations in the homodimer-favoring electrostatic interaction pairs K370-E357/S364 or D399-K392/K409 at the CH3 domain interface. High-throughput screening of the libraries using flow cytometry yielded heterodimeric Fc variants with heterodimer-favoring CH3 domain interface mutation pairs, some of them showed high heterodimerization yields (~80-90%) with previously unidentified CH3 domain interface mutation pairs, such as hydrogen bonds and cation-π interactions. Our study provides a new approach for engineering Fc heterodimers that could be used to engineer other heterodimeric protein-protein interactions through directed evolution combined with yeast surface display.

Crystal structures of immunoglobulin Fc heterodimers reveal the molecular basis for heterodimer formation.

We determined the X-ray crystal structure of an immunoglobulin fragment crystallizable (Fc) heterodimer, EW-RVT, at a resolution of 2.5Å and found that the designed asymmetric interaction residues located in the heterodimeric CH3 interface favor Fc heterodimer formation. We further generated an inter-CH3 disulfide-bonded heterodimeric Fc variant, EW-RVT(S-S), which exhibited improved heterodimer formation and thermodynamic stability compared with the parent EW-RVT variant. The crystal structure of EW-RVTS-S superimposed very closely with the wild-type Fc structure. Our results provide the detailed structure of heterodimeric Fc scaffolds, which will be useful for the generation of immunoglobulin G (IgG)-like bispecific antibodies.

The benefit of microsatellite instability is attenuated by chemotherapy in stage II and stage III gastric cancer: Results from a large cohort with subgroup analyses.

We previously reported that the prognosis of microsatellite instability high (MSI-H) gastric cancer is similar to that of MSI-low/microsatellite stable (MSI-L/MSS) gastric cancer. The reason for this seemed to be related to the effects of chemotherapy. To verify this hypothesis, we expanded the study population and reanalyzed the prognosis of MSI-H gastric cancer. Data from 1,276 patients with Stage II and III gastric cancer who underwent gastrectomy with curative intent between January 2005 and June 2010 were reviewed. The prognosis of MSI-H tumors in comparison with MSI-L/MSS tumors was analyzed, according to the administration of chemotherapy and other clinicopathologic features. A total of 361 (28.3%) patients did not receive chemotherapy (MSI-H = 47 and MSI-L/MSS = 314), whereas 915 (71.7%) patients did receive chemotherapy (MSI-H = 58 and MSI-L/MSS = 857). The hazard ratio of MSI-H versus MSI-L/MSS was 0.49 (95% confidence interval: 0.26-0.94, p = 0.031) when chemotherapy was not received and 1.16 (95% confidence interval: 0.78-1.71, p = 0.466) when chemotherapy was received. In subgroup analyses, the prognosis of MSI-H was better in Stage III, women, with lymph node metastasis, and undifferentiated histology subgroups when chemotherapy was not received. However, in patients treated with chemotherapy, prognosis was worse for MSI-H tumors in Stage III, undifferentiated histology, and diffuse type subgroups of gastric cancer. In conclusion, MSI-H tumors were associated with a good prognosis in Stage II and III gastric cancer when patients were treated by surgery alone, and the benefits of MSI-H status were attenuated by chemotherapy.

A heterodimeric Fc-based bispecific antibody simultaneously targeting VEGFR-2 and Met exhibits potent antitumor activity.

Heterodimeric Fc designed by engineering the CH3 homodimeric interface of immunoglobulin G1 serves as an attractive scaffold for the generation of bispecific antibodies (bsAb) due to the favorable properties of the Fc region. In this study, we describe a heterodimeric Fc generated by substituting the conserved electrostatic interactions at the CH3 core interface with asymmetric hydrophobic interactions and introducing asymmetric, long-range electrostatic interactions at the rim of the CH3 interface. Coexpression of Fc proteins carrying the combined CH3 variant pairs in HEK293F cells produced the heterodimer, which was purified with more than 90% yield, and retained wild-type Fc biophysical properties. The heterodimeric Fc was exploited to generate a bsAb simultaneously targeting both the Met receptor tyrosine kinase and the VEGF receptor 2 (VEGFR-2), with two respective antigen-specific, single-chain variable fragments (scFv) into the N-terminus. The Met × VEGFR-2 bsAb bound concurrently to the two target antigens, efficiently inhibited the downstream signaling and tube formation stimulated by the two receptors in human endothelial cells, and exhibited more potent antitumor efficacy in MKN45 human gastric cancer xenograft models than both the parent monospecific antibody alone. Collectively, based on the newly designed heterodimeric Fc-based bsAb, our results provide the therapeutic potential of bsAb targeting both Met and VEGFR-2 simultaneously for the treatment of human cancers.

The proteasome inhibitor MG132 potentiates TRAIL receptor agonist-induced apoptosis by stabilizing tBid and Bik in human head and neck squamous cell carcinoma cells.

Head and neck squamous cell carcinoma (HNSCC) is often resistant to conventional chemotherapy and thus requires novel treatment regimens. Here, we investigated the effects of the proteasome inhibitor MG132 in combination with tumor necrosis factor-related apoptosis inducing ligand (TRAIL) or agonistic TRAIL receptor 1 (DR4)-specific monoclonal antibody, AY4, on sensitization of TRAIL- and AY4-resistant human HNSCC cell lines. Combination treatment of HNSCC cells synergistically induced apoptotic cell death accompanied by caspase-8, caspase-9, and caspase-3 activation and Bid cleavage into truncated Bid (tBid). Generation and accumulation of tBid through the cooperative action of MG132 with TRAIL or AY4 and Bik accumulation through MG132-mediated proteasome inhibition are critical to the synergistic apoptosis. In HNSCC cells, Bak was constrained by Mcl-1 and Bcl-X(L), but not by Bcl-2. Conversely, Bax did not interact with Mcl-1, Bcl-X(L), or Bcl-2. Importantly, tBid plays a major role in Bax activation, and Bik indirectly activates Bak by displacing it from Mcl-1 and Bcl-X(L), pointing to the synergistic mechanism of the combination treatment. In addition, knockdown of both Mcl-1 and Bcl-X(L) significantly sensitized HNSCC cells to TRAIL and AY4 as a single agent, suggesting that Bak constraint by Mcl-1 and Bcl-X(L) is an important resistance mechanism of TRAIL receptor-mediated apoptotic cell death. Our results provide a novel molecular mechanism for the potent synergy between MG132 proteasome inhibitor and TRAIL receptor agonists in HNSCC cells, suggesting that the combination of these agents may offer a new therapeutic strategy for HNSCC treatment.

Expression of soluble and functional human neonatal Fc receptor in Pichia pastoris.

The neonatal Fc receptor (FcRn) is a non-covalently associated heterodimeric protein composed of a transmembrane anchored heavy chain (alphaFcRn) and a soluble light chain beta2-microglobulin (beta2m). In addition to its role in the transfer of maternal immunoglobulin Gs (IgGs) to the fetus, FcRn plays a key role in prolonging the serum half-life of IgGs in vivo. Herein, we report a strategy for functional expression of soluble human FcRn (shFcRn) in Pichia pastoris using a two-promoter vector system, where alphaFcRn and beta2m are co-expressed under their respective promoters in a single vector. The purified shFcRn from the culture supernatants correctly assembled to form the heterodimer with the typical secondary structures. At acidic pHs between 5.0 and 6.4, shFcRn exhibited substantial binding to the four subclasses of human IgGs at acidic pHs between 5.0 and 6.4, but at pHs between 6.8 and 8.0, its binding was negligible binding. No cross-reactivity with mouse IgG was exhibited even at acidic pH. This was consistent with the pH-dependent binding profiles of the shFcRn prepared from the mammalian cell expression. Furthermore, the shFcRn exhibited about 10-fold higher binding affinity with the tumor necrosis factor-alpha antagonists of monoclonal antibodies Infliximab and Adalimumab than that of Etanercept, providing a clue to their different serum half-lives in vivo. Our results suggest that the functionally expressed shFcRn from Pichia can be used for the biochemical and biological studies and as a screening probe for Fc engineering of human IgGs.