The role of tapasin in MHC class I antigen presentation

The cell-surface presentation of antigenic peptides by MHC class I molecules is an important event in human immunity that protects individuals against viral infections and cancer. Studies aimed at elucidating molecular and cellular aspects of the MHC class I antigen presentation pathway have consistently pointed to an endoplasmic reticulum (ER)-resident protein, namely tapasin, as playing a critical role in optimizing peptide loading to MHC class I molecules. To date, however, the mechanism of action of tapasin is unexplained. Through my dissertation research, I characterized tapasin and its function in peptide loading. The results of my study, which are summarized as below, allow me to propose a mechanistic model for the function of tapasin.^ The ER-lumenal region of tapasin (referred to as TPN) adopts an asymmetric, elongated structure with relatively high content of β-sheets. TPN has a thermal denaturation curve centered at ∼45°C. TPN consists of two major domains separated by a solvent-exposed linker; these two domains also associate together through non-covalent interactions.^ TPN weakly associates with the ER-lumenal domain of MHC class I molecules. TPN also has weak interactions with the complex of calreticulin and ERp57. MHC Class I molecules and TPN form complexes through Fos/Jun leucine-zipper dimerization motifs. The functions of TPN can be probed in the zippered complexes. ^ TPN stabilizes the active conformation of peptide-deficient MHC class I molecules. TPN increases the rates of peptide dissociation via a peptide-specific manner. TPN also increases the rates of peptide association. Kinetic studies enable us to draw two conclusions: (1) TPN acts as a catalyst and a chaperone by widening the peptide binding groove of MHC class I molecules. (2) The widening effect of TPN involves disruption of both peptide sequence-independent and -dependent interactions between peptide and MHC class I residues. The biological significance of the function of TPN is to maximize the diversity of minimally stable MHC class I/peptide complexes presented at the cell surface. ^ The knowledge and understanding derived from my studies strengthen our abilities to manipulate MHC class I antigen presentation, which has broad medical applications such as for developing vaccines against viral infections and cancer.

The role of tapasin in MHC class I antigen presentation

The cell-surface presentation of antigenic peptides by MHC class I molecules is an important event in human immunity that protects individuals against viral infections and cancer. Studies aimed at elucidating molecular and cellular aspects of the MHC class I antigen presentation pathway have consistently pointed to an endoplasmic reticulum (ER)-resident protein, namely tapasin, as playing a critical role in optimizing peptide loading to MHC class I molecules. To date, however, the mechanism of action of tapasin is unexplained. Through my dissertation research, I characterized tapasin and its function in peptide loading. The results of my study, which are summarized as below, allow me to propose a mechanistic model for the function of tapasin.^ The ER-lumenal region of tapasin (referred to as TPN) adopts an asymmetric, elongated structure with relatively high content of β-sheets. TPN has a thermal denaturation curve centered at ∼45°C. TPN consists of two major domains separated by a solvent-exposed linker; these two domains also associate together through non-covalent interactions.^ TPN weakly associates with the ER-lumenal domain of MHC class I molecules. TPN also has weak interactions with the complex of calreticulin and ERp57. MHC Class I molecules and TPN form complexes through Fos/Jun leucine-zipper dimerization motifs. The functions of TPN can be probed in the zippered complexes. ^ TPN stabilizes the active conformation of peptide-deficient MHC class I molecules. TPN increases the rates of peptide dissociation via a peptide-specific manner. TPN also increases the rates of peptide association. Kinetic studies enable us to draw two conclusions: (1) TPN acts as a catalyst and a chaperone by widening the peptide binding groove of MHC class I molecules. (2) The widening effect of TPN involves disruption of both peptide sequence-independent and -dependent interactions between peptide and MHC class I residues. The biological significance of the function of TPN is to maximize the diversity of minimally stable MHC class I/peptide complexes presented at the cell surface. ^ The knowledge and understanding derived from my studies strengthen our abilities to manipulate MHC class I antigen presentation, which has broad medical applications such as for developing vaccines against viral infections and cancer.

Measurement of bivariate attributes using a novel statistical model

Reducing process variability is essential to many organisations. According to the pertinent literature, a quality system that utilizes quality techniques to reduce process variability is necessary. Quality programs that respond to measurement precision are central to quality systems, and the most common method of assessing the precision of a measurement system is repeatability and reproducibility (R&R). Few studies have investigated R&R using attribute data. In modern manufacturing environments, automated manufacturing is becoming increasingly common; however, a measurement resolution problem exists in automatic inspection equipment, resulting in clusters and product defects. It is vital to monitor effectively these bivariate quality characteristics. This study presents a novel model for calculating R&R for bivariate attribute data. An alloy manufacturing case is utilized to illustrate the process and potential of the proposed model. Findings can be employed to evaluate and improve measurement systems with bivariate attribute data.measurement system analysis, attribute data, repeatability, reproducibility,

Information swimmer: Self-propulsion without energy dissipation

We study an information-based mechanism of self-propulsion in noisy environment. An information swimmer maintains directional motion by periodically measuring its velocity and accordingly adjusting its friction coefficient. Assuming that the measurement and adjustment are reversible and hence cause no energy dissipation, an information swimmer may move without external energy input. There is however no violation of the second law of thermodynamics, because the information entropy stored in the memory of swimmer increases monotonically. By optimizing its control parameters, the swimmer can achieve a steady velocity that is comparable to the root-mean-square velocity of an analogous Brownian particle. We also define a swimming efficiency in terms of information entropy production rate and find that, in equilibrium media with white noises, information swimmers are generally less efficient than Brownian particles driven by constant forces. For colored noises with long correlation times, the frequency of measurement can be greatly reduced without affecting the efficiency of information swimmers

Exploring the Influence Mechanism of Meteorological Conditions on the Concentration of Suspended Solids and Chlorophyll-a in Large Estuaries Based on MODIS Imagery

In estuary areas, meteorological conditions have become unstable under the continuous effects of climate change, and the ecological backgrounds of such areas have strongly been influenced by anthropic activities. Consequently, the water quality of these areas is obviously affected. In this research, we identified periods of fluctuation of the general meteorological conditions in the Yangtze River Estuary using a wavelet analysis. Additionally, we performed a spatiotemporal evaluation of the water quality in the fluctuating period by using remote sensing modeling. Then, we explored how the fluctuating meteorological factors affect the distribution of total suspended solids (TSS) and chlorophyll-a (Chla) concentration. (1) The results show that from 2000 to 2015, temperature did not present significant fluctuations, while wind speed (WS) and precipitation (PR) presented the same fluctuation period from January 2012 to December 2012. (2) Based on the measured water sample data associated with Moderate Resolution Imaging Spectroradiometer (MODIS) imagery, we developed a water quality algorithm and depicted the TSS and Chla concentrations within the WS and PR fluctuating period. (3) We found that the TSS concentration decreased with distance from the shore, while the Chla concentration showed an initially decreasing trend followed by an increasing trend; moreover, these two water quality parameters presented different inter-annual variations. Then, we discussed the correlation between the changes in the TSS and Chla concentrations and the WS and PR variables. The contribution of this research is reflected in two aspects: 1. variations in water quality parameters over a wide range of water bodies can be evaluated based on MODIS data; 2. data from different time periods showed that the fluctuations of meteorological elements had different impacts on water bodies based on the distance from the shore. The results provide new insights for the management of estuary water environments

An attempt to interpret a biochemical mechanism of C4 photosynthetic thermo-tolerance under sudden heat shock on detached leaf in elevated CO2 grown maize.

Detached leaves at top canopy structures always experience higher solar irradiance and leaf temperature under natural conditions. The ability of tolerance to high temperature represents thermotolerance potential of whole-plants, but was less of concern. In this study, we used a heat-tolerant (B76) and a heat-susceptible (B106) maize inbred line to assess the possible mitigation of sudden heat shock (SHS) effects on photosynthesis (PN) and C4 assimilation pathway by elevated [CO2]. Two maize lines were grown in field-based open top chambers (OTCs) at ambient and elevated (+180 ppm) [CO2]. Top-expanded leaves for 30 days after emergence were suddenly exposed to a 45°C SHS for 2 hours in midday during measurements. Analysis on thermostability of cellular membrane showed there was 20% greater electrolyte leakage in response to the SHS in B106 compared to B76, in agreement with prior studies. Elevated [CO2] protected PN from SHS in B76 but not B106. The responses of PN to SHS among the two lines and grown CO2 treatments were closely correlated with measured decreases of NADP-ME enzyme activity and also to its reduced transcript abundance. The SHS treatments induced starch depletion, the accumulation of hexoses and also disrupted the TCA cycle as well as the C4 assimilation pathway in the both lines. Elevated [CO2] reversed SHS effects on citrate and related TCA cycle metabolites in B106 but the effects of elevated [CO2] were small in B76. These findings suggested that heat stress tolerance is a complex trait, and it is difficult to identify biochemical, physiological or molecular markers that accurately and consistently predict heat stress tolerance

iTEP Nanoparticle-Delivered Salinomycin Displays an Enhanced Toxicity to Cancer Stem Cells in Orthotopic Breast Tumors

Salinomycin (Sali) has selective toxicity to cancer stem cells (CSCs), a subpopulation of cancer cells that have been recently linked with tumor multidrug resistance (MDR). To utilize its selective toxicity for cancer therapy, we sought to devise a nanoparticle (NP) carrier to deliver Sali to solid tumors through the enhanced permeability and retention effect and, hence, to increase its exposure to CSCs. First, hydrophobic Sali was conjugated to a hydrophilic, immune-tolerant, elastin-like polypeptide (iTEP); the amphiphilic iTEP–Sali conjugates self-assemble into NPs. Next, free Sali was encapsulated into the NPs alone or with two additives, <i>N</i>,<i>N</i>-dimethylhexylamine (DMHA) and α-tocopherol. The coencapsulation significantly improved the loading efficiency and release profile of Sali. The resulting NPs of the coencapsulation, termed as iTEP–Sali NP3s, have an <i>in vitro</i> release half-life of 4.1 h, four times longer than iTEP–Sali NP2s, the NPs that have encapsulated Sali only. Further, the NP3 formulation increases the plasma area under curve and the tumor accumulation of Sali by 10 and 2.4 times, respectively. Lastly, these improved pharmacokinetic and tumor accumulation profiles are consistent with a boost of CSC-elimination effect of Sali <i>in vivo</i>. In NP3-treated 4T1 orthotopic tumors, the mean CSC frequency is 55.62%, a significant reduction from the mean frequencies of untreated tumors, 75.00%, or free Sali-treated tumors, 64.32%. The CSC-elimination effect of the NP3 can further translate to a delay of tumor growth. Given the role of CSCs in driving tumor MDR and recurrence, it could be a promising strategy to add the NP3 to conventional cancer chemotherapies to prevent or reverse the MDR

An Anti-Programmed Death‑1 Antibody (αPD-1) Fusion Protein That Self-Assembles into a Multivalent and Functional αPD‑1 Nanoparticle

Cancer immune checkpoint therapy has achieved remarkable clinical successes in various cancers. However, current immune checkpoint inhibitors block the checkpoint of not only the immune cells that are important to cancer therapy but also the immune cells that are irrelevant to the therapy. Such an indiscriminate blockade limits the efficacy and causes the autoimmune toxicity of the therapy. It might be beneficial to use a carrier to target immune checkpoint inhibitors to cancer-reactive immune cells. Here, we explore a method to load the inhibitors into carriers. We used the anti-programmed death-1 antibody (αPD-1) as a model immune checkpoint inhibitor. First, we generated a recombinant single-chain variable fragment (scFv) of αPD-1. Then, we designed and generated a fusion protein consisting of the scFv and an amphiphilic immune-tolerant elastin-like polypeptide (iTEP). Because of the amphiphilic iTEP, the fusion was able to self-assemble into a nanoparticle (NP). The NP was proved to block the PD-1 immune checkpoint <i>in vitro</i> and <i>in vivo</i>. Particularly, the NP exacerbated diabetes development in nonobese diabetic mice as effectively as natural, intact αPD-1. In summary, we successfully expressed αPD-1 as a recombinant protein and linked αPD-1 to a NP, which lays a foundation to develop a delivery system to target αPD-1 to a subpopulation of immune cells