Measurement of LAG-3 Expression Across Multiple Staining Platforms With the 17B4 Antibody Clone.

CONTEXT.­: An immunohistochemistry (IHC) assay developed to detect lymphocyte-activation gene 3 (LAG-3), a novel immune checkpoint inhibitor target, has demonstrated high analytic precision and interlaboratory reproducibility using a Leica staining platform, but it has not been investigated on other IHC staining platforms. OBJECTIVE.­: To evaluate the performance of LAG-3 IHC assays using the 17B4 antibody clone across widely used IHC staining platforms: Agilent/Dako Autostainer Link 48 and VENTANA BenchMark ULTRA compared to Leica BOND-RX (BOND-RX). DESIGN.­: Eighty formalin-fixed, paraffin-embedded melanoma tissue blocks were cut into consecutive sections and evaluated using staining platform-specific IHC assays with the 17B4 antibody clone. Duplicate testing was performed on the BOND-RX platform to assess intraplatform agreement. LAG-3 expression using a numeric score was evaluated by a pathologist and with a digital scoring algorithm. LAG-3 positivity was determined from manual scores using a 1% or greater cutoff. RESULTS.­: LAG-3 IHC staining patterns and intensities were visually similar across all 3 staining platforms. Spearman and Pearson correlations were 0.75 or greater for interplatform and BOND-RX intraplatform concordance when LAG-3 expression was evaluated with a numeric score determined by a pathologist. Correlation increased with a numeric score determined with a digital scoring algorithm (Spearman and Pearson correlations ≥0.88 for all comparisons). Overall percentage agreement was 77.5% or greater for interplatform and BOND-RX intraplatform comparisons when LAG-3 positivity was determined using a 1% or greater cutoff. CONCLUSIONS.­: Data presented here demonstrate that LAG-3 expression can be robustly and reproducibly assessed across 3 major commercial IHC staining platforms using the 17B4 antibody clone.

Cu1+, but not Cu2+ is capable of inhibition of AQP4 permeability in an in vitro CHO cell based model.

Aquaporin 4 (AQP4) is an important water channel in the central nervous system which is implicated in several neurological disorders. Due to its significance, the identification of molecules which are able to modulate its activity is quite important for potential therapeutic applications. Here we used a novel screening method involving CHO cell lines which stably express AQP4 to test for potential molecules of interest. Using this method we identified a metal ion, Cu1+, which is able to inhibit AQP4 activity in a cell model, an interaction which has not been previously described. This inhibition was effective at concentrations greater than 500 nM in the CHO cell model, and was confirmed in a proteoliposome based model. Furthermore, the binding sites for Cu1+ inhibition of AQP4 are identified as cysteine 178 and cysteine 253 on the intracellular domain of the protein via the synthesis of AQP4 containing point mutations to remove these cysteines. These results suggest that Cu1+ is able to access intracellular binding sites and inhibit AQP4 in a cell based model.

Human keratinocyte-derived extracellular vesicles activate the MAPKinase pathway and promote cell migration and proliferation in vitro.

BACKGROUND: Wound healing is a complex biological process and complete skin regeneration is still a critical challenge. Extracellular vesicles (EVs) play essential roles in cell communication and cell regeneration, and recent studies have suggested that EVs may contribute to wound healing, though the molecular mechanisms behind this contribution remain unclear. For these reasons, we decided to use EVs isolated from human keratinocytes (HaCaT) in vitro to determine the potential mechanism of action of EV-derived wound healing. METHOD: Scratch assays were used to determine cell migration and proliferation. Scratched cells were exposed to EVs in multiple conditions to determine how they affect wound healing. Statistical analysis between groups was carried out to using Student's two-sided t test. A p value of < 0.05 was considered statistically significant. RESULT: We found that proteomic analysis of purified EVs shows enrichment of proteins associated with cell communication and signal transduction, such as MAPK pathways, and keratinocyte and fibroblast cultures exposed to EVs had higher levels of proliferation, migration, and ERK1/2 and P38 activation. Moreover, we found that treatment with specific ERK1/2 and P38 signaling inhibitors PD98059 and SB239063 impaired EV-mediated cell migration, which suggests that ERK1/2 and P38 signaling is essential for EV-induced wound healing. CONCLUSION: HaCaT cell-derived EVs accelerate the migration and proliferation of human keratinocytes and fibroblasts and may promote wound healing via the activation of MAPKinase pathways. These findings may be key in developing new methods to treat wounds and accelerate wound healing in the future.

Di-lysine motif-like sequences formed by deleting the C-terminal domain of aquaporin-4 prevent its trafficking to the plasma membrane.

Aquaporin-4 is a transmembrane water channel protein, the C-terminal domain of which is facing the cytosol. In the process of investigating the role of the C-terminal domain of aquaporin-4 with regard to intracellular trafficking, we observed that a derivative of aquaporin-4, in which the C-terminal 53 amino acids had been removed (Δ271-323), was localized to intracellular compartments, including the endoplasmic reticulum, but was not expressed on the plasma membranes. This was determined by immunofluorescence staining and labeling of the cells with monoclonal antibody specifically recognizing the extracellular domain of aquaporin-4, followed by confocal microscopy and flow cytometry. Deletion of additional amino acids in the C-terminal domain of aquaporin-4 led to its redistribution to the plasma membrane. This suggests that the effect of the 53-amino acid deletion on the subcellular localization of aquaporin-4 could be attributed to the formation of a signal at the C terminus that retained aquaporin-4 in intracellular compartments, rather than the loss of a signal required for plasma membrane targeting. Substitution of the lysine at position 268 with alanine could rescue the Δ271-323-associated retention in the cytosol, suggesting that the C-terminal sequence of the mutant served as a signal similar to a di-lysine motif.

Regulation of AQP4 in the Central Nervous System.

Aquaporin-4 (AQP4) is the main water channel protein expressed in the central nervous system (CNS). AQP4 is densely expressed in astrocyte end-feet, and is an important factor in CNS water and potassium homeostasis. Changes in AQP4 activity and expression have been implicated in several CNS disorders, including (but not limited to) epilepsy, edema, stroke, and glioblastoma. For this reason, many studies have been done to understand the various ways in which AQP4 is regulated endogenously, and could be regulated pharmaceutically. In particular, four regulatory methods have been thoroughly studied; regulation of gene expression via microRNAs, regulation of AQP4 channel gating/trafficking via phosphorylation, regulation of water permeability using heavy metal ions, and regulation of water permeability using small molecule inhibitors. A major challenge when studying AQP4 regulation is inter-method variability. A compound or phosphorylation which shows an inhibitory effect in vitro may show no effect in a different in vitro method, or even show an increase in AQP4 expression in vivo. Although a large amount of variability exists between in vitro methods, some microRNAs, heavy metal ions, and two small molecule inhibitors, acetazolamide and TGN-020, have shown promise in the field of AQP4 regulation.

Serum D-serine accumulation after proximal renal tubular damage involves neutral amino acid transporter Asc-1.

Chiral separation has revealed enantio-specific changes in blood and urinary levels of amino acids in kidney diseases. Blood D-/L-serine ratio has been identified to have a correlation with creatinine-based kidney function. However, the mechanism of distinctive behavior in serine enantiomers is not well understood. This study was performed to investigate the role of renal tubules in derangement of serine enantiomers using a mouse model of cisplatin-induced tubular injury. Cisplatin treatment resulted in tubular damage histologically restricted to the proximal tubules and showed a significant increase of serum D-/L-serine ratio with positive correlations to serum creatinine and blood urine nitrogen (BUN). The increased D-/L-serine ratio did not associate with activity of a D-serine degrading enzyme, D-amino acid oxidase, in the kidney. Screening transcriptions of neutral amino acid transporters revealed that Asc-1, found in renal tubules and collecting ducts, was significantly increased after cisplatin-treatment, which correlates with serum D-serine increase. In vitro study using a kidney cell line showed that Asc-1 is induced by cisplatin and mediated influx of D-serine preferably to L-serine. Collectively, these results suggest that cisplatin-induced damage of proximal tubules accompanies Asc-1 induction in tubules and collecting ducts and leads to serum D-serine accumulation.