Identification of transglutaminase 2 kinase substrates using a novel on-chip activity assay

Linker-Preserved Iron Metal-Organic Framework-Based Lateral Flow Assay for Sensitive Transglutaminase 2 Detection in Urine Through Machine Learning-Assisted Colorimetric Analysis

A groundbreaking demonstration of the utilization of the metal-organic framework MIL-101(Fe) as an exceptionally perceptive visual label in colorimetric lateral flow assays (LFA) is described. This pioneering approach enables the precise identification of transglutaminase 2 (TGM2), a recognized biomarker for chronic kidney disease (CKD), in urine specimens, which offers a remarkably sensitive naked-eye detection mechanism. The surface of MIL-101(Fe) was modified with oxalyl chloride, adipoyl chloride, and poly(acrylic) acid (PAA); these not only improved the labeling material stability in a complex matrix but also achieved a systematic control in the detection limit of the TGM2 concentration using our LFA platform. The advanced LFA with the MIL-101(Fe)-PAA label can detect TGM2 concentrations down to 0.012, 0.009, and 0.010 nM in Tris-HCl buffer, urine, and desalted urine, respectively, which are approximately 55-fold lower than those for a conventional AuNP-based LFAs. Aside from rapid TGM2 detection (i.e., within 20 min), the performance of the MIL-101(Fe)-PAA-based LFA on reproducibility [coefficients of variation (CV) < 2.9%] and recovery (95.9-103.2%) along with storage stability within 25 days of observation (CV < 6.0%) shows an acceptable parameter range for quantitative analysis. A sophisticated sensing method grounded in machine learning principles was also developed, specifically aimed at precisely deducing the TGM2 concentration by analyzing immunoreaction sites. More importantly, our developed LFA offers potential for clinical measurement of TGM2 concentration in normal human urine and CKD patients' samples.

TfR Aptamer Enhanced Blood-Brain Barrier Penetration of Biomimetic Nanocomplexes for Intracellular Transglutaminase 2 Imaging and Silencing in Glioma

Engineering a versatile nanocomplex integrating effective penetration of the blood-brain barrier (BBB), accurate diagnosis, and boosting therapy has always been an intractable challenge in glioblastoma multiforme (GBM). Herein, biomimetic nanocomplexes (TMPsM) for single intracellular transglutaminase 2 (TG2)-triggered self-assembly imaging and RNAi therapy for GBM are subtly developed. To prove the concept, transferrin receptor (TfR) aptamer-modified brain metastatic tumor cell membrane is prepared as the shell for dual BBB targeting capability and prolonged blood retention time. Upon targeting entering into GBM, hollow MnO₂ is decomposed to release KKGKGQQ-tetraphenylethene (Pep-TPE) and siRNA. Owing to TG2 dependence, the non-emissive Pep-TPE would be self-aggregated to induce the emission turn-on in GBM that contain overexpressed TG2. The resulting aggregation-induced emission fluorescence imaging with a high signal-to-noise ratio can achieve the precise localization of the tumor and dynamic detection of TG2 activity, thereby allowing the GBM accurate diagnosis. Notably, the TG2 can be silenced by the released siRNA to cause cell apoptosis and increase chemotherapeutic sensitivity, ultimately realizing excellent antitumor efficacy. In vitro and in vivo results demonstrate that the as-prepared TMPsM indeed possess superior BBB penetration, precise diagnosis, and effective therapy of GBM. The proposed strategy may pioneer a new path for the theranostics of brain tumors.

Nuclear Transglutaminase 2 interacts with topoisomerase II⍺ to promote DNA damage repair in lung cancer cells

BACKGROUND

To block repairs of DNA damages, especially the DNA double strand break (DSB) repair, can be used to induce cancer cell death. DSB repair depends on a sequential activation of DNA repair factors that may be potentially targeted for clinical cancer therapy. Up to now, many protein components of DSB repair complex remain unclear or poorly characterized. In this study, we discovered that Transglutaminase 2 (TG2) acted as a new component of DSB repair complex.

METHODS

A bioinformatic analysis was performed to identify DNA damage relative genes from dataset from The Cancer Genome Atlas. Immunofluorescence and confocal microscopy were used to monitor the protein localization and recruitment kinetics. Furthermore, immunoprecipitation and mass spectrometry analysis were performed to determine protein interaction of both full-length and fragments or mutants in distinct domain. In situ lung cancer model was used to study the effects cancer therapy in vivo.

RESULTS

After DSB induction, cytoplasmic TG2 was extensively mobilized and translocated into nucleus after phosphorylated at T162 site by DNA-PKcs. Nuclear TG2 quickly accumulated at DSB sites and directly interacting with Topoisomerase IIα (TOPOIIα) with its TGase domain to promote DSB repair. TG2 deficient cells lost capacity of DSB repair and become susceptible to ionizing radiation. Specific inhibition of TG2-TOPOIIα interaction by glucosamine also significantly inhibited DSB repair, which increased sensitivity in lung cancer cells and engrafted lung cancers.

CONCLUSIONS

These findings elucidate new mechanism of TG2 in DSB repair trough directly interacting with TOPOIIα, inhibition of which provided potential target for overcoming cancer resistance.

High-throughput investigation of transglutaminase 2 kinase regulation using a novel cysteine-modified peptide array

Transglutaminase 2 (TGase2) kinase has emerged as an important regulator of apoptosis as well as chromatin structure and function; however, details about the pathophysiological functions of TGase2 kinase have been limited because of the lack of a suitable activity assay for systematic investigation of TGase2 kinase regulation in a high-throughput manner. Thus, we developed a novel on-chip TGase2 kinase activity assay using a cysteine-modified insulin-like growth factor-binding protein-3-derived peptide (CMI peptide) on an array platform. This peptide array-based activity assay was reproducible, with a detection limit of 2.127 μg/ml. We successfully applied this assay to investigate the effects of thiol-reactive compounds and divalent cations on TGase2 kinase by determining the half maximal inhibitory concentrations (IC₅₀). Thiol-reactive compounds inhibited TGase2 kinase activity in a concentration-dependent manner, with IC₅₀ values ranging from 0.125 to 5.550 mM. Divalent metal cations also showed a concentration-dependent inhibition, with IC₅₀ values ranging from 0.005 to 1.937 mM; however, Ca²⁺ had no effect on TGase2 kinase activity. Thus, this novel kinase activity assay using the CMI peptide array described here is suitable for systematic investigation of TGase2 kinase regulation and may be useful for investigating the roles of TGase2 kinase in pathogenesis of kinase-mediated diseases.

Systematic investigation of protein kinase A substrate proteins using on-chip protein kinase kinetic profiling

An on-chip protein kinase assay for profiling kinase kinetic parameters by introducing the substrate affinity (K_m) and the phosphorylation rate (V_p) under physiological conditions.