proximity-ligand-assay-to-localize-proteins-in-dna-damage-sites

Proximity Ligand Assay to Localize Proteins in DNA Damage Sites

The DNA damage response is a genetic information safeguard that protects cells from perpetuating damaged DNA. The characterization of the proteins that ...

University of Campinas

This study describes the characterization of pharmacokinetic (PK) properties of acetaminophen (APAP) in the Two-Organ-Chip platform (2-OC), a two-chamber device able to cultivate 3D tissues under flow. The APAP intestinal absorption and hepatic metabolism were emulated by human intestine and liver equivalents respectively. The intestinal barrier was produced using Caco-2 and HT-29 cells. The liver spheroids were produced with HepaRG and HHSTeC cells. Cell viability and toxicity were assessed by MTT assay, histology, confocal immunohistochemistry, and multiparametric high content analysis. Gene expression of intestine and liver equivalents were assessed by real-time PCR. Three assemblies of Microphysiological System (MPS) were applied: Intestine 2-OC, Liver 2-OC, and Intestine/Liver 2-OC. The oral administration was emulated by APAP placement over the apical side of the intestinal barrier and the intravenous routes were mimic by the application in the medium. Samples were analyzed by HPLC/UV. APAP 12 μM or 2 μM treatment did not induce cytotoxicity for the intestinal barrier (24 h time-point) or for the liver spheroids 12 h time-point), respectively. All preparations showed slower APAP absorption than reported for humans: Peak time (Tmax) = 12 h for Intestine 2-OC and 6 h for Intestine/Liver 2-OC in both static and dynamic conditions, against reported Tmax of 0,33 to 1,4 h after oral administration to humans. APAP metabolism was also slower than reported for humans. The APAP half-life (T) was 12 h in the dynamic Liver 2-OC, against T = 2 ± 0,4 h reported for humans. Samples taken from the Liver 2-OC static preparation did not show APAP concentration decrease. These findings show the MPS capability and potential to emulate human PK properties and highlight the critical role of mechanical stimulus over cell functionality, especially by demonstrating the clear positive influence of the microfluidic flow over the liver equivalents metabolic performance.

Acetaminophen absorption and metabolism in an intestine/liver microphysiological system.

Little is known about Nima-related kinase (NEKs), a widely conserved family of kinases that have key roles in cell-cycle progression. Nevertheless, it is now clear that multiple NEK family members act in networks, not only to regulate specific events of mitosis, but also to regulate metabolic events independently of the cell cycle. NEK5 was shown to act in centrosome disjunction, caspase-3 regulation, myogenesis, and mitochondrial respiration. Here, we demonstrate that NEK5 interacts with LonP1, an AAA+ mitochondrial protease implicated in protein quality control and mtDNA remodeling, within the mitochondria and it might be involved in the LonP1-TFAM signaling module. Moreover, we demonstrate that NEK5 kinase activity is required for maintaining mitochondrial mass and functionality and mtDNA integrity after oxidative damage. Taken together, these results show a new role of NEK5 in the regulation of mitochondrial homeostasis and mtDNA maintenance, possibly due to its interaction with key mitochondrial proteins, such as LonP1.

NEK5 interacts with LonP1 and its kinase activity is essential for the regulation of mitochondrial functions and mtDNA maintenance.

NIMA-related kinases, or NEKs, are a family of Ser/Thr protein kinases involved in cell cycle and mitosis, centrosome disjunction, primary cilia functions, and DNA damage responses among other biological functional contexts in vertebrate cells. In human cells, there are 11 members, termed NEK1 to 11, and the research has mainly focused on exploring the more predominant roles of NEKs in mitosis regulation and cell cycle. A possible important role of NEKs in DNA damage response (DDR) first emerged for NEK1, but recent studies for most NEKs showed participation in DDR. A detailed analysis of the protein interactions, phosphorylation events, and studies of functional aspects of NEKs from the literature led us to propose a more general role of NEKs in DDR. In this review, we express that NEK1 is an activator of ataxia telangiectasia and Rad3-related (ATR), and its activation results in cell cycle arrest, guaranteeing DNA repair while activating specific repair pathways such as homology repair (HR) and DNA double-strand break (DSB) repair. For NEK2, 6, 8, 9, and 11, we found a role downstream of ATR and ataxia telangiectasia mutated (ATM) that results in cell cycle arrest, but details of possible activated repair pathways are still being investigated. NEK4 shows a connection to the regulation of the nonhomologous end-joining (NHEJ) repair of DNA DSBs, through recruitment of DNA-PK to DNA damage foci. NEK5 interacts with topoisomerase IIβ, and its knockdown results in the accumulation of damaged DNA. NEK7 has a regulatory role in the detection of oxidative damage to telomeric DNA. Finally, NEK10 has recently been shown to phosphorylate p53 at Y327, promoting cell cycle arrest after exposure to DNA damaging agents. In summary, this review highlights important discoveries of the ever-growing involvement of NEK kinases in the DDR pathways. A better understanding of these roles may open new diagnostic possibilities or pharmaceutical interventions regarding the chemo-sensitizing inhibition of NEKs in various forms of cancer and other diseases.

On Broken Ne(c)ks and Broken DNA: The Role of Human NEKs in the DNA Damage Response.

NEK6 is a central kinase in developing castration-resistant prostate cancer (CRPC). However, the pathways regulated by NEK6 in CRPC are still unclear. Cancer cells have high reactive oxygen species (ROS) levels and easily adapt to this circumstance and avoid cell death by increasing antioxidant defenses. We knocked out the NEK6 gene and evaluated the redox state and DNA damage response in DU-145 cells. The knockout of NEK6 decreases the clonogenic capacity, proliferation, cell viability, and mitochondrial activity. Targeting the NEK6 gene increases the level of intracellular ROS; decreases the expression of antioxidant defenses (SOD1, SOD2, and PRDX3); increases JNK phosphorylation, a stress-responsive kinase; and increases DNA damage markers (p-ATM and γH2AX). The exogenous overexpression of NEK6 also increases the expression of these same antioxidant defenses and decreases γH2AX. The depletion of NEK6 also induces cell death by apoptosis and reduces the antiapoptotic Bcl-2 protein. NEK6-lacking cells have more sensitivity to cisplatin. Additionally, NEK6 regulates the nuclear localization of NF-κB2, suggesting NEK6 may regulate NF-κB2 activity. Therefore, NEK6 alters the redox balance, regulates the expression of antioxidant proteins and DNA damage, and its absence induces the death of DU-145 cells. NEK6 inhibition may be a new strategy for CRPC therapy.

Fernanda Luisa Basei

Faculty of Pharmaceutical Sciences

University of Campinas

Proximity Ligand Assay to Localize Proteins in DNA Damage Sites

Fernanda Luisa Basei

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Faculty of Pharmaceutical Sciences

University of Campinas

Proximity Ligand Assay to Localize Proteins in DNA Damage Sites

Faculty of Pharmaceutical Sciences