Evidence that knock down of GSK-3β in Chronic Myelogenous Leukemia cells augments IFN-γ-induced apoptosis

HAP1, a new revolutionary cell model for gene editing using CRISPR-Cas9

The use of next-generation sequencing (NGS) technologies has been instrumental in the characterization of the mutational landscape of complex human diseases like cancer. But despite the enormous rise in the identification of disease candidate genetic variants, their functionality is yet to be fully elucidated in order to have a clear implication in patient care. Haploid human cell models have become the tool of choice for functional gene studies, since they only contain one copy of the genome and can therefore show the unmasked phenotype of genetic variants. Over the past few years, the human near-haploid cell line HAP1 has widely been consolidated as one of the favorite cell line models for functional genetic studies. Its rapid turnover coupled with the fact that only one allele needs to be modified in order to express the subsequent desired phenotype has made this human cell line a valuable tool for gene editing by CRISPR-Cas9 technologies. This review examines the recent uses of the HAP1 cell line model in functional genetic studies and high-throughput genetic screens using the CRISPR-Cas9 system. It covers its use in an attempt to develop new and relevant disease models to further elucidate gene function, and create new ways to understand the genetic basis of human diseases. We will cover the advantages and potential of the use of CRISPR-Cas9 technology on HAP1 to easily and efficiently study the functional interpretation of gene function and human single-nucleotide genetic variants of unknown significance identified through NGS technologies, and its implications for changes in clinical practice and patient care.

Pathobiology and Therapeutic Relevance of GSK-3 in Chronic Hematological Malignancies

Glycogen synthase kinase-3 (GSK-3) is an evolutionarily conserved, ubiquitously expressed, multifunctional serine/threonine protein kinase involved in the regulation of a variety of physiological processes. GSK-3 comprises two isoforms (α and β) which were originally discovered in 1980 as enzymes involved in glucose metabolism via inhibitory phosphorylation of glycogen synthase. Differently from other proteins kinases, GSK-3 isoforms are constitutively active in resting cells, and their modulation mainly involves inhibition through upstream regulatory networks. In the early 1990s, GSK-3 isoforms were implicated as key players in cancer cell pathobiology. Active GSK-3 facilitates the destruction of multiple oncogenic proteins which include β-catenin and Master regulator of cell cycle entry and proliferative metabolism (c-Myc). Therefore, GSK-3 was initially considered to be a tumor suppressor. Consistently, GSK-3 is often inactivated in cancer cells through dysregulated upstream signaling pathways. However, over the past 10–15 years, a growing number of studies highlighted that in some cancer settings GSK-3 isoforms inhibit tumor suppressing pathways and therefore act as tumor promoters. In this article, we will discuss the multiple and often enigmatic roles played by GSK-3 isoforms in some chronic hematological malignancies (chronic myelogenous leukemia, chronic lymphocytic leukemia, multiple myeloma, and B-cell non-Hodgkin’s lymphomas) which are among the most common blood cancer cell types. We will also summarize possible novel strategies targeting GSK-3 for innovative therapies of these disorders.

Lipid Composition of the Cell Membrane Outer Leaflet Regulates Endocytosis of Nanomaterials through Alterations in Scavenger Receptor Activity

Understanding the principles that guide the uptake of engineered nanomaterials (ENMs) by cells is of interest in biomedical and occupational health research. While evidence has started to accumulate on the role of membrane proteins in ENM uptake, the role of membrane lipid chemistry in regulating ENM endocytosis has remained largely unexplored. Here, we have addressed this issue by altering the plasma membrane lipid composition directly in live cells using a methyl-α-cyclodextrin (MαCD)-catalyzed lipid exchange method. Our observations, in an alveolar epithelial cell line and using silica nanoparticles, reveal that the lipid composition of the plasma membrane outer leaflet plays a significant role in ENM endocytosis and the intracellular fate of ENMs, by affecting nonspecific ENM diffusion into the cell, changing membrane fluidity, and altering the activity of scavenger receptors (SRs) involved in active endocytosis. These results have implications for understanding ENM uptake in different subsets of cells, depending on cell membrane lipid composition.

A novel GSK-3 inhibitor binds to GSK-3β via a reversible, time and Cys-199-dependent mechanism

Glycogen synthase kinase-3 (GSK-3) has been implicated in numerous pathologies making GSK-3 an attractive therapeutic target. Our group has identified a compound termed COB-187 that is a potent and selective inhibitor of GSK-3. In this study, we probed the mechanism by which COB-187 inhibits GSK-3β. Progress curves, generated via real-time monitoring of kinase activity, indicated that COB-187 inhibition of GSK-3β is time-dependent and subsequent jump dilution assays revealed that COB-187 binding to GSK-3β is reversible. Further, a plot of the kinetic constant (k_obs) versus COB-187 concentration suggested that, within the range of concentrations studied, COB-187 binds to GSK-3β via an induced-fit mechanism. There is a critical cysteine residue at the entry to the active site of GSK-3β (Cys-199). We generated a mutant version of GSK-3β wherein Cys-199 was substituted with an alanine. This mutation caused a dramatic decrease in the activity of COB-187; specifically, an IC₅₀ in the nM range for wild type versus >100 µM for the mutant. A screen of COB-187 against 34 kinases that contain a conserved cysteine in their active site revealed that COB-187 is highly selective for GSK-3 indicating that COB-187's inhibition of GSK-3β via Cys-199 is specific. Combined, these findings suggest that COB-187 inhibits GSK-3β via a specific, reversible, time and Cys-199-dependent mechanism.