MALT1 is a cysteine protease and the only human paracaspase. It is implicated in various human diseases. Here, an overview of the currently available molecular tools is given. Furthermore, their application and future possibilities are discussed. We expect that future research with these and improved tools will provide novel insights into MALT1’s pathobiological roles and enable use as diagnostic tools.

Abstract

The paracaspase MALT1 is a key regulator of the human immune response. It is implicated in a variety of human diseases. For example, deregulated protease activity drives the survival of malignant lymphomas and is involved in the pathophysiology of autoimmune/inflammatory diseases. Thus, MALT1 has attracted attention as promising drug target. Although many MALT1 inhibitors have been identified, molecular tools to study MALT1 activity, target engagement and inhibition in complex biological samples, such as living cells and patient material, are still scarce. Such tools are valuable to validate MALT1 as a drug target in vivo and to assess yet unknown biological roles of MALT1. In this review, we discuss the recent literature on the development and biological application of molecular tools to study MALT1 activity and inhibition.

Polyketides represent an area of significant interest for drug discovery efforts. Leveraging a combination of chemical synthesis and enzymology, researchers have routinely demonstrated that the best of both strategies are conferred and result in improved outcomes. This review highlights the success of such an approach and provides an outlook for polyketide synthetic biology.

Abstract

Polyketide natural products have significant promise as pharmaceutical targets for human health and as molecular tools to probe disease and complex biological systems. While the biosynthetic logic of polyketide synthases (PKS) is well-understood, biosynthesis of designer polyketides remains challenging due to several bottlenecks, including substrate specificity constraints, disrupted protein-protein interactions, and protein solubility and folding issues. Focusing on substrate specificity, PKSs are typically interrogated using synthetic thioesters. PKS assembly lines and their products offer a wealth of information when studied in a chemoenzymatic fashion. This review provides an overview of the past two decades of polyketide chemoenzymatic synthesis and their contributions to the field of chemical biology. These synthetic strategies have successfully yielded natural product derivatives while providing critical insights into enzymatic promiscuity and mechanistic activity.

Hypoxia in tumors alters cellular processes, affecting cancer cell behavior. Cobalt chloride-induced hypoxia reduced proliferation but increased migration and invasion in cancer cells. Short hypoxia increased galectin3 endocytosis, but prolonged hypoxia decreased it. Organelle changes indicated adaptation to hypoxic stress. Hypoxia modulates endocytic pathways, reducing proliferation and enhancing cell migration and invasion.

Abstract

Hypoxia, a decrease in cellular or tissue level oxygen content, is characteristic of most tumors and has been shown to drive cancer progression by altering multiple subcellular processes. We hypothesized that the cancer cells in a hypoxic environment might have slower proliferation rates and increased invasion and migration rates with altered endocytosis compared to the cancer cells in the periphery of the tumor mass that experience normoxic conditions. We induced cellular hypoxia by exposing cells to cobalt chloride, a chemical hypoxic mimicking agent. This study measured the effect of hypoxia on cell proliferation, migration, and invasion. Uptake of fluorescently labeled transferrin, galectin3, and dextran that undergo endocytosis through major endocytic pathways (Clathrin-mediated pathway (CME), Clathrin-independent pathway (CIE), Fluid phase endocytosis (FPE)) were analyzed during hypoxia. Also, the organelle changes associated with hypoxia were studied with organelle trackers. We found that the proliferation rate decreased, and the migration and invasion rate increased in cancer cells in hypoxic conditions compared to normoxic cancer cells. A short hypoxic exposure increased galectin3 uptake in hypoxic cancer cells, but a prolonged hypoxic exposure decreased clathrin-independent endocytic uptake of galectin 3. Subcellular organelles, such as mitochondria, increased to withstand the hypoxic stress, while other organelles, such as Endoplasmic reticulum (ER), were significantly decreased. These data suggest that hypoxia modulates cellular endocytic pathways with reduced proliferation and enhanced cell migration and invasion.

Rhomboid proteases are serine proteases that reside inside the lipid bilayer of a membrane. They are implicated in several diseases. We here report 4-oxo-β-lactam as a new scaffold for covalent rhomboid inhibitors and activity-based probes.

Abstract

Intramembrane serine proteases (rhomboid proteases) are involved in a variety of biological processes and are implicated in several diseases. Here, we report 4-oxo-β-lactams as a novel scaffold for inhibition of rhomboids. We show that they covalently react with the active site and that the covalent bond is sufficiently stable for detection of the covalent rhomboid-lactam complex. 4-Oxo-β-lactams may therefore find future use as both inhibitors and activity-based probes for rhomboid proteases.

We constructed a bifunctional fusion protein for FADH₂ regeneration and successfully coexpressed it with different flavin-dependent halogenases, as well as a dioxygenase that converts 6-chlorotryptophan to 4-Cl-Kynurenine. The figure is a still life of a laboratory bench, with a single oversized E. coli bacterium hovering over an Erlenmeyer flask. Cell disruption is depicted in visual analogy to cracking an egg with the lysate appearing like egg yolk. The lysate in the flask contains all necessary enzymes for the biocatalytic cascade described in the paper rendered as ribbon structures with coloring consistent with the paper. Shown as permanent marker notes on the bench surface are a key reaction scheme as well as a “ToDo-list” that checks off some important goals of the research work. More information can be found in the Research article by N. Montua, N. Sewald.