Developing PROTACs to redirect the ubiquitination activity of E3 ligases and potently degrade a target protein within cells can be a lengthy and unpredictable process, and it remains unclear whether any combination of E3 and target might be productive for degradation. We describe a probe-quality degrader for a ligase–target pair deemed unsuitable: the von Hippel–Lindau (VHL) and BRD9, a bromodomain-containing subunit of the SWI/SNF chromatin remodeling complex BAF. VHL-based degraders could be optimized from suboptimal compounds in two rounds by systematically varying conjugation patterns and linkers and monitoring cellular degradation activities, kinetic profiles, and ubiquitination, as well as ternary complex formation thermodynamics. The emerged structure–activity relationships guided the discovery of VZ185, a potent, fast, and selective degrader of BRD9 and of its close homolog BRD7. Our findings qualify a new chemical tool for BRD7/9 knockdown and provide a roadmap for PROTAC development against seemingly incompatible target–ligase combinations.

The pancreatic Kunitz inhibitor, also known as aprotinin, bovine basic pancreatic trypsin inhibitor (BPTI), and trypsin-kallikrein inhibitor, is one of the most extensively studied globular proteins. It has proved to be a particularly attractive and powerful tool for studying protein conformation as well as molecular bases of protein/protein interaction(s) and (macro)molecular recognition. BPTI has a relatively broad specificity, inhibiting trypsin- as well as chymotrypsin- and elastase-like serine (pro)enzymes endowed with very different primary specificity. BPTI reacts rapidly with serine proteases to form stable complexes, but the enzyme: inhibitor complex formation may involve several intermediates corresponding to discrete reaction steps. Moreover, BPTI inhibits the nitric oxide synthase type-I and -II action and impairs K+ transport by Ca2+-activated K+ channels. Clinically, the use of BPTI in selected surgical interventions, such as cardiopulmonary surgery and orthotopic liver transplantation, is advised, as it significantly reduces hemorrhagic complications and thus blood-transfusion requirements. Here, the structural, inhibition, and bio-medical aspects of BPTI are reported.

Anthrax is a severe bacterial infection that occurs when Bacillus anthracis spores gain access into the body and germinate in macrophages, causing septicemia and toxemia. Anthrax toxin is a binary A^B toxin composed of protective antigen (PA), lethal factor (LF), and edema factor (EF). PA mediates the entry of either LF or EF into the cytosol of host cells. LF is a zinc metalloprotease that inactivates mitogen-activated protein kinase kinase inducing cell death, and EF is an adenylyl cyclase impairing host defences. Inhibitors targeting di¡erent steps of toxin activity have recently been developed. Anthrax toxin has also been exploited as a therapeutic agent against cancer.

NK cells discriminate between normal and abnormal cells by means of surface inhibitory receptors able to Universita `di Genova Via L.B. Alberti 1 detect human leukocyte antigen (HLA) class I molecules. Cells expressing normal amounts of HLA class I mole-16132 Genova Italy cules are protected from NK cell-mediated cell lysis, whereas cells that display lowered levels of HLA class 2 Istituto Giannina Gaslini Largo G. Gaslini 5 I expression are recognized and efficiently killed by NK cells (Biron, 1997; Moretta et al., 1996, 2001). In fact, 16147 Genova Italy downregulation of HLA class I expression is often induced by tumor transformation or viral infection (Gar-

The lack of selective inhibitors toward the long, short, or supershort phosphodiesterases (PDE4s) prevented researchers from carefully defining the connection between different enzyme isoforms, their brain localization, and their role in neurodegenerative diseases such as Alzheimer's disease (AD). In the search for new therapeutic agents for treating memory and learning disorders, we synthesized new rolipram related PDE4 inhibitors, which had some selectivity toward the long form PDE4D3. The first series was synthesized as racemate and then resolved by semipreparative HPLC on chiral supports. Herein we report the synthetic pathways to obtain compounds 1a-c, 2a-c, 3a-c, 4a-f, 5a,b, 6a,b, 7a,b, the chiral analytical study to resolve compounds 1a-c, 2a-c, 3a-c, the molecular docking study for compound 1c, and the biological results and some SAR considerations that provide some insights and hints for the structural requirements for PDE4D subtype selectivity and enzyme inhibition.