The presenilin (PS) genes associated with Alzheimer disease encode polytopic transmembrane proteins which undergo physiologic endoproteolytic cleavage to generate stable NH 2 -and COOH-terminal fragments (NTF or CTF) which co-localize in intracellular membranes, but are tightly regulated in their stoichiometry and abundance. We have used linear glycerol velocity and discontinuous sucrose gradient analysis to investigate the distribution and native conformation of PS1 and PS2 during this regulated processing in cultured cells and in brain. The PS1 NTF and CTF co-localize in the endoplasmic reticulum (ER) and in the Golgi apparatus, where they are components of a ϳ250-kDa complex. This complex also contains ␤-catenin but not ␤-amyloid precursor protein (APP). In contrast, the PS1 holoprotein precursor is predominantly localized to the rough ER and smooth ER, where it is a component of a ϳ180-kDa native complex. PS2 forms similar but independent complexes. Restricted incorporation of the presenilin NTF and CTF along with a potentially functional ligand (␤-catenin) into a multimeric complex in the ER and Golgi apparatus may provide an explanation for the regulated accumulation of the NTF and CTF.Mutations in the genes encoding the presenilin (PS) 1 1 (PS1) and presenilin 2 (PS2) account for the majority of early-onset familial Alzheimer's disease (1-3). Both genes encode polytopic transmembrane proteins that are predominantly localized in intracellular membranes, including the nuclear envelope, the endoplasmic reticulum, and the Golgi apparatus (4, 5). Structural studies suggested that these proteins contain either six or eight transmembrane (TM) domains, and that the amino and carboxyl termini as well as a large hydrophilic loop following the sixth TM domain are located in the cytoplasm (5-7). The presenilins undergo physiological endoproteolytic processing within the large cytoplasmic loop following TM6 by an unknown protease that produces heterogeneous ϳ29-kDa aminoterminal and ϳ18 -20-kDa carboxyl-terminal fragments (8, 9). The presenilin holoproteins are maintained at low steady levels both in brain and in other peripheral tissues, probably by proteasome-mediated degradation (10, 11). As a result, the presenilin species most readily detected are the stable NH 2 -and COOH-terminal endoproteolytic fragments, the stoichiometry of which appears to be tightly regulated (8).The functional role of the presenilins is still unknown, although roles in cellular differentiation, in signal transduction, in apoptosis, or in intracellular protein trafficking have been proposed. To better understand the presenilin proteins and their biological functions, we have investigated both the native state of these proteins and their biochemical subcellular localization in membrane fractions derived from cultured cells and from the human brain. Our data suggest that the presenilins form detergent-sensitive high molecular mass complexes. The PS1 holoprotein is a component of a complex of ϳ180 kDa, while the endoproteolytic fragments are ...

This paper investigates the effect of varying the geometry of the die on the cell nucleation behavior of extruded PS foams blown with CO2. Three interchangeable groups of carefully calibrated filamentary dies have been used in the experimental study. The dies were deliberately designed to have either different pressure drop rates while having identical die pressures and flow rates, or different die pressures while having identical pressure drop rates and flow rates. The experimental results revealed that the geometry of the die governs the cell density of extruded PS foams, especially because of its significant effect on the pressure drop rate across the die. However, the effect of the die back pressure on the cell density was found to be marginal, whereas its effect on the cell morphology was found to be predominant. In addition, regardless of die geometry, the CO2 content proved to be a very sensitive parameter with respect to the cell nucleation behavior of extruded PS foams. On the other hand, the cell density was slightly improved by an increase of the tale content, especially at reduced concentrations of CO2.

The presenilin proteins are components of high-molecular-weight protein complexes in the endoplasmic reticulum and Golgi apparatus that also contain beta-catenin. We report here that presenilin mutations associated with familial Alzheimer disease (but not the non-pathogenic Glu318Gly polymorphism) alter the intracellular trafficking of beta-catenin after activation of the Wnt/beta-catenin signal transduction pathway. As with their effect on betaAPP processing, the effect of PS1 mutations on trafficking of beta-catenin arises from a dominant 'gain of aberrant function' activity. These results indicate that mistrafficking of selected presenilin ligands is a candidate mechanism for the genesis of Alzheimer disease associated with presenilin mutations, and that dysfunction in the presenilin-beta-catenin protein complexes is central to this process.

We report the discovery of a new potent allosteric effector of sickle cell hemoglobin, GBT440 (), that increases the affinity of hemoglobin for oxygen and consequently inhibits its polymerization when subjected to hypoxic conditions. Unlike earlier allosteric activators that bind covalently to hemoglobin in a 2:1 stoichiometry, binds with a 1:1 stoichiometry. Compound is orally bioavailable and partitions highly and favorably into the red blood cell with a RBC/plasma ratio of ∼150. This partitioning onto the target protein is anticipated to allow therapeutic concentrations to be achieved in the red blood cell at low plasma concentrations. GBT440 () is in Phase 3 clinical trials for the treatment of sickle cell disease (NCT03036813).

This paper discusses the research conducted to achieve an accurate bubble-growth model and simulation scheme to describe precisely the bubble-growth phenomena that occur in polymeric foaming. Using the accurately measured thermophysical and rheological properties of polymer/gas mixtures (i.e., the solubility, the diffusivity, the surface tension, the viscosity, and the relaxation time) as the inputs for computer simulation, the growth profiles for bubbles nucleated at different times were predicted and carefully compared to experimentally observed data obtained from batch foaming simulation with online visualization. A polystyrene/carbon dioxide (PS/CO2) system is used herein as a case example. It was verified that the cell-growth model is capable of thoroughly depicting the growth behaviors of bubble nuclei nucleated under varying processing conditions without using any fitting parameter. These results indicate that the established model accounts for most of the physics behind the bubble-growth phenomena. Furthermore, the effects of the aforementioned thermophysical and rheological parameters on the cell-growth dynamics were demonstrated by a series of sensitivity studies.

We report the design, synthesis, and optimization of the first, selective activators of cardiac myosin. Starting with a poorly soluble, nitro-aromatic hit compound (1), potent, selective, and soluble myosin activators were designed culminating in the discovery of omecamtiv mecarbil (24). Compound 24 is currently in clinical trials for the treatment of systolic heart failure.

The identification and optimization of the first activators of fast skeletal muscle are reported. Compound 1 was identified from high-throughput screening (HTS) and subsequently found to improve muscle function via interaction with the troponin complex. Optimization of 1 for potency, metabolic stability, and physical properties led to the discovery of tirasemtiv (25), which has been extensively characterized in clinical trials for the treatment of amyotrophic lateral sclerosis.

No abstract