👤 Emily Briggs

The cholesterol ester transfer protein (CETP) inhibitor dalcetrapib has been under evaluation for its potential to prevent cardiovascular (CV) events for almost two decades. The current clinical development program, representing new advances in precision medicine and focused on a genetically defined population with acute coronary syndrome (ACS), is supported by a large body of pharmacokinetic and pharmacodynamic data as well as substantial clinical experience in over 13,000 patients and volunteers. Dalcetrapib treatment of 600 mg/day produces significant inhibition of CETP activity, and has been utilized in phase II and III studies, including CV endpoint trials. Numerous studies have investigated the interactions between dalcetrapib and most drugs commonly prescribed to CV patients and have not demonstrated any clinically significant effects. Evaluations in patients with renal and hepatic impairment demonstrate a greater exposure to dalcetrapib than in the non-impaired population, but long-term clinical studies including patients with mild to moderate hepatic and renal dysfunction demonstrate no increase in adverse events. Safety pharmacology and toxicology studies as well as the clinical safety experience support the continuing development of dalcetrapib as an adjunct to 'standard of care' for the ACS population. This article provides a full review of the pharmacokinetics, as well as pharmacodynamics and pharmacology, of dalcetrapib in the context of a large clinical program. Show less

Atrial natriuretic factor (ANF) is abundantly expressed in atrial cardiomyocytes throughout ontogeny and in ventricular cardiomyocytes in the developing heart. However, during cardiac failure and hypertrophy, ANF expression can reappear in adult ventricular cardiomyocytes. The transcription factor Nkx2-5 is one of the major transactivators of the ANF gene in the developing heart. We identified Nkx2-5 binding at three 5' regulatory elements (kb -34, -31, and -21) and at the proximal ANF promoter by ChIP assay using neonatal mouse cardiomyocytes. 3C analysis revealed close proximity between the distal elements and the promoter region. A 5.8-kb fragment consisting of these elements transactivated a reporter gene in vivo recapitulating endogenous ANF expression, which was markedly reduced in tamoxifen-inducible Nkx2-5 gene knockout mice. However, expression of a reporter gene was increased and expanded toward the outer compact layer in the absence of the transcription repressor Hey2, similar to endogenous ANF expression. Functional Nkx2-5 and Hey2 binding sites separated by 59 bp were identified in the -34 kb element in neonatal cardiomyocytes. In adult hearts, this fragment did not respond to pressure overload, and ANF was induced in the absence of Nkx2-5. These results demonstrate that Nkx2-5 and its responsive cis-regulatory DNA elements are essential for ANF expression selectively in the developing heart. Show less

Nuclear pores span the nuclear envelope and act as gated aqueous channels to regulate the transport of macromolecules between the nucleus and cytoplasm, from individual proteins and RNAs to entire viral genomes. By far the largest subunit of the nuclear pore is the Nup107-160 complex, which consists of nine proteins and is critical for nuclear pore assembly. At mitosis, the Nup107-160 complex localizes to kinetochores, suggesting that it may also function in chromosome segregation. To investigate the dual roles of the Nup107-160 complex at the pore and during mitosis, we set out to identify binding partners by immunoprecipitation from both interphase and mitotic Xenopus egg extracts and mass spectrometry. ELYS, a putative transcription factor, was discovered to copurify with the Nup107-160 complex in Xenopus interphase extracts, Xenopus mitotic extracts, and human cell extracts. Indeed, a large fraction of ELYS localizes to the nuclear pore complexes of HeLa cells. Importantly, depletion of ELYS by RNAi leads to severe disruption of nuclear pores in the nuclear envelope, whereas lamin, Ran, and tubulin staining appear normal. At mitosis, ELYS targets to kinetochores, and RNAi depletion from HeLa cells leads to an increase in cytokinesis defects. Thus, we have identified an unexpected member of the nuclear pore and kinetochore that functions in both pore assembly at the nucleus and faithful cell division. Show less

The Nup107-160 complex is a critical subunit of the nuclear pore. This complex localizes to kinetochores in mitotic mammalian cells, where its function is unknown. To examine Nup107-160 complex recruitment to kinetochores, we stained human cells with antisera to four complex components. Each antibody stained not only kinetochores but also prometaphase spindle poles and proximal spindle fibers, mirroring the dual prometaphase localization of the spindle checkpoint proteins Mad1, Mad2, Bub3, and Cdc20. Indeed, expanded crescents of the Nup107-160 complex encircled unattached kinetochores, similar to the hyperaccumulation observed of dynamic outer kinetochore checkpoint proteins and motors at unattached kinetochores. In mitotic Xenopus egg extracts, the Nup107-160 complex localized throughout reconstituted spindles. When the Nup107-160 complex was depleted from extracts, the spindle checkpoint remained intact, but spindle assembly was rendered strikingly defective. Microtubule nucleation around sperm centrosomes seemed normal, but the microtubules quickly disassembled, leaving largely unattached sperm chromatin. Notably, Ran-GTP caused normal assembly of microtubule asters in depleted extracts, indicating that this defect was upstream of Ran or independent of it. We conclude that the Nup107-160 complex is dynamic in mitosis and that it promotes spindle assembly in a manner that is distinct from its functions at interphase nuclear pores. Show less