CD38 inhibitor 78c increases mice lifespan and healthspan in a model of chronological aging.

Nicotinamide adenine dinucleotide (NAD) levels decline during aging, contributing to physical and metabolic dysfunction. The NADase CD38 plays a key role in age-related NAD decline. Whether the inhibition of CD38 increases lifespan is not known.

Rapid recruitment of p53 to DNA damage sites directs DNA repair choice and integrity.

SignificanceOur work focuses on the critical longstanding question of the nontranscriptional role of p53 in tumor suppression. We demonstrate here that poly(ADP-ribose) polymerase (PARP)-dependent modification of p53 enables rapid recruitment of p53 to damage sites, where it in turn directs early repair pathway selection. Specifically, p53-mediated recruitment of 53BP1 at early time points promotes nonhomologous end joining over the more error-prone microhomology end-joining.

Sugar phosphate activation of the stress sensor eIF2B.

The multi-subunit translation initiation factor eIF2B is a control node for protein synthesis. eIF2B activity is canonically modulated through stress-responsive phosphorylation of its substrate eIF2. The eIF2B regulatory subcomplex is evolutionarily related to sugar-metabolizing enzymes, but the biological relevance of this relationship was unknown.

eIF2B activator prevents neurological defects caused by a chronic integrated stress response.

The integrated stress response (ISR) attenuates the rate of protein synthesis while inducing expression of stress proteins in cells. Various insults activate kinases that phosphorylate the GTPase eIF2 leading to inhibition of its exchange factor eIF2B. Vanishing White Matter (VWM) is a neurological disease caused by eIF2B mutations that, like phosphorylated eIF2, reduce its activity.

The small molecule ISRIB rescues the stability and activity of Vanishing White Matter Disease eIF2B mutant complexes.

eIF2B is a dedicated guanine nucleotide exchange factor for eIF2, the GTPase that is essential to initiate mRNA translation. The integrated stress response (ISR) signaling pathway inhibits eIF2B activity, attenuates global protein synthesis and upregulates a set of stress-response proteins. Partial loss-of-function mutations in eIF2B cause a neurodegenerative disorder called Vanishing White Matter Disease (VWMD).

Chromosome Mis-segregation Generates Cell-Cycle-Arrested Cells with Complex Karyotypes that Are Eliminated by the Immune System.

Aneuploidy, a state of karyotype imbalance, is a hallmark of cancer. Changes in chromosome copy number have been proposed to drive disease by modulating the dosage of cancer driver genes and by promoting cancer genome evolution. Given the potential of cells with abnormal karyotypes to become cancerous, do pathways that limit the prevalence of such cells exist? By investigating the immediate consequences of aneuploidy on cell physiology, we identified mechanisms that eliminate aneuploid cells.

Polo-like kinase phosphorylation determines Caenorhabditis elegans centrosome size and density by biasing SPD-5 toward an assembly-competent conformation.

Centrosomes are major microtubule-organizing centers composed of centrioles surrounded by an extensive proteinacious layer called the pericentriolar material (PCM). In Caenorhabditis elegans embryos, the mitotic PCM expands by Polo-like kinase 1 (PLK-1) phosphorylation-accelerated assembly of SPD-5 molecules into supramolecular scaffolds. However, how PLK-1 phosphorylation regulates SPD-5 assembly is not known.

A Cell Biologist's Field Guide to Aurora Kinase Inhibitors.

Aurora kinases are essential for cell division and are frequently misregulated in human cancers. Based on their potential as cancer therapeutics, a plethora of small molecule Aurora kinase inhibitors have been developed, with a subset having been adopted as tools in cell biology. Here, we fill a gap in the characterization of Aurora kinase inhibitors by using biochemical and cell-based assays to systematically profile a panel of 10 commercially available compounds with reported selectivity for Aurora A (MLN8054, MLN8237, MK-5108, MK-8745, Genentech Aurora Inhibitor 1), Aurora B (Hesperadin, ZM447439, AZD1152-HQPA, GSK1070916), or Aurora A/B (VX-680).

Cell biology. Reversible centriole depletion with an inhibitor of Polo-like kinase 4.

Centrioles are ancient organelles that build centrosomes, the major microtubule-organizing centers of animal cells. Extra centrosomes are a common feature of cancer cells. To investigate the importance of centrosomes in the proliferation of normal and cancer cells, we developed centrinone, a reversible inhibitor of Polo-like kinase 4 (Plk4), a serine-threonine protein kinase that initiates centriole assembly.

Crystal structures of the CPAP/STIL complex reveal its role in centriole assembly and human microcephaly.

Centrioles organise centrosomes and template cilia and flagella. Several centriole and centrosome proteins have been linked to microcephaly (MCPH), a neuro-developmental disease associated with small brain size. CPAP (MCPH6) and STIL (MCPH7) are required for centriole assembly, but it is unclear how mutations in them lead to microcephaly.

Direct binding of SAS-6 to ZYG-1 recruits SAS-6 to the mother centriole for cartwheel assembly.

Assembly of SAS-6 dimers to form the centriolar cartwheel requires the ZYG-1/Plk4 kinase. Here, we show that ZYG-1 recruits SAS-6 to the mother centriole independently of its kinase activity; kinase activity is subsequently required for cartwheel assembly. We identify a direct interaction between ZYG-1 and the SAS-6 coiled coil that explains its kinase activity-independent function in SAS-6 recruitment.

PINK1 and Parkin target Miro for phosphorylation and degradation to arrest mitochondrial motility.

Cells keep their energy balance and avoid oxidative stress by regulating mitochondrial movement, distribution, and clearance. We report here that two Parkinson's disease proteins, the Ser/Thr kinase PINK1 and ubiquitin ligase Parkin, participate in this regulation by arresting mitochondrial movement. PINK1 phosphorylates Miro, a component of the primary motor/adaptor complex that anchors kinesin to the mitochondrial surface.

Kinesin's light chains inhibit the head- and microtubule-binding activity of its tail.

Kinesin-1 is a microtubule-based motor comprising two heavy chains (KHCs) and two light chains (KLCs). Motor activity is precisely regulated to avoid futile ATP consumption and to ensure proper intracellular localization of kinesin-1 and its cargoes. The KHC tail inhibits ATPase activity by interacting with the enzymatic KHC heads, and the tail also binds microtubules.

The Kinesin-1 tail conformationally restricts the nucleotide pocket.

We have used electron paramagnetic resonance and fluorescence spectroscopy to study the interaction between the kinesin-1 head and its regulatory tail domain. The interaction between the tails and the enzymatically active heads has been shown to inhibit intrinsic and microtubule-stimulated ADP release. Here, we demonstrate that the probe mobility of two different spin-labeled nucleotide analogs in the kinesin-1 nucleotide pocket is restricted upon binding of the tail domain to kinesin-1 heads.