Kinase domain autophosphorylation rewires the activity and substrate specificity of CK1 enzymes.

CK1s are acidophilic serine/threonine kinases with multiple critical cellular functions; their misregulation contributes to cancer, neurodegenerative diseases, and sleep phase disorders. Here, we describe an evolutionarily conserved mechanism of CK1 activity: autophosphorylation of a threonine (T220 in human CK1δ) located at the N terminus of helix αG, proximal to the substrate binding cleft. Crystal structures and molecular dynamics simulations uncovered inherent plasticity in αG that increased upon T220 autophosphorylation. The phosphorylation-induced structural changes significantly altered the conformation of the substrate binding cleft, affecting substrate specificity. In T220 phosphorylated yeast and human CK1s, activity toward many substrates was decreased, but we also identified a high-affinity substrate that was phosphorylated more rapidly, and quantitative phosphoproteomics revealed that disrupting T220 autophosphorylation rewired CK1 signaling in Schizosaccharomyces pombe. T220 is present exclusively in the CK1 family, thus its autophosphorylation may have evolved as a unique regulatory mechanism for this important family.

Fission yeast Duc1 links to ER-PM contact sites and influences PM lipid composition and cytokinetic ring anchoring.

Cytokinesis is the final stage of the cell cycle that results in the physical separation of daughter cells. To accomplish cytokinesis, many organisms build an actin- and myosin-based cytokinetic ring (CR) that is anchored to the plasma membrane (PM). Defects in CR-PM anchoring can arise when the PM lipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is depleted. In Schizosaccharomyces pombe, reduced PM PI(4,5)P2 results in a CR that cannot maintain a medial position and slides toward one cell end, resulting in two differently sized daughter cells. S. pombe PM PI(4,5)P2 is synthesized by the phosphatidylinositol 4-phosphate 5-kinase (PI5-kinase) Its3, but what regulates this enzyme to maintain appropriate PM PI(4,5)P2 levels in S. pombe is not known. To identify Its3 regulators, we used proximity-based biotinylation, and the uncharacterized protein Duc1 was specifically detected. We discovered that Duc1 decorates the PM except at the cell division site and that its unique localization pattern is dictated by binding to the endoplasmic reticulum (ER)-PM contact site proteins Scs2 and Scs22. Our evidence suggests that Duc1 also binds PI(4,5)P2 and helps enrich Its3 at the lateral PM, thereby promoting PM PI(4,5)P2 synthesis and robust CR-PM anchoring.

Engineering a High-Loading Sub-4 nm Intermetallic Platinum-Cobalt Alloy on Atomically Dispersed Cobalt-Nitrogen-Carbon for Efficient Oxygen Reduction in Fuel Cells.

Developing a high-performance membrane electrode assembly (MEA) poses a formidable challenge for fuel cells, which lies in achieving both high metal loading and efficient catalytic activity concurrently for MEA catalysts. Here, we introduce a porous Co@NC carrier to synthesize sub-4 nm PtCo intermetallic nanocrystals, achieving an impressive Pt loading of 27 wt %. The PtCo-CoNC catalyst demonstrates exceptional catalytic activity and remarkable stability for the oxygen reduction reaction. Advanced characterization techniques and theoretical calculations emphasize the synergistic effect between PtCo alloys and single Co atoms, which enhances the desorption of the OH* intermediate. Furthermore, the PtCo-CoNC-based cathode delivers a high power density of 1.22 W cm-2 in the MEA test owing to the enhanced mass transport, which is verified by the simulation results of the O2 distributions and current density inside the catalyst layer. This study lays the groundwork for the design of efficient catalysts with practical applications in fuel cells.

Regulating Electron Filling and Orbital Occupancy of Anti-Bonding States of Transition Metal Nitride Heterojunction for High Areal Capacity Lithium-Sulfur Full Batteries.

The commercialization of lithium-sulfur (Li-S) battery is seriously hindered by the shuttle behavior of lithium (Li) polysulfide, slow conversion kinetics, and Li dendrite growth. Herein, a novel hierarchical p-type iron nitride and n-type vanadium nitride (p-Fe2N/n-VN) heterostructure with optimal electronic structure, confined in vesicle-like N-doped nanofibers (p-Fe2N/n-VN⊂PNCF), is meticulously constructed to work as "one stone two birds" dual-functional hosts for both the sulfur cathode and Li anode. As demonstrated, the d-band center of high-spin Fe atom captures more electrons from V atom to realize more π* and moderate σ* bond electron filling and orbital occupation; thus, allowing moderate adsorption intensity for polysulfides and more effective d-p orbital hybridization to improve reaction kinetics. Meanwhile, this unique structure can dynamically balance the deposition and transport of Li on the anode; thereby, more effectively inhibiting Li dendrite growth and promoting the formation of a uniform solid electrolyte interface. The as-assembled Li-S full batteries exhibit the conspicuous capacities and ultralong cycling lifespan over 2000 cycles at 5.0 C. Even at a higher S loading (20 mg cm-2) and lean electrolyte (2.5 µL mg-1), the full cells can still achieve an ultrahigh areal capacity of 16.1 mAh cm-2 after 500 cycles at 0.1 C.

NbC Nanoparticles Decorated Carbon Nanofibers as Highly Active and Robust Heterostructural Electrocatalysts for Ammonia Synthesis.

Transition-metal carbides with metallic properties have been extensively used as electrocatalysts due to their excellent conductivity and unique electronic structures. Herein, NbC nanoparticles decorated carbon nanofibers (NbC@CNFs) are proposed as an efficient and robust catalyst for electrochemical synthesis of ammonia from nitrate/nitrite reduction, which achieves a high Faradaic efficiency (FE) of 94.4 % and a large ammonia yield of 30.9 mg h-1 mg-1 cat.. In situ electrochemical tests reveal the nitrite reduction at the catalyst surface follows the *NO pathway and theoretical calculations reveal the formation of NbC@CNFs heterostructure significantly broadens density of states nearby the Fermi energy. Finite element simulations unveil that the current and electric field converge on the NbC nanoparticles along the fiber, suggesting the dispersed carbides are highly active for nitrite reduction.

Phosphorylation in the intrinsically disordered region of F-BAR protein Imp2 regulates its contractile ring recruitment.

The F-BAR protein Imp2 is an important contributor to cytokinesis in the fission yeast Schizosaccharomyces pombe. Because cell cycle-regulated phosphorylation of the central intrinsically disordered region (IDR) of the Imp2 paralog Cdc15 controls Cdc15 oligomerization state, localization and ability to bind protein partners, we investigated whether Imp2 is similarly phosphoregulated. We found that Imp2 is endogenously phosphorylated on 28 sites within its IDR, with the bulk of phosphorylation being constitutive. In vitro, the casein kinase 1 (CK1) isoforms Hhp1 and Hhp2 can phosphorylate 17 sites, and Cdk1 (also known as Cdc2) can phosphorylate the remaining 11 sites. Mutations that prevent Cdk1 phosphorylation result in precocious Imp2 recruitment to the cell division site, and mutations designed to mimic these phosphorylation events delay Imp2 accumulation at the contractile ring (CR). Mutations that eliminate CK1 phosphorylation sites allow CR sliding, and phosphomimetic substitutions at these sites reduce Imp2 protein levels and slow CR constriction. Thus, like Cdc15, the Imp2 IDR is phosphorylated at many sites by multiple kinases. In contrast to Cdc15, for which phosphorylation plays a major cell cycle regulatory role, Imp2 phosphorylation is primarily constitutive, with milder effects on localization and function. This article has an associated First Person interview with the first author of the paper.

Phosphoregulation of the cytokinetic protein Fic1 contributes to fission yeast growth polarity establishment.

Cellular polarization underlies many facets of cell behavior, including cell growth. The rod-shaped fission yeast Schizosaccharomyces pombe is a well-established, genetically tractable system for studying growth polarity regulation. S. pombe cells elongate at their two cell tips in a cell cycle-controlled manner, transitioning from monopolar to bipolar growth in interphase when new ends established by the most recent cell division begin to extend. We previously identified cytokinesis as a critical regulator of new end growth and demonstrated that Fic1, a cytokinetic factor, is required for normal polarized growth at new ends. Here, we report that Fic1 is phosphorylated on two C-terminal residues, which are each targeted by multiple protein kinases. Endogenously expressed Fic1 phosphomutants cannot support proper bipolar growth, and the resultant defects facilitate the switch into an invasive pseudohyphal state. Thus, phosphoregulation of Fic1 links the completion of cytokinesis to the re-establishment of polarized growth in the next cell cycle. These findings broaden the scope of signaling events that contribute to regulating S. pombe growth polarity, underscoring that cytokinetic factors constitute relevant targets of kinases affecting new end growth.This article has an associated First Person interview with Anthony M. Rossi, joint first author of the paper.

Fission yeast Opy1 is an endogenous PI(4,5)P2 sensor that binds to the phosphatidylinositol 4-phosphate 5-kinase Its3.

Phosphoinositides (PIPs) are a dynamic family of lipids that execute diverse roles in cell biology. PIP levels are regulated by numerous enzymes, but our understanding of how these enzymes are controlled in space and time is incomplete. One role of the PIP phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is to anchor the cytokinetic ring (CR) to the plasma membrane (PM) in Schizosaccharomyces pombe While examining potential PI(4,5)P2-binding proteins for roles in CR anchoring, we identified the dual pleckstrin homology (PH) domain-containing protein Opy1. Although related proteins are implicated in PIP regulation, we found no role for S. pombe Opy1 in CR anchoring, which would be expected if it modulated PM PI(4,5)P2 levels. Our data indicate that although Opy1 senses PM PI(4,5)P2 levels and binds to the phosphatidylinositol 4-phosphate 5-kinase (PI5-kinase) Its3, Opy1 does not regulate Its3 kinase activity or PM PI(4,5)P2 levels, a striking difference from its Saccharomyces cerevisiae homolog. However, overexpression of Opy1 resulted in cytokinesis defects, as might be expected if it sequestered PI(4,5)P2 Our results highlight the evolutionary divergence of dual PH domain-containing proteins and the need for caution when interpreting results based on their overexpression.This article has an associated First Person interview with the first author of the paper.

Coupling Atomically Dispersed Fe-N5 Sites with Defective N-Doped Carbon Boosts CO2 Electroreduction.

Atomically dispersed iron immobilized on nitrogen-doped carbon catalyst has attracted enormous attention for CO2 electroreduction, but still suffers from low current density and poor selectivity. Herein, atomically dispersed FeN5 active sites supported on defective N-doped carbon successfully formed by a multistep thermal treatment strategy with the aid of dicyandiamide are reported. This dual-functional strategy can not only construct intrinsic carbon defects by selectively etching pyridinic-N and pyrrolic-N, but also introduces an additional N from the neighboring carbon layer coordinating to the commonly observed FeN4 , thus creating an FeN5 active site supported on defective porous carbon nanofibers (FeN5 /DPCF) with a local 3D configuration. The optimized FeN5 /DPCF achieves a high CO Faradaic efficiency (>90%) over a wide potential range of -0.4 to -0.6 V versus RHE with a maximal FECO of 93.1%, a high CO partial current density of 9.4 mA cm-2 at the low overpotential of 490 mV, and a remarkable turnover frequency of 2965 h-1 . Density functional theory calculations reveal that the synergistic effect between the FeN5 sites and carbon defects can enhance electronic localization, thus reducing the energy barrier for the CO2 reduction reaction and suppressing the hydrogen evolution reaction, giving rise to the superior activity and selectivity.

Atomically Dispersed Cu in Zeolitic Imidazolate Framework Nanoflake Array for Dendrite-Free Zn Metal Anode.

Aqueous Zn metal batteries (AZMBs) have been considered as a promising alternative to the existing Li-ion batteries. Nevertheless, the large-scale application of the AZMBs is restricted by the dendrite formation and side reactions within the Zn metal anodes (ZMAs) during cycling. Herein, an atomically dispersed Cu in leaf-like Zn-coordinated zeolitic imidazolate framework (ZIF-L) nanoflakes on Ti mesh (CuZIF-L@TM) as ZMA host is developed. The 3D conductive network formed by the interconnected ZIF-L nanoflakes can reduce the local current density and homogenize the electric field distribution. Moreover, experimental data and theoretical calculations reveal the Cu single atoms within the ZIF-L can serve as the zincophilic sites to facilitate the Zn deposition. As expected, the CuZIF-L@TM host enables a homogeneous Zn deposition on the surface without dendrites. The resultant CuZIF-L@TM/Zn electrode shows stable Zn plating/stripping over 1100 h at 1 mA cm-2 with a low voltage hysteresis of about 50 mV. As a proof of concept, a full cell based on the designed CuZIF-L@TM/Zn anode shows a stable cycling performance over 1000 cycles.

Self-Supported Transition Metal-Based Nanoarrays for Efficient Energy Storage.

Rechargeable batteries and supercapacitors are currently considered as promising electrochemical energy storage (EES) systems to address the energy and environment issues. Self-supported transition metal (Ni, Co, Mn, Mo, Cu, V)-based materials are promising electrodes for EES devices, which offer highly efficient charge transfer kinetics. This review summarizes the latest development of transition metal-based materials with self-supported structures for EES systems. Special focus has been taken on the synthetic methods, the selection of substrates, architectures and chemical compositions of different self-supported nanoarrays in energy storage systems. Finally, the challenges and opportunities of these materials for future development in this field are briefly discussed. We believe that the advancement in self-supported electrode materials would pave the way towards next-generation EES.

SeC Bonding Promoting Fast and Durable Na+ Storage in Yolk-Shell SnSe2 @SeC.

Tin-based compounds have received much attention as anode materials for lithium/sodium ion batteries owing to their high theoretical capacity. However, the huge volume change usually leads to the pulverization of electrode, giving rise to a poor cycle performance, which have severely hampered their practical application. Herein, highly durable yolk-shell SnSe2 nanospheres (SnSe2 @SeC) are prepared by a multistep templating method, with an in situ gas-phase selenization of the SnO2 @C hollow nanospheres. During this process, Se can be doped into the carbon shell with a tunable amount and form SeC bonds. Density functional theory calculation results reveal that the SeC bonding can enhance the charge transfer properties as well as the binding interaction between the SnSe2 core and the carbon shell, favoring an improved rate performance and a superior cyclability. As expected, the sample delivers reversible capacities of 441 and 406 mAh g-1 after 2000 cycles at 2 and 5 A g-1 , respectively, as the anode material for a sodium-ion battery. Such performances are significantly better than the control sample without the SeC bonding and also other metal selenide-based anodes, evidently showing the advantage of Se doping in the carbon shell.

Dephosphorylation of F-BAR protein Cdc15 modulates its conformation and stimulates its scaffolding activity at the cell division site.

Cytokinesis in Schizosaccharomyces pombe requires the function of Cdc15, the founding member of the pombe cdc15 homology (PCH) family of proteins. As an early, abundant contractile ring component with multiple binding partners, Cdc15 plays a key role in organizing the ring. We demonstrate that Cdc15 phosphorylation at many sites generates a closed conformation, inhibits Cdc15 assembly at the division site in interphase, and precludes interaction of Cdc15 with its binding partners. Cdc15 dephosphorylation induces an open conformation, oligomerization, and scaffolding activity during mitosis. Cdc15 mutants with reduced phosphorylation precociously appear at the division site in filament-like structures and display increased association with protein partners and the membrane. Our results indicate that Cdc15 phosphoregulation impels both assembly and disassembly of the contractile apparatus and suggest a regulatory strategy that PCH family and BAR superfamily members might broadly employ to achieve temporal specificity in their roles as linkers between membrane and cytoskeleton.

A Degenerate Cohort of Yeast Membrane Trafficking DUBs Mediates Cell Polarity and Survival.

Deubiquitinating enzymes (DUBs), cysteine or metallo- proteases that cleave ubiquitin chains or protein conjugates, are present in nearly every cellular compartment, with overlapping protein domain structure, localization, and functions. We discovered a cohort of DUBs that are involved in membrane trafficking (ubp4, ubp5, ubp9, ubp15, and sst2) and found that loss of all five of these DUBs but not loss of any combination of four, significantly impacted cell viability in the fission yeast Schizosaccharomyces pombe (1). Here, we delineate the collective and individual functions and activities of these five conserved DUBs using comparative proteomics, biochemistry, and microscopy. We find these five DUBs are degenerate rather than redundant at the levels of cell morphology, substrate selectivity, ubiquitin chain specificity, and cell viability under stress. These studies reveal the complexity of interplay among these enzymes, providing a foundation for understanding DUB biology and providing another example of how cells utilize degeneracy to improve survival.

Discovery of genes involved in mitosis, cell division, cell wall integrity and chromosome segregation through construction of Schizosaccharomyces pombe deletion strains.

The fission yeast model system Schizosaccharomyces pombe is used to study fundamental biological processes. To continue to fill gaps in the Sz. pombe gene deletion collection, we constructed a set of 90 haploid gene deletion strains covering many previously uncharacterized genes. To begin to understand the function of these genes, we exposed this collection of strains to a battery of stress conditions. Using this information in combination with microscopy, proteomics and mini-chromosome loss assays, we identified genes involved in cell wall integrity, cytokinesis, chromosome segregation and DNA metabolism. This subset of non-essential gene deletions will add to the toolkits available for the study of biological processes in Sz. pombe. Copyright © 2016 John Wiley & Sons, Ltd.

Comprehensive proteomics analysis reveals new substrates and regulators of the fission yeast clp1/cdc14 phosphatase.

The conserved family of Cdc14 phosphatases targets cyclin-dependent kinase substrates in yeast, mediating late mitotic signaling events. To discover substrates and regulators of the Schizosaccharomyces pombe Cdc14 phosphatase Clp1, TAP-tagged Clp1, and a substrate trapping mutant (Clp1-C286S) were purified from asynchronous and mitotic (prometaphase and anaphase) cells and binding partners were identified by 2D-LC-MS/MS. Over 100 Clp1-interacting proteins were consistently identified, over 70 of these were enriched in Clp1-C286S-TAP (potential substrates) and we and others detected Cdk1 phosphorylation sites in over half (44/73) of these potential substrates. According to GO annotations, Clp1-interacting proteins are involved in many essential cellular processes including mitosis, cytokinesis, ribosome biogenesis, transcription, and trafficking among others. We confirmed association and dephosphorylation of multiple candidate substrates, including a key scaffolding component of the septation initiation network called Cdc11, an essential kinase of the conserved morphogenesis-related NDR kinase network named Shk1, and multiple Mlu1-binding factor transcriptional regulators. In addition, we identified Sal3, a nuclear ß-importin, as the sole karyopherin required for Clp1 nucleoplasmic shuttling, a key mode of Cdc14 phosphatase regulation. Finally, a handful of proteins were more abundant in wild type Clp1-TAP versus Clp1-C286S-TAP, suggesting that they may directly regulate Clp1 signaling or serve as scaffolding platforms to localize Clp1 activity.

Dynamics of SIN asymmetry establishment.

Timing of cell division is coordinated by the Septation Initiation Network (SIN) in fission yeast. SIN activation is initiated at the two spindle pole bodies (SPB) of the cell in metaphase, but only one of these SPBs contains an active SIN in anaphase, while SIN is inactivated in the other by the Cdc16-Byr4 GAP complex. Most of the factors that are needed for such asymmetry establishment have been already characterized, but we lack the molecular details that drive such quick asymmetric distribution of molecules at the two SPBs. Here we investigate the problem by computational modeling and, after establishing a minimal system with two antagonists that can drive reliable asymmetry establishment, we incorporate the current knowledge on the basic SIN regulators into an extended model with molecular details of the key regulators. The model can capture several peculiar earlier experimental findings and also predicts the behavior of double and triple SIN mutants. We experimentally tested one prediction, that phosphorylation of the scaffold protein Cdc11 by a SIN kinase and the core cell cycle regulatory Cyclin dependent kinase (Cdk) can compensate for mutations in the SIN inhibitor Cdc16 with different efficiencies. One aspect of the prediction failed, highlighting a potential hole in our current knowledge. Further experimental tests revealed that SIN induced Cdc11 phosphorylation might have two separate effects. We conclude that SIN asymmetry is established by the antagonistic interactions between SIN and its inhibitor Cdc16-Byr4, partially through the regulation of Cdc11 phosphorylation states.

New mutations in the core Schizosaccharomyces pombe spindle pole body scaffold Ppc89 reveal separable functions in regulating cell division.

Centrosomes and spindle pole bodies (SPB) are important for mitotic spindle formation and also serve as signaling platforms. In the fission yeast Schizosaccharomyces pombe, genetic ablation and high-resolution imaging indicate that the ɑ-helical Ppc89 is central to SPB structure and function. Here, we developed and characterized conditional and truncation mutants of ppc89. Alleles with mutations in two predicted ɑ-helices near the C-terminus were specifically defective in anchoring Sid4, the scaffold for the septation initiation network (SIN), and proteins dependent on Sid4 (Cdc11, Dma1, Mto1 and Mto2). Artificial tethering of Sid4 to the SPB fully rescued these ppc89 mutants. Another ppc89 allele had mutations located throughout the coding region. While this mutant was also defective in Sid4 anchoring, it displayed additional defects including fragmented SPBs and forming and constricting a second cytokinetic ring in one daughter cell. These defects were shared with a ppc89 allele truncated of the most C-terminal predicted ɑ-helices that is still able to recruit Sid4 and the SIN. We conclude that Ppc89 not only tethers the SIN to the SPB but is also necessary for the integrity of the SPB and faithful coordination of cytokinesis with mitosis.

Substrate displacement of CK1 C-termini regulates kinase specificity.

CK1 kinases participate in many signaling pathways, and their regulation is of meaningful biological consequence. CK1s autophosphorylate their C-terminal noncatalytic tails, and eliminating these tails increases substrate phosphorylation in vitro, suggesting that the autophosphorylated C-termini act as inhibitory pseudosubstrates. To test this prediction, we comprehensively identified the autophosphorylation sites on Schizosaccharomyces pombe Hhp1 and human CK1ε. Phosphoablating mutations increased Hhp1 and CK1ε activity toward substrates. Peptides corresponding to the C-termini interacted with the kinase domains only when phosphorylated, and substrates competitively inhibited binding of the autophosphorylated tails to the substrate binding grooves. Tail autophosphorylation influenced the catalytic efficiency with which CK1s targeted different substrates, and truncating the tail of CK1δ broadened its linear peptide substrate motif, indicating that tails contribute to substrate specificity as well. Considering autophosphorylation of both T220 in the catalytic domain and C-terminal sites, we propose a displacement specificity model to describe how autophosphorylation modulates substrate specificity for the CK1 family.

Crystalline modulation of zirconia for efficient nitrate reduction to ammonia under ambient conditions.

Zirconia as a polycrystalline catalyst can be effectively tuned by doping low-valence elements and meanwhile form abundant oxygen vacancies. Herein, the crystalline structures of zirconia are modulated by scandium doping and proposed as a robust catalyst for nitrate reduction to ammonia. The tetragonal zirconia achieves a maximum ammonia yield of 16.03 mg h-1 mgcat.-1, superior to the other crystal forms. DEMS tests unveil the reaction pathway and theoretical calculations reveal the low free energy of -0.22 eV for nitrate adsorption at the tetragonal zirconia.