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The bidirectional movement of lysosomes on microtubule tracks regulates their whole-cell spatial arrangement. Arl8b, a small GTP-binding (G) protein, promotes lysosome anterograde trafficking mediated by kinesin-1. Herein, we report an Arl8b effector, RUFY3, which regulates the retrograde transport of lysosomes. We show that RUFY3 interacts with the JIP4-dynein-dynactin complex and facilitates Arl8b association with the retrograde motor complex. Accordingly, RUFY3 knockdown disrupts the positioning of Arl8b-positive endosomes and reduces Arl8b colocalization with Rab7-marked late endosomal compartments. Moreover, we find that RUFY3 regulates nutrient-dependent lysosome distribution, although autophagosome-lysosome fusion and autophagic cargo degradation are not impaired upon RUFY3 depletion. Interestingly, lysosome size is significantly reduced in RUFY3 depleted cells, which could be rescued by inhibition of the lysosome reformation regulatory factor PIKFYVE. These findings suggest a model in which the perinuclear cloud arrangement of lysosomes regulates both the positioning and size of these proteolytic compartments.

One of the earliest studies on human pancreas regeneration dates from the beginning of the 1900s when the American pathologist Russel Cecil noted signs of attempted islet regeneration in samples from organ donors with diabetes. A century later, the quest is on to enhance the limited regenerative potential of the pancreas in order to develop new therapies for diabetes. While regeneration is incomplete in mammals, zebrafish can naturally recover from extreme β-cell destruction and hyperglycemia by producing new β-cells. Here, we discuss how a unique blend of in vivo imaging, genetics and drug discovery in zebrafish could reveal the secrets of natural β-cell regeneration. Specifically, we explore the essential steps for successful regeneration, from the induction of pancreas plasticity to the integration of cells into networks that establish functional islet communities.

A multifunctional molecular design of fluorescent discotic liquid crystal (DLC) consisting of a tetraphenylethylene core is reported, which is found to serve as an excellent solid-state emitter in OLED devices with EQE of 4.4% and tunable mechanochromism. X-ray diffraction studies unveiled that change in supramolecular self-assembly is the physical origin of mechanochromism. The luminescent DLC molecule has been shown to act as a highly selective probe for labelling acidic cellular compartments (such as lysosomes) in bio-imaging using HeLa cells.

Cytoplasmic dynein is a retrograde microtubule-based motor transporting cellular cargo, including organelles, vesicular intermediates, RNA granules, and proteins, thus regulating their subcellular distribution and function. Mammalian dynein associates with dynactin, a multisubunit protein complex that is necessary for the processive motility of dynein along the microtubule tracks. Recent studies have shown that the interaction between dynein and dynactin is enhanced in the presence of a coiled-coil activating adaptor protein, which performs dual functions of recruiting dynein and dynactin to their cargoes and inducing the superprocessive motility of the motor complex. One such family of coiled-coil activating adaptor proteins is the Hook family of proteins that are conserved across evolution with three paralogs in the case of mammals, namely, HOOK1-HOOK3. This Perspective aims to provide an overview of the Hook protein structure and the cellular functions of Hook proteins, with an emphasis on the recent developments in understanding their role as activating dynein adaptors.

The whole-cell scale spatial organization of lysosomes is regulated by their bidirectional motility on microtubule tracks. Small GTP-binding (G) protein, Arl8b, stimulates the anterograde transport of lysosomes by recruiting adaptor protein SKIP (also known as PLEKHM2), which in turn couples the microtubule motor kinesin-1. Here, we have identified an Arl8b effector, RUN and FYVE domain-containing protein family member 3, RUFY3, which drives the retrograde transport of lysosomes. Artificial targeting of RUFY3 to the surface of mitochondria was sufficient to drive their perinuclear positioning. We find that RUFY3 interacts with the JIP4-Dynein-Dynactin complex and mediates Arl8b association with the retrograde motor complex. The mobile fraction of the total lysosomes per cell was significantly enhanced upon RUFY3 depletion, suggesting that RUFY3 maintains the lysosomes clustering within the perinuclear cloud. Expectedly, RUFY3 knockdown disrupted the perinuclear positioning of lysosomes upon nutrient starvation and/or serum depletion, although lysosome continued to undergo fusion with autophagosomes. Interestingly, lysosome fission events were more frequent in RUFY3-depleted cells and accordingly, there was a striking reduction in lysosome size, an effect that was also observed in dynein and JIP4 depleted cells. These findings indicate that the dynein-dependent “perinuclear cloud” arrangement of lysosomes also regulates the size of these proteolytic compartments and, likely, their cellular roles.

Quantum walk has been regarded as a primitive to universal quantum computation. By using the operations required to describe the single particle discrete-time quantum walk on a position space we demonstrate the realization of the universal set of gates on two-and three-qubit system. The idea is to reap the effective Hilbert space of the single qubit and the position space on which it evolves in superposition of position space in order to realize multi-qubit states and universal set of quantum gates on them. Realization of many non-trivial gates in the form of engineering arbitrary states is simpler in the proposed quantum walk model when compared to the circuit based model of computation. We will also discuss the scalability of the model and some propositions for using lesser number of qubits in realizing larger qubit systems.

Quantum walk has been regarded as a primitive to universal quantum computation. By using the operations required to describe the single particle discrete-time quantum walk on a position space we demonstrate the realization of the universal set of quantum gates on two- and three-qubit systems. The idea is to utilize the effective Hilbert space of the single qubit and the position space on which it evolves in order to realize multi-qubit states and universal set of quantum gates on them. Realization of many non-trivial gates and engineering arbitrary states is simpler in the proposed quantum walk model when compared to the circuit based model of computation. We will also discuss the scalability of the model and some propositions for using lesser number of qubits in realizing larger qubit systems., Comment: Updated to latest version, corrected grammar and moved appendix to main text

Aromaticity is a well-known phenomenon in both physics and chemistry, and is responsible for many unique chemical and physical properties of aromatic molecules. The primary feature contributing to the stability of polycyclic aromatic hydrocarbons is the delocalised $\pi$-electron clouds in the $2p_z$ orbitals of each of the $N$ carbon atoms. While it is known that electrons delocalize among the hybridized $sp^2$ orbitals, this paper proposes quantum walk as the mechanism by which the delocalization occurs, and also obtains how the functional chemical structures of these molecules arise naturally out of such a construction. We present results of computations performed for some benzoid polycyclic aromatic hydrocarbons in this regard, and show that the quantum walk-based approach does correctly predict the reactive sites and stability order of the molecules considered., Comment: 15 Pages, 10 Figures

Teaching an introductory course in Digital Signal Processing (DSP) involves the careful selection and arrangement of essential topics from the vast expanse of the subject. A substantial amount of effort from the teacher is required to deliver mathematical and algorithmic concepts. In this paper, we present a Windows Store App which can be used as a teaching aid for an introductory undergraduate DSP course. The app has six modules. Four of the modules demonstrate problems which require complex calculations, viz. linear convolution, circular convolution, radix-2 Fast Fourier Transform (FFT), and Finite Impulse Response (FIR) filter design. These modules display elaborate butterfly diagrams and matrix multiplications to enhance pedagogy. The other two modules form a digital signal processor toolkit based on a hypothetical 16-bit floating-point digital signal processor, with a simple instruction set. The app has been used to teach a course on DSP and a positive feedback was received from the students. © 2017 Wiley Periodicals, Inc. Comput Appl Eng Educ 25:530–541, 2017; View this article online at wileyonlinelibrary.com/journal/cae; DOI 10.1002/cae.21819

We present a quantum algorithm for ranking the nodes on a network in their order of importance. The algorithm is based on a directed discrete-time quantum walk, and works on all directed networks. This algorithm can theoretically be applied to the entire internet, and thus can function as a quantum PageRank algorithm. Our analysis shows that the hierarchy of quantum rank matches well with the hierarchy of classical rank for directed tree network and for non-trivial cyclic networks, the hierarchy of quantum ranks do not exactly match to the hierarchy of the classical rank. This highlights the role of quantum interference and fluctuations in networks and the importance of using quantum algorithms to rank nodes in quantum networks. Another application this algorithm can envision is to model the dynamics on networks mimicking the chemical complexes and rank active centers in order of reactivities. Since discrete-time quantum walks are implementable on current quantum processing systems, this algorithm will also be of practical relevance in analysis of quantum architecture., 10 Pages, 11 figures

We study the percolation of a quantum particle on quasicrystal lattices and compare it with the square lattice. For our study, we have considered quasicrystal lattices modelled on the pentagonally symmetric Penrose tiling and the octagonally symmetric Ammann-Beenker tiling. The dynamics of the quantum particle is modelled using continuous-time quantum walk (CTQW) formalism. We present a comparison of the behaviour of the CTQW on the two aperiodic quasicrystal lattices and the square lattice when all the vertices are connected and when disorder is introduced in the form of disconnections between the vertices. Unlike on a square lattice, we see a significant fraction of quantum state localised around the origin in quasicrystal lattice. With increase in disorder, the percolation probability of a particle on a quasicrystal lattice decreases significantly faster when compared to the square lattice. This study sheds light on the minimum fraction of disconnections allowed to see percolation of quantum particle on these quasicrystal lattices., 9 pages, 14 figures