Signal Relay Research Articles

Expression of authentic post-translationally modified proteins in organisms with expanded genetic codes.

Cellular signaling and regulatory cascades often rely on post-translational modification of proteins, particularly phosphorylation, to quickly and effectively relay signals from a variety of inputs. Numerous kinases, the effectors of phosphorylation, and kinase networks have been implicated in human diseases. Until recently, an inability to produce high yields of physiologically phosphorylated proteins has proven to be a substantial barrier toward our understanding of many enzymatic processes. Orthogonal translation systems provide the means to overcome many of these limitations by enabling site-specific incorporation of phosphorylated amino acids into recombinantly expressed proteins. Site-by-site, combinatorial assessment of phosphorylation site function is unique to orthogonal translation system based approaches and offers unmatched precision in the study of PTM-enzymology, extending well beyond the scope of kinase biology.

Targeting brown fat to make less fat

Physiology Brown fat can release energy from food as heat instead of storing it and could thus help in battling obesity. Li et al. found that after a meal, brown fat in mice was stimulated to increase thermogenesis by direct action of the gut hormone secretin. The heat produced may be detected by the brain and thus induce a sense of satiety. This signaling relay may increase energy expenditure and decrease appetite, making it a potential target for therapies that attempt to control obesity. Cell 175 , 1561 (2018).

Spatial Presentation of Cholesterol Units on a DNA Cube as a Determinant of Membrane Protein-Mimicking Functions.

Cells use membrane proteins as gatekeepers to transport ions and molecules, catalyze reactions, relay signals, and interact with other cells. DNA nanostructures with lipidic anchors are promising as membrane protein mimics because of their high tunability. However, the design features specifying DNA nanostructures' functions in lipid membranes are yet to be fully understood. Here, we show that altering patterns of cholesterol units on a cubic DNA scaffold dramatically changes its interaction mode with lipid membranes. This results in simple design rules that allow a single DNA nanostructure to reproduce multiple membrane protein functions: peripheral anchoring, nanopore behavior, and conformational switching to reveal membrane-binding units. Strikingly, the DNA-cholesterol cubes constitute the first open-walled DNA nanopores, as only a quarter of their wall is made of DNA. This functional diversity can increase our fundamental understanding of membrane phenomena and result in sensing, drug delivery, and cell manipulation tools.

The SnRK1-eIFiso4G1 signaling relay regulates the translation of specific mRNAs in Arabidopsis under submergence.

Cellular responses to oxygen deprivation are essential for survival during energy crises in plants and animals. Hypoxia caused by submergence results in reprogramming of translation dynamic in plants, but the molecular mechanisms are not well understood. Here we show that Arabidopsis Snf1-related protein kinase 1 (SnRK1) phosphorylates the translation initiation factor eIFiso4G to regulate translation dynamic under submergence. In Arabidopsis, there are two eIFiso4G genes, eIFiso4G1 and eIFiso4G2, which belong to the eIF4G family. Both eIFiso4Gs were phosphorylated by SnRK1 under submergence. Interestingly, the eIFiso4G1 knockout mutant, but not the eIFiso4G2 mutant, became more sensitive to submergence, implying that eIFiso4G1 is involved in regulating submergence tolerance in Arabidopsis. Comparison of RNA sequences in the polysome fraction and the RNAs immunoprecipitated by eIFiso4G1 from Col-0 and the SnRK1 and eIFiso4G1 mutants revealed that lack of eIFiso4G1 phosphorylation disrupts the translation of specific mRNAs under submergence. Taken together, our findings suggest that the SnRK1-eIFiso4G1 relay controls the translation of an array of genes under hypoxia, including core hypoxia response genes and genes related to stress response and biosynthetic process.

Central amygdala circuit dynamics underlying the benzodiazepine anxiolytic effect

Benzodiazepines (BZDs) have been a standard treatment for anxiety disorders for decades, but the neuronal circuit interactions mediating their anxiolytic effect remain largely unknown. Here, we find that systemic BZDs modulate central amygdala (CEA) microcircuit activity to gate amygdala output. Combining connectome data with immediate early gene (IEG) activation maps, we identified the CEA as a primary site for diazepam (DZP) anxiolytic action. Deep brain calcium imaging revealed that brain-wide DZP interactions shifted neuronal activity in CEA microcircuits. Chemogenetic silencing showed that PKCδ+/SST− neurons in the lateral CEA (CEAl) are necessary and sufficient to induce the DZP anxiolytic effect. We propose that BZDs block the relay of aversive signals through the CEA, in part by local binding to CEAl SST+/PKCδ− neurons and reshaping intra-CEA circuit dynamics. This work delineates a strategy to identify biomedically relevant circuit interactions of clinical drugs and highlights the critical role for CEA circuitry in the pathophysiology of anxiety.

Encoding prediction signals during appetitive and aversive Pavlovian conditioning in the primate lateral hypothalamus.

The lateral hypothalamus (LH), which plays a role in homeostatic functions such as appetite regulation, is also linked to arousal and motivational behavior. However, little is known about how these components are encoded in the LH. Thus cynomolgus monkeys were conditioned with two distinct contexts, i.e., an appetitive context with available rewards and an aversive context with predicted air puffs. Different LH neuron groups encoded different degrees of expectation, predictability, and risks of rewards in a specific manner. A nearly equal number of one-third of the recorded LH neurons showed a positive or negative correlation between their response to visual conditioned stimuli (CS) that predicted the probabilistic delivery of rewards (0%, 50%, and 100%) and the associative values. For another one-third of recorded neurons, a nearly equal number showed a positive or negative correlation between their responses to rewards [appetitive unconditioned stimulus (US)] and reward predictability. Some neurons exhibited their highest or lowest trace-period responses in the 50% reward trials. These response modulations were represented independently and overlaid on a consistent excitatory or inhibitory response across the conditioning events. LH neurons also showed consistent responses in the aversive context. However, the responses to aversive conditioning events depending on the air puff value and predictability were less common. The multifaceted modulation of consistent activity related to outcome predictions may reflect motivational and arousal signals. Furthermore, it may underlie the role the LH plays in the integration and relay of signals to cortices for adaptive and goal-directed physiological and behavioral responses to environmental changes. NEW & NOTEWORTHY The lateral hypothalamus (LH) is implicated in motivational and arousal behavior; however, the detailed information carried by single LH neurons remains unclear. We demonstrate that primate LH neurons encode multiple combinations of signals concerning different degrees of expectation, appreciation, and uncertainty of rewards in consistent responses across conditioning events and between different contexts. This multifaceted modulation of activity may underlie the role of the LH as a critical node integrating motivational signals with arousal signals.

Patterning the insect eye: From stochastic to deterministic mechanisms.

While most processes in biology are highly deterministic, stochastic mechanisms are sometimes used to increase cellular diversity. In human and Drosophila eyes, photoreceptors sensitive to different wavelengths of light are distributed in stochastic patterns, and one such patterning system has been analyzed in detail in the Drosophila retina. Interestingly, some species in the dipteran family Dolichopodidae (the “long legged” flies, or “Doli”) instead exhibit highly orderly deterministic eye patterns. In these species, alternating columns of ommatidia (unit eyes) produce corneal lenses of different colors. Occasional perturbations in some individuals disrupt the regular columns in a way that suggests that patterning occurs via a posterior-to-anterior signaling relay during development, and that specification follows a local, cellular-automaton-like rule. We hypothesize that the regulatory mechanisms that pattern the eye are largely conserved among flies and that the difference between unordered Drosophila and ordered dolichopodid eyes can be explained in terms of relative strengths of signaling interactions rather than a rewiring of the regulatory network itself. We present a simple stochastic model that is capable of explaining both the stochastic Drosophila eye and the striped pattern of Dolichopodidae eyes and thereby characterize the least number of underlying developmental rules necessary to produce both stochastic and deterministic patterns. We show that only small changes to model parameters are needed to also reproduce intermediate, semi-random patterns observed in another Doli species, and quantification of ommatidial distributions in these eyes suggests that their patterning follows similar rules.

B Cell-Intrinsic STING Signaling Triggers Cell Activation, Synergizes with B Cell Receptor Signals, and Promotes Antibody Responses.

Generation of protective immune responses requires coordinated stimulation of innate and adaptive immune responses. An important mediator of innate immunity is stimulator of IFN genes (STING, MPYS, MITA), a ubiquitously but differentially expressed adaptor molecule that functions in the relay of signals initiated by sensing of cytosolic DNA and bacterial cyclic dinucleotides (CDNs). Whereas systemic expression of STING is required for CDN-aided mucosal Ab responses, its function in B cells in particular is unclear. In this study, we show that B cells can be directly activated by CDNs in a STING-dependent manner in vitro and in vivo. Direct activation of B cells by CDNs results in upregulation of costimulatory molecules and cytokine production and this can be accompanied by caspase-dependent cell death. CDN-induced cytokine production by B cells and other cell types also contributes to activation and immune responses. Type I IFN is primarily responsible for this indirect stimulation although other cytokines may contribute. BCR and STING signaling pathways act synergistically to promote Ab responses independent of type I IFN. B cell expression of STING is required for optimal in vivo IgG and mucosal IgA Ab responses induced by T cell-dependent Ags and cyclic-di-GMP but plays no discernable role in Ab responses in which alum is used as an adjuvant. Thus, STING functions autonomously in B cells responding to CDNs, and its activation synergizes with Ag receptor signals to promote B cell activation.

Decoding and Relay of Calcium Signals by CBL-CIPK Module in Plants

Decoding and Relay of Calcium Signals by CBL-CIPK Module in Plants

Relay-Assisted Proactive Eavesdropping With Cooperative Jamming and Spoofing

In this paper, we consider a legitimate proactive eavesdropping scenario where a distant central monitor covertly wiretaps the communication between a pair of suspicious users via several multi-antenna full-duplex spoofing relays and a multi-antenna cooperative jammer. Assuming an adaptive transmission policy at the suspicious users, the spoofing relays not only intercept but also forward the manipulated information to control the data rate of the suspicious users in collaboration with the jammer. We provide a technique which jointly optimizes the receive combining vector at the central monitor, the precoders at the relays, and the transmit covariance matrix at the jammer for maximizing the eavesdropping rate. To reveal some fundamental properties of the optimal operation, we first study a single-relay system. It is shown that when the central monitor experiences a poor eavesdropping channel link, the spoofing relay and the jammer should transmit destructive signals and jamming signals, respectively. In this case, the suspicious users are forced to decrease their data rate, while the intercepted information can be successfully decoded by the central monitor. On the other hand, when the eavesdropping channel condition is favorable, the spoofing relay forwards constructive signals to further increase the data rate at the suspicious users in a way that more information can be intercepted from the suspicious users. We then formulate a general eavesdropping rate maximization problem for multiple relays and present a semi-definite relaxation approach. A low-complexity design is also proposed based on our analysis for the single-relay system. Simulation results verify the efficiency of the proposed solutions compared to other baseline schemes in various practical setups.

The Role of Accessory Cells in Islet Homeostasis.

Scattered throughout the pancreas, the endocrine islets rely on neurovascular support for signal relay to regulate hormone secretion and for maintaining tissue homeostasis. The islet accessory cells (or components) of neurovascular tissues include the endothelial cells, pericytes, smooth muscle cells, neurons (nerve fibers), and glia. Research results derived from experimental diabetes and islet transplantation indicate that the accessory cells are reactive in islet injury and can affect islet function and homeostasis in situ or in an ectopic environment. Recent advances in cell labeling and tissue imaging have enabled investigation of islet accessory cells to gain insights into their network structures, functions, and remodeling in disease. It has become clear that in diabetes, the islet neurovascular tissues are not just bystanders damaged in neuropathy and vascular complications; rather, they participate in islet remodeling in response to changes in the microenvironment. Because of the fundamental differences between humans and animal models in neuroinsular cytoarchitecture and cell proliferation, examination of islet accessory cells in clinical specimens and donor pancreases warrants further attention.

Hypothalamic Epigenetics Driving Female Puberty

Puberty involves a series of morphological, physiological and behavioural changes during the last part of the juvenile period that culminates in the attainment of fertility. The activation of the pituitary-gonadal axis by increased hypothalamic secretion of gonadotrophin-releasing hormone (GnRH) is an essential step in the process. The current hypothesis postulates that a loss of transsynaptic inhibition and a rise in excitatory inputs are responsible for the activation of GnRH release. Similarly, a shift in the balance in the expression of puberty activating and puberty inhibitory genes exists during the pubertal transition. In addition, recent evidence suggests that the epigenetic machinery controls this genetic balance, giving rise to the tantalising possibility that epigenetics serves as a relay of environmental signals known for many years to modulate pubertal development. Here, we review the contribution of epigenetics as a regulatory mechanism in the hypothalamic control of female puberty.

A unified mitochondria mechanistic target of rapamycin acyl-coenzyme A dehydrogenase 10 signal relay modulation for metformin growth inhibition in human immortalized keratinocytes cells.

Metformin exhibits antiproliferative and proapoptotic effects in a variety of diseases, characterized by malignant and nonmalignant hyperplastic cells; however, the underlying molecular mechanism of metformin in psoriasis has not been elucidated. In the current study, we found that after metformin treatment the proliferation of human immortalized keratinocytes (HaCaT) was significantly inhibited, while cell apoptosis was increased in a dose-dependent manner, accompanied with enhanced protein expression of acyl-coenzyme A dehydrogenase 10 (ACAD10). Furthermore, mechanism analysis revealed that ACAD10 expression is induced by downregulated activities of mechanistic target of rapamycin 1 (mTORC1) signaling rather than AMP-activated protein kinase signaling. The inactivation of mTORC1 by rapamycin pretreatment or rotenone-induced mitochondrial complex inhibition showed a similar effect because of the metformin treatment on the proliferation and apoptosis of HaCaT keratinocytes. Overexpression of mTORC1 almost reversed the antiproliferation and proapoptosis effects induced by metformin. This study showed that the metformin treatment inhibited HaCaT cells proliferation and promoted apoptosis by affecting the mitochondrial-mTORC1 signaling and elevated the ACAD10 expression. Hence, metformin can be used as a potential therapeutic agent for psoriasis.

Design of Analog Front-end Circuit for Audio-frequency Magnetotelluric Instrument

High-performance audio-frequency magnetotelluric (AMT) instrument is one means of obtaining high-quality electromagnetic (EM) data. To improve the ability of AMT system to obtain high-quality data, this paper presents a design for a high-performance analog front-end circuit for AMT instrument. It mainly consists of the input protection, preamplifier, passive high pass filter, power frequency notch filter, programmable amplifier, and active low pass filter. In addition, this paper proposes a design of low-noise, high-performance preamplifier, which improves the common-mode rejection ratio (CMRR) of analog front-end circuit and effectively enhances the signal-to-noise ratio (SNR) of the circuit. The front-end circuit utilized two-stage twin-T notch filter to effectively suppress the strong interference of fundamental component of power frequency. Also, it used signal relays to control circuit gain and selection of cutoff frequency of anti-aliasing filter, resulting in the improvement of the capability of the analog-to-digital Converter (ADC) to distinguish weak EM signal. The measured results of the electric field and magnetic field channel showed that: 1) The circuit works in frequency range of 1 Hz∼100 kHz; 2) The CMRR values of the preamplifier of electric field channel at low frequencies (1 Hz∼1 kHz) are 111 dB and 97 dB when the gains are 20 dB and 6 dB respectively; 3) The maximum attenuation fundamental power frequency can reach −39.46 dB and −39.04 dB respectively; 4) The total harmonic distortion rate at 1 kHz is 0.022% and 0.029% respectively; 5) The input noise levels of electric field channel are 12.67nV / [Formula: see text] @10Hz and 8.15V / [Formula: see text] @1kHz, while the input noise levels of magnetic field channel are 8.97nV / [Formula: see text] @10Hz and 6.16V / [Formula: see text] @1kHz; and 6) In conclusion, the analog front-end circuit is superior to meet the requirements of the AMT methods, and provides a useful reference for the development of AMT instrument.

Itch suppression in mice and dogs by modulation of spinal \u03b12 and \u03b13GABAA receptors

Chronic itch is a highly debilitating condition affecting about 10% of the general population. The relay of itch signals is under tight control by inhibitory circuits of the spinal dorsal horn, which may offer a hitherto unexploited therapeutic opportunity. Here, we found that specific pharmacological targeting of inhibitory α2 and α3GABAA receptors reduces acute histaminergic and non-histaminergic itch in mice. Systemic treatment with an α2/α3GABAA receptor selective modulator alleviates also chronic itch in a mouse model of atopic dermatitis and in dogs sensitized to house dust mites, without inducing sedation, motor dysfunction, or loss of antipruritic activity after prolonged treatment. Transsynaptic circuit tracing, immunofluorescence, and electrophysiological experiments identify spinal α2 and α3GABAA receptors as likely molecular targets underlying the antipruritic effect. Our results indicate that drugs targeting α2 and α3GABAA receptors are well-suited to alleviate itch, including non-histaminergic chronic itch for which currently no approved treatment exists.

A Hybrid Adaptive Relay Technique for Cooperative Communication System

Cooperative communication will increase the channel capacity, when the communicating terminals exceed more than two. Therefore, a relay is termed, as three-terminal unit is a fundamental for user cooperation. The cooperation provides throughput enhancement, reliability, and coverage improvement for wireless communication. Relay technique plays a vital role in cooperative communication in terms of increasing coverage range as well as spectral efficiency. In existing techniques Amplify Forward increase the noise and Decode Forward increase the computational cost of the receiver. In order to overcome the above limitation, a hybrid adaptive relay technique is proposed for cooperative communication system, which will initially check the channel quality of the end user received SNR. When the receiver does not able to decode the message, then the user will choose relay signal. We derived a closed form expression to find the outage probability and channel capacity for the Rayleigh fading channel. Finally, simulation results show the performance of proposed adaptive relay technique in comparison with traditional relay technique by considering both perfect and imperfect CSI.

Ethylene-gibberellin signaling underlies adaptation of rice to periodic flooding.

Most plants do poorly when flooded. Certain rice varieties, known as deepwater rice, survive periodic flooding and consequent oxygen deficiency by activating internode growth of stems to keep above the water. Here, we identify the gibberellin biosynthesis gene, SD1 (SEMIDWARF1), whose loss-of-function allele catapulted the rice Green Revolution, as being responsible for submergence-induced internode elongation. When submerged, plants carrying the deepwater rice-specific SD1 haplotype amplify a signaling relay in which the SD1 gene is transcriptionally activated by an ethylene-responsive transcription factor, OsEIL1a. The SD1 protein directs increased synthesis of gibberellins, largely GA4, which promote internode elongation. Evolutionary analysis shows that the deepwater rice-specific haplotype was derived from standing variation in wild rice and selected for deepwater rice cultivation in Bangladesh.

Selective relay of afferent sensory-induced action potentials from peripheral nerve to brain and the effects of electrical stimulation.

Electrical stimulation of peripheral nerve fibers and dorsal column fibers is used to treat acute and chronic pain. Recent studies have shown that sensitized A-fibers maybe involved in the relay of pain information. These nerve fibers also carry sensory-induced action potentials (APs), such as proprioception, mechanoreception, etc. Electrical stimulation of these nerve fibers can result in interactions between sensory-induced APs and stimulation-induced APs. For example, the sensory-induced APs can collide with stimulus APs, and thus may never be relayed to the brain. In this study, we aimed to quantify the effects of stimulation frequency on these interactions. Specifically, we focused on the goal of stimulation to simultaneously (i) block noxious sensory signals while (ii) relaying innocuous sensory signals from the periphery to the brain via a myelinated nerve fiber. We defined a performance metric called the "selective relay $(SR)$ " measure. Specifically, we constructed a tractable model of a nerve fiber that receives two inputs: the underlying sensory activity at the bottom of the fiber (noxious or innocuous), and the external stimulus applied to the middle of the fiber. We then defined relay reliability, $R$, as the percentage of sensory APs that make it to the top of the fiber. $SR$ is then a product of relaying innocuous sensory information while blocking noxious pain stimuli, i.e., $SR=R_{\mathrm {s}\mathrm {e}\mathrm {n}}(1-R_{\mathrm {p}\mathrm {a}\mathrm {i}\mathrm {n}})$. We applied the two inputs to the fiber at various frequencies and analyzed relay reliability and then we studied selective relay assuming noxious and innocuous stimuli produce APs with distinct frequencies. We found that frequency stimulation between 50-100Hz effectively blocks relay of low-frequency pain signals, allowing mid-to-high frequency sensory signals to transmit to the brain.

Hypothalamic epigenetics driving female puberty.

Puberty involves a series of morphological, physiological and behavioural changes during the last part of the juvenile period that culminates in the attainment of fertility. The activation of the pituitary-gonadal axis by increased hypothalamic secretion of gonadotrophin-releasing hormone (GnRH) is an essential step in the process. The current hypothesis postulates that a loss of transsynaptic inhibition and a rise in excitatory inputs are responsible for the activation of GnRH release. Similarly, a shift in the balance in the expression of puberty activating and puberty inhibitory genes exists during the pubertal transition. In addition, recent evidence suggests that the epigenetic machinery controls this genetic balance, giving rise to the tantalising possibility that epigenetics serves as a relay of environmental signals known for many years to modulate pubertal development. Here, we review the contribution of epigenetics as a regulatory mechanism in the hypothalamic control of female puberty.

Abstract 3155: Loss of YAP1 dysregulates RhoA signaling and promotes cell invasion

Abstract While Hippo pathway signaling undoubtedly plays an important role in cancer, the role of its effector YAP1 as an oncogene or tumor suppressor is context dependent. The precise conditions that support the tumor-promoting or tumor-suppressing roles of YAP1 remain largely undefined. While YAP1 can drive oncogenic programs through its nuclear function as a transcriptional coactivator of TEAD and other transcription factors, previous findings from our lab and others suggest that loss of YAP1 function can also have tumor promoting consequences. One well-characterized role of YAP1 is that of a nuclear relay of signals triggered by mechanical forces that lead to activation of Rho GTPases. Our new studies using a combination of genetic, biochemical, and microscopy techniques provide evidence that YAP1 is not only activated by Rho, but can also regulate Rho activation and the actin cytoskeleton. Knockdown of YAP1 in MCF10A immortalized mammary epithelial cells resulted in increased lamellipodia formation in culture as seen by time-lapse microscopy, and increased protrusive, invasive activity in 3D Matrigel culture. YAP1 knockdown also induced a scattering phenotype, characterized by cell dissociation from the leading edge of a wounded monolayer. While E-cadherin protein levels were unaffected by YAP1 knockdown, adherens junction maturation at cell-cell junctions was compromised. These morphological alterations were associated with decreased levels of active RhoA, as well as a decrease in downstream myosin light chain phosphorylation. Our results indicate loss of YAP1 decreases active RhoA, leading to reduced cell-cell adhesion and increased protrusive cellular behavior. Our findings raise the possibility that YAP1 is not only a Rho-sensor, but also mediates a feedforward regulatory loop to maintain Rho-regulated cytoskeletal structures, and that loss of YAP1 through genetic deletion in tumor cells could promote invasive behavior. Citation Format: Natalie M. Hendrick, Marcin P. Iwanicki, Carman Man-Chung Li, Duyen Amy Bui, Laura M. Selfors, Joan S. Brugge. Loss of YAP1 dysregulates RhoA signaling and promotes cell invasion [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3155.