Unexpected Roles Research Articles

NRT1.1 Dual-Affinity Nitrate Transport/Signalling and its Roles in Plant Abiotic Stress Resistance.

NRT1.1 is the first nitrate transport protein cloned in plants and has both high- and low-affinity functions. It imports and senses nitrate, which is modulated by the phosphorylation on Thr101 (T101). Structural studies have revealed that the phosphorylation of T101 either induces dimer decoupling or increases structural flexibility within the membrane, thereby switching the NRT1.1 protein from a low- to high-affinity state. Further studies on the adaptive regulation of NRT1.1 in fluctuating nitrate conditions have shown that, at low nitrate concentrations, nitrate binding only at the high-affinity monomer initiates NRT1.1 dimer decoupling and priming of the T101 site for phosphorylation activated by CIPK23, which functions as a high-affinity nitrate transceptor. However, nitrate binding in both monomers retains the unmodified NRT1.1, maintaining the low-affinity mode. This NRT1.1-mediated nitrate signalling and transport may provide a key to improving the efficiency of plant nitrogen use. However, recent studies have revealed that NRT1.1 is extensively involved in plant tolerance of several adverse environmental conditions. In this context, we summarise the recent progress in the molecular mechanisms of NRT1.1 dual-affinity nitrate transport/signalling and focus on its expected and unexpected roles in plant abiotic stress resistance and their regulation processes.

They Might Cut It-Lysosomes and Autophagy in Mitotic Progression.

The division of one cell into two looks so easy, as if it happens without any control at all. Mitosis, the hallmark of mammalian life is, however, tightly regulated from the early onset to the very last phase. Despite the tight control, errors in mitotic division occur frequently and they may result in various chromosomal instabilities and malignancies. The flow of events during mitotic progression where the chromosomes condensate and rearrange with the help of the cytoskeletal network has been described in great detail. Plasma membrane dynamics and endocytic vesicle movement upon deadhesion and reattachment of dividing cells are also demonstrated to be functionally important for the mitotic integrity. Other cytoplasmic organelles, such as autophagosomes and lysosomes, have until recently been considered merely as passive bystanders in this process. Accordingly, at the onset of nuclear envelope breakdown in prometaphase, the number of autophagic structures and lysosomes is reduced and the bulk autophagic machinery is suppressed for the duration of mitosis. This is believed to ensure that the exposed nuclear components are not unintentionally delivered to autophagic degradation. With the evolving technologies that allow the detection of subtle alterations in cytoplasmic organelles, our understanding of the small-scale regulation of intracellular organelles has deepened rapidly and we discuss here recent discoveries revealing unexpected roles for autophagy and lysosomes in the preservation of genomic integrity during mitosis.

The Evolving Roles of Cardiac Macrophages in Homeostasis, Regeneration, and Repair.

Macrophages were first described as phagocytic immune cells responsible for maintaining tissue homeostasis by the removal of pathogens that disturb normal function. Historically, macrophages have been viewed as terminally differentiated monocyte-derived cells that originated through hematopoiesis and infiltrated multiple tissues in the presence of inflammation or during turnover in normal homeostasis. However, improved cell detection and fate-mapping strategies have elucidated the various lineages of tissue-resident macrophages, which can derive from embryonic origins independent of hematopoiesis and monocyte infiltration. The role of resident macrophages in organs such as the skin, liver, and the lungs have been well characterized, revealing functions well beyond a pure phagocytic and immunological role. In the heart, recent research has begun to decipher the functional roles of various tissue-resident macrophage populations through fate mapping and genetic depletion studies. Several of these studies have elucidated the novel and unexpected roles of cardiac-resident macrophages in homeostasis, including maintaining mitochondrial function, facilitating cardiac conduction, coronary development, and lymphangiogenesis, among others. Additionally, following cardiac injury, cardiac-resident macrophages adopt diverse functions such as the clearance of necrotic and apoptotic cells and debris, a reduction in the inflammatory monocyte infiltration, promotion of angiogenesis, amelioration of inflammation, and hypertrophy in the remaining myocardium, overall limiting damage extension. The present review discusses the origin, development, characterization, and function of cardiac macrophages in homeostasis, cardiac regeneration, and after cardiac injury or stress.

Striatal low-threshold spiking interneurons locally gate dopamine

The dorsomedial striatum (DMS) is a central hub supporting goal-directed learning and motor performance. Recent evidence has revealed unexpected roles for local inhibitory GABAergic networks in modulating striatal output and behavior.1 The sparse low-threshold spiking interneuron subtype (LTSI), which exhibits robust reward-circumscribed population activity, is a bidirectional regulator of initial goal-directed learning.2 Striatal dopamine signaling is a central reward-related neuromodulatory system mediating goal-directed action and performance, serving as a teaching signal,3 facilitating synaptic plasticity,4 and invigorating motor behaviors.5 Given the dynamic modulation of LTSIs during goal-directed behavior, we hypothesized that they could provide a novel GABAergic mechanism of local striatal dopaminergic regulation to shape early learning. We provide anatomical evidence for close proximation of LTSI terminals and dopaminergic processes in striatum, suggesting that LTSIs directly control dopaminergic axon activity. Using invitro fast scan cyclic voltammetry, we demonstrate that LTSIs directly attenuate optogenetically evoked dopamine via GABAB receptor signaling. Invivo, GRABDA dopamine sensor imaging shows that LTSIs strongly modulate striatal dopamine dynamics during operant learning, while pharmacological stabilization of dopamine via intra-striatal aripiprazole microinjection suppresses the effects of LTSI inhibition on learning. Together, these results uncover an unexpected function for LTSIs in gating striatal dopamine to facilitate goal-directed learning.

Forkhead box family transcription factors as versatile regulators for cellular reprogramming to pluripotency

Forkhead box (Fox) transcription factors play important roles in mammalian development and disease. However, their function in mouse somatic cell reprogramming remains unclear. Here, we report that FoxD subfamily and FoxG1 accelerate induced pluripotent stem cells (iPSCs) generation from mouse fibroblasts as early as day4 while FoxA and FoxO subfamily impede this process obviously. More importantly, FoxD3, FoxD4 and FoxG1 can replace Oct4 respectively and generate iPSCs with germline transmission together with Sox2 and Klf4. On the contrary, FoxO6 almost totally blocks reprogramming through inhibiting cell proliferation, suppressing the expression of pluripotent genes and hindering the process of mesenchymal to epithelial transition (MET). Thus, our study uncovers unexpected roles of Fox transcription factors in reprogramming and offers new insights into cell fate transition.

Role of Dipeptidyl Peptidase-4 in Atherosclerotic Cardiovascular Disease in Humans and Animals with Chronic Stress.

Exposure to psychosocial stress is a risk factor for cardiovascular disease, including vascular atherosclerosis-based cardiovascular disease (ACVD). Dipeptidyl peptidase-4 (DPP-4) is a complex enzyme that acts as a membrane-anchored cell surface exopeptidase. DPP-4 is upregulated in metabolic and inflammatory cardiovascular disorders. DPP-4 exhibits many physiological and pharmacological functions by regulating its extremely abundant substrates, such as glucagon-like peptide-1 (GLP-1). Over the last 10 years, emerging data have demonstrated unexpected roles of DPP-4 in extracellular and intracellular signaling, immune activation, inflammation, oxidative stress production, cell apoptosis, insulin resistance, and lipid metabolism. This mini-review focuses on recent novel findings in this field, highlighting a DPP-4-mediated regulation of GLP-1-dependent and -independent signaling pathways as a potential therapeutic molecular target in treatments of chronic psychological stress-related ACVD in humans and animals.

Novel mechanisms of epithelial ion transport: insights from the cryptonephridial system of lepidopteran larvae.

Lepidopterans are among the most widespread and easily recognized insects. Whereas adult lepidopterans are known for their beauty and ecological importance as pollinators and sources of food for other animals, larvae are economically important pests of forests and agricultural crops. In the larval body, rapid growth while feeding on plant-based diet is associated with extreme alkalinity (up to pH = 11) of the midgut lumen that helps digest plant proteins. Additionally, the presence of plant secondary metabolites which serve as anti-herbivory agents requires uninterrupted excretory function, accomplished primarily by the Malpighian tubules (MTs). The so-called cryptonephridial condition, along with extreme regional heterogeneity of the MTs, and the ability to rapidly and reversibly alter the direction of epithelial ion transport are features that allow uninterrupted MT functioning and recycling of base equivalents. Studies of MTs in lepidopteran larvae have revealed that rapid adjustments in epithelial ion transport include unexpected roles for voltage-gated, ligand-gated and mechanosensitive ion channels, as well as gap junctions. These molecular components are present in epithelia of a variety of vertebrates and invertebrates and thus are likely to constitute a universal epithelial toolkit for rapid autonomous regulation of epithelial function.

Women Community Warriors of St. Croix

Abstract This essay highlights some of the unexpected leadership roles that women have played in relation to the oil industry on St. Croix in the U.S. Virgin Islands (USVI) from 1965 to the present. The people of St. Croix (Crucians) have a long and proud history of strong women as community and family leaders. Despite their invisibility in contemporary narratives of oil refining under U.S. colonialism on St. Croix, Crucian women have contested commonly held stereotypes of women’s roles and contributed to, as well as challenged, the refinery on their own terms. This article is part of a broader literature about women’s leadership across civil society, the private sector, and the public sector in the Caribbean and Latin America that focuses on women’s agency. This essay is also about the unequal situations that places like St. Croix face when negotiating with multinational corporations under colonial circumstances. While the oil industry generates income for the USVI, the refinery has environmental impacts injurious to the local population. Despite colonial, neocolonial, and patriarchal characteristics of their societies, women leaders on St. Croix, across the Caribbean, and Latin America have been a constant phenomenon, not just a recent occurrence. All the women in this essay demonstrate the centrality that women’s guidance, leadership, and actions play in the fostering, functioning, and protection of families, communities, and public and private institutions on St. Croix. The women in this essay created their own opportunities and took matters into their own hands, demonstrating alternative expressions of self and community values, as well as local action and agency, whether through personal relations, labor protests, stringent economic negotiations, occupying political office, and/or community-based activism.

Plant SWEETs: from sugar transport to plant-pathogen interaction and more unexpected physiological roles.

Sugars Will Eventually be Exported Transporters (SWEETs) have important roles in numerous physiological mechanisms where sugar efflux is critical, including phloem loading, nectar secretion, seed nutrient filling, among other less expected functions. They mediate low affinity and high capacity transport, and in angiosperms this family is composed by 20 paralogs on average. As SWEETs facilitate the efflux of sugars, they are highly susceptible to hijacking by pathogens, making them central players in plant–pathogen interaction. For instance, several species from the Xanthomonas genus are able to upregulate the transcription of SWEET transporters in rice (Oryza sativa), upon the secretion of transcription-activator-like effectors. Other pathogens, such as Botrytis cinerea or Erysiphe necator, are also capable of increasing SWEET expression. However, the opposite behavior has been observed in some cases, as overexpression of the tonoplast AtSWEET2 during Pythium irregulare infection restricted sugar availability to the pathogen, rendering plants more resistant. Therefore, a clear-cut role for SWEET transporters during plant–pathogen interactions has so far been difficult to define, as the metabolic signatures and their regulatory nodes, which decide the susceptibility or resistance responses, remain poorly understood. This fuels the still ongoing scientific question: what roles can SWEETs play during plant–pathogen interaction? Likewise, the roles of SWEET transporters in response to abiotic stresses are little understood. Here, in addition to their relevance in biotic stress, we also provide a small glimpse of SWEETs importance during plant abiotic stress, and briefly debate their importance in the particular case of grapevine (Vitis vinifera) due to its socioeconomic impact.

The Nerves to Conduct a Multiple Sclerosis Crime Investigation.

Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative autoimmune disease characterized by the aberrant infiltration of immune cells into the central nervous system (CNS) and by the loss of myelin. Sclerotic lesions and various inhibitory factors hamper the remyelination processes within the CNS. MS patients typically experience gradual cognitive and physical disabilities as the disease progresses. The etiology of MS is still unclear and emerging evidence suggests that microbiome composition could play a much more significant role in disease pathogenesis than was initially thought. Initially believed to be isolated to the gut microenvironment, we now know that the microbiome plays a much broader role in various tissues and is essential in the development of the immune system. Here, we present some of the unexpected roles that the microbiome plays in MS and discuss approaches for the development of next-generation treatment strategies.

Why and How to Dig into Plant Metabolite-Protein Interactions.

Interaction between metabolites and proteins drives cellular regulatory processes within and between organisms. Recent reports highlight that numerous plant metabolites embrace multiple biological activities, beyond a sole role as substrates, products, or cofactors of enzymes, or as defense or growth-regulatory compounds. Though several technologies have been developed to identify and characterize metabolite-protein interactions, the systematic implementation of such methods in the plant field remains limited. Here, we discuss the plant metabolic space, with a specific focus on specialized metabolites and their roles, and review the technologies to study their interaction with proteins. We approach it both from a plant's perspective, to increase our understanding of plant metabolite-dependent regulatory networks, and from a human perspective, to empower agrochemical and drug discoveries.

The pleiotropic functions of autophagy in metastasis.

Autophagy is deregulated in many cancers and represents an attractive target for therapeutic intervention. However, the precise contributions of autophagy to metastatic progression, the principle cause of cancer-related mortality, is only now being uncovered. While autophagy promotes primary tumor growth, metabolic adaptation and resistance to therapy, recent studies have unexpectedly revealed that autophagy suppresses the proliferative outgrowth of disseminated tumor cells into overt and lethal macrometastases. These studies suggest autophagy plays unexpected and complex roles in the initiation and progression of metastases, which will undoubtedly impact therapeutic approaches for cancer treatment. Here, we discuss the intricacies of autophagy in metastatic progression, highlighting and integrating the pleiotropic roles of autophagy on diverse cell biological processes involved in metastasis.

RIPK3 modulates growth factor receptor expression in endothelial cells to support angiogenesis.

Receptor-interacting protein kinase 3 (RIPK3) is a multifunctional intracellular protein that was first recognized as an important component of the necroptosis programmed cell death pathway. RIPK3 is also highly expressed in non-necroptotic murine embryonic endothelial cells (ECs) during vascular development, indicating its potential contribution to angiogenesis. To test this hypothesis, we generated mice lacking endothelial RIPK3 and found non-lethal embryonic and perinatal angiogenesis defects in multiple vascular beds. Our in vitro data indicate that RIPK3 supports angiogenesis by regulating growth factor receptor degradation in ECs. We found that RIPK3 interacted with the membrane trafficking protein myoferlin to sustain expression of vascular endothelial growth factor receptor 2 (VEGFR2) in cultured ECs following vascular endothelial growth factor A (VEGFA) stimulation. Restoration of myoferlin, which was diminished after RIPK3 knockdown, rescued decreased VEGFR2 expression and vascular sprouting in RIPK3-deficient ECs after VEGFA treatment. In addition, we found that RIPK3 modulated expression of genes involved in endothelial identity by inhibiting ERK signaling independently of growth factor receptor turnover. Altogether, our data reveal unexpected non-necroptotic roles for RIPK3 in ECs and evidence that RIPK3 promotes developmental angiogenesis in vivo.

Analyzing Urban Public Policies of the City of Ensenada in Mexico Using an Attractive Land Footprint Agent-Based Model

The Urban Development Plan of the city of Ensenada, México (UDPE) states four major strategic projects, one of which mandates to “Acquire and enable new land reserves and expand opportunities for economic and social development.” This is of vital importance given the large number of vacant lots that perforates the urban surface in contrast to the physical limitations of growth demarcated by hill areas of a steep slope, which forces a sustainable use of the land. These are important growth challenges, affecting aspects such as the real estate market, in particular, that related to industrial activities, which has not matured due to outdated planning practice, resulting in industrial sprawl. This paper shows an institutional effort to analyze the UDPE from a Complex Systems approach with an Agent-Based Model, adapting Peter Allen’s concept of Structural Attractor. This attraction results from an agglomeration of UDPE’s regulatory attributes and real estate investor’s land-acquisition criteria that affects the spatial behavior of vacant land that is attractive for industrial activity. Unlike physical land uses, these attractive zones emerge, grow, move, diminish, and emerge again over time in the form of Attractive Land Footprints. Understanding these phenomena is vital for local policymakers. The findings indicate that the current Urban Plan is ill-suited regarding current industry development expectations. The model also showed unexpected roles played by population density, road network, and residential land use in Attractive Land Footprint dynamics, acting as a thought-provoking process for policymakers and real estate investors, as it helped them to understand Ensenada’s industry phenomena.

Tau and DNA Damage in Neurodegeneration.

Neurodegenerative disorders are a family of incurable conditions. Among them, Alzheimer’s disease and tauopathies are the most common. Pathological features of these two disorders are synaptic loss, neuronal cell death and increased DNA damage. A key pathological protein for the onset and progression of the conditions is the protein tau, a microtubule-binding protein highly expressed in neurons and encoded by the MAPT (microtubule-associated protein tau) gene. Tau is predominantly a cytosolic protein that interacts with numerous other proteins and molecules. Recent findings, however, have highlighted new and unexpected roles for tau in the nucleus of neuronal cells. This review summarizes the functions of tau in the metabolism of DNA, describing them in the context of the disorders.

Abstract IA21: Metabolic phenotypes and liabilities in human cancer

Abstract Metabolic reprogramming in cancer arises from a complex, incompletely-defined combination of factors intrinsic and extrinsic to malignant cells. In some cases, reprogrammed pathways contribute to the process of transformation, and in many others they enable cancer progression by supporting cell survival and excessive growth. The clinical relevance of cancer metabolism is emphasized by the fact that numerous imaging modalities and therapeutic strategies in cancer capitalize on the altered metabolic states present in tumors. Recent work has emphasized that metabolic phenotypes and liabilities evolve as cancer progresses, such that pathways required for cancer initiation may be dispensable in more advanced stages, and vice versa. A key challenge is to define metabolic properties that support key aspects of cancer progression, particularly metastasis and acquired therapy resistance, which account for the majority of cancer-related deaths. Because these processes are difficult to model in culture, we have developed clinical approaches to study cancer metabolism in vivo, in patients, and to uses these approaches to identify features that drive cancer progression. I will discuss approaches using metabolomics and intra-operative infusions with 13C-labeled nutrients to assess metabolic pathway utilization in human tumors. We use this approach to characterize metabolic heterogeneity among tumors arising in different organs, to identify areas of regional metabolic heterogeneity within solid tumors and to predict which activities support cancer progression. Our work to this point demonstrates marked diversity of fuel preferences in primary tumors and unexpected roles of particular pathways in cancer cell biology. Citation Format: Ralph J. DeBerardinis. Metabolic phenotypes and liabilities in human cancer [abstract]. In: Abstracts: AACR Special Virtual Conference on Epigenetics and Metabolism; October 15-16, 2020; 2020 Oct 15-16. Philadelphia (PA): AACR; Cancer Res 2020;80(23 Suppl):Abstract nr IA21.

Proteomic changes in the hippocampus and motor cortex in a rat model of cerebral palsy: Effects of topical treatment

Cerebral palsy (CP) is a non-progressive motor-impairment disorder related to brain injury early in development. To gain new insights into the mechanisms of CP and the therapeutic efficacy of Baimai ointment, we used a high-throughput quantitative proteomic approach to evaluate proteomic changes in the hippocampus and motor cortex in a rat model of CP induced by lipopolysaccharide (LPS) combined with hypoxia/ischemia (H/I). More than 2000 proteins were identified in each brain region with high confidence. Quantitative analysis demonstrated profound disturbances in the proteomes of the hippocampus and motor cortex after LPS + H/I, in addition to the disruption of the motor system. In contrast, the topical application of Baimai ointment not only alleviated the motor deficit in the CP model rats, but also restored the proteomes in the brain cortex. Furthermore, astrocytes in the hippocampus were strongly activated in the Baimai-treated CP rat brains, associated with an increase in neurotrophic factors. Proteomic analysis demonstrated that the CP model induced neuroinflammatory responses in the brain which were reversed by the topical application of Baimai ointment. This study highlights the unexpected roles of hippocampus and motor cortex neurons in CP progress and treatment, thus providing potentially novel therapeutic targets for CP.

Non‐apoptotic caspase activation preserves Drosophila intestinal progenitor cells in quiescence

Caspase malfunction in stem cells often precedes the appearance and progression of multiple types of cancer, including human colorectal cancer. However, the caspase‐dependent regulation of intestinal stem cell properties remains poorly understood. Here, we demonstrate that Dronc, the Drosophila ortholog of caspase‐9/2 in mammals, limits the number of intestinal progenitor cells and their entry into the enterocyte differentiation programme. Strikingly, these unexpected roles for Dronc are non‐apoptotic and have been uncovered under experimental conditions without epithelial replenishment. Supporting the non‐apoptotic nature of these functions, we show that they require the enzymatic activity of Dronc, but are largely independent of the apoptotic pathway. Alternatively, our genetic and functional data suggest that they are linked to the caspase‐mediated regulation of Notch signalling. Our findings provide novel insights into the non‐apoptotic, caspase‐dependent modulation of stem cell properties that could improve our understanding of the origin of intestinal malignancies.

Vimentin's side gig: Regulating cellular proteostasis in mammalian systems.

Intermediate filaments (IFs) perform a diverse set of well-known functions including providing structural support for the cell and resistance to mechanical stress, yet recent evidence has revealed unexpected roles for IFs as stress response proteins. Previously, it was shown that the type III IF protein vimentin forms cage-like structures around centrosome-associated proteins destined for degradation, structures referred to as aggresomes, suggesting a role for vimentin in protein turnover. However, vimentin's function at the aggresome has remained largely understudied. In a recent report, vimentin was shown to be dispensable for aggresome formation, but played a critical role in protein turnover at the aggresome through localizing proteostasis-related machineries, such as proteasomes, to the aggresome. Here, we review evidence for vimentin's function in proteostasis and highlight the organismal implications of these findings.

Hippocampal inputs engage CCK+ interneurons to mediate endocannabinoid-modulated feed-forward inhibition in the prefrontal cortex.

Connections from the ventral hippocampus (vHPC) to the prefrontal cortex (PFC) regulate cognition, emotion, and memory. These functions are also tightly controlled by inhibitory networks in the PFC, whose disruption is thought to contribute to mental health disorders. However, relatively little is known about how the vHPC engages different populations of interneurons in the PFC. Here we use slice physiology and optogenetics to study vHPC-evoked feed-forward inhibition in the mouse PFC. We first show that cholecystokinin (CCK+), parvalbumin (PV+), and somatostatin (SOM+) expressing interneurons are prominent in layer 5 (L5) of infralimbic PFC. We then show that vHPC inputs primarily activate CCK+ and PV+ interneurons, with weaker connections onto SOM+ interneurons. CCK+ interneurons make stronger synapses onto pyramidal tract (PT) cells over nearby intratelencephalic (IT) cells. However, CCK+ inputs undergo depolarization-induced suppression of inhibition (DSI) and CB1 receptor modulation only at IT cells. Moreover, vHPC-evoked feed-forward inhibition undergoes DSI only at IT cells, confirming a central role for CCK+ interneurons. Together, our findings show how vHPC directly engages multiple populations of inhibitory cells in deep layers of the infralimbic PFC, highlighting unexpected roles for both CCK+ interneurons and endocannabinoid modulation in hippocampal-prefrontal communication.