Dual imaging of dendritic spines and mitochondria in vivo reveals hotspots of plasticity and metabolic adaptation to stress

Actin turnover in dendritic spines influences spine development, morphology, and plasticity, with functional consequences on learning and memory formation. In nonneuronal cells, protein kinase D (PKD) has an important role in stabilizing F-actin via multiple molecular pathways. Using in vitro models of neuronal plasticity, such as glycine-induced chemical long-term potentiation (LTP), known to evoke synaptic plasticity, or long-term depolarization block by KCl, leading to homeostatic morphological changes, we show that actin stabilization needed for the enlargement of dendritic spines is dependent on PKD activity. Consequently, impaired PKD functions attenuate activity-dependent changes in hippocampal dendritic spines, including LTP formation, cause morphological alterations in vivo, and have deleterious consequences on spatial memory formation. We thus provide compelling evidence that PKD controls synaptic plasticity and learning by regulating actin stability in dendritic spines.

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NIK promotes metabolic adaptation of glioblastoma cells to bioenergetic stress

Cell Death and Disease ◽

10.1038/s41419-020-03383-z ◽

2021 ◽

Vol 12 (3) ◽

Author(s):

Michael L. Kamradt ◽

Ji-Ung Jung ◽

Kathryn M. Pflug ◽

Dong W. Lee ◽

Victor Fanniel ◽

...

Keyword(s):

Stress Responses ◽

Glucose Deprivation ◽

Metabolic Adaptation ◽

Mitochondrial Morphology ◽

Atp Production ◽

Tumor Microenvironments ◽

Iκb Kinase ◽

Critical Measure

AbstractCancers, including glioblastoma multiforme (GBM), undergo coordinated reprogramming of metabolic pathways that control glycolysis and oxidative phosphorylation (OXPHOS) to promote tumor growth in diverse tumor microenvironments. Adaptation to limited nutrient availability in the microenvironment is associated with remodeling of mitochondrial morphology and bioenergetic capacity. We recently demonstrated that NF-κB-inducing kinase (NIK) regulates mitochondrial morphology to promote GBM cell invasion. Here, we show that NIK is recruited to the outer membrane of dividing mitochondria with the master fission regulator, Dynamin-related protein1 (DRP1). Moreover, glucose deprivation-mediated metabolic shift to OXPHOS increases fission and mitochondrial localization of both NIK and DRP1. NIK deficiency results in decreased mitochondrial respiration, ATP production, and spare respiratory capacity (SRC), a critical measure of mitochondrial fitness. Although IκB kinase α and β (IKKα/β) and NIK are required for OXPHOS in high glucose media, only NIK is required to increase SRC under glucose deprivation. Consistent with an IKK-independent role for NIK in regulating metabolism, we show that NIK phosphorylates DRP1-S616 in vitro and in vivo. Notably, a constitutively active DRP1-S616E mutant rescues oxidative metabolism, invasiveness, and tumorigenic potential in NIK−/− cells without inducing IKK. Thus, we establish that NIK is critical for bioenergetic stress responses to promote GBM cell pathogenesis independently of IKK. Our data suggest that targeting NIK may be used to exploit metabolic vulnerabilities and improve therapeutic strategies for GBM.

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Synaptopodin: An Actin-associated Protein in Telencephalic Dendrites and Renal Podocytes

The Journal of Cell Biology ◽

10.1083/jcb.139.1.193 ◽

1997 ◽

Vol 139 (1) ◽

pp. 193-204 ◽

Cited By ~ 385

Author(s):

Peter Mundel ◽

Hans W. Heid ◽

Thomas M. Mundel ◽

Meike Krüger ◽

Jochen Reiser ◽

...

Keyword(s):

Dendritic Spines ◽

Cultured Cells ◽

Rat Kidney ◽

Amino Acid Sequences ◽

Cdna Clones ◽

Globular Domain ◽

Postnatal Maturation ◽

Human And Mouse

Synaptopodin is an actin-associated protein of differentiated podocytes that also occurs as part of the actin cytoskeleton of postsynaptic densities (PSD) and associated dendritic spines in a subpopulation of exclusively telencephalic synapses. Amino acid sequences determined in purified rat kidney and forebrain synaptopodin and derived from human and mouse brain cDNA clones show no significant homology to any known protein. In particular, synaptopodin does not contain functional domains found in receptor-clustering PSD proteins. The open reading frame of synaptopodin encodes a polypeptide with a calculated Mr of 73.7 kD (human)/74.0 kD (mouse) and an isoelectric point of 9.38 (human)/9.27 (mouse). Synaptopodin contains a high amount of proline (∼20%) equally distributed along the protein, thus virtually excluding the formation of any globular domain. Sequence comparison between human and mouse synaptopodin revealed 84% identity at the protein level. In both brain and kidney, in vivo and in vitro, synaptopodin gene expression is differentiation dependent. During postnatal maturation of rat brain, synaptopodin is first detected by Western blot analysis at day 15 and reaches maximum expression in the adult animal. The exclusive synaptopodin synthesis in the telencephalon has been confirmed by in situ hybridization, where synaptopodin mRNA is only found in perikarya of the olfactory bulb, cerebral cortex, striatum, and hippocampus, i.e., the expression is restricted to areas of high synaptic plasticity. From these results and experiments with cultured cells we conclude that synaptopodin represents a novel kind of proline-rich, actin-associated protein that may play a role in modulating actin-based shape and motility of dendritic spines and podocyte foot processes.

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In vivo imaging of dendritic spines during electrographic seizures

Annals of Neurology ◽

10.1002/ana.20658 ◽

2005 ◽

Vol 58 (6) ◽

pp. 888-898 ◽

Cited By ~ 33

Author(s):

Nicholas Rensing ◽

Yannan Ouyang ◽

Xiao-Feng Yang ◽

Kelvin A. Yamada ◽

Steven M. Rothman ◽

...

Keyword(s):

Dendritic Spines ◽

In Vivo Imaging ◽

Electrographic Seizures

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Dendritic spines: from structure to in vivo function

EMBO Reports ◽

10.1038/embor.2012.102 ◽

2012 ◽

Vol 13 (8) ◽

pp. 699-708 ◽

Cited By ~ 165

Author(s):

Nathalie L Rochefort ◽

Arthur Konnerth

Keyword(s):

Dendritic Spines

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Growth hormone signaling and action in obese versus lean human subjects

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00431.2018 ◽

2019 ◽

Vol 316 (2) ◽

pp. E333-E344 ◽

Cited By ~ 5

Author(s):

Morten Lyng Høgild ◽

Ann Mosegaard Bak ◽

Steen Bønløkke Pedersen ◽

Jørgen Rungby ◽

Jan Frystyk ◽

...

Keyword(s):

Insulin Resistance ◽

Growth Hormone ◽

Human Subjects ◽

Glucose Production ◽

Relative Increase ◽

Antagonistic Effect ◽

Endogenous Glucose Production ◽

Metabolic Adaptation ◽

Igf I

Growth hormone (GH) levels are blunted in obesity, but it is not known whether this relates to altered GH sensitivity and whether this influences the metabolic adaptation to fasting. Therefore, we investigated the effect of obesity on GH signal transduction and fasting-induced changes in GH action. Nine obese (BMI 35.7 kg/m2) and nine lean (BMI 21.5 kg/m2) men were studied in a randomized crossover design with 1) an intravenous GH bolus, 2) an intravenous saline bolus, and 3) 72 h of fasting. Insulin sensitivity (hyperinsulinemic, euglycemic clamp) and substrate metabolism (glucose tracer and indirect calorimetry) were measured in studies 1 and 2. In vivo GH signaling was assessed in muscle and fat biopsies. GH pharmacokinetics did not differ between obese and lean subjects, but endogenous GH levels were reduced in obesity. GH signaling (STAT5b phosphorylation and CISH mRNA transcription), and GH action (induction of lipolysis and peripheral insulin resistance) were similar in the two groups, but a GH-induced insulin antagonistic effect on endogenous glucose production only occurred in the obese. Fasting-induced IGF-I reduction was completely abrogated in obese subjects despite a comparable relative increase in GH levels (ΔIGF-I: lean, −66 ± 10 vs. obese, 27 ± 16 µg/l; P < 0.01; ΔGH: lean, 647 ± 280 vs. obese, 544 ± 220%; P = 0.76]. We conclude that 1) GH signaling is normal in obesity, 2) in the obese state, the preservation of IGF-I with fasting and the augmented GH-induced central insulin resistance indicate increased hepatic GH sensitivity, 3) blunted GH levels in obesity may protect against insulin resistance without compromising IGF-I status.

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Voltage compartmentalization in dendritic spines in vivo

Science ◽

10.1126/science.abg0501 ◽

2021 ◽

Author(s):

Victor Hugo Cornejo ◽

Netanel Ofer ◽

Rafael Yuste

Keyword(s):

Dendritic Spines

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Distal axotomy enhances retrograde presynaptic excitability onto injured pyramidal neurons via trans-synaptic signaling

10.1101/065391 ◽

2016 ◽

Author(s):

Tharkika Nagendran ◽

Rylan S. Larsen ◽

Rebecca L. Bigler ◽

Shawn B. Frost ◽

Benjamin D. Philpot ◽

...

Keyword(s):

Dendritic Spines ◽

Dendritic Spine ◽

Pyramidal Neurons ◽

Spine Density ◽

Axon Injury ◽

Synaptic Remodeling ◽

Nerve Tracts ◽

Specific Increase ◽

Microfluidic Chambers

AbstractInjury of CNS nerve tracts remodels circuitry through dendritic spine loss and hyper-excitability, thus influencing recovery. Due to the complexity of the CNS, a mechanistic understanding of injury-induced synaptic remodeling remains unclear. Using microfluidic chambers to separate and injure distal axons, we show that axotomy causes retrograde dendritic spine loss at directly injured pyramidal neurons followed by retrograde presynaptic hyper-excitability. These remodeling events require activity at the site of injury, axon-to-soma signaling, and transcription. Similarly, directly injured corticospinal neurons in vivo also exhibit a specific increase in spiking following axon injury. Axotomy-induced hyper-excitability of cultured neurons coincides with elimination of inhibitory inputs onto injured neurons, including those formed onto dendritic spines. Netrin-1 downregulation occurs following axon injury and exogenous netrin-1 applied after injury normalizes spine density, presynaptic excitability, and inhibitory inputs at injured neurons. Our findings show that intrinsic signaling within damaged neurons regulates synaptic remodeling and involves netrin-1 signaling.

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Microglia motility depends on neuronal activity and promotes structural plasticity in the hippocampus

10.1101/515759 ◽

2019 ◽

Cited By ~ 1

Author(s):

Felix C. Nebeling ◽

Stefanie Poll ◽

Lena C. Schmid ◽

Manuel Mittag ◽

Julia Steffen ◽

...

Keyword(s):

Neuronal Activity ◽

Dendritic Spines ◽

Synapse Formation ◽

Brain Parenchyma ◽

Two Photon ◽

Contact Rates ◽

Health And Disease ◽

The Impact ◽

The Brain

AbstractMicroglia, the resident immune cells of the brain, play a complex role in health and disease. They actively survey the brain parenchyma by physically interacting with other cells and structurally shaping the brain. Yet, the mechanisms underlying microglia motility and their significance for synapse stability, especially during adulthood, remain widely unresolved. Here we investigated the impact of neuronal activity on microglia motility and its implication for synapse formation and survival. We used repetitive two-photon in vivo imaging in the hippocampus of awake mice to simultaneously study microglia motility and their interaction with synapses. We found that microglia process motility depended on neuronal activity. Simultaneously, more dendritic spines emerged in awake compared to anesthetized mice. Interestingly, microglia contact rates with individual dendritic spines were associated with their stability. These results suggest that microglia are not only sensing neuronal activity, but participate in synaptic rewiring of the hippocampus during adulthood, which has profound relevance for learning and memory processes.

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