Mitochondrial calcium cycling in neuronal function and neurodegeneration.

Mitochondria are essential for proper cellular function through their critical roles in ATP synthesis, reactive oxygen species production, calcium (Ca) buffering, and apoptotic signaling. In neurons, Ca buffering is particularly important as it helps to shape Ca signals and to regulate numerous Ca-dependent functions including neuronal excitability, synaptic transmission, gene expression, and neuronal toxicity. Over the past decade, identification of the mitochondrial Ca uniporter (MCU) and other molecular components of mitochondrial Ca transport has provided insight into the roles that mitochondrial Ca regulation plays in neuronal function in health and disease.

The BBSome regulates mitochondria dynamics and function.

Objective: The essential role of mitochondria in regulation of metabolic function and other physiological processes has garnered enormous interest in understanding the mechanisms controlling the function of this organelle. We assessed the role of the BBSome, a protein complex composed of eight Bardet-Biedl syndrome (BBS) proteins, in the control of mitochondria dynamic and function.

Methods: We used a multidisciplinary approach that include CRISPR/Cas9 technology-mediated generation of a stable Bbs1 gene knockout hypothalamic N39 neuronal cell line.

The voltage-gated Ca2+ channel subunit α2δ-4 regulates locomotor behavior and sensorimotor gating in mice.

Voltage-gated Ca2+ channels are critical for the development and mature function of the nervous system. Variants in the CACNA2D4 gene encoding the α2δ-4 auxiliary subunit of these channels are associated with neuropsychiatric and neurodevelopmental disorders. α2δ-4 is prominently expressed in the retina and is crucial for vision, but extra-retinal functions of α2δ-4 have not been investigated.

MCU (mitochondrial Ca uniporter) makes the calcium go round.

Store-operated Ca entry (SOCE) is a major mechanism controlling Ca signaling and Ca-dependent functions and has been implicated in immunity, cancer, and organ development. SOCE-dependent cytosolic Ca signals are affected by mitochondrial Ca transport through several competing mechanisms. However, how these mechanisms interact in shaping Ca dynamics and regulating Ca-dependent functions remains unclear.

The complement cascade in the regulation of neuroinflammation, nociceptive sensitization, and pain.

The complement cascade is a key component of the innate immune system that is rapidly recruited through a cascade of enzymatic reactions to enable the recognition and clearance of pathogens and promote tissue repair. Despite its well-understood role in immunology, recent studies have highlighted new and unexpected roles of the complement cascade in neuroimmune interaction and in the regulation of neuronal processes during development, aging, and in disease states. Complement signaling is particularly important in directing neuronal responses to tissue injury, neurotrauma, and nerve lesions.

Stay or go? Neuronal activity in medial frontal cortex during a voluntary tactile preference task in head-fixed mice.

The decision to move is influenced by sensory, attentional, and motivational cues. One such cue is the quality of the tactile input, with noxious or unpleasant sensations causing an animal to move away from the cue. Processing of painful and unpleasant sensation in the cortex involves multiple brain regions, although the specific role of the brain areas involved in voluntary, rather than reflexive movement away from unpleasant stimuli is not well understood.

Distinct properties of Ca efflux from brain, heart and liver mitochondria: The effects of Na, Li and the mitochondrial Na/Ca exchange inhibitor CGP37157.

Mitochondrial Ca transport is essential for regulating cell bioenergetics, Ca signaling and cell death. Mitochondria accumulate Ca via the mitochondrial Ca uniporter (MCU), whereas Ca is extruded by the mitochondrial Na/Ca (mtNCX) and H/Ca exchangers. The balance between these processes is essential for preventing toxic mitochondrial Ca overload.

FGF21 Signals to Glutamatergic Neurons in the Ventromedial Hypothalamus to Suppress Carbohydrate Intake.

Fibroblast growth factor 21 (FGF21) is an endocrine hormone produced by the liver that regulates nutrient and metabolic homeostasis. FGF21 production is increased in response to macronutrient imbalance and signals to the brain to suppress sugar intake and sweet-taste preference. However, the central targets mediating these effects have been unclear.

Deletion of a Neuronal Drp1 Activator Protects against Cerebral Ischemia.

Mitochondrial fission catalyzed by dynamin-related protein 1 (Drp1) is necessary for mitochondrial biogenesis and maintenance of healthy mitochondria. However, excessive fission has been associated with multiple neurodegenerative disorders, and we recently reported that mice with smaller mitochondria are sensitized to ischemic stroke injury. Although pharmacological Drp1 inhibition has been put forward as neuroprotective, the specificity and mechanism of the inhibitor used is controversial.

Loss of tau and Fyn reduces compensatory effects of MAP2 for tau and reveals a Fyn-independent effect of tau on calcium.

Microtubule-associated protein tau associates with Src family tyrosine kinase Fyn and is tyrosine phosphorylated by Fyn. The presence of tyrosine phosphorylated tau in AD and the involvement of Fyn in AD has drawn attention to the tau-Fyn complex. In this study, a tau-Fyn double knockout (DKO) mouse was generated to investigate the role of the complex.

The BBSome in POMC and AgRP Neurons Is Necessary for Body Weight Regulation and Sorting of Metabolic Receptors.

The BBSome, a complex of eight Bardet-Biedl syndrome (BBS) proteins involved in cilia function, has emerged as an important regulator of energy balance, but the underlying cellular and molecular mechanisms are not fully understood. Here, we show that the control of energy homeostasis by the anorexigenic proopiomelanocortin (POMC) neurons and orexigenic agouti-related peptide (AgRP) neurons require intact BBSome. Targeted disruption of the BBSome by gene deletion in POMC or AgRP neurons increases body weight and adiposity.

Mechanisms underlying mechanical sensitization induced by complement C5a: the roles of macrophages, TRPV1, and calcitonin gene-related peptide receptors.

The complement system significantly contributes to the development of inflammatory and neuropathic pain, but the underlying mechanisms are poorly understood. Recently, we identified the signaling pathway responsible for thermal hypersensitivity induced by the complement system component C5a. Here, we examine the mechanisms of another important action of C5a, induction of mechanical hypersensitivity.

Arginine vasopressin infusion is sufficient to model clinical features of preeclampsia in mice.

Copeptin, a marker of arginine vasopressin (AVP) secretion, is elevated throughout human pregnancies complicated by preeclampsia (PE), and AVP infusion throughout gestation is sufficient to induce the major phenotypes of PE in mice. Thus, we hypothesized a role for AVP in the pathogenesis of PE. AVP infusion into pregnant C57BL/6J mice resulted in hypertension, renal glomerular endotheliosis, intrauterine growth restriction, decreased placental growth factor (PGF), altered placental morphology, placental oxidative stress, and placental gene expression consistent with human PE.

Deletion of mitochondrial calcium uniporter incompletely inhibits calcium uptake and induction of the permeability transition pore in brain mitochondria.

Ca influx into mitochondria is mediated by the mitochondrial calcium uniporter (MCU), whose identity was recently revealed as a 40-kDa protein that along with other proteins forms the mitochondrial Ca uptake machinery. The MCU is a Ca-conducting channel spanning the inner mitochondrial membrane. Here, deletion of the MCU completely inhibited Ca uptake in liver, heart, and skeletal muscle mitochondria.

AKAP1 Protects from Cerebral Ischemic Stroke by Inhibiting Drp1-Dependent Mitochondrial Fission.

Mitochondrial fission and fusion impact numerous cellular functions and neurons are particularly sensitive to perturbations in mitochondrial dynamics. Here we describe that male mice lacking the mitochondrial A-kinase anchoring protein 1 (AKAP1) exhibit increased sensitivity in the transient middle cerebral artery occlusion model of focal ischemia. At the ultrastructural level, AKAP1 mice have smaller mitochondria and increased contacts between mitochondria and the endoplasmic reticulum in the brain.

Angiotensin II Triggers Peripheral Macrophage-to-Sensory Neuron Redox Crosstalk to Elicit Pain.

Injury, inflammation, and nerve damage initiate a wide variety of cellular and molecular processes that culminate in hyperexcitation of sensory nerves, which underlies chronic inflammatory and neuropathic pain. Using behavioral readouts of pain hypersensitivity induced by angiotensin II (Ang II) injection into mouse hindpaws, our study shows that activation of the type 2 Ang II receptor (AT2R) and the cell-damage-sensing ion channel TRPA1 are required for peripheral mechanical pain sensitization induced by Ang II in male and female mice. However, we show that AT2R is not expressed in mouse and human dorsal root ganglia (DRG) sensory neurons.

Hydrogen Peroxide Induces Muscle Nociception via Transient Receptor Potential Ankyrin 1 Receptors.

Background: H2O2 has a variety of actions in skin wounds but has been rarely studied in deep muscle tissue. Based on response to the transient receptor potential ankyrin 1 antagonists after plantar incision, we hypothesized that H2O2 exerts nociceptive effects via the transient receptor potential ankyrin 1 in muscle.

Methods: Nociceptive behaviors in rats (n = 269) and mice (n = 16) were evaluated after various concentrations and volumes of H2O2 were injected into the gastrocnemius muscle or subcutaneous tissue.

Culture, Transfection, and Immunocytochemical Analysis of Primary Macrophages.

Macrophages are the primary phagocytes of the body and found in every tissue; often with tissue specific subtypes, e.g., microglia or Kupffer Cells.

The Complement System Component C5a Produces Thermal Hyperalgesia via Macrophage-to-Nociceptor Signaling That Requires NGF and TRPV1.

Unlabelled: The complement cascade is a principal component of innate immunity. Recent studies have underscored the importance of C5a and other components of the complement system in inflammatory and neuropathic pain, although the underlying mechanisms are largely unknown. In particular, it is unclear how the complement system communicates with nociceptors and which ion channels and receptors are involved.

Nerve growth factor (NGF) regulates activity of nuclear factor of activated T-cells (NFAT) in neurons via the phosphatidylinositol 3-kinase (PI3K)-Akt-glycogen synthase kinase 3β (GSK3β) pathway.

The Ca(2+)/calcineurin-dependent transcription factor nuclear factor of activated T-cells (NFAT) plays an important role in regulating many neuronal functions, including excitability, axonal growth, synaptogenesis, and neuronal survival. NFAT can be activated by action potential firing or depolarization that leads to Ca(2+)/calcineurin-dependent dephosphorylation of NFAT and its translocation to the nucleus. Recent data suggest that NFAT and NFAT-dependent functions in neurons can also be potently regulated by NGF and other neurotrophins.

Red fluorescent genetically encoded Ca2+ indicators for use in mitochondria and endoplasmic reticulum.

Ca2+ is a key intermediary in a variety of signalling pathways and undergoes dynamic changes in its cytoplasmic concentration due to release from stores within the endoplasmic reticulum (ER) and influx from the extracellular environment. In addition to regulating cytoplasmic Ca2+ signals, these responses also affect the concentration of Ca2+ within the ER and mitochondria. Single fluorescent protein-based Ca2+ indicators, such as the GCaMP series based on GFP, are powerful tools for imaging changes in the concentration of Ca2+ associated with intracellular signalling pathways.

Acid-sensing ion channel 3 decreases phosphorylation of extracellular signal-regulated kinases and induces synoviocyte cell death by increasing intracellular calcium.

Introduction: Acid-sensing ion channel 3 (ASIC3) is expressed in synoviocytes, activated by decreases in pH, and reduces inflammation in animal models of inflammatory arthritis. The purpose of the current study was to characterize potential mechanisms underlying the control of inflammation by ASIC3 in fibroblast-like synoviocytes (FLS).

Methods: Experiments were performed in cultured FLS from wild-type (WT) and ASIC3-/- mice, ASIC1-/- mice, and people with rheumatoid arthritis.

Pharmacological correction of gating defects in the voltage-gated Ca(v)2.1 Ca²⁺ channel due to a familial hemiplegic migraine mutation.

Voltage-gated ion channels exhibit complex properties, which can be targeted in pharmacological therapies for disease. Here, we report that the pro-oxidant, tert-butyl dihydroquinone (BHQ), modulates Ca(v)2.1 Ca²⁺ channels in ways that oppose defects in channel gating and synaptic transmission resulting from a familial hemiplegic migraine mutation (S218L).