Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

Calcium Ions in the Physiology and Pathology of the Central Nervous System

Calcium ions play a key role in the physiological processes of the central nervous system. The intracellular calcium signal, in nerve cells, is part of the neurotransmission mechanism. They are responsible for stabilizing membrane potential and controlling the excitability of neurons. Calcium ions are a universal second messenger that participates in depolarizing signal transduction and contributes to synaptic activity. These ions take an active part in the mechanisms related to memory and learning. As a result of depolarization of the plasma membrane or stimulation of receptors, there is an extracellular influx of calcium ions into the cytosol or mobilization of these cations inside the cell, which increases the concentration of these ions in neurons. The influx of calcium ions into neurons occurs via plasma membrane receptors and voltage-dependent ion channels. Calcium channels play a key role in the functioning of the nervous system, regulating, among others, neuronal depolarization and neurotransmitter release. Channelopathies are groups of diseases resulting from mutations in genes encoding ion channel subunits, observed including the pathophysiology of neurological diseases such as migraine. A disturbed ability of neurons to maintain an appropriate level of calcium ions is also observed in such neurodegenerative processes as Alzheimer's disease, Parkinson's disease, Huntington's disease, and epilepsy. This review focuses on the involvement of calcium ions in physiological and pathological processes of the central nervous system. We also consider the use of calcium ions as a target for pharmacotherapy in the future.

Epigallocatechin gallate improves neuronal damage in animal model of ischemic stroke and glutamate-exposed neurons via modulation of hippocalcin expression

Epigallocatechin gallate (EGCG) is a polyphenolic component of green tea that has anti-oxidative and anti-inflammatory effects in neurons. Ischemic stroke is a major neurological disease that causes irreversible brain disorders. It increases the intracellular calcium concentration and induces apoptosis. The regulation of intracellular calcium concentration is important to maintain the function of the nervous system. Hippocalcin is a neuronal calcium sensor protein that controls intracellular calcium concentration. We investigated whether EGCG treatment regulates the expression of hippocalcin in stroke animal model and glutamate-induced neuronal damage. We performed middle cerebral artery occlusion (MCAO) to induce cerebral ischemia. EGCG (50 mg/kg) or phosphate buffered saline was injected into the abdominal cavity just before MCAO surgery. The neurobehavioral tests were performed 24 h after MCAO surgery and cerebral cortex tissue was collected. MCAO damage induced severe neurobehavioral disorders, increased infarct volume, and decreased the expression of hippocalcin in the cerebral cortex. However, EGCG treatment improved these deficits and alleviated the decrease in hippocalcin expression in cerebral cortex. In addition, EGCG dose-dependently alleviated neuronal cell death and intracellular calcium overload in glutamate-exposed neurons. Glutamate exposure reduced hippocalcin expression, decreased Bcl-2 expression, and increased Bax expression. However, EGCG treatment mitigated these changes caused by glutamate toxicity. EGCG also attenuated the increase in caspase-3 and cleaved caspase-3 expressions caused by glutamate exposure. The effect of EGCG was more pronounced in non-transfected cells than in hippocalcin siRNA-transfected cells. These findings demonstrate that EGCG protects neurons against glutamate toxicity through the regulation of Bcl-2 family proteins and caspase-3. It is known that hippocalcin exerts anti-apoptotic effect through the modulation of apoptotic pathway. Thus, we can suggest evidence that EGCG has a neuroprotective effect by regulating hippocalcin expression in ischemic brain damage and glutamate-exposed cells.

Transcriptomic analysis reveals novel molecular signaling networks involved in low voluntary running behavior after AP-1 inhibition

Understanding the neuro-molecular mechanisms that mediate the quantity of daily physical activity (PA) level is of medical significance, given the tremendous health benefits associated with greater physical activity. Here, we examined the effects of intra-nucleus accumbens (NAc) inhibition of activator protein-1 (AP-1), an important transcriptional factor downstream of cAMP response element binding protein (CREB; a reward-related transcriptional regulator), on voluntary wheel running behavior in wild-type (WT) and low voluntary running (LVR) female rats. Transcriptome analysis of the nucleus accumbens (NAc; a brain region critical for PA reward and motivation) was performed to further determine molecular responses to intra-NAc AP-1 inhibition in these rat lines. Within WT rats, intra-NAc AP-1 inhibition caused a significant decrease in overnight running distance in comparison to control rats (p = 0.009). Transcriptomic and bioinformatic analysis in WT rats identified involvement of gene products that regulate cellular proliferation and development, which were cellular processes regulated by AP-1. In contrast to above decreased WT distances, intra-NAc AP-1 inhibition in LVR rats increased nightly running distance in comparison to LVR control rats (p = 0.0008). Further analysis identified gene products that are associated with regulating intracellular Ca²⁺ homeostasis, calcium ion binding and neuronal excitability. In short, our study aims to gain a comprehensive understanding of transcriptional profile that was due to AP-1 inhibition in NAc, in which it could not only enhance the knowledge regarding molecular regulatory loops within NAc for modulating voluntary running behavior, but also provide further insights into molecular targets for future investigations.

Regulation of Presynaptic Calcium Channels

Voltage-gated calcium channels (VGCCs), especially Cav2.1 and Cav2.2, are the major mediators of Ca2+ influx at the presynaptic membrane in response to neuron excitation, thereby exerting a predominant control on synaptic transmission. To guarantee the timely and precise release of neurotransmitters at synapses, the activity of presynaptic VGCCs is tightly regulated by a variety of factors, including auxiliary subunits, membrane potential, G protein-coupled receptors (GPCRs), calmodulin (CaM), Ca2+-binding proteins (CaBP), protein kinases, various interacting proteins, alternative splicing events, and genetic variations.

Differential protein expression of GABA A receptor alpha 1 subunit and calbindin in rat spermatozoa associated with proteomic analysis in testis following methamphetamine administration

Methamphetamine (METH) can induce spermatogenesis impairment, testicular apoptosis, and abnormal sperm quality. It also promotes changes in the expression of receptors for sex hormones and neurotransmitters, including GABA receptors in the testis. Proteomic assessment focusing on proteins involved in the calcium signalling pathway in the testis can facilitate diagnostic factors contributing to testicular and sperm functions, especially those related to spermatogenesis and fertilisation. In this study, we proposed to determine the localisation and differential expression of GABA A receptor alpha 1 subunit (GABA A-α1) in the spermatozoa of METH-administered rats. The differential proteomic profile of the testis was also observed by focusing on proteins in the KEGG pathways belonging to the calcium signalling pathway. There were 212 differentially expressed proteins in the rat testis, based on the cut-off value of 1.2-fold change. Most of those proteins, 13 proteins, were classified in the calcium signalling pathway, including 4 down-regulated and 9 up-regulated proteins. An immunolocalisation study of the GABA A-α1 receptor and calbindin revealed their localisation in the equatorial segment of the head in the rat spermatozoa. The expression of calbindin is also found in the middle piece of sperm. An increase in GABA A-α1 receptor in rat spermatozoa was correlated with an increase in abnormal sperm motility and morphology after methamphetamine exposure. Moreover, calbindin expression in sperm decreased in METH-administered rats. All our findings demonstrate that METH influences intracellular calcium homeostasis by acting through the calcium signalling pathway-associated proteins. Moreover, it might disrupt ion homeostasis in sperm through the GABA A-α1 receptor and calbindin, triggering a change in intracellular calcium and chloride ions. These changes may cause abnormalities in spermatogenesis, testicular apoptosis, and sperm quality impairment.

Expression of Calbindin-D28K in the Developing and Adult Mouse Cochlea

Herein, we aimed to use double-labeling immunofluorescence to describe the expression pattern of Calbindin-D28K (CaBP28K) in the mouse cochlea from late embryonic (E) stages to the adulthood. CaBP28K was expressed in the inner hair cells (IHCs) and the greater epithelial ridge (GER) at E17. In addition, its expression was observed in the interdental cells. On postnatal day 1 (P1), CaBP28K immunoreactivity was observed in the IHCs and outer hair cells (OHCs) and was also specifically expressed in the nucleus and the cytoplasm of spiral ganglion neurons (SGNs). At P8, CaBP28K labeling disappeared from the interdental cells, and the CaBP28K-positive domain within the GER shifted from the entire cytoplasm to only the apical and basal regions. At P14, CaBP28K immunoreactivity was lost from the GER; however, its expression in the IHCs and OHCs, as well as the SGNs, persisted into adulthood. The identification of CaBP28K in the hair cells (HCs) and cuticular plates, as well as SGNs, was confirmed by its colocalization with several markers for Sox2, Myosin VIIa, Phalloidin, and Tuj1. We also detected colocalization with calmodulin in the cytoplasm of both HCs and SGNs. Western blot revealed an increase in CaBP28K postnatal expression in the mouse cochlea.

Fibrillarin RNA methylase is an interacting protein of Cryptosporidium parvum calmodulin-like protein (CpCML)

Cryptosporidium parvum is an obligate protozoan parasite invading epithelial cells of small intestine of human and animals, and causing diarrheal disease. In apicomplexan parasites, calcium signaling can regulate many essential biological processes such as invasion and migration. As the main intracellular receptor for calcium ions, calmodulins control the activities of hundreds of enzymes and proteins. Calmodulin-like protein (CML) is an important member of the calmodulin family and may play a key role in C. parvum, however, the actual situation is still not clear. The present study aimed to identify the parasite interaction partner proteins of C. parvum calmodulin-like protein (CpCML). By constructing the cpcml bait plasmid, 5 potential CpCML - interacting proteins in C. parvum oocyst were screened by yeast-two-hybrid system (Y2H). Bimolecular fluorescence complementation (BiFC) and Co-immunoprecipitation (Co-IP) were performed as subsequent validations. Fibrillarin RNA methylase (FBL) was identified via this screening method as CpCML interacting protein in C. parvum. The identification of this interaction made it possible to get a further understanding of the function of CpCML and its contribution to the pathogenicity of C. parvum.

Andrographolide protects against isoproterenol-induced myocardial infarction in rats through inhibition of L-type Ca2+ and increase of cardiac transient outward K+ currents

Myocardial infarction (MI) is the irreversible injury of the myocardium caused by prolonged myocardial ischemia and is a major cause of heart failure and eventual death among ischemic patients. The present study assessed the protective potentials of andrographolide against isoproterenol-induced myocardial infarction in rats. Animals were randomly divided into four groups: Control (Ctr) group received 0.9% saline solution once daily for 21 days, Isoproterenol (Iso) group received 0.9% saline solution once daily for 19 days followed by 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21, Andrographolide (Andro) group received 20 mg/kg/day of andrographolide for 21 days, and Andrographolide plus Isoproterenol (Andro + Iso) group received 20 mg/kg/day of andrographolide for 21 days with co-administration of 80 mg/kg/day of isoproterenol hydrochloride solution on day 20 and 21. After all treatments, cardiac-specific parameters that define cardiac health and early subacute MI were measured in all groups using both biophysical and pharmacological assay methods. Isoproterenol administration significantly (P < 0.05) increased cardiac mass indexes, systemic cardiac biomarkers, infarct size and caused cardiac histological alterations; significantly (P < 0.05) increased heart rate, QRS & QTc intervals and caused ST-segment elevation; significantly (P < 0.05) increased myocytes shortening, action potential duration (APD), L-type Ca²⁺ current (I_Ca,L) density and significantly (P < 0.05) decreased transient outward K⁺ current (I_to) density typical of the early subacute MI. Interestingly, pretreatment with andrographolide prevented and or minimized these anomalies, notably, by reducing I_Ca,L density and increasing I_to density significantly. Therefore, andrographolide could be seen as a promising therapeutic agent capable of making the heart resistant to early subacute infarction and it could be used as template for the development of semisynthetic drug(s) for cardiac protection against MI.

Sodium channel β1 subunits participate in regulated intramembrane proteolysis-excitation coupling

Loss-of-function (LOF) variants in SCN1B, encoding voltage-gated sodium channel β1 subunits, are linked to human diseases with high risk of sudden death, including developmental and epileptic encephalopathy and cardiac arrhythmia. β1 Subunits modulate the cell-surface localization, gating, and kinetics of sodium channel pore-forming α subunits. They also participate in cell-cell and cell-matrix adhesion, resulting in intracellular signal transduction, promotion of cell migration, calcium handling, and regulation of cell morphology. Here, we investigated regulated intramembrane proteolysis (RIP) of β1 by BACE1 and γ-secretase and show that β1 subunits are substrates for sequential RIP by BACE1 and γ-secretase, resulting in the generation of a soluble intracellular domain (ICD) that is translocated to the nucleus. Using RNA sequencing, we identified a subset of genes that are downregulated by β1-ICD overexpression in heterologous cells but upregulated in Scn1b-null cardiac tissue, which lacks β1-ICD signaling, suggesting that the β1-ICD may normally function as a molecular brake on gene transcription in vivo. We propose that human disease variants resulting in SCN1B LOF cause transcriptional dysregulation that contributes to altered excitability. Moreover, these results provide important insights into the mechanism of SCN1B-linked channelopathies, adding RIP-excitation coupling to the multifunctionality of sodium channel β1 subunits.

Elevation of gene expression of calcineurin, calmodulin and calsyntenin in oxidative stress induced PC12 cells

In normal physiological conditions, reactive oxygen and nitrogen species are used as important signaling molecules in the cell. However, in excess it causes the disruption of cell resulting in their death. Oxidative stress causes influx in intracellular calcium levels leading to higher concentrations of calcium in the cell. This accelerated calcium affects both the mitochondria and nuclei leading to excitotoxicity in neurons. Intracellular calcium levels are controlled by voltage dependent calcium channels located in the plasma membrane, calcium stores like endoplasmic/sarcoplasmic reticulum and majorly by calcium binding proteins. Our study was aimed at analyzing the gene expression of major calcium binding proteins namely calcineurin, calmodulin, calreticulin, synaptotagamin and calsyntenin in stress induced PC 12 cells. Rotenone (1 μM), Peroxynitrite (10 μM), H2O2 (100 μM) and High glucose (33 mM) were used to induce oxidative stress in PC12 cells. Results obtained from the study suggest that calcineurin, calmodulin and calsyntenin gene expression were enhanced compared to the control due to oxidative stress. However, synaptotagmin and calreticulin gene expression were down regulated. Further, Akt protein expression (stress marker) was enhanced in PC12 cells with all other stress inducers except in hyperglycemic condition.

Disrupting polycystin-2 EF hand Ca2+ affinity does not alter channel function or contribute to polycystic kidney disease

Approximately 15% of autosomal dominant polycystic kidney disease (ADPKD) is caused by variants in PKD2PKD2 encodes polycystin-2, which forms an ion channel in primary cilia and endoplasmic reticulum (ER) membranes of renal collecting duct cells. Elevated internal Ca2+ modulates polycystin-2 voltage-dependent gating and subsequent desensitization - two biophysical regulatory mechanisms that control its function at physiological membrane potentials. Here, we refute the hypothesis that Ca2+ occupancy of the polycystin-2 intracellular EF hand is responsible for these forms of channel regulation, and, if disrupted, results in ADPKD. We identify and introduce mutations that attenuate Ca2+-EF hand affinity but find channel function is unaltered in the primary cilia and ER membranes. We generated two new mouse strains that harbor distinct mutations that abolish Ca2+-EF hand association but do not result in a PKD phenotype. Our findings suggest that additional Ca2+-binding sites within polycystin-2 or Ca2+-dependent modifiers are responsible for regulating channel activity.

Voltage-gated ion channels mediate the electrotaxis of glioblastoma cells in a hybrid PMMA/PDMS microdevice

Transformed astrocytes in the most aggressive form cause glioblastoma, the most common cancer in the central nervous system with high mortality. The physiological electric field by neuronal local field potentials and tissue polarity may guide the infiltration of glioblastoma cells through the electrotaxis process. However, microenvironments with multiplex gradients are difficult to create. In this work, we have developed a hybrid microfluidic platform to study glioblastoma electrotaxis in controlled microenvironments with high throughput quantitative analysis by machine learning-powered single cell tracking software. By equalizing the hydrostatic pressure difference between inlets and outlets of the microchannel, uniform single cells can be seeded reliably inside the microdevice. The electrotaxis of two glioblastoma models, T98G and U-251MG, requires an optimal laminin-containing extracellular matrix and exhibits opposite directional and electro-alignment tendencies. Calcium signaling is a key contributor in glioblastoma pathophysiology but its role in glioblastoma electrotaxis is still an open question. Anodal T98G electrotaxis and cathodal U-251MG electrotaxis require the presence of extracellular calcium cations. U-251MG electrotaxis is dependent on the P/Q-type voltage-gated calcium channel (VGCC) and T98G is dependent on the R-type VGCC. U-251MG electrotaxis and T98G electrotaxis are also mediated by A-type (rapidly inactivating) voltage-gated potassium channels and acid-sensing sodium channels. The involvement of multiple ion channels suggests that the glioblastoma electrotaxis is complex and patient-specific ion channel expression can be critical to develop personalized therapeutics to fight against cancer metastasis. The hybrid microfluidic design and machine learning-powered single cell analysis provide a simple and flexible platform for quantitative investigation of complicated biological systems.

Interrelation of Ca2+ and PE_PGRS proteins during Mycobacterium tuberculosis pathogenesis

In today's era tuberculosis is a major threat to human population. The lethality of this disease is caused by very efficiently thrived bacteria Mycobacterium tuberculosis (M. tuberculosis). Ca²⁺ plays crucial role in maintenance of cellular homeostasis. Bacilli survival in human alveolar macrophages majorly depends on disruption in Ca²⁺ signaling. Bacilli sustainability in phagosome lies in the interruption of phagolysosomal fusion, which is possible because of low intracellular Ca²⁺ concentration. Bacilli contain various Ca²⁺ binding proteins which help in regulation of Ca²⁺ signaling for its own benefit. For the survival of pathogen, it requires alteration in normal Ca²⁺ concentration in healthy cell. In this review we aim to find the various Ca²⁺ binding domains which are present in several Ca²⁺ binding proteins of M. tuberculosis and variety of roles played by Ca²⁺ to survive bacilli within host cell. This manuscript emphasizes the Ca²⁺ binding domains present in PE_PGRS group of gene family and their functionality in M. tuberculosis survival and pathogenesis.

Voltage-Dependent Calcium Channels, Calcium Binding Proteins, and Their Interaction in the Pathological Process of Epilepsy

As an important second messenger, the calcium ion (Ca²⁺) plays a vital role in normal brain function and in the pathophysiological process of different neurodegenerative diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and epilepsy. Ca²⁺ takes part in the regulation of neuronal excitability, and the imbalance of intracellular Ca²⁺ is a trigger factor for the occurrence of epilepsy. Several anti-epileptic drugs target voltage-dependent calcium channels (VDCCs). Intracellular Ca²⁺ levels are mainly controlled by VDCCs located in the plasma membrane, the calcium-binding proteins (CBPs) inside the cytoplasm, calcium channels located on the intracellular calcium store (particular the endoplasmic reticulum/sarcoplasmic reticulum), and the Ca²⁺-pumps located in the plasma membrane and intracellular calcium store. So far, while many studies have established the relationship between calcium control factors and epilepsy, the mechanism of various Ca²⁺ regulatory factors in epileptogenesis is still unknown. In this paper, we reviewed the function, distribution, and alteration of VDCCs and CBPs in the central nervous system in the pathological process of epilepsy. The interaction of VDCCs with CBPs in the pathological process of epilepsy was also summarized. We hope this review can provide some clues for better understanding the mechanism of epileptogenesis, and for the development of new anti-epileptic drugs targeting on VDCCs and CBPs.

Channeling Vision: CaV1.4-A Critical Link in Retinal Signal Transmission

Voltage-gated calcium channels (VGCC) are key to many biological functions. Entry of Ca2+ into cells is essential for initiating or modulating important processes such as secretion, cell motility, and gene transcription. In the retina and other neural tissues, one of the major roles of Ca2+-entry is to stimulate or regulate exocytosis of synaptic vesicles, without which synaptic transmission is impaired. This review will address the special properties of one L-type VGCC, CaV1.4, with particular emphasis on its role in transmission of visual signals from rod and cone photoreceptors (hereafter called "photoreceptors," to the exclusion of intrinsically photoreceptive retinal ganglion cells) to the second-order retinal neurons, and the pathological effects of mutations in the CACNA1F gene which codes for the pore-forming α1F subunit of CaV1.4.

Distinct Neural Properties in the Low-Frequency Region of the Chicken Cochlear Nucleus Magnocellularis

Topography in the avian cochlear nucleus magnocellularis (NM) is represented as gradually increasing characteristic frequency (CF) along the caudolateral-to-rostromedial axis. In this study, we characterized the organization and cell biophysics of the caudolateral NM (NMc) in chickens (Gallus gallus). Examination of cellular and dendritic architecture first revealed that NMc contains small neurons and extensive dendritic processes, in contrast to adendritic, large neurons located more rostromedially. Individual dye-filling study further demonstrated that NMc is divided into two subregions, with NMc2 neurons having larger and more complex dendritic fields than NMc1. Axonal tract tracing studies confirmed that NMc1 and NMc2 neurons receive afferent inputs from the auditory nerve and the superior olivary nucleus, similar to the adendritic NM. However, the auditory axons synapse with NMc neurons via small bouton-like terminals, unlike the large end bulb synapses on adendritic NM neurons. Immunocytochemistry demonstrated that most NMc2 neurons express cholecystokinin but not calretinin, distinct from NMc1 and adendritic NM neurons that are cholecystokinin negative and mostly calretinin positive. Finally, whole-cell current clamp recordings revealed that NMc neurons require significantly lower threshold current for action potential generation than adendritic NM neurons. Moreover, in contrast to adendritic NM neurons that generate a single-onset action potential, NMc neurons generate multiple action potentials to suprathreshold sustained depolarization. Taken together, our data indicate that NMc contains multiple neuron types that are structurally, connectively, molecularly, and physiologically different from traditionally defined NM neurons, emphasizing specialized neural properties for processing low-frequency sounds.

Regulation of L-type Voltage Gated Calcium Channel CACNA1S in Macrophages upon Mycobacterium tuberculosis Infection

We demonstrated earlier the inhibitory role played by Voltage Gated Calcium Channels (VGCCs) in regulating Mycobacterium tuberculosis (M. tb) survival and pathogenesis. In this report, we investigated mechanisms and key players that regulate the surface expression of VGCC-CACNA1S by Rv2463 and M. tb infection in macrophages. Our earlier work identified Rv2463 to be expressed at early times post infection in macrophages that induced suppressor responses to dendritic cells and macrophages. Our results in this study demonstrate a role of MyD88 independent TLR pathway in mediating CACNA1S expression. Dissecting the role for second messengers, we show that calcium homeostasis plays a key role in CACNA1S expression during M. tb infection. Using siRNAs against molecular sensors of calcium regulation, we show an involvement of ER associated Stromal Interaction Molecules 1 and 2 (STIM1 and STIM2), and transcription factor pCREB, towards CACNA1S expression that also involved the MyD88 independent pathway. Interestingly, reactive oxygen species played a negative role in M. tb mediated CACNA1S expression. Further, a cross-regulation of ROS and pCREB was noted that governed CACNA1S expression. Characterizing the mechanisms governing CACNA1S expression would improve our understanding of the regulation of VGCC expression and its role in M. tb pathogenesis during M. tb infection.

Low-expressed testis-specific calcium-binding protein CBP86-IV (CABYR) is observed in idiopathic asthenozoospermia

OBJECTIVES

To investigate the expression level of testis-specific calcium-binding protein CBP86-IV in normal and asthenozoospermic human sperm.

METHODS

The total RNA was extracted from human sperm, and target cDNA was obtained by reverse transcription-polymerase chain reaction. Then the cDNA was used for quantitative PCR analysis and cloned into the prokaryotic expression vector pET-28a, respectively. The fusion protein was induced and expressed as inclusion body which was used to produce the polyclonal antibody against TSCBP86-IV. The protein expression level of TSCBP86-IV from normal human sperm and idiopathic asthenozoospermic samples was detected by the purified antibody.

RESULTS

The experimental results showed that the protein expression of TSCBP86-IV was reduced in idiopathic asthenozoospermia and consistent with the transcriptional changing tendency which was detected by quantitative PCR analysis.

CONCLUSIONS

The stable and reliable change of TSCBP86-IV may be taken as a new molecular marker for clinical diagnosis of idiopathic asthenozoospermia.

Reciprocal regulation of reactive oxygen species and phospho-CREB regulates voltage gated calcium channel expression during Mycobacterium tuberculosis infection

Our previous work has demonstrated the roles played by L-type Voltage Gated Calcium Channels (VGCC) in regulating Mycobacterium tuberculosis (M. tb) survival and pathogenesis. Here we decipher mechanisms and pathways engaged by the pathogen to regulate VGCC expression in macrophages. We show that M. tb and its antigen Rv3416 use phospho-CREB (pCREB), Reactive Oxygen Species (ROS), Protein Kinase C (PKC) and Mitogen Activated Protein Kinase (MAPK) to modulate VGCC expression in macrophages. siRNA mediated knockdown of MyD88, IRAK1, IRAK2 or TRAF6 significantly inhibited antigen mediated VGCC expression. Inhibiting Protein Kinase C (PKC) or MEK-ERK1/2 further increased VGCC expression. Interestingly, inhibiting intracellular calcium release upregulated antigen mediated VGCC expression, while inhibiting extracellular calcium influx had no significant effect. siRNA mediated knockdown of transcription factors c-Jun, SOX5 and CREB significantly inhibited Rv3416 mediated VGCC expression. A dynamic reciprocal cross-regulation between ROS and pCREB was observed that in turn governed VGCC expression with ROS playing a limiting role in the process. Further dissection of the mechanisms such as the interplay between ROS and pCREB would improve our understanding of the regulation of VGCC expression during M. tb infection.

CSF levels of the neuronal injury biomarker visinin-like protein-1 in Alzheimer's disease and dementia with Lewy bodies

The overlapping clinical features of Alzheimer's disease (AD) and Dementia with Lewy bodies (DLB) make differentiation difficult in the clinical environment. Evaluating the CSF levels of biomarkers in AD and DLB patients could facilitate clinical diagnosis. CSF Visinin-like protein-1 (VILIP-1), a calcium-mediated neuronal injury biomarker, has been described as a novel biomarker for AD. The aim of this study was to investigate the diagnostic utility of CSF VILIP-1 and VILIP-1/Aβ1-42 ratio to distinguish AD from DLB. Levels of CSF VILIP-1, t-tau, p-tau181P , Aβ1-42 , and α-synuclein were measured in 61 AD patients, 32 DLB patients, and 40 normal controls using commercial ELISA kits. The results showed that the CSF VILIP-1 level had significantly increased in AD patients compared with both normal controls and DLB patients. The CSF VILIP-1 and VILIP-1/Aβ1-42 levels had enough diagnostic accuracy to allow the detection and differential diagnosis of AD. Additionally, CSF VILIP-1 levels were positively correlated with t-tau and p-tau181P within each group and with α-synuclein in the AD and control groups. We conclude that CSF VILIP-1 could be a diagnostic marker for AD, differentiating it from DLB. The analysis of biomarkers, representing different neuropathologies, is an important approach reflecting the heterogeneous features of AD and DLB. Neuronal Ca(2+) -sensor protein VILIP-1 has been implicated in the calcium-mediated neuronal injury and pathological change of AD. The CSF VILIP-1 and VILIP-1/Aβ1-42 levels had enough diagnostic accuracy to allow the detection and differential diagnosis of AD. CSF VILIP-1 is a useful biomarker for AD. Evaluating the CSF levels of VILIP-1 in AD and DLB patients could facilitate clinical diagnosis.

Complex regulation of voltage-dependent activation and inactivation properties of retinal voltage-gated Cav1.4 L-type Ca2+ channels by Ca2+-binding protein 4 (CaBP4)

Cav1.4 L-type Ca(2+) channels are crucial for synaptic transmission in retinal photoreceptors and bipolar neurons. Recent studies suggest that the activity of this channel is regulated by the Ca(2+)-binding protein 4 (CaBP4). In the present study, we explored this issue by examining functional effects of CaBP4 on heterologously expressed Cav1.4. We show that CaBP4 dramatically increases Cav1.4 channel availability. This effect crucially depends on the presence of the C-terminal ICDI (inhibitor of Ca(2+)-dependent inactivation) domain of Cav1.4 and is absent in a Cav1.4 mutant lacking the ICDI. Using FRET experiments, we demonstrate that CaBP4 interacts with the IQ motif of Cav1.4 and that it interferes with the binding of the ICDI domain. Based on these findings, we suggest that CaBP4 increases Cav1.4 channel availability by relieving the inhibitory effects of the ICDI domain on voltage-dependent Cav1.4 channel gating. We also functionally characterized two CaBP4 mutants that are associated with a congenital variant of human night blindness and other closely related nonstationary retinal diseases. Although both mutants interact with Cav1.4 channels, the functional effects of CaBP4 mutants are only partially preserved, leading to a reduction of Cav1.4 channel availability and loss of function. In conclusion, our study sheds new light on the functional interaction between CaBP4 and Cav1.4. Moreover, it provides insights into the mechanism by which CaBP4 mutants lead to loss of Cav1.4 function and to retinal disease.

S100 calcium binding proteins and ion channels

S100 Ca(2+)-binding proteins have been associated with a multitude of intracellular Ca(2+)-dependent functions including regulation of the cell cycle, cell differentiation, cell motility and apoptosis, modulation of membrane-cytoskeletal interactions, transduction of intracellular Ca(2+) signals, and in mediating learning and memory. S100 proteins are fine tuned to read the intracellular free Ca(2+) concentration and affect protein phosphorylation, which makes them candidates to modulate certain ion channels and neuronal electrical behavior. Certain S100s are secreted from cells and are found in extracellular fluids where they exert unique extracellular functions. In addition to their neurotrophic activity, some S100 proteins modulate neuronal electrical discharge activity and appear to act directly on ion channels. The first reports regarding these effects suggested S100-mediated alterations in Ca(2+) fluxes, K(+) currents, and neuronal discharge activity. Recent reports revealed direct and indirect interactions with Ca(2+), K(+), Cl(-), and ligand activated channels. This review focuses on studies of the physical and functional interactions of S100 proteins and ion channels.