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The L-type voltage-gated Ca2+ channel gene CACNA1C is a risk gene for various psychiatric conditions, including schizophrenia and bipolar disorder. However, the cellular mechanism by which CACNA1C contributes to psychiatric disorders has not been elucidated. Here, we report that the embryonic deletion of Cacna1c in neurons destined for the cerebral cortex using an Emx1-Cre strategy disturbs spontaneous Ca2+ activity and causes abnormal brain development and anxiety. By combining computational modeling with electrophysiological membrane potential manipulation, we found that neural network activity was driven by intrinsic spontaneous Ca2+ activity in distinct progenitor cells expressing marginally increased levels of voltage-gated Ca2+ channels. MRI examination of the Cacna1c knockout mouse brains revealed volumetric differences in the neocortex, hippocampus, and periaqueductal gray. These results suggest that Cacna1c acts as a molecular switch and that its disruption during embryogenesis can perturb Ca2+ handling and neural development, which may increase susceptibility to psychiatric disease. [ABSTRACT FROM AUTHOR]

Abstract Background Polycystin-2 (PC2), encoded by the gene that is mutated in autosomal dominant polycystic kidney disease (ADPKD), functions as a calcium (Ca2+) permeable ion channel. Considerable controversy remains regarding the subcellular localization and signaling function of PC2 in kidney cells. Methods We investigated the subcellular PC2 localization by immunocytochemistry and confocal microscopy in primary cultures of human and rat proximal tubule cells after stimulating cytosolic Ca2+ signaling. Plasma membrane (PM) Ca2+ permeability was evaluated by Fura-2 manganese quenching using time-lapse fluorescence microscopy. Results We demonstrated that PC2 exhibits a dynamic subcellular localization pattern. In unstimulated human or rat proximal tubule cells, PC2 exhibited a cytosolic/reticular distribution. Treatments with agents that in various ways affect the Ca2+ signaling machinery, those being ATP, bradykinin, ionomycin, CPA or thapsigargin, resulted in increased PC2 immunostaining in the PM. Exposing cells to the steroid hormone ouabain, known to trigger Ca2+ oscillations in kidney cells, caused increased PC2 in the PM and increased PM Ca2+ permeability. Intracellular Ca2+ buffering with BAPTA, inositol 1,4,5-trisphosphate receptor (InsP3R) inhibition with 2-aminoethoxydiphenyl borate (2-APB) or Ca2+/Calmodulin-dependent kinase inhibition with KN-93 completely abolished ouabain-stimulated PC2 translocation to the PM. Conclusions These novel findings demonstrate intracellular Ca2+-dependent PC2 trafficking in human and rat kidney cells, which may provide new insight into cyst formations in ADPKD.

Multicellular organisms rely on intercellular communication to regulate important cellular processes critical to life. To further our understanding of those processes there is a need to scrutinize dynamical signaling events and their functions in both cells and organisms. Here, we report a method and provide MATLAB code that analyzes time-lapse microscopy recordings to identify and characterize network structures within large cell populations, such as interconnected neurons. The approach is demonstrated using intracellular calcium (Ca2+) recordings in neural progenitors and cardiac myocytes, but could be applied to a wide variety of biosensors employed in diverse cell types and organisms. In this method, network structures are analyzed by applying cross-correlation signal processing and graph theory to single-cell recordings. The goal of the analysis is to determine if the single cell activity constitutes a network of interconnected cells and to decipher the properties of this network. The method can be applied in many fields of biology in which biosensors are used to monitor signaling events in living cells. Analyzing intercellular communication in cell ensembles can reveal essential network structures that provide important biological insights. [ABSTRACT FROM AUTHOR]

Ca2+ signals control cell migration by regulating forward movement and cell adhesion. However, it is not well understood how Ca2+-regulatory proteins and second messengers are spatially organized in migrating cells. Here we show that receptor tyrosine kinase and phospholipase C signalling are restricted to the front of migrating endothelial leader cells, triggering local Ca2+ pulses, local depletion of Ca2+ in the endoplasmic reticulum and local activation of STIM1, supporting pulsatile front retraction and adhesion. At the same time, the mediator of store-operated Ca2+ influx, STIM1, is transported by microtubule plus ends to the front. Furthermore, higher Ca2+ pump rates in the front relative to the back of the plasma membrane enable effective local Ca2+ signalling by locally decreasing basal Ca2+. Finally, polarized phospholipase C signalling generates a diacylglycerol gradient towards the front that promotes persistent forward migration. Thus, cells employ an integrated Ca2+ control system with polarized Ca2+ signalling proteins and second messengers to synergistically promote directed cell migration. [ABSTRACT FROM AUTHOR]

Human embryonic stem (hES) cell differentiation into dopamine neurons is considered a promising strategy for cell replacement therapy in Parkinson's disease, yet the functional properties of hES cell-derived dopamine neurons remain poorly defined. The objective of this study was to characterize intracellular calcium (Ca2+) and sub-plasma membrane cyclic AMP-signaling properties in hES cell-derived dopamine neurons. We found that hES cell-derived dopamine neurons and neural progenitors raised Ca2+from intra- and extracellular compartments in response to depolarization, glutamate, ATP, and dopamine D2receptor activation, while undifferentiated hES cells only mobilized Ca2+from intracellular stores in response to ATP and D2receptor-induced activation. Interestingly, we also found that hES cell-derived dopamine neurons in addition to primary ventral midbrain dopamine neurons were more prone to release Ca2+from intracellular stores than non-dopamine neurons following treatment with the neuropeptide neurotensin. Furthermore, hES cell-derived dopamine neurons showed cAMP elevations in response to forskolin and 3-isobutyl-methylxanthine, similar to primary dopamine neurons. Taken together, these results unravel the temporal sequence by which hES cells acquire Ca2+and cAMP signaling competence during dopamine differentiation. [ABSTRACT FROM AUTHOR]

Synchronized network activity among groups of interconnected cells is essential for diverse functions in the brain. However, most studies have been made on cellular networks in the mature brain when chemical synapses have been formed. Much less is known about the situation earlier in development. When studying neural progenitors derived from embryonic stem cells and neural progenitors from mice embryos, we found networks of gap junction coupled cells with vivid spontaneous non-random calcium (Ca2+) activity driven by electrical depolarization that stimulated cell growth. Network activity was revealed by single-cell live Ca2+ imaging and further analyzed for correlations and net- work topology. The analysis revealed the networks to have small-world characteristics with scale-free properties. Taken together, these results demonstrate that immature cells in the developing brain organize in small-world networks that critically regulate neural progenitor proliferation. [ABSTRACT FROM AUTHOR]

Store-operated calcium entry (SOCE) regulates a wide variety of essential cellular functions. SOCE is mediated by STIM1 and STIM2, which sense depletion of ER Ca(2+) stores and activate Orai channels in the plasma membrane. Although the amplitude and dynamics of SOCE are considered important determinants of Ca(2+)-dependent responses, the underlying modulatory mechanisms are unclear. In this paper, we identify STIM2β, a highly conserved alternatively spliced isoform of STIM2, which, in contrast to all known STIM isoforms, is a potent inhibitor of SOCE. Although STIM2β does not by itself strongly bind Orai1, it is recruited to Orai1 channels by forming heterodimers with other STIM isoforms. Analysis of STIM2β mutants and Orai1-STIM2β chimeras suggested that it actively inhibits SOCE through a sequence-specific allosteric interaction with Orai1. Our results reveal a previously unrecognized functional flexibility in the STIM protein family by which alternative splicing creates negative and positive regulators of SOCE to shape the amplitude and dynamics of Ca(2+) signals., (© 2015 Rana et al.)

Increasing evidence suggests that alpha-chemokines serve several important functions in the nervous system, including regulation of neuroimmune responses, neurotransmission, neuronal survival, and central nervous system development. In this study, we first examined the function of two alpha-chemokines, chemokine ligand (CXCL) 6 and CXCL8, and their receptors, CXCR1 and CXCR2, in the developing rat ventral midbrain (VM). We found that CXCR2 and CXCL6 are regulated during VM development and that CXCL6 promotes the differentiation of nurr77-related receptor (Nurr1)+ precursors into dopaminergic (DA) neurons in vitro. Intriguingly, CXCL8, a ligand expressed only in Homo sapiens, enhanced progenitor cell division, neurogenesis, and tyrosine hydroxylase-positive (TH+) cell number in rodent precursor and neurosphere cultures. CXCL1, the murine ortholog of CXCL8, was developmentally regulated in the VM and exhibited activities similar but not identical to those of CXCL8. TH+ cells derived from chemokine-treated VM neurospheres coexpressed Nurr1 and VMAT and were functionally active, as shown by calcium (Ca(2+)) fluxes in response to AMPA. In conclusion, our data demonstrate that CXCL1, CXCL6, and CXCL8 increase the number of DA neurons in VM precursor and neurosphere cultures by diverse mechanisms. Thus, alpha-chemokines may find an application in the preparation of cells for drug development or Parkinson's disease cell replacement therapy.