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Increased risk of neurodegenerative diseases has been envisaged for air pollution exposure. On the other hand, environmental risk factors, including air pollution, have been suggested for Amyotrophic Lateral Sclerosis (ALS) pathomechanism. Therefore, the neurotoxicity of ultrafine particulate matter (PM0.1) (PM < 0.1 μm size) and its sub-20 nm nanoparticle fraction (NP20) has been investigated in motor neuronal-like cells and primary cortical neurons, mainly affected in ALS. The present data showed that PM0.1 and NP20 exposure induced endoplasmic reticulum (ER) stress, as occurred in cortex and spinal cord of ALS mice carrying G93A mutation in SOD1 gene. Furthermore, NSC-34 motor neuronal-like cells exposed to PM0.1 and NP20 shared the same proteomic profile on some apoptotic factors with motor neurons treated with the L-BMAA, a neurotoxin inducing Amyotrophic Lateral Sclerosis/Parkinson–Dementia Complex (ALS/PDC). Of note ER stress induced by PM0.1 and NP20 in motor neurons was associated to pathological changes in ER morphology and dramatic reduction of organellar Ca2+ level through the dysregulation of the Ca2+-pumps SERCA2 and SERCA3, the Ca2+-sensor STIM1, and the Ca2+-release channels RyR3 and IP3R3. Furthermore, the mechanism deputed to ER Ca2+ refilling (e.g. the so called store operated calcium entry-SOCE) and the relative currents ICRAC were also altered by PM0.1 and NP20 exposure. Additionally, these carbonaceous particles caused the exacerbation of L-BMAA-induced ER stress and Caspase-9 activation. In conclusion, this study shows that PM0.1 and NP20 induced the aberrant expression of ER proteins leading to dysmorphic ER, organellar Ca2+ dysfunction, ER stress and neurotoxicity, providing putative correlations with the neurodegenerative process occurring in ALS. [Display omitted] • Particulate matter of ultrafine size PM0.1 (PM < 0.1 μm) and its sub-20 nm fraction (the so-called nanoparticles, NP20) induced endoplasmic reticulum (ER) stress in motor neurons, a mechanism occurring in Amyotrophic Lateral Sclerosis (ALS) models. • PM0.1 and NP20 induced the aberrant expression of ER proteins leading to dysmorphic ER and organellar Ca2+ dysfunction in motor neurons, mainly affected by ALS. • PM0.1 and NP20 exacerbated neurotoxicity in motor neurons exposed to L-BMAA, a neurotoxin inducing a form of ALS called ALS/PDC. • This study provides a foundation for further research on air pollution-induced neurotoxicity and putative correlations with the neurodegenerative process of ALS. [ABSTRACT FROM AUTHOR]

• NCX2 promoter is up-regulated by CREB1, Sp1 and Sp4 in PC12 cells. • NCX2 promoter has many putative binding sites for TFs involved in neuronal development and plasticity, regulation of processes related to metabolism, cell proliferation and oncogenesis. The isoform 2 of sodium-calcium exchanger family (NCX2) is selectively expressed in neuronal and glial cells where it participates in Ca2+-clearance following neuronal depolarization, synaptic plasticity, hippocampal-dependent learning and memory consolidation processes. On the other hand, NCX2 is also involved in a neuroprotective effect following stroke. Despite the relevance of this antiporter under physiological and pathophysiological conditions, no studies have been reported on its genetic/epigenetic regulation. Therefore, we identified, cloned, and characterized a transcriptional regulatory region (R3) of rat Slc8a2 gene encoding for NCX2. In particular, R3 sequence displayed a promoter activity in PC12, SH-SY5Y and U87MG cell lines consistent with their endogenous NCX2 expression levels. On the other hand, R3 failed to induce detectable luciferase activity in BHK cell line that does not express NCX2 under control conditions. These data support the hypothesis that R3 represents the promoter region of NCX2. Moreover, among several conserved binding sequences for transcription factors identified by in-silico analysis, we evaluated the transcriptional regulation and the binding sites of Sp1, Sp4, NFkB1, GATA2 and CREB1 on R3 sequence by using site-direct mutagenesis and ChIP assays. In particular, transfection of Sp1, Sp4, and CREB1 enhanced both R3 promoter activity and NCX2 transcription in PC12 cell line. More important, CREB1 transfection also enhanced NCX2 protein levels and NCX reverse mode activity in PC12 cells. Altogether, these data suggested that: (i) the identified region contained the regulatory promoter of the antiporter; (ii) NCX2 might represent a downstream effector of transcription factors involved in synaptic plasticity and neuronal survival. [Display omitted] [ABSTRACT FROM AUTHOR]

• Na+/Ca2+ exchanger 1 (NCX1) activity is modulated by STIM1 in cortical neurons • NCX1 is recruited by STIM1 to take part in neuronal SOCE • TRPC6 is recruited by STIM1 in primary cortical neurons • Thapsigargin-mediated activation of TRPC6 produces a Na+ gradient useful for NCX1 reverse mode activation Excessive calcium (Ca2+) release from the endoplasmic reticulum (ER) represents an important hallmark of several neurodegenerative diseases. ER is recharged from Ca2+ through the so-called Store-Operated Calcium Entry (SOCE) thus providing Ca2+ signals to regulate critical cell functions. Single transmembrane-spanning domain protein stromal interacting molecule 1 (STIM1), mainly residing in the ER, and plasmalemmal channel Orai1 represent the SOCE key components at neuronal level. However, many other proteins participate to ER Ca2+ refilling including the Na+/Ca2+ exchanger isoform 1 (NCX1), whose regulation by ER remains unknown. In this study, we tested the possibility that neuronal NCX1 may take part to SOCE through the interaction with STIM1. In rat primary cortical neurons and in nerve growth factor (NGF)-differentiated PC12 cells NCX1 knocking down by siRNA strategy significantly prevented SOCE as well as SOCE pharmacological inhibition by SKF-96365 and 2-APB. A significant reduction of SOCE was recorded also in synaptosomes from ncx1−/− mice brain compared with ncx1+/+ mice. Double labeling confocal experiments showed a large co-localization between NCX1 and STIM1 in rat primary cortical neurons. Accordingly, NCX1 and STIM1 co-immunoprecipitated and functionally interacted each other during ischemic preconditioning, a phenomenon inducing ischemic tolerance. However, STIM1 knocking down reduced NCX1 activity recorded by either patch-clamp electrophysiology or Fura-2 single-cell microfluorimetry. Furthermore, canonical transient receptor potential channel 6 (TRPC6) was identified as the mechanism mediating local increase of sodium (Na+) useful to drive NCX1 reverse mode and, therefore, NCX1-mediated Ca2+ refilling. In fact, TRPC6 not only interacted with STIM1, as shown by the co-localization and co-immunoprecipitation with the ER Ca2+ sensor, but it also mediated 1,3-Benzenedicarboxylic acid, 4,4′-[1,4,10-trioxa-7,13-diazacyclopentadecane-7,13-diylbis(5-methoxy-6,12-benzofurandiyl)]bis-, tetrakis[(acetyloxy)methyl] ester (SBFI)-monitored Na+ increase elicited by thapsigargin in primary cortical neurons. Accordingly, efficient TRPC6 knockdown prevented thapsigargin-induced intracellular Na+ elevation and SOCE. Collectively, we identify NCX1 as a new partner of STIM1 in mediating SOCE, whose activation in the reverse mode may be facilitated by the local increase of Na+ concentration due to the interaction between STIM1 and TRPC6 in primary cortical neurons. [Display omitted] [ABSTRACT FROM AUTHOR]

Schematic representation of the most important channels, receptors, pumps and exchangers localized on plasma membrane, ER, mitochondria and nucleus that are responsible for the maintenance of intracellular Ca2+ ions in a physiological range of concentration. • Nuclear calcium (Ca2+) concentration is controlled independently from cytosolic events by a local machinery. • Nuclear Na+/Ca2+ exchanger (nuNCX) allows local Ca2+ flowing from nucleoplasm into nuclear envelope. • nuNCX shares some relevant regulatory features with the plasma membrane form of the exchanger. • nuNCX controls the activity of NFAT, CREB and DREAM through the modulation of nuclear Ca2+ level. • nuNCX controls neuronal differentiation through PTEN/Akt pathway and other cellular functions. Numerous lines of evidence indicate that nuclear calcium concentration ([Ca2+] n) may be controlled independently from cytosolic events by a local machinery. In particular, the perinuclear space between the inner nuclear membrane (INM) and the outer nuclear membrane (ONM) of the nuclear envelope (NE) likely serves as an intracellular store for Ca2+ ions. Since ONM is contiguous with the endoplasmic reticulum (ER), the perinuclear space is adjacent to the lumen of ER thus allowing a direct exchange of ions and factors between the two organelles. Moreover, INM and ONM are fused at the nuclear pore complex (NPC), which provides the only direct passageway between the nucleoplasm and cytoplasm. However, due to the presence of ion channels, exchangers and transporters, it has been generally accepted that nuclear ion fluxes may occur across ONM and INM. Within the INM, the Na+/Ca2+ exchanger (NCX) isoform 1 seems to play an important role in handling Ca2+ through the different nuclear compartments. Particularly, nuclear NCX preferentially allows local Ca2+ flowing from nucleoplasm into NE lumen thanks to the Na+ gradient created by the juxtaposed Na+/K+-ATPase. Such transfer reduces abnormal elevation of [Ca2+] n within the nucleoplasm thus modulating specific transductional pathways and providing a protective mechanism against cell death. Despite very few studies on this issue, here we discuss those making major contribution to the field, also addressing the pathophysiological implication of nuclear NCX malfunction. [ABSTRACT FROM AUTHOR]