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  • Intracellular trafficking of KA2 kainate receptors mediated by interactions with coatomer protein complex I (COPI) and 14-3-3 chaperone systems. 16595684

    Assembly and trafficking of neurotransmitter receptors are processes contingent upon interactions between intracellular chaperone systems and discrete determinants in the receptor proteins. Kainate receptor subunits, which form ionotropic glutamate receptors with diverse roles in the central nervous system, contain a variety of trafficking determinants that promote either membrane expression or intracellular sequestration. In this report, we identify the coatomer protein complex I (COPI) vesicle coat as a critical mechanism for retention of the kainate receptor subunit KA2 in the endoplasmic reticulum. COPI subunits immunoprecipitated with KA2 subunits from both cerebellum and COS-7 cells, and beta-COP protein interacted directly with immobilized KA2 peptides containing the arginine-rich retention/retrieval determinant. Association between COPI proteins and KA2 subunits was significantly reduced upon alanine substitution of this signal in the cytoplasmic tail of KA2. Temperature-sensitive degradation of COPI complex proteins was correlated with an increase in plasma membrane localization of the homologous KA2 receptor. Assembly of heteromeric GluR6a/KA2 receptors markedly reduced association of KA2 and COPI. Finally, the reduction in COPI binding was correlated with an increased association with 14-3-3 proteins, which mediate forward trafficking of other integral signaling proteins. These interactions therefore represent a critical early checkpoint for biosynthesis of functional KARs.
    Document Type:
    Reference
    Product Catalog Number:
    06-315
    Product Catalog Name:
    Anti-KA2/GRIK5 (Kainate Receptor) Antibody

  • Functional cooperation between KA2 and GluR6 subunits is involved in the ischemic brain injury. 17639597

    We investigated the possible relationships between KA2 subunit and GluR6 subunit, as well as the role of KA2 subunit in neuronal death induced by cerebral ischemia/reperfusion. Our results indicated that intracerebroventricular infusion of KA2 antisense oligodeoxynucleotides (AS) not only knocked down the expressions of KA2 and GluR6, but also suppressed the assembly of the GluR6/KA2-PSD95-MLK3 signaling module, and inhibited JNK activation and phosphorylation of c-jun. In addition, infusion of KA2 AS increased neuronal survival in CA1 region after 5 days of reperfusion. More interestingly, we found that the combination of KA2 and GluR6 AS exerted more significant effects than when pretreated with KA2 AS or GluR6 AS alone. Our results suggest that the KA2 subunit is involved in delayed neuronal death induced by cerebral ischemia, at the same time, it is noteworthy that the functional cooperation between KA2 and GluR6 subunits plays a critical role in the ischemic brain injury by PSD95-MLK3-MKK4/7-JNK3 signal pathway.
    Document Type:
    Reference
    Product Catalog Number:
    06-315
    Product Catalog Name:
    Anti-KA2/GRIK5 (Kainate Receptor) Antibody

  • The Na+/Ca2+ exchanger-1 mediates left ventricular dysfunction in mice with chronic intermittent hypoxia. 20947716

    Chronic intermittent hypoxia (CIH) and cardiovascular dysfunction occur in patients with obstructive sleep apnea. We hypothesized that the Na(+)/Ca(2+) exchanger-1 (NCX1) mediates, at least partially, left ventricular (LV) dysfunction in CIH. Four groups of mice (N = 15-17 per group), either cardiac-specific NCX1 knockouts (KO) or wild types (WT), were exposed to either CIH or normoxia [i.e., handled controls (HC)] 10 h/day for 8 wk. As expected, myocardial expression of NCX1 was greater in WT than in KO animals, both in HC and CIH-exposed groups. In both CIH groups (WT or KO), but not the HC groups, blood pressure increased by 10% at week 1 over their baseline and remained elevated for all 8 wk, with no differences between WT and KO. LV dilation (increased diastolic and systolic dimension) and hypertrophy (increased left heart weight), along with LV dysfunction (greater end-diastolic pressure and lower ejection fraction), were observed in the WT animals compared with the KO following CIH exposure. Compared with HC, CIH exposure was associated with apoptosis (terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling and caspase-3) in WT, but not KO, mice. We conclude that myocardial NCX1 does not mediate changes in blood pressure, but is one of the mediators for LV global dysfunction and cardiomyocyte injury in CIH.
    Document Type:
    Reference
    Product Catalog Number:
    AB3516P
    Product Catalog Name:
    Anti-Sodium-Calcium Exchanger 1 Antibody

  • Ca2+/calmodulin-dependent kinase kinase alpha is expressed by monocytic cells and regulates the activation profile. 18270593

    Macrophages are capable of assuming numerous phenotypes in order to adapt to endogenous and exogenous challenges but many of the factors that regulate this process are still unknown. We report that Ca(2+)/calmodulin-dependent kinase kinase alpha (CaMKKalpha) is expressed in human monocytic cells and demonstrate that its inhibition blocks type-II monocytic cell activation and promotes classical activation. Affinity chromatography with paramagnetic beads isolated an approximately 50 kDa protein from nuclear lysates of U937 human monocytic cells activated with phorbol-12-myristate-13-acetate (PMA). This protein was identified as CaMKKalpha by mass spectrometry and Western analysis. The function of CaMKKalpha in monocyte activation was examined using the CaMKKalpha inhibitors (STO-609 and forskolin) and siRNA knockdown. Inhibition of CaMKKalpha, enhanced PMA-dependent CD86 expression and reduced CD11b expression. In addition, inhibition was associated with decreased translocation of CaMKKalpha to the nucleus. Finally, to further examine monocyte activation profiles, TNFalpha and IL-10 secretion were studied. CaMKKalpha inhibition attenuated PMA-dependent IL-10 production and enhanced TNFalpha production indicating a shift from type-II to classical monocyte activation. Taken together, these findings indicate an important new role for CaMKKalpha in the differentiation of monocytic cells.
    Document Type:
    Reference
    Product Catalog Number:
    06-182

  • A family of Ca2+-dependent activator proteins for secretion: comparative analysis of structure, expression, localization, and function. 14530279

    Ca2+-dependent activator protein for secretion (CAPS) 1 is an essential cytosolic component of the protein machinery involved in large dense-core vesicle (LDCV) exocytosis and in the secretion of a subset of neurotransmitters. In the present study, we report the identification, cloning, and comparative characterization of a second mammalian CAPS isoform, CAPS2. The structure of CAPS2 and its function in LDCV exocytosis from PC12 cells are very similar to those of CAPS1. Both isoforms are strongly expressed in neuroendocrine cells and in the brain. In subcellular fractions of the brain, both CAPS isoforms are enriched in synaptic cytosol fractions and also present on vesicular fractions. In contrast to CAPS1, which is expressed almost exclusively in brain and neuroendocrine tissues, CAPS2 is also expressed in lung, liver, and testis. Within the brain, CAPS2 expression seems to be restricted to certain brain regions and cell populations, whereas CAPS1 expression is strong in all neurons. During development, CAPS2 expression is constant between embryonic day 10 and postnatal day 60, whereas CAPS1 expression is very low before birth and increases after postnatal day 0 to reach a plateau at postnatal day 21. Light microscopic data indicate that both CAPS isoforms are specifically enriched in synaptic terminals. Ultrastructural analyses show that CAPS1 is specifically localized to glutamatergic nerve terminals. We conclude that at the functional level, CAPS2 is largely redundant with CAPS1. Differences in the spatial and temporal expression patterns of the two CAPS isoforms most likely reflect as yet unidentified subtle functional differences required in particular cell types or during a particular developmental period. The abundance of CAPS proteins in synaptic terminals indicates that they may also be important for neuronal functions that are not exclusively related to LDCV exocytosis.
    Document Type:
    Reference
    Product Catalog Number:
    LP1
    Product Catalog Name:
    VLDL, human

  • Ca2+-induced PARP-1 activation and ANF expression are coupled events in cardiomyocytes. 21635224

    The nuclear protein PARP-1 [poly(ADP-ribose) polymerase-1] is activated in cardiomyocytes exposed to hypoxia causing DNA breaks. Unlike this stress-induced PARP-1 activation, our results provide evidence for Ca(2+)-induced PARP-1 activation in contracting newborn cardiomyocytes treated with growth factors and hormones that increased their contraction rate, induced intracellular Ca(2+) mobilization and its rhythmical and transient translocation into the nucleus. Furthermore, activated PARP-1 up-regulated the activity of phosphorylated ERK (extracellular-signal-regulated kinase) in the nucleus, promoting expression of the Elk1 target gene c-fos. Up-regulation of the transcription factor c-Fos/GATA-4 promoted ANF (atrial natriuretic factor) expression. Given that expression of ANF is known to be implicated in morphological changes, growth and development of cardiomyocytes, these results outline a PARP-1-dependent signal transduction mechanism that links contraction rate and Ca(2+) mobilization with the expression of genes underlying morphological changes in cardiomyocytes.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Ca2+-independent, inhibitory effects of cyclic adenosine 5'-monophosphate on Ca2+ regulation of phosphoinositide 3-kinase C2alpha, Rho, and myosin phosphatase in vascular ... 17110524

    We have recently demonstrated in vascular smooth muscle (VSM) that membrane depolarization by high KCl induces Ca(2+)-dependent Rho activation and myosin phosphatase (MLCP) inhibition (Ca(2+)-induced Ca(2+)-sensitization) through the mechanisms involving phosphorylation of myosin-targeting protein 1 (MYPT1) and 17-kDa protein kinase C (PKC)-potentiated inhibitory protein of PP1 (CPI-17). In the present study, we investigated whether and how cAMP affected Ca(2+)-dependent MLCP inhibition by examining the effects of forskolin, cell-permeable dibutyryl cAMP (dbcAMP), and isoproterenol. Forskolin, but not its inactive analog 1,9-dideoxyforskolin, inhibited KCl-induced contraction and the 20-kDa myosin light chain (MLC) phosphorylation without inhibiting Ca(2+) mobilization in rabbit aortic VSM. dbcAMP mimicked these forskolin effects. We recently suggested that Ca(2+)-mediated Rho activation is dependent on class II alpha-isoform of phosphoinositide 3-kinase (PI3K-C2alpha). Forskolin inhibited KCl-induced stimulation of PI3K-C2alpha activity. KCl-induced membrane depolarization stimulated Rho in a manner dependent on a PI3K but not PKC and stimulated phosphorylation of MYPT1 at Thr(850) and CPI-17 at Thr(38) in manners dependent on both PI3K and Rho kinase, but not PKC. Forskolin, dbcAMP, and isoproterenol inhibited KCl-induced Rho activation and phosphorylation of MYPT1 and CPI-17. Consistent with these data, forskolin, isoproterenol, a PI3K inhibitor, or a Rho kinase inhibitor, but not a PKC inhibitor, abolished KCl-induced diphosphorylation of MLC. These observations indicate that cAMP inhibits Ca(2+)-mediated activation of the MLCP-regulating signaling pathway comprising PI3K-C2alpha, Rho, and Rho kinase in a manner independent of Ca(2+) and point to the novel mechanism of the cAMP actions in the regulation of vascular smooth muscle contraction.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Axonal localization of Ca2+-dependent activator protein for secretion 2 is critical for subcellular locality of brain-derived neurotrophic factor and neurotrophin-3 relea ... 24923991

    Ca2+-dependent activator protein for secretion 2 (CAPS2) is a protein that is essential for enhanced release of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) from cerebellar granule cells. We previously identified dex3, a rare alternative splice variant of CAPS2, which is overrepresented in patients with autism and is missing an exon 3 critical for axonal localization. We recently reported that a mouse model CAPS2Δex3/Δex3 expressing dex3 showed autistic-like behavioral phenotypes including impaired social interaction and cognition and increased anxiety in an unfamiliar environment. Here, we verified impairment in axonal, but not somato-dendritic, localization of dex3 protein in cerebellar granule cells and demonstrated cellular and physiological phenotypes in postnatal cerebellum of CAPS2Δex3/Δex3 mice. Interestingly, both BDNF and NT-3 were markedly reduced in axons of cerebellar granule cells, resulting in a significant decrease in their release. As a result, dex3 mice showed developmental deficits in dendritic arborization of Purkinje cells, vermian lobulation and fissurization, and granule cell precursor proliferation. Paired-pulse facilitation at parallel fiber-Purkinje cell synapses was also impaired. Together, our results indicate that CAPS2 plays an important role in subcellular locality (axonal vs. somato-dendritic) of enhanced BDNF and NT-3 release, which is indispensable for proper development of postnatal cerebellum.
    Document Type:
    Reference
    Product Catalog Number:
    AB1778