MDGAs interact selectively with neuroligin-2 but not other neuroligins to regulate inhibitory synapse development
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2013; 110 (1): 336-341
Glutamate receptor delta 1 induces preferentially inhibitory presynaptic differentiation of cortical neurons by interacting with neurexins through cerebellin precursor protein subtypes
JOURNAL OF NEUROCHEMISTRY
2012; 121 (5): 705-716
The MAM domain-containing GPI anchor proteins MDGA1 and MDGA2 are Ig superfamily adhesion molecules composed of six IG domains, a fibronectin III domain, a MAM domain, and a GPI anchor. MDGAs contribute to the radial migration and positioning of a subset of cortical neurons during early neural development. However, MDGAs continue to be expressed in postnatal brain, and their functions during postnatal neural development remain unknown. Here, we demonstrate that MDGAs specifically and with a nanomolar affinity bind to neuroligin-2, a cell-adhesion molecule of inhibitory synapses, but do not bind detectably to neuroligin-1 or neuroligin-3. We observed no cell adhesion between cells expressing neuroligin-2 and MDGA1, suggesting a cis interaction. Importantly, RNAi-mediated knockdown of MDGAs increased the abundance of inhibitory but not excitatory synapses in a neuroligin-2-dependent manner. Conversely, overexpression of MDGA1 decreased the numbers of functional inhibitory synapses. Likewise, coexpression of both MDGA1 and neuroligin-2 reduced the synaptogenic capacity of neuroligin-2 in an artificial synapse-formation assay by abolishing the ability of neuroligin-2 to form an adhesion complex with neurexins. Taken together, our data suggest that MDGAs inhibit the activity of neuroligin-2 in controlling the function of inhibitory synapses and that MDGAs do so by binding to neuroligin-2.
View details for DOI 10.1073/pnas.1219987110
View details for Web of Science ID 000313630300073
View details for PubMedID 23248271
Interleukin-1 Receptor Accessory Protein Organizes Neuronal Synaptogenesis as a Cell Adhesion Molecule
JOURNAL OF NEUROSCIENCE
2012; 32 (8): 2588-2600
Glutamate receptor (GluR) ?1 is widely expressed in the developing forebrain, whereas GluR?2 is selectively expressed in cerebellar Purkinje cells. Recently, we found that trans-synaptic interaction of postsynaptic GluR?2 and pre-synaptic neurexins (NRXNs) through cerebellin precursor protein (Cbln) 1 mediates excitatory synapse formation in the cerebellum. Thus, a question arises whether GluR?1 regulates synapse formation in the forebrain. In this study, we showed that the N-terminal domain of GluR?1 induced inhibitory presynaptic differentiation of some populations of cultured cortical neurons. When Cbln1 or Cbln2 was added to cultures, GluR?1 expressed in HEK293T cells induced preferentially inhibitory presynaptic differentiation of cultured cortical neurons. The synaptogenic activity of GluR?1 was suppressed by the addition of the extracellular domain of NRXN1? or NRXN1? containing splice segment 4. Cbln subtypes directly bound to the N-terminal domain of GluR?1. The synaptogenic activity of GluR?1 in the presence of Cbln subtypes correlated well with their binding affinities. When transfected to cortical neurons, GluR?1 stimulated inhibitory synapse formation in the presence of Cbln1 or Cbln2. These results together with differential interactions of Cbln subtypes with NRXN variants suggest that GluR?1 induces preferentially inhibitory presynaptic differentiation of cortical neurons by interacting with NRXNs containing splice segment 4 through Cbln subtypes.
View details for DOI 10.1111/j.1471-4159.2011.07631.x
View details for Web of Science ID 000303387800004
View details for PubMedID 22191730
IL-1 Receptor Accessory Protein-Like 1 Associated with Mental Retardation and Autism Mediates Synapse Formation by Trans-Synaptic Interaction with Protein Tyrosine Phosphatase delta
JOURNAL OF NEUROSCIENCE
2011; 31 (38): 13485-13499
Interleukin-1 receptor accessory protein (IL-1RAcP) is the essential component of receptor complexes mediating immune responses to interleukin-1 family cytokines. IL-1RAcP in the brain exists in two isoforms, IL-1RAcP and IL-1RAcPb, differing only in the C-terminal region. Here, we found robust synaptogenic activities of IL-1RAcP in cultured cortical neurons. Knockdown of IL-1RAcP isoforms in cultured cortical neurons suppressed synapse formation as indicated by decreases of active zone protein Bassoon puncta and dendritic protrusions. IL-1RAcP recovered the accumulation of presynaptic Bassoon puncta, while IL-1RAcPb rescued both Bassoon puncta and dendritic protrusions. Consistently, the expression of IL-1RAcP in cortical neurons enhances the accumulation of Bassoon puncta and that of IL-1RAcPb stimulated both Bassoon puncta accumulation and spinogenesis. IL-1RAcP interacted with protein tyrosine phosphatase (PTP) ? through the extracellular domain. Mini-exon peptides in the Ig-like domains of PTP? splice variants were critical for their efficient binding to IL-1RAcP. The synaptogenic activities of IL-1RAcP isoforms were diminished in cortical neurons from PTP? knock-out mice. Correspondingly, PTP? required IL-1RAcPb to induce postsynaptic differentiation. Thus, IL-1RAcPb bidirectionally regulated synapse formation of cortical neurons. Furthermore, the spine densities of cortical and hippocampal pyramidal neurons were reduced in IL-1RAcP knock-out mice lacking both isoforms. These results suggest that IL-1RAcP isoforms function as trans-synaptic cell adhesion molecules in the brain and organize synapse formation. Thus, IL-1RAcP represents an interesting molecular link between immune systems and synapse formation in the brain.
View details for DOI 10.1523/JNEUROSCI.4637-11.2012
View details for Web of Science ID 000300716600003
View details for PubMedID 22357843
Differential interactions of cerebellin precursor protein (Cbln) subtypes and neurexin variants for synapse formation of cortical neurons
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
2011; 406 (4): 627-632
Mental retardation (MR) and autism are highly heterogeneous neurodevelopmental disorders. IL-1-receptor accessory protein-like 1 (IL1RAPL1) is responsible for nonsyndromic MR and is associated with autism. Thus, the elucidation of the functional role of IL1RAPL1 will contribute to our understanding of the pathogenesis of these mental disorders. Here, we showed that knockdown of endogenous IL1RAPL1 in cultured cortical neurons suppressed the accumulation of punctate staining signals for active zone protein Bassoon and decreased the number of dendritic protrusions. Consistently, the expression of IL1RAPL1 in cultured neurons stimulated the accumulation of Bassoon and spinogenesis. The extracellular domain (ECD) of IL1RAPL1 was required and sufficient for the presynaptic differentiation-inducing activity, while both the ECD and cytoplasmic domain were essential for the spinogenic activity. Notably, the synaptogenic activity of IL1RAPL1 was specific for excitatory synapses. Furthermore, we identified presynaptic protein tyrosine phosphatase (PTP) ? as a major IL1RAPL1-ECD interacting protein by affinity chromatography. IL1RAPL1 interacted selectively with certain forms of PTP? splice variants carrying mini-exon peptides in Ig-like domains. The synaptogenic activity of IL1RAPL1 was abolished in primary neurons from PTP? knock-out mice. IL1RAPL1 showed robust synaptogenic activity in vivo when transfected into the cortical neurons of wild-type mice but not in PTP? knock-out mice. These results suggest that IL1RAPL1 mediates synapse formation through trans-synaptic interaction with PTP?. Our findings raise an intriguing possibility that the impairment of synapse formation may underlie certain forms of MR and autism as a common pathogenic pathway shared by these mental disorders.
View details for DOI 10.1523/JNEUROSCI.2136-11.2011
View details for Web of Science ID 000295083300014
View details for PubMedID 21940441
Trans-Synaptic Interaction of GluR delta 2 and Neurexin through Cbln1 Mediates Synapse Formation in the Cerebellum
2010; 141 (6): 1068-1079
Trans-synaptic interaction of postsynaptic glutamate receptor ?2 and presynaptic neurexins (NRXNs) through cerebellin precursor protein (Cbln) 1 mediates synapse formation in the cerebellum [T. Uemura, S.J. Lee, M. Yasumura, T. Takeuchi, T. Yoshida, M. Ra, R. Taguchi, K. Sakimura, M. Mishina, Cell 141 (2010) 1068-1079]. This finding raises a question whether other Cbln family members interact with NRXNs to regulate synapse formation in the forebrain. Here, we showed that Cbln1 and Cbln2 induced presynaptic differentiation of cultured cortical neurons, while Cbln4 exhibited little activity. When compared with neuroligin 1, Cbln1 and Cbln2 induced preferentially inhibitory presynaptic differentiation rather than excitatory one in cortical cultures. The synaptogenic activities of Cbln1 and Cbln2 were suppressed by the addition of the extracellular domain of NRXN1? to the cortical neuron cultures. Consistently, Cbln1 and Cbln2 showed robust binding activities to NRXN1? and three ?-NRXNs, while only weak interactions were observed between Cbln4 and NRXNs. The interactions of Cbln1, Cbln2 and Cbln4 were selective for NRXN variants containing splice segment (S) 4. Affinities for NRXNs estimated by surface plasmon resonance analysis were variable among Cbln subtypes. Cbln1 showed higher affinities to NRXNs than Cbln2, while the binding ability of Cbln4 was much lower than those of Cbln1 and Cbln2. The affinities of Cbln1 and Cbln2 were comparable between NRXN1? and NRXN1?, but those for NRXN2? and NRXN3? were lower. These results suggest that Cbln subtypes exert synaptogenic activities in cortical neurons by differentially interacting with NRXN variants containing S4.
View details for DOI 10.1016/j.bbrc.2011.02.108
View details for Web of Science ID 000289036600024
View details for PubMedID 21356198
Stabilization and activation of p53 induced by Cdk5 contributes to neuronal cell death
JOURNAL OF CELL SCIENCE
2007; 120 (13): 2259-2271
Elucidation of molecular mechanisms that regulate synapse formation is required for the understanding of neural wiring, higher brain functions, and mental disorders. Despite the wealth of in vitro information, fundamental questions about how glutamatergic synapses are formed in the mammalian brain remain unanswered. Glutamate receptor (GluR) delta2 is essential for cerebellar synapse formation in vivo. Here, we show that the N-terminal domain (NTD) of GluRdelta2 interacts with presynaptic neurexins (NRXNs) through cerebellin 1 precursor protein (Cbln1). The synaptogenic activity of GluRdelta2 is abolished in cerebellar primary cultures from Cbln1 knockout mice and is restored by recombinant Cbln1. Knockdown of NRXNs in cerebellar granule cells also hinders the synaptogenic activity of GluRdelta2. Both the NTD of GluRdelta2 and the extracellular domain of NRXN1beta suppressed the synaptogenic activity of Cbln1 in cerebellar primary cultures and in vivo. These results suggest that GluRdelta2 mediates cerebellar synapse formation by interacting with presynaptic NRXNs through Cbln1.
View details for DOI 10.1016/j.cell.2010.04.035
View details for Web of Science ID 000278618800020
View details for PubMedID 20537373
Norepinephrine activates store-operated Ca2+ entry coupled to large-conductance Ca2+-activated K+ channels in rat pinealocytes
AMERICAN JOURNAL OF PHYSIOLOGY-CELL PHYSIOLOGY
2006; 290 (4): C1060-C1066
The p53 tumor suppressor protein is a key regulator of cellular functions including responses to numerous stress signals, and triggers apoptosis in many cell types, including neurons. The major mechanisms known to regulate p53 stabilization and activation include phosphorylation and ubiquitin ligase-mediated proteasomal degradation. Cyclin-dependent kinase 5 (Cdk5), a proline-directed serine/threonine kinase, is most active in the central nervous system and plays a variety of roles in neuronal degeneration. Here, we demonstrate for the first time that Cdk5 interacts with p53 and increases its stability through posttranslational regulation, leading to accumulation of p53, particularly in the nucleus. We show that Cdk5 phosphorylates p53 on Ser15, Ser33 and Ser46 in vitro, and that increased Cdk5 activity in the nucleus mediates these phosphorylation events in response to genotoxic and oxidative stresses. Cdk5 mediates disruption of the interaction between p53 and Hdm2 (also known as Mdm2), and prevents Hdm2-induced p53 ubiquitylation and downregulation. Cdk5 additionally enhances phosphorylation-dependent binding of the p300 coactivator, inducing acetylation of p53. Cdk5-stabilized p53 protein is transcriptionally active, resulting in the induction of pro-apoptotic genes and subsequent mitochondria-mediated apoptosis in response to genotoxic or oxidative stress. Collectively, these novel findings help define the mechanisms underlying neuronal apoptosis occurring as a result of Cdk5-mediated p53 stabilization and transcriptional activation.
View details for DOI 10.1242/jcs.03468
View details for Web of Science ID 000247732100014
View details for PubMedID 17591690
Regulation of p53 by activated protein kinase C-delta during nitric oxide-induced dopaminergic cell death
JOURNAL OF BIOLOGICAL CHEMISTRY
2006; 281 (4): 2215-2224
Norepinephrine (NE) is one of the major neurotransmitters that determine melatonin production in the pineal gland. Although a substantial amount of Ca(2+) influx is triggered by NE, the Ca(2+) entry pathway and its physiological relevance have not been elucidated adequately. Herein we report that the Ca(2+) influx triggered by NE significantly regulates the protein level of serotonin N-acetyltransferase, or arylalkylamine N-acetyltransferase (AANAT), a critical enzyme in melatonin production, and is responsible for maintaining the Ca(2+) response after repetitive stimulation. Ca(2+) entry evoked by NE was dependent on PLC activation. NE evoked a substantial amount of Ca(2+) entry even after cells were treated with 1-oleoyl-2-acetyl-sn-glycerol (OAG), an analog of diacylglycerol. To the contrary, further OAG treatment after cells had been exposed to OAG did not evoke additional Ca(2+) entry. Moreover, NE failed to induce further Ca(2+) entry after the development of Ca(2+) entry induced by thapsigargin (Tg), suggesting that the pathway of Ca(2+) entry induced by NE might be identical to that of Tg. Interestingly, Ca(2+) entry evoked by NE or Tg induced membrane hyperpolarization that was reversed by iberiotoxin (IBTX), a specific inhibitor of large-conductance Ca(2+)-activated K(+) (BK) channels. Moreover, IBTX-sensitive BK current was observed during application of NE, suggesting that activation of the BK channels was responsible for the hyperpolarization. Furthermore, the activation of BK channels triggered by NE contributed to regulation of the protein level of AANAT. Collectively, these results suggest that NE triggers Ca(2+) entry coupled to BK channels and that NE-induced Ca(2+) entry is important in the regulation of AANAT.
View details for DOI 10.1152/ajpcell.00343.2005
View details for Web of Science ID 000236573300014
View details for PubMedID 16282194
Selective cell death of dopaminergic neurons in the substantia nigra is the major cause of Parkinson disease. Current evidence suggests that this cell death could be mediated by nitric oxide by-products such as nitrate and peroxynitrite. Because protein kinase C (PKC)-delta is implicated in apoptosis of various cell types, we studied its roles and activation mechanisms in nitric oxide (NO)-induced apoptosis of SN4741 dopaminergic cells. When cells were treated with sodium nitroprusside (SNP), a NO donor, endogenous PKC-delta was nitrated and activated. Immunoprecipitation revealed that p53 co-immunoprecipitated with PKC-delta and was phosphorylated at the 15th serine residue in SNP-treated cells. An in vitro kinase assay revealed that p53 was directly phosphorylated by SNP-activated PKC-delta. The p53 Ser-15 phosphorylation was suppressed in SNP-treated cells when the NO-mediated activation of PKC-delta was inhibited by rottlerin or (-)-epigallocatechin gallate. Within 3 h of p53 phosphorylation, its protein levels increased because of decreased ubiquitin-dependent proteosomal proteolysis, whereas the protein levels of MDM2, ubiquitin-protein isopeptide ligase, were down-regulated in a p53 phosphorylation-dependent fashion. Taken together, these results demonstrate that nitration-mediated activation of PKC-delta induces the phosphorylation of the Ser-15 residue in p53, which increases its protein stability, thereby contributing to the nitric oxide-mediated apoptosis-like cell death pathway. These findings may be expanded to provide new insight into the cellular mechanisms of Parkinson disease.
View details for DOI 10.1074/jbc.M509509200
View details for Web of Science ID 000234760400045
View details for PubMedID 16314418