Symposia
Perineuronal nets and neuroregulation／ペリニューロナルネットによる神経制御 |
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| 2S9-1
Regulation of glutamatergic transmission by hyaluronan
Mariko K Hayashi1,2，Kaoru Sato2
1Int. Univ. Health Welfare，2Nat.Inst.Health Sci.
As we grow beyond the critical period, synaptic connections are stabilized. Perineuronal nets are dense extracellular matrix structures with hyaluronan at their backbone. The perineuronal nets appear around the end of the critical period and limits the neuronal plasticity. Despite the importance of the perineuronal nets in brain maturation, little was known about how they affect synaptic transmission. Here we show that hyaluronan synthesis supports clearance of glutamate by glutamate transporters to turn off the excitatory neurotransmission. Hyaluronidase treatment reversibly suppressed the glutamate transporter activity and caused their retraction from cellular processes. The glutamate transporter interacts with a hyaluronan synthase, which synthesizes, secretes and anchors hyaluronan to the plasma membrane. Knockout studies of all three subtypes of hyaluronan synthases proved their requirement for activity and localization of the glutamate transporter. Furthermore, hyaluronidase stimulated glutamatergic neurotransmission, and caused neuronal damage due to glutamate excitotoxicity. Taken together, hyaluronan at the backbone of perineuronal nets supports glutamate clearance to restrict expansion of excitatory signals. | | 2S9-2
Chondroitin sulfation is relevant to perineuronal net formation and temporal lobe epilepsy
Hiroshi Kitagawa
Dept Biochem. Kobe Pharmaceutical Univ.
Chondroitin sulfate proteoglycans (CSPGs) are predominant components of the extracellular matrix in the central nervous system (CNS). Previously, we found an increase in the 4-sulfation/6-sulfation (4S/6S) ratio of CSPGs is required for perineuronal net (PNN) formation and results in functional maturation of parvalbumin-expressing interneurons (PV cells) and termination of the critical period in the visual cortex (1). However, the mechanism of PNN formation regulated by CS sulfation remains unknown. Here we found that overexpression of chondroitin 6-sulfotransferase-1 (C6ST-1), which catalyzes 6-sulfation of CS chains, selectively decreased aggrecan, a major CSPG in PNNs, in the aged brain without affecting other PNN components. In addition, we found that increased 6-sulfation accelerated proteolysis of aggrecan by a disintegrin and metalloproteinase domain with thrombospondin motif (ADAMTS) protease (2). Moreover, chondroitin 6-sulfation and chondroitin 6-sulfation-enriched PNNs increased in the mouse cerebral cortex after kainic acid (KA) treatment; simultaneously, chondroitin 4-sulfation-enriched PNNs and the 4S/6S ratio decreased. Furthermore, C6ST-1 transgenic mice, which overexpress chondroitin 6-sulfated chains and have a decreased 4S/6S ratio, were more susceptible to KA-induced seizures than wild-type mice (3). These results suggested that chondroitin 6-sulfation is relevant to epilepsy most probably because of dysregulated PNN formation and PV cell maturation. References1.Miyata, S. et al. (2012) Nature Neurosci. 15, 414-422.2. Miyata, S. and Kitagawa, H. (2016) Neural Plasticity, 2016, 1305801.3. Yutsudo, N. and Kitagawa, H. (2015) Exp. Neurol. 274, 126-133. | | 2S9-3
Chondroitin Sulfate Is Required for Critical Period Plasticity in Visual Cortex
Sayaka Sugiyama
Lab of Neuronal Dev, Grad Sch Med Dent Sci, Niigata Univ
Ocular dominance plasticity is easily observed during the critical period in early postnatal life. Inputs from the two eyes first converge in the primary visual cortex, where competitive interactions determine which eye will eventually dominate both functionally and anatomically. Chondroitin sulfate (CS) is the most abundant component in extracellular structures called perineuronal nets (PNNs), which surround parvalbumin-expressing interneurons (PV-cells). CS accumulates in PNNs at the critical period, but its function in earlier life is unclear. Here, we show that initiation of ocular dominance plasticity was impaired with reduced CS, using mice lacking a key CS-synthesizing enzyme, CSGalNAcT1. Two-photon in vivo imaging showed a weaker visual response of PV-cells with reduced CS compared to wild-type mice. Plasticity onset was restored by a homeoprotein Otx2, which binds the major CS-proteoglycan aggrecan and promotes its further expression. Continuous CS accumulation together with Otx2 contributed bidirectionally to both onset and offset of plasticity, and was substituted by diazepam, which enhances GABA function. Therefore, CS and Otx2 may act as common inducers of both onset and offset of the critical period by promoting PV-cell function throughout the lifetime. | | 2S9-4
New insights into the heterogeneity of perineuronal nets and GABAergic neurons in the hippocampus
Shozo Jinno
Dept Anat Neurosci, Grad Sch Med Sci, Kyushu Univ
The perineuronal net (PNN), a specialized aggregate of the extracellular matrix, is considered to play an important role in regulation of neuronal plasticity. Since the late 1980s, a number of studies have documented that perineuronal nets (PNNs) are closely associated with parvalbumin-positive (PV+) GABAergic neurons. However, most studies have not taken into account the fact that not only PNNs but also PV+ GABAergic neurons are heterogeneous. We thus have engaged in the research of PNNs and PV+ GABAergic neurons in the hippocampus from the viewpoint of their heterogeneity, and have obtained several novel findings. First, the vast majority of PV+ basket cells were surrounded with Wisteria floribunda agglutinin-positive (WFA+) PNNs while PV+ axo-axonic cells, oriens-lacunosum-moleculare (O-LM) cells, and hippocampo-septal projection (H-S) cells were rarely enwrapped by WFA+ PNNs. By contrast, the majority of PV+ O-LM cells and H-S cells were enwrapped with aggrecan+ PNNs. These findings indicate that the molecular composition of PNNs in the hippocampus may differ in a subclass-specific manner. Next, the densities of GABAergic synapses were higher around PV+ bistratified cells enwrapped with aggrecan+ PNNs than around those without aggrecan+ PNNs. We thus have hypothesized that PNNs may affect the synaptic formation around PV+ GABAergic neurons in the hippocampus. Finally, the expression levels of Cat-315 epitope, human natural killer-1 glycan on aggrecan-based PNNs, were increased during normal brain ageing, and an open-channel blocker of NMDA receptor, memantine, counteracted the age-related changes in Cat-315 epitope. I will show the results of our ongoing projects at the symposium, and discuss the future direction of PNN research. | | 2S9-5
In vivo regulation of chondroitin sulfate gene to recovery from spinal cord injury and brain infarction.
Kosei Takeuchi
Dept CellBiol. Aichi Medical Univ.
Injured adult neurons in the mammalian central nervous system (CNS) rarely regenerate, because some of the intracellular and cell-surface environmental factors inhibit axon regrowth. Chondroitin sulfate (CS) is the most abundant and potent exogenous inhibitor of axonal regeneration. CS degradation induces some of the axonal regrowth following spinal cord injury by treatment of chondroitinase ABC (ChABC). We generated null (KO) mice of CSGalNAcT1, a key enzyme in CS biosynthesis. We show that KO mice recovered much faster and more completely from induced SCI than do wild-type mice and even ChABC treatment mice. Cerebral Infarct volumes of CSGalNAcT1 KO mice were smaller than those of WT in mice subjected to cerebral artery ligation. Our results show that reduction of CS synthesis by the controlling the CSGalNAcT1-expression is a best strategy for spinal cord injury and stroke treatment. We try to establish the accurate inhibition systems of CS-expressions in vivo from the drug screening system (small molecule compound) and siRNA and antisense oligo study, to regulate of the CSGalNAcT1-expression in the injury area. We selected the many kinds of drugs to regulate the CS-expressions and siRNAs to inhibit the up-regulations of those genes. The sponge forms biomaterials impregnated with a mixture containing small molecule compounds or siRNAs was placed on the lesion area in mice suffered neural injuries. The recovery of these mice which treated with drug delivery systems reached the levels of satisfactory amelioration comparable to those of KO mice. Taken together, our results indicated that our drug and delivery system is a promising therapeutic target for treatment of the spinal cord injury and brain infarction, and many treatments of the neural damage. | | | |
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