Transport activities and expression patterns of glycine transporters 1 and 2 in the developing murine brain stem and spinal cord (original) (raw)
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The glycine transporter GLYT2 is a reliable marker for glycine-immunoreactive neurons
Molecular Brain Research, 1997
The glycine transporter GLYT2 is present in neurons of the spinal cord, the brain stem and the cerebellum. This localization is similar to that of glycine immunoreactivity, suggesting a causal relationship between GLYT2 expression and glycine distribution. In this report, we analyzed if such a relationship does exist by using neuronal cultures derived from embryonic spinal cord. GLYT2 was synthesized in a small subpopulation of neurons where it was targeted both to dendrites and to axons, being the axonal content higher than the dendritic one. At early stages in the development of cultured spinal neurons, the highest GLYT2 levels were found in the axonal growth cones. As the culture matured, immunoreactivity extended to the axonal shaft. Double-immunofluorescence experiments indicated a perfect co-localization of GLYT2 and glycine immunoreactivity in cultured neurons. Moreover, the concentration of glycine into neurons expressing GLYT2 was proportional to the concentration of the transporter. This observation was reproduced in GLYT2-transfected COS cells. These evidences indicate that the high content of glycine observed in some neurons in culture is indeed achieved by the concentrative task performed by GLYT2, and that GLYT2 can be used as a reliable marker for identification of glycine-enriched neurons. q 1997 Elsevier Science B.V.
Glycine transporters are differentially expressed among CNS cells
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1995
Glycine is the major inhibitory neurotransmitter in the spinal cord and brainstem and is also required for the activation of NMDA receptors. The extracellular concentration of this neuroactive amino acid is regulated by at least two glycine transporters (GLYT1 and GLYT2). To study the localization and properties of these proteins, sequence-specific antibodies against the cloned glycine transporters have been raised. Immunoblots show that the 50-70 kDa band corresponding to GLYT1 is expressed at the highest concentrations in the spinal cord, brainstem, diencephalon, and retina, and, in a lesser degree, to the olfactory bulb and brain hemispheres, whereas it is not detected in peripheral tissues. Pre-embedding light and electron microscopic immunocytochemistry show that GLYT1 is expressed in glial cells around both glycinergic and nonglycinergic neurons except in the retina, where it is expressed by amacrine neurons, but not by glia. The expression of a 90-110 kDa band corresponding t...
Journal of Neurochemistry, 2002
We studied by immunocytochemical localization, the glycine neurotransmitter transporter (GLYT2) in mouse brain, using polyclonal antibodies raised against recombinant N-terminus and loop fusion proteins. Western analysis and immunocytochemistry of mouse brain frozen sections revealed caudal-rostrai gradient of GLYT2 distribution with massive accumulation in the spinal cord, brainstem, and less in the cerebellum. Immunereactivity was detected in processes with varicosities but not cell bodies. A correlation was observed between the pattern we obtained and previously reported strychnine binding studies. The results indicate that GLYT2 is involved in the termination of glycine neurotransmission accompanying the glycine receptor at the classic inhibitory system in the hindbrain.
The Journal of biological chemistry, 1993
A novel glycine transporter (GLYT2) was cloned from a rat brain cDNA library. GLYT2 is about 48 and 50% homologous to the previously cloned mouse glycine transporter (GLYT1) and rat proline transporter (PROT), respectively. GLYT2 differs from GLYT1 in molecular structure, tissue specificity, and pharmacological properties. The cDNA of GLYT2 encodes for 799 amino acid residues with an extended amino-terminal peptide containing 200 amino acids before the first transmembrane domain. Potential phosphorylation sites for protein kinase C, cAMP-dependent kinase, and calmodulin-dependent kinase were identified in the amino-terminal region. GLYT2 mRNA was shown to be specifically localized in spinal cord, brain stem, and to a lesser extent in the cerebellum. In contrast, GLYT1 mRNA distribution in the brain has been found previously to be more ubiquitous. Xenopus oocytes injected with GLYT2 cRNA transport glycine with a Km of 17 microM, and the uptake of glycine is resistant to inhibition by...
Differential Properties of Two Stably Expressed Brain-Specific Glycine Transporters
Journal of Neurochemistry, 2002
Clonal cell lines stably expressing the glial glycine transporter lb (GLYT1b) and the neuronal glycine transporter 2 (GLYT2)from rat brain have been generated and used comparatively to examine their kinetics, ion dependence, and electrical properties. Differential sensitivity of the transporters to sarcosine is clearly exhibited by the clonal cell lines. GLYT2 transports glycine with higher apparent affinity than GLYT1b and is not inhibited by any assayed compound, as deduced by glycine transport assays and electrophysiological recordings. A sigmoidal Nadependence of the glycine uptake by the stable cell lines is observed, indicating the involvement of more than one Na~in the transport process. A more cooperative behavior for Naõf GLYT2 than GLYT1b is suggested. One CL is required for GLYT1b and GLYT2 transport cycles, although GLYT1 b shows three times higher affinity for this ion than GLYT2. The number of expressed transporters was sufficient to allow electrophysiological recordings of the uptake current in the two stable cell lines. GLYT2 exhibits more voltage dependence in both its glycine-evoked current and its capacitive currents recorded in the absence of substrate. Key Words: Glycine transporters-Brain-Expression.
Development of synaptic inhibition in glycine transporter 2 deficient mice
Molecular and Cellular Neuroscience, 2010
Mice deficient for the neuronal glycine transporter subtype 2 (GlyT2) die during the second postnatal week after developing neuromotor deficiencies, which resembles severe forms of human hyperekplexia. This phenotype has been attributed to a dramatic reduction in glycinergic neurotransmission. In the present study we analyzed the development of GABAergic and glycinergic synaptic transmission in GlyT2-knockout mice during early postnatal life. Anti-glycine immunohistochemistry in spinal cord and brainstem slices and whole-cell voltage-clamp recordings of glycinergic inhibitory postsynaptic currents (IPSCs) from hypoglossal motoneurons revealed strikingly reduced levels of synaptic glycine already at birth. Since GABA and glycine use the same vesicular inhibitory amino acid transporter (VIAAT or VGAT) we also analysed GABAergic neurotransmission. No increase of GABA immunoreactivity was observed in the spinal cord and brainstem of GlyT2(-/-) mice at any stage of postnatal development. Correspondingly no up-regulation of GABAergic IPSCs was detected in GlyT2(-/-) hypoglossal motoneurons. These data suggest that in the first postnatal week, loss of the glycine transporter 2 is neither compensated by glycine de-novo synthesis nor by up-regulation of the GABAergic transmission in GlyT2(-/-) mice.
Glycine neurotransmission: Its role in development
Frontiers in Neuroscience
The accurate function of the central nervous system (CNS) depends of the consonance of multiple genetic programs and external signals during the ontogenesis. A variety of molecules including neurotransmitters, have been implied in the regulation of proliferation, survival, and cell-fate of neurons and glial cells. Among these, neurotransmitters may play a central role since functional ligand-gated ionic channel receptors have been described before the establishment of synapses. This review argues on the function of glycine during development, and show evidence indicating it regulates morphogenetic events by means of their transporters and receptors, emphasizing the role of glycinergic activity in the balance of excitatory and inhibitory signals during development. Understanding the mechanisms involved in these processes would help us to know the etiology of cognitive dysfunctions and lead to improve brain repair strategies.