Transient Association of the HNK‐1 Epitope with 5′‐Nucleotidase during Development of the Cat Visual Cortex

Abstract

During early postnatal development of the kitten visual cortex the ectoenzyme 5'-nucleotidase undergoes a characteristic redistribution. Until about postnatal week 6 it is essentially confined to synaptic contacts in input layer IV and its expression is related to the use-dependent segregation of thalamic afferents into ocular dominance columns. Subsequently, 5'-nucleotidase becomes distributed uniformly throughout all layers and is then associated selectively with glial cells. Here we describe an age-dependent alteration in the expression of a carbohydrate epitope of 5'-nucleotidase which correlates with the developmental change of the enzyme's localization. We have isolated 5'-nucleotidase from the occipital cortex of kittens of varying age and from adult cats and investigated by immunoblotting the association of the HNK-1 carbohydrate epitope with the protein. 5'-Nucleotidase carries the HNK-1 epitope in kittens of 3-9 weeks but the epitope is absent from 12-week-old kittens or adult cats. Thus, the appearance of the HNK-1 epitope correlates with the transient localization of the enzyme at synapses. The HNK-1 carrying 5'-nucleotidase may be involved in synaptogenesis and use-dependent modifications of synaptic connections.

Nucleotide signaling in nervous system development

“…During this developmental phase, ecto-5′-nucleotidase is associated with synaptic contacts and shifts to a glial location only when the processes of synapse formation and remodeling have come to an end. Furthermore, the cell adhesion carbohydrate epitope HNK-1 is transiently associated with the kitten ecto-5′-nucleotidase during the period of its synaptic expression [185]. These observations support the notion that ecto-5′-nucleotidase plays a significant role in neurogenesis and in cellular contact formation within the synaptic cleft.…”

Tenascin‐R–deficient mice show structural alterations of symmetric perisomatic synapses in the CA1 region of the hippocampus

“…The decrease in the mean amplitude of evoked pIPSCs after application of HNK-1 antibodies was accompanied by an increase in the variation of the pIPSC amplitude, number of failures, and changes in frequency but not by amplitude of miniature IPSCs, suggesting that HNK-1 antibodies reduce the efficacy of evoked GABA release (Saghatelyan et al, 2000). Further, expression of the HNK-1 carbohydrate correlates with stabilization of synapses in the cat visual cortex during the early postnatal development (Vogel et al, 1993) and is involved in retinotopic map sharpening in fish (Schmidt and Schachner, 1998). Further analysis of inhibitory synapses in mutants deficient in binding partners of TN-R and of the HNK-1 carbohydrate and determination of the function of different domains in the TN-R molecule will be instrumental in characterizing the mechanisms involved in synaptogenic activity of this ECM glycoprotein.…”

Extracellular ATP Selectively Upregulates Ecto-Nucleoside Triphosphate Diphosphohydrolase 2 and Ecto-5′-Nucleotidase by Rat Cortical Astrocytes In Vitro

“…This may represent an additional mechanism for their regulation, coupling to downstream signaling pathways and integration with other signaling events. In that sense, it is of note that eN functions not only just as the enzyme converting AMP to adenosine, but also as cell adhesion molecule (CD73), implicated in cell-cell and cell-extracellular matrix interactions (Vogel et al 1993;Olmo et al 1992). Specifically, eN establishes highly specific interactions with tenascin C and several other extracellular matrix proteins (Sadej et al 2008), whereas the interactions influence cell adhesion, migration, and adenosine generation (Sadej and Skladanowski, 2012).…”