Barker-Gibb ML, Einheber S, Milner TA (1999) Hippocampal Trk-A receptors are compartmentalized within axonal transport vesicle sites and present in select astrocytes. Neuroscience 1999 Abstracts 803.6. Society for Neuroscience, Miami, FL. PMID: 0
Summary: Trk-A is a high affinity transmembrane tyrosine kinase receptor which is activated by its ligand, nerve growth factor (NGF), to mediate cell survival and the retrograde transport of NGF by septohippocampal cholinergic neurons. To determine its subcellularlocalization, antibodies to the extracellular domain of the Trk-A receptor (Chemicon; Upstate) were localized immunocytochemically in rat dentate gyrus by light & electron microscopy (LM; EM). These antibodies recognized two bands migrating at -125 and 140 kD on immunoblots of septal and hippocampal lysates. Consistent with previous LM reports, Trk-A-immuno- reactivity (-I) with both antibodies was found in fine, varicose fibers, primarily in the hilus. However, the Chemicon antibody also labeled fibers in the granule and molecular layers (ML) as well as numerous astrocytic profiles in the external and medial zones of the ML and the superficial blade of the hilus. EM analysis of the dentate gyrus using the Chemicon antibody revealed that Trk-A-I was in axons, axon terminals and astrocytes. Trk-A-I in axons was not homogeneous, but was concentrated in patches near regions where vesicles accumulated. Trk-A-I in terminals was affiliated with clusters of small synaptic vesicles frequently located away from synaptic specializations. In both axons and axon terminals, the clusters of Trk-A-labeled vesicles often were adjacent to somatic and dendritic profiles. Trk-A-labeled astrocytes in the hilus regularly closely apposed terminals presynaptic to dendritic spines. The findings support evidence that hippocampal Trk-A receptors are compartmentalized within transport vesicle sites. Also, they suggest that astrocytes play a role in the uptake and retrograde transport of NGF by septohippocampal cholinergic neurons to support their survival. (Support: MH42834; DA 08259)
Related Products: trkA Rabbit Polyclonal (Cat. #AB-N03)