Synaptic localization of growth‐associated protein 43 in cultured hippocampal neurons during synaptogenesis

Abstract

Growth-associated protein 43 (GAP-43), a novel axonal phosphoprotein, is originally identified as a growth-cone-specific protein of developing neurons in vitro. The expression of GAP-43 is also shown to be up-regulated concomitant with increased synaptic plasticity in the brains in vivo, but how GAP-43 is concerned with synaptic plasticity is not well understood. In the present study, therefore, we aimed to elucidate subcellular localization of GAP-43 as culture development of rat hippocampal neurons. Western blotting showed that the expression of GAP-43 in the cerebral and hippocampal tissues was prominently high at postnatal days 14 and 21 or the active period of synaptogenesis. Double-labelling immunohistochemistry with an axonal marker Tau revealed that the immunoreactivity of GAP-43 was seen throughout axons of cultured hippocampal neurons but stronger at axonal puncta of developing neurons than axonal processes. Double-labelling immunohistochemistry with presynaptic terminal markers of synapsin and synaptotagmin revealed that the immunoreactivity of GAP-43 was observed mostly at weak synapsin- and synaptotagmin-positive puncta rather than strong ones. The quantitative analysis of immunofluorescent intensity showed a clear inverse correlation between GAP-43 and either synapsin or synaptotagmin expression. These data indicate that GAP-43 is highly expressed at immature growing axonal terminals and its expression is decreased along with the maturation of synaptogenesis.

Biohybrids for spinal cord injury repair

“…Importantly, a significant preservation of the longitudinal axis orientation of the surviving neuronal fibres was found in all animals with the HA‐PLLA conduits (Figure a,b) with higher number of fibres showing an inclination degree close to 0 (horizontal plane) in comparison with the control condition. However, only the HA‐PLLA + epSPC conduit significantly enhanced the percentage of neuronal fibres expressing GAP43, a growth cone marker (Morita & Miyata, ; green; Figure c,d), indicating an activated process for axonal regrowth.…”

An N-terminal motif unique to primate tau enables differential protein–protein interactions

“…In cultured neurons, Gap43 shows synaptic localization in dependence of synaptic maturation (34). Interestingly, its synaptic localization inversely correlates with presence of synapsin/synaptotagmin during maturation of axonal synapses.…”

A Shift from a Pivotal to Supporting Role for the Growth-Associated Protein (GAP-43) in the Coordination of Axonal Structural and Functional Plasticity

“…GAP-43 is largely absent from dendrites and myelinated axons as shown by a lack of double labeling with microtubule-associated protein 2 (MAP-2) and the large neurofilament proteins (Ramakers et al, 1992 ). Double-immunohistochemical labeling in cultured hippocampal neurons shows that GAP-43 colocalizes with the axonal marker Tau with the strongest signal at axonal puncta of developing neurons (Morita and Miyata, 2013 ). During the period of neurite extension in cultured neurons, the soma shows reduced GAP-43 staining and the growing tips of the axons (i.e., growth cones) show increased, punctate GAP-43 staining (Meiri et al, 1988 ).…”