Drebrin A is a postsynaptic protein that localizes in vivo to the submembranous surface of dendritic sites forming excitatory synapses.
Drebrin A is a neuron-specific, actin binding protein. Evidence to date is from in vitro studies, consistently supporting the involvement of drebrin A in spinogenesis and synaptogenesis. We sought to determine whether drebrin A arrives at the plasma membrane of neurons, in vivo, in time to orchestrate spinogenesis and synaptogenesis. To this end, a new antibody was used to locate drebrin A in relation to electron microscopically imaged synapses during early postnatal days. Western blotting showed that drebrin A emerges at postnatal day (PNd) 6 and becomes progressively more associated with F-actin in the pellet fraction. Light microscopy showed high concentrations of drebrin A in the synaptic layers of the hippocampus and cortex. Electron microscopy revealed that drebrin A in these regions is located exclusively in dendrites both neonatally and in adulthood. In adulthood, nearly all of the synaptic drebrin A is within spines forming asymmetric excitatory synapses, verified by gamma-aminobutyric acid (GABA) negativity. At PNd7, patches of drebrin A immunoreactivity were discretely localized to the submembranous surfaces of dendrites forming slight protrusions-protospines. The drebrin A sites exhibited only thin postsynaptic densities and lacked axonal associations or were contacted by axons that contained only a few vesicles. Yet, because of their immunoreactivity to the NR2B subunit of N-methyl-D-aspartate receptors and immunonegativity of axon terminals to GABA, these could be presumed to be nascent, excitatory synapses. Thus, drebrin A may be involved in organizing the dendritic pool of actin for the formation of spines and of axospinous excitatory synapses during early postnatal periods.
Aoki
Chiye
C
Center for Neural Science, New York University, New York, New York 10003, USA. chiye@cns.nyu.edu
Sekino
Yuko
Y
Hanamura
Kenji
K
Fujisawa
Sho
S
Mahadomrongkul
Veeravan
V
Ren
Yong
Y
Shirao
Tomoaki
T
D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western / Q000379:methods; D001921:Brain / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D003712:Dendrites / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D007150:Immunohistochemistry / Q000379:methods; D016253:Microscopy, Immunoelectron / Q000379:methods; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009479:Neuropeptides / Q000145:classification / Q000378:metabolism*; D017729:Presynaptic Terminals / Q000378:metabolism / Q000648:ultrastructure; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
C121001:NR2B NMDA receptor; D009479:Neuropeptides; D020033:Protein Isoforms; D016194:Receptors, N-Methyl-D-Aspartate; C053386:drebrins; D005680:gamma-Aminobutyric Acid