Biochemistry of Drebrin and Its Binding to Actin Filaments. In: Shirao T, Sekino Y, editors. Drebrin. Tokyo: Springer Japan; 2017. pp. 37-47. [DOI: 10.1007/978-4-431-56550-5_3]

Long-term effect of neonatal antagonism of ionotropic glutamate receptors on dendritic spines and cognitive function in rats

Glutamate is the most abundant excitatory neurotransmitter in the hippocampus where mediates its actions by activating glutamate receptors. The activation of these receptors is essential for the maintenance and dynamics of dendritic spines and plasticity that correlate with learning and memory processes during neurodevelopment and adulthood. We studied in adults the effect of blocking ionotropic glutamate receptors (NMDAR, AMPAR, and KAR) functions at neonatal age (PD1-PD15) with their respective antagonists D-AP5, GYKI-53655 and UBP-302. We first evaluated memory using a new object recognition test in adults. Second, we evaluated the levels of glial fibrillary acidic protein, synaptophysin and actin with immunohistochemistry in the CA1, CA3, and dentate gyrus regions of the hippocampus and, finally, the number of dendritic spines and their dynamics using Golgi-Cox staining. We found that ionotropic glutamate receptor function blockade at neonatal age causes a reduction in short and long-term memory in adulthood and a reduction in the expression of synaptophysin and actin protein levels in the hippocampus regions studied. This blockade also reduced the number of dendritic spines and modified dendritic dynamics in the CA1 region. The antagonism of the three types of ionotropic glutamate receptors reduced the mushrooms and bifurcated types of spines and increased the thin spines. The number of stubby spines was reduced by D-AP5, increased by UPB-302, and not affected by GYKI-53655. Our results indicate that the blockade of neonatal ionotropic glutamate receptors produces alterations that persist until adulthood.

Microscopic Temperature Control Reveals Cooperative Regulation of Actin-Myosin Interaction by Drebrin E

Drebrin E is a regulatory protein of intracellular force produced by actomyosin complexes, that is, myosin molecular motors interacting with actin filaments. The expression level of drebrin E in nerve cells decreases as the animal grows, suggesting its pivotal but unclarified role in neuronal development. Here, by applying the microscopic heat pulse method to actomyosin motility assay, the regulatory mechanism is examined from the room temperature up to 37 °C without a thermal denaturing of proteins. We show that the inhibition of actomyosin motility by drebrin E is eliminated immediately and reversibly during heating and depends on drebrin E concentration. The direct observation of quantum dot-labeled drebrin E implies its stable binding to actin filaments during the heat-induced sliding. Our results suggest that drebrin E allosterically modifies the actin filament structure to regulate cooperatively the actomyosin activity at the maintained in vivo body temperature.

Effects of neuronal drebrin on actin dynamics

Drebrin is a key regulator of actin cytoskeleton in neuronal cells which is critical for synaptic plasticity, neuritogenesis, and neuronal migration. It is also known to orchestrate a cross-talk between actin and microtubules. Decreased level of drebrin is a hallmark of multiple neurodegenerative disorders such as Alzheimer's disease. Despite its established importance in health and disease, we still have a lot to learn about drebrin's interactome and its effects on cytoskeletal dynamics. This review aims to summarize the recently reported novel effects of drebrin on actin and its regulators. Here I will also reflect on the most recent progress made in understanding of the role of drebrin isoforms and posttranslational modifications on its functionality.