A large-scale examination of the protein composition of dendritic spines


View of a part of the newly reconstructed synapse. Credit: Helm et al.

Dendritic spines, small membranous protrusions that protrude from the dendrite of a brain cell, help transmit electrical signals to neurons. These thorns can have a variety of different shapes, ranging from the so-called “chubby” to “mushroom-like.”

Mushroom thorns have been found to be of key importance for the functioning of the human brain in adulthood. Instead, stupid spines are known to disappear as the brain matures and develops.

Over the past few decades, many neuroscientists have investigated the functions and structure of . However, the only protein of different types of spines is still unknown.

Researchers at Göttingen University Medical Center in Germany have recently conducted a study aimed at examining the composition of postsynaptic dendritic spines in the human brain. His article, published in Neurosciences of nature, could help explain previous experimental observations describing the response patterns of different dendritic spines.

“Most neuroscientists understand this they have the function of transmitting information from one neuron to the next, “Silvio Rizzoli, one of the researchers who conducted the study, told Medical Xpress.” The function of synapses is based on many types of proteins that need to work in synchrony. The problem is that no one knows how many of these proteins are in the synapse and how they work together. “

Rizzoli and colleagues initially set out to examine the protein composition of pre-synapses (the synapses of the parts that arise from transmitting neurons) and presented their results to an article published in Science. In his recent study appeared in Neurosciences of natureon the other hand, they analyzed the protein composition of the post-synapses (the part of the synapses that approaches the receptor neurons).

A large-scale examination of the protein composition of dendritic spines

A synapse section. Credit: Helm et al.

The general aim of his research was to obtain a quantitative understanding of the so-called synaptic machinery, as opposed to the qualitative one obtained by other works. In other words, the researchers wanted to understand how many different types of proteins are in dendritic spines (or post-synapses), rather than simply identifying what they are made of.

“In our article, we take an integrative, cultivated approach , analyzing the number of copies of proteins per neuron using quantitative biochemistry and , then the synapse copy numbers are determined using conventional epifluorescence images and finally the positions of the proteins are analyzed by high-resolution STED microscopy, “Rizzoli explained.” The 3D morphology of the synapses was analyzed by electron microscopy and finally all these elements were joined by modeling. “

Previous neuroscience studies assumed that the composition and structural organization of small, plump, transient synapses and large, mushroom-like permanent synapses would be different. Interestingly, however, analyzes by Rizzoli and colleagues showed that plump, mushroom-like synapses have virtually identical organization, with an average number of copies and topologies of similar proteins.

A more detailed analysis of the correlation of each protein with postsynaptic density mass, suggested that mushroom-like spines had greater synaptic strength. In other words, plump dendritic spines appeared to be less likely to respond adequately to dynamic changes in synaptic transmission than mushroom-like spines.

The findings of this team of researchers could have several important implications. For example, they could explain in part why plump dendritic spines are transient and disappear as the human brain develops, while mushroom-like spines are permanent and play a key role in adult functioning. .

“We are now working on a similar topic composition model for an entire cell (neuron), ”Rizzoli said.

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More information:
Large-scale analysis of nanoscopy and biochemistry of postsynaptic dendritic spines. Neurosciences of nature(2021). DOI: 10.1038 / s41593-021-00874-w

The composition of isolated synaptic pimples reveals the amount of vesicle-carrying proteins. Science(2014). DOI: 10.1126 / science.1252884

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