eLife︱Xu Junyu/Wang Ziyi/Xia Jun/Luo Jianhong reveal for the first time the mechanism by which the microtubule depolymerization protein KIF2C regulates the dynamic stability of neuronal microtubules and affects cognitive behavior in mice

Written by Du Yonglan, edited by Zheng Rui, Wang Sizhen Microtubules (MTs) are cytoskeletal polymers composed of repeated stacking of microtubule subunit proteins (tubulin), which are ubiquitously expressed in eukaryotic cells
.

In the nervous system, microtubules are involved in neuronal differentiation and are an important structural basis for intracellular substance transport
.

Microtubules have dynamic stability, which is not only conducive to the rapid reorganization of microtubules to complete material transport more efficiently [1], but also involved in the development and plasticity of neuronal synaptic structures, and the formation and maintenance of memory are also affected.
The influence of dynamic microtubule changes [1-4]
.

Studies in recent years have shown that microtubule dynamic stability plays an important role in brain function and disease.
Abnormal microtubule dynamic stability has been observed in many neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease research.
phenomenon [5]
.

Studying the mechanism of microtubule dynamic stability can provide new intervention approaches and potential drug targets for the treatment of related diseases.
However, the specific functional mechanism of regulating dynamic microtubules is still unclear
.

 On February 9, 2022, Xu Junyu's team from the School of Brain Science and Brain Medicine, Zhejiang University published a research paper "KIF2C regulates synaptic plasticity and cognition in mice through dynamic microtubule depolymerization" online in eLife magazine
.

For the first time, the researchers explored the function of mitotic centromere-associated kinesin (MCAK/KIF2C) in the nervous system, and found that the microtubule depolymerization function of KIF2C was important for neuronal synaptic transmission and plasticity, as well as Regulation of cognitive deficits in memory in mice
.

In this study, the researchers found that KIF2C is enriched in the postsynaptic dense area, is stably expressed in neuronal development and maturation, and is widely distributed in various brain regions of mice
.

KIF2C regulates neuronal microtubule dynamics by exerting the function of depolymerizing microtubules, mediating synaptic invasion of microtubules and AMAP receptor membrane expression, thereby affecting synaptic plasticity and learning and memory
.

This article is the first to discover in the nervous system the microtubule depolymerization function of KIF2C in the regulation of neuronal synaptic transmission and plasticity, as well as memory and cognitive deficits in mice
.

Previous studies have shown that KIF2C can affect the dynamic stability of microtubules by consuming the energy generated by ATP hydrolysis at the end of microtubules and changing the binding conformation of tubulin to promote microtubule depolymerization [6-8]
.

Therefore KIF2C can be involved in many microtubule-dependent events, including mitosis, cilia formation,
etc.

The current research on the function of KIF2C is mainly reflected in mitotic cells, and its function in the central nervous system has not yet been found
.

According to the previous results of the researchers' previous experiments, it was found that KIF2C is likely to exist in the nervous system and participate in synaptic-related functions, so the researchers decided to systematically study KIF2C
.

 The researchers first detected the expression and localization of KIF2C in the nervous system by using primary cell culture of hippocampal neurons, western blotting and immunofluorescence staining, and found that KIF2C was stably expressed in the development and maturation of neurons and was widely distributed in mice.
various brain regions
.

The separation and extraction of mouse hippocampal tissue fractions revealed that KIF2C was enriched in the postsynaptic dense region, suggesting the possibility that KIF2C functions in synapses (Fig.
1)
.

Figure 1 Expression of KIF2C in the central nervous system (Source: Zheng Rui, et al.
, eLife, 2022) Next, the researchers constructed the KIF2C protein in kif2cflox/flox; NestinCre (cKO) mice conditionally knocked out neurons Expression levels, as observed by Golgi staining and transmission electron microscopy, abnormal KIF2C expression resulted in altered dendritic spine types in hippocampal CA1 neurons, with a significant decrease in the density of synaptic distribution in the mushroom type (mature type) and a marked decrease in the filopodia type (immature type).
increase
.

Observation of postsynaptic densities in CA1 neurons by cryo-TEM revealed that KIF2C deletion resulted in a significant reduction in the thickness and length of postsynaptic densities
.

The above results suggest that KIF2C is involved in neuronal synaptic development (Fig.
2)
.

Figure 2 Abnormal hippocampal synaptic structure in KIF2C knockout mice (Source: Zheng Rui, et al.
, eLife, 2022) The researchers examined the regulatory effect of KIF2C deletion on neuronal synaptic transmission and synaptic plasticity by electrophysiological means
.

The results showed that decreased KIF2C expression (KIF2C shRNA) or deletion (KIF2C cKO) resulted in increased amplitude of microexcitatory synaptic currents (mEPSCs), defective long-term potentiation (LTP)-induced maintenance, membrane ionotropic glutamate Increased expression of the acid receptor α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR)
.

At the same time, the researchers unexpectedly found that KIF2C exhibited activity-dependent displacement changes in dendritic spines during chemical stimulation mimicking neuronal excitability enhancement
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The above findings reveal for the first time the distribution of KIF2C in the nervous system and its important role in the maintenance of synaptic function (Fig.
3)
.

Figure 3 KIF2C knockout affects synaptic transmission and plasticity (Source: Zheng Rui, et al.
, eLife, 2022) However, does KIF2C function through the regulation of dynamic microtubules? The researchers first identified abnormal microtubule dynamics in cKO hippocampal neurons through live-cell imaging analysis.
When neuronal excitability was observed by labeling newly aggregated microtubules, the microtubules moved into dendritic spines compared to the control group.
The probability of events in
.

In order to further verify the function of KIF2C, the researchers constructed KIF2C (WT) and KIF2C (G491A) mutants lacking the depolymerization function of KIF2C respectively for compensation experiments.
The results showed that KIF2C (WT) could restore abnormal synaptic transmission and synapses.
plasticity, while KIF2C (G491A) cannot
.

This indicates that KIF2C participates in synaptic function by regulating neuronal microtubule dynamics by exerting the function of depolymerizing microtubules (Fig.
4)
.

Fig.
4 Changes in synaptic transmission and plasticity caused by abnormal MT dynamics (Source: Zheng Rui, et al.
, eLife, 2022) A behavioral paradigm examined the effect of neuronal deletion of KIF2C on behavior in mice
.

It was found that knocking out KIF2C led to cognitive learning behavioral impairment in mice
.

Re-introduction of KIF2C (WT) and mutant KIF2C (G491A) into the hippocampal neurons of cKO mice, it was found that the behavior of the mice that re-expressed KIF2C (WT) could be restored, while the mice expressing KIF2C (G491A) still had behavioral disturbances
.

In conclusion, the researchers discovered for the first time in the nervous system the microtubule depolymerization function of KIF2C in the regulation of neuronal synaptic transmission and plasticity and the cognitive deficits of memory in mice (Figure 5)
.

Figure 5 KIF2C knockout leads to memory impairment (Source: Zheng Rui, et al.
, eLife, 2022) Conclusion and discussion, inspiration and prospect of the article , revealing that the microtubule depolymerization kinesin KIF2C/MCAK plays an important role in hippocampal neuron function, synaptic transmission, and plasticity
.

The researchers found that acute knockdown or knockout of KIF2C impaired LTP expression and maintenance and increased the amplitude of miniEPSC, suggesting that KIF2C plays an important role in regulating synaptic transmission and plasticity in hippocampal neurons
.

The researchers found that the expression of surface AMPA receptors was increased by biochemical detection.
Combined with the electrophysiological results, the researchers speculated that the increased expression of ionotropic glutamate receptors, especially AMPA receptors, at synapses may lead to impaired LTP expression
.

Using live-cell imaging of KIF2C cKO hippocampal neurons to observe MT dynamics, the researchers found that KIF2C loss resulted in faster dendritic MT growth
.

At the same time, KIF2C deletion also increased the frequency of MT invasion under basal conditions, and the researchers speculated that this may be caused by the lack of MT aggregation inhibitory ability
.

MTs are also responsible for intracellular trafficking, and other members of the KIF family can transport NMDA receptors [9] and AMPA receptors [10], and previous studies have shown that MT dynamic stability modulates the postsynaptic localization and synaptic plasticity of AMPA receptors [11] , 12]
.

We speculate that KIF2C may regulate membrane receptor trafficking by regulating MT stability
.

 This study is the first to discover the important function of KIF2C in the nervous system.
By mining its mechanism of action, it is found that cellular microtubules depend on neural activity to regulate synaptic receptor transport and synaptic plasticity, thereby further participating in the higher cognitive processes of the brain
.

Research provides an updated understanding of how microtubule dynamics in the nervous system are involved in the regulation of neural function
.

In the paper, the authors propose that KIF2C regulates microtubule dynamics through the pathway of synaptic invasion of microtubules.
The study also provides evidence that KIF2C can regulate the synaptic invasion process of microtubules in a neural activity-dependent manner
.

However, this study has not yet further resolved its functional differences and consequences within dendrites and synapses, and the research group said that in the future, they will continue to focus on elucidating the regulatory mechanism of microtubule dynamics within synapses
.

Link to the original text: https://doi.
org/10.
7554/eLife.
72483 Associate Professor Xu Junyu (left), the main corresponding author; Dr.
Zheng Rui (middle), co-first author; Dr.
Du Yonglan (right), co-first author
.

(Photo courtesy of Xu Junyu's research group) Zheng Rui, a doctoral student at the School of Brain Science and Brain Medicine, Zhejiang University, and Du Yonglan, a doctoral student, are the co-first authors of this article
.

Associate Professor Xu Junyu, School of Brain Science and Brain Medicine, Zhejiang University, Dr.
Wang Ziyi, Institute of Basic Medical Innovation, Zhejiang University, Professor Xia Jun, Hong Kong University of Science and Technology, and Professor Luo Jianhong, School of Brain Science and Brain Medicine, Zhejiang University are the co-corresponding authors of this article
.

This work was supported by the National Natural Science Foundation of China (31970902, 3192010300, 32000692, 31871418, 81821091), the Natural Science Foundation of Zhejiang Province (LD19H090002, LR19H090001), the Guangdong Provincial Key Field R&D Program (2019B030335001) and the Hong Kong Research Grants Council (1610352).

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Xu Junyu's team is dedicated to the molecular mechanism of synapse formation and maturation, and its pathological mechanism in autism
.

He has published many papers in journals such as Nature Neuroscience, Neuron, and Journal of Neuroscience
.

The research group is looking for postdoctoral fellows and research assistants, please contact us! Featured in previous articles[1]Science︱Breakthrough! Single-cell atlas of normal and abnormal human cerebrovascular system【2】J Neurosci︱Guo Weixiang’s group reveals the pathological mechanism of neurometabolic disorders in type II hyperlysinemia【3】Cereb Cortex︱Cui Fang/Liu Jie/Gu Ruo Lei's group collaborated to reveal the neural mechanism of resource scarcity inhibiting prosocial behavior [4] Neuron︱Cao Gang's research group revealed a new mechanism for the nervous system to sense pathogenic infection and fine-tune immune response [5] J Neuroinflammation︱Ge Jinfang/Xia Qingrong's research group revealed the bone marrow Partial therapeutic mechanism of mesenchymal stem cell exosomes on Alzheimer's disease【6】Sci Transl Med︱GABAB receptor may rescue abnormal visual processing in patients with autism 【7】Sci Adv︱Xu Yong/Xu Jingping /He Yanlin collaborated to discover the neural circuit mechanism of estrogen receptor neurons regulating body temperature and movement 【8】PNAS︱Han Chun’s group revealed a new mechanism of neuronal degeneration caused by external phagocytosis 【9】Nat Neurosci︱VTA dopaminergic neurons are involved Coding Social Prediction Error and Social Reinforcement Learning [10] Nature︱ New discovery! Inflammatory lymphocytes or new targets mediating CNS inflammation? Recommended high-quality scientific research training courses [1] Training courses︱Scientific research drawing and academic image special training [2] Multimodal Magnetic Resonance Brain Network Analysis Introductory Course (Online: 2022.
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