Li Dan/Liu Cong's team discovered a new therapeutic target mediating neuroinflammation caused by Parkinson's disease α-syn fibers Cell Press Conversation Scientists

Life Sciences

Life science

On September 20, 2022, the team of Professor Li Dan of Shanghai Jiao Tong University and the team of researcher Liu Cong of the Shanghai Institute of Organic Chemistry of the Chinese Academy of Sciences published a research paper entitled "Interaction of RAGE with α-synuclein fibrils mediates inflammatory response of microglia" in the journal Cell Reports of Cell Press
。 The study found that α-α syn pathological fibers induce cellular inflammatory responses by directly binding to RAGE receptor for Advanced Glycation Endproducts on the surface of microglia and reveal the molecular mechanism by
which RAGE recognizes α-syn pathological fibers.
The work offers potential new targets for the treatment of Parkinson's disease (PD) by inhibiting neuroinflammation
.
Dr.
Houfang Long and Shengnan Zhang are the first authors of this paper, and Professor Li Dan and Professor Liu Cong are the corresponding authors
.

▲Long press the picture to identify the two-dimensional code to read the original article

α-Syn fiber aggregation is the main pathological marker
of PD.
As the course of PD progresses, α-syn fibers are able to mediate their pathological spread and spread
between neurons through membrane receptors on the surface of neurons.
At the same time, α-syn fiber aggregation can induce microglial activation and inflammatory response
.
Identification and characterization of membrane receptors on microglial membranes that recognize α-syn pathological fibers and activate cellular inflammatory responses are essential
to illustrate the pathotoxicity of α-syn fibers and the molecular mechanisms of the resulting cellular inflammatory response.
RAGE receptors act as an important class of membrane receptors for microglia, recognizing and binding to many different ligands and playing a role in a
variety of diseases.
There is evidence that RAGE receptors are expressed in both the substantia nigra and frontal cortex of patients with PD, but their role in PD is unclear
.

In this context, the research team used a series of experimental methods of biochemistry, biophysics and cell biology to discover the important role of RAGE in mediating the neuroinflammation of cells triggered by α-syn fibers, and to explain the molecular mechanisms
of their interaction 。 The study found that: 1) the V-shaped domain (vRAGE) of RAGE combined with the negatively charged C-terminal enriched on the surface of the α-syn fiber, and exhibited a strong binding force at the nanoscale; 2) α-syn fibers can specifically bind to RAGE receptors on microglia; 3) RAGE receptors mediate the activation of microglia by α-syn fibers and further trigger an inflammatory response; 4) Inhibition of RAGE receptor activity can significantly weaken the inflammatory response
of microglia triggered by α-syn fibers.

Schematic
of the role of RAGE in the pathological toxicity of α-syn.

In summary, the study reported the molecular mechanism of RAGE-α-syn recognition and interaction, revealing the molecular mechanism of microglia membrane receptors triggering cellular inflammatory responses by binding to α-syn pathological fibers, and providing new strategies and targets for the inhibition of neuroinflammation by targeting the α-syn binding to microglia receptors, and then providing a new strategy and target for the treatment of PD
.
This research has been supported
by projects and funds such as the National Key R&D Program of China, the National Natural Science Foundation of China and the Shanghai Municipal Science and Technology Commission.

Interview with the author

The public account of Cell Press Cell Publishing House specially invited Dr.
Long Houfang to accept an interview on behalf of the research team and asked her to further explain
it in detail.

CellPress：

How were key RAGE receptors found on the membranes of small glia in the study?

Dr.
Houfang Long:

Our team has been based on the structure
and pathotoxicity mechanism of PD pathogenic protein α-syn pathological fiber aggregates.
In the previous study, multiple receptor-mediated molecular mechanisms of α-syn fibers propagating between cells were found on the neuronal membrane, including the LAG3 (lymphocyte-activation gene 3) receptor, and it was found that the LAG3 receptor used its surface positive charge region to bind to the negative charge at the α-syn C terminus to mediate the propagation of fibers in neurons and induce the formation
of new pathological aggregations in neurons.
The pathotoxic effects of α-Syn fiber aggregation in the pathological process of PD are diverse
.
We believe that α-syn fibers may bind to multiple receptors from different cell types, mediating their many different pathological toxicities
.
Therefore, we have been committed to discovering new membrane receptors, so as to explain and understand the pathological toxicity of α-syn fibers, and provide a more comprehensive theoretical basis and support
for the research and development of anti-PD drugs.
In this work, based on structural prediction and analysis, we found that RAGE receptors localized in microglia associated with PD have similar structural characteristics to neuronal receptor LAG3 (with an Ig folding structure and surface rich in positive charge), and that RAGE receptors themselves are closely related to
neuroinflammatory responses.
Therefore, the RAGE receptor is locked for further study
.

CellPress：

The study showed that the binding affinity of RAGE to α-syn fibers reached the nM level, while the binding to monomers was weak
.
Why is the binding affinity of RAGE so different from α-syn monomers and fibers?

Dr.
Houfang Long:

Our study shows that the binding force of RAGE to α-syn fibers is more than 50 times higher than that of α-syn monomers, whether it is a monomer or a fiber state, RAGE is bound
to the C-terminal of α-syn.
α-Syn monomer conformation presents an amorphous structure, but there is a weak long-range interaction
between its C-terminal domain and the fiber core domain.
Therefore, there is a certain self-locking effect in the monomer state, and the interaction between the fiber core domain and the C-terminal inhibits the binding
of the C-terminal to the RAGE receptor.
When α-syn monomer aggregates to form fibers, its C-terminal loses its interaction with the core region of the fibers and enriches on the fiber surface
.
Therefore, the high binding affinity of RAGE to α-syn PFF mainly comes from the negatively charged C-terminal being enriched and fully exposed to the surface of the pathological fiber, thereby enhancing the binding
to RAGE.

CellPress：

In the study, after inhibiting or knocking out RAGE receptors, the expression of cytoinflammatory factors decreased, but did not drop to normal levels, why?

Dr.
Houfang Long:

The results of this experiment suggest that the process of α-syn pathological fibers that trigger cellular inflammation is not only mediated by RAGE receptors, it is likely that there are other receptors on microglia that play a role
in them.
For example, previous studies have reported that the Toll-like receptor 2/4 (TLR2/4) plays a role
in activating microglia α-syn.
Therefore, exploring the pathological mechanism of α-syn fibers in neuroinflammation needs to be gradually deepened from multiple angles, which is a difficult and long process that requires us to work together
.

CellPress：

RAGE receptors mediate Aβ into the brain in Alzheimer's
disease.
So in PD, does RAGE have other functions or mechanisms of action?

Dr.
Houfang Long:

According to the expression of RAGE in the brain, in addition to microglia, RAGE is expressed
on both neurons and astrocytes.
Therefore, in addition to participating in the neuroinflammatory process in PD, RAGE is likely to be involved in other pathological processes, which is also the direction that needs to be further explored in the
future.

CellPress：

What work will continue in the future?

Dr.
Houfang Long:

Our work is more detailed in the study of the molecular mechanism of the direct interaction between RAGE-α-syn, but the downstream signaling pathway and in vivo research links of RAGE are relatively weak
.
Therefore, we will further explore the specific pathway mechanisms for the role of RAGE in PD, and explore and refine the work
of animal models.

About the author

Li Dan

professor

Professor and doctoral supervisor
of Bio-X Research Institute of Shanghai Jiao Tong University.
Li Dan's research group focused on protein phase separation and phase transition, developed cutting-edge technologies such as electron diffraction based on cryo-electron microscopy, spiral fiber imaging, and in-cell nuclear magnetism, and studied the atomic and molecular basis of normal physiological function of protein phase separation, and the molecular mechanism
of protein phase change aggregation leading to neurodegenerative diseases 。 He has published several corresponding author papers
in high-level journals such as Cell, Cell Research, Nature Reviews Neuroscience, Nature Communications, Nature Structural and Molecular Biology.
At present, the research group undertakes a number of national, provincial and ministerial projects
such as the National Natural Science Foundation of China and the Shanghai Municipal Science and Technology Commission.

Liu Cong

researcher

He is a researcher and doctoral supervisor
at the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Through the intersection of biological and chemical research methods and means, the molecular mechanism of pathogenic protein α-synuclein and TDP-43 in Parkinson's disease and cryophilia is studied, and small molecule inhibitors and tracers are
developed.
In recent years, nearly 50 SCI papers
have been published.
Among them, more than 30 articles have been published by (co)corresponding authors, including Cell, Nature sub-journal (10), PNAS (6), Cell Research (5), Molecular Cell, Science Advances, etc
.
He has written several review and review articles
for the Nature series, Cell, and Trends in Cell Biology.

Long Houfang

Doctoral

Ph.
D.
candidate
, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
Main research directions: 1) Pathological mechanisms of structural heterogeneity of α-Syn fibers in Parkinson's disease; 2) Receptor-mediated exploration
of α-syn pathological processes in PD.
His research achievements have been published in PNAS, Nature Communications, Cell Reports, etc
.

Zhang Shengnan

Associate Researcher

Associate Professor, Shanghai Institute of Organic Chemistry, Chinese Academy of
Sciences.
Shengnan Zhang, an associate researcher, has been engaged in the study of the
structure and function of important proteins related to human diseases.
In 2016, he joined the Interdisciplinary Research Center of Biology and Chemistry of Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences as an associate researcher, mainly developing and using a variety of biophysical and biochemical technical means, especially biomacromolecular nuclear magnetic resonance technology, to study the molecular mechanism and pathological toxicity basis
of important amyloid and chaperone interactions.
In the past five years, he has published 17 articles, including PNAS, NSMB, NC, JBC, etc
.

Relevant thesis information

The original article was published in Cell Reports, a journal owned by CellPress Cell Press.