When discussing the disease itself, Sun Lien can at least interject. But when the discussion deepened into the pathogenic mechanism and special channel proteins, Sun Lien's eyes were completely blackened and he was completely confused.

Fortunately, Yuan Ping'an also had some explanations when he described it, which at least allowed Sun Lien to sit firmly in his seat, and not quickly turn on his mobile phone and start searching for various keywords.

The full name of AQP4 protein is "aquaporin 4" (AQP4), which is one of the important aquaporins in the central nervous system, which is mainly expressed in astrocytes and ependymal epithelial cells, except for a few neurons in the hippocampus, supraoptic nucleus and paraventricular nucleus.

Astrocytes are the mesenchymal cells of the nervous system, while ependymal epithelial cells are located on the surface of the walls of the ventricles and central canal of the spinal cord and are involved in constituting the choroid tissue.

In addition to participating in the regulation of water metabolism balance in the central nervous system such as cerebrospinal fluid absorption, secretion and absorption, AQP4 protein can also affect the migration of astrocytes and the healing of glial scars, affect the transmission of nerve signals, regulate the reuptake of K+ and glutamate by astrocytes, change the release of neuronal transmitters, and participate in the formation of synapses and intercellular junctions. According to the current research results, AQP4 protein is not only a key factor affecting the balance of water and electrolytes in the central nervous system, but also one of the important molecular bases that determine the structure and function of astrocytes.

In 1998, Agre discovered aquaporin 1 (AQP1) on human red blood cells, and after winning the 2003 or Chemistry Prize, the AQP family was discovered one by one. This is a good way for humans to study the molecular mechanism of water molecules passing through the phospholipid bilayer of the cell membrane, and also for the in-depth study of the structure and function of the AQP family. From the perspective of the AQP family proteins discovered so far, there are two major classification patterns. One is that all AQP proteins can be classified as water-specific and non-specific according to their operational characteristics. The other is divided into two categories: mercury-sensitive and mercury-insensitive according to whether its permeability can be inhibited by Hg2+.

AQP4 is the only highly specific aquaporin that is insensitive to mercury among all known AQP proteins, and it is also one of the most important AQP proteins in the mammalian central nervous system.

According to the current study, AQP4 is mainly expressed in astrocytes and is polarly distributed. The expression level of AQP4 on the microvascular foot plate side was about 10 times that on the non-foot plate side.

This unique and highly specific aquaporin usually exerts biological effects in the form of tetramers, which are three to four times more permeable to water than other AQP proteins, and its main physiological function is to mediate the movement of water molecules across biomembranes, maintain humoral and osmotic balance, and regulate cerebrospinal fluid formation. And in terms of pathology, it is mainly involved in the formation and elimination of cerebral edema.

The assumption proposed by Yuan Ping'an is a bold inference based on the pathological impact and polarity distribution of AQP4.

"AQP4 is not universally expressed in the brain, and the content of AQP4 cells in astrocytes and ependymal endothelial cells is significantly higher than in other regions. Yuan Ping'an explained the reason for his inference. "Except for some expression on nerve cells in the hippocampus, supraoptic nucleus, and paraventricular nucleus, there is no or low AQP4 expression in nerve cells in other regions. ”

Yuan Ping'an had already explained the results of this research before, but Sun Lien suddenly remembered something, grabbed a bound case book from the stool on the side and began to flip through it. Soon, he found what he wanted to see in it - Tang Min's intracranial hyposignal area did include the hippocampus, the supraoptic nucleus and the paraventricular nucleus. It's just that because the low-signal area is a bit too large, they didn't notice it at first.

This assumption seems to be a little bit more reliable all of a sudden.

"Moreover, the AQP4 protein also affects the migration of astrocytes, which affects the rate of brain repair. Yuan Ping'an continued, "Maybe this can explain why Tang Min had more serious sequelae after receiving a biopsy." ”

Tang Min underwent two biopsies in the frontal lobe, which is of great significance in dealing with primary movements. Sun Lien has never diverged his thinking here, and even now he feels that the inability to move his feet is a common sequelae of frontal lobe biopsy.

"You just got your hands, AQP4 protein affects the production and absorption of cerebrospinal fluid?" Sun Lien pondered here, and suddenly grasped a key point, he looked up at Yuan Ping'an and said, "Tang Min has done lateral ventricular drainage, and he also has cerebellar tonsillar herniation. This means that she must have had stubborn and severe hydrocephalus before - could it be because of the AQP4 protein?"

"This is not a possibility, and it can even be said that it is very likely. Yuan Ping'an nodded with interest, "The AQP4 protein itself is of great significance to hydrocephalus, and the intractable spontaneous hydrocephalus that cannot be explained may indeed be due to the patient's AQP4 protein problem." ”

It's been two days, and Tang Min's diagnosis finally has a seemingly reliable development direction. This sudden progress made Sun Lien even tremble with excitement. Imaging evidence, biopsy sequelae and hydrocephalus have all been explained in a unified way, which makes Yuan Ping'an's assumptions stand on the same starting line as the previous three speculations. All of them can explain Tang Min's condition, which means that the AQP4 protein-related issues have the value of being verified at this moment.

After listening to the conversation between Sun Lien and Yuan Ping'an, Professor Zhang Zhifu was silent for a while and asked, "So, what's wrong with her AQP4 protein?"

The question was like a hammer slamming into the air. Yuan Ping'an and Sun Lien, you look at me, I look at you, and only after a long time did they shake their heads together, "This...... We don't know either. ”

The AQP4 protein is a specific aquaporin that rapidly mediates the movement of water molecules into and out of cells. But what happened to this protein that caused Tang Min's current symptoms, which Sun Lien and Yuan Ping'an didn't know.

The status bar suggests that it is not so microscopic, and there seems to be no precedent for AQP4 protein to cause disease in the existing literature.

"Or there is another possibility...... "the AQP4 protein itself is not the direct cause of her illness, it is just influencing the real cause of the disease in some way." ”

This assumption is even broader. Sun Lien didn't know anything about this, while Yuan Ping'an, who knew a little more, scratched his head, "The AQP4 protein seems to be able to reduce the invasion ability of glioblastoma...... It can't be gliocytoma, right? With so many areas of mass lesions, it doesn't look like the result of reduced invasion. ”

"The assumptions are there, but your assumptions need to be refined. It takes a lot of mind and time to perfect. Professor Zhang Zhifu seems to be very interested in Yuan Ping'an's AQP4 protein theory. "But you still have to think twice about whether to refine this assumption or to prioritize other issues. After all, there is relatively ample time for research and topics, but Tang Min ...... She probably doesn't have that much time left. ”