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# System prepended metadata

title: Angiotensinogen in the brain
tags: [angiotensinogen]

---

---
title: Angiotensinogen in the brain
disqus: hackmd
---
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> Documentation [name=MrDr.Staffan]
###### tags: `angiotensinogen`

### Table of Contents
[TOC]
:::
[Top](#Table-of-Contents)



![](https://hackmd.io/_uploads/B1ZEAvWai.png)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3169127/






<br><br><br><br><br><br><br>


![](https://i.imgur.com/zdrMEQx.png)






""



Human genes:
Ace  Ace2 Agt Agtr1 Agtr2 Anpep Atp6ap2 Cma1 Cpa3 Ctsa Ctsd Ctsg Dpp3 Egfr Enpep Igf2r Klk1 Lnpep Mas1 Mme Nln Prep Ren1 Rnpep Thop1 Akr1c4 Akr1d1 Cyp11a1 Cyp11b1 Cyp11b2 Cyp17a1 Cyp21a2 Gper1 Hsd11b1 Hsd11b2 Nr3c1 Nr3c2

Mouse genes
Ace  Ace2 Agt Agtr1a Agtr1b Agtr2 Anpep Atp6ap2 Cma1 Cpa3 Ctsa Ctsd Ctsg Dpp3 Egfr Enpep Igf2r Klk1 Lnpep Mas1 Mme Nln Prep Ren1 Rnpep Thop1 ~~Akr1c4~~ Akr1d1 Cyp11a1 Cyp11b1 Cyp11b2 Cyp17a1 Cyp21a1 **Gper1** **Hsd11b1** Hsd11b2 Nr3c1 Nr3c2

![](https://i.imgur.com/0rtkUrx.png)
![](https://i.imgur.com/UTrVPLg.png)
![](https://i.imgur.com/lBJ4eYn.png)
![](https://i.imgur.com/0nGJkdP.png)


# Agt in blood

ANGPT2 // Ang2 // Angiopoietin-1


# AGT in the brain
    
    ...seems to exhibit similar properties because brain astrocytes
    produce a non-glycosylated form of AGT, which is not
    secreted and is targeted to the nucleus [18]

https://sci-hub.hkvisa.net/10.1016/j.tem.2007.05.001
Sherrod, M. et al. (2004) Nuclear localization of angiotensinogen in
astrocytes.Am. J. Physiol. Regul. Integr. Comp. Physiol.

## Agtrap
Diseases associated with AGTRAP include Childhood Astrocytic Tumor and Hypertension, Essential

Appears to be a negative regulator of type-1 angiotensin II receptor-mediated signaling by regulating receptor internalization as well as mechanism of receptor desensitization such as phosphorylation. Induces also a decrease in cell proliferation and angiotensin II-stimulated transcriptional activity

[![](https://i.imgur.com/9sL8rAz.png "Agtrap next to vessels?"=200x)](https://www.proteinatlas.org/ENSG00000177674-AGTRAP/tissue/basal+ganglia#img)


# AGT & astrocytes

2011 O’Callaghan - Regulation of angiotensinogen by angiotensin II in mouse primary astrocyte cultures
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1471-4159.2011.07406.x


1990 Intebi - Angiotensinogen production by rat astroglial cells in vitro and in vivo. 
https://sci-hub.se/10.1016/0306-4522(90)90163-X

1988 Stornetta - Astrocytes synthesize angiotensinogen in brain
https://sci-hub.se/10.1126/science.3201232.


# Angiotensinogen in the brain
![](https://i.imgur.com/VtZIfIQ.png =300x)


AGT production rises remarkably after birth and **reaches adult level within 24 hours**.[31]
1988 Gomez et al. Fetal expression of the angiotensinogen gene.

# Recent
2020 Insulin-Regulated Aminopeptidase in Women with Breast Cancer: A Role beyond the Regulation of Oxytocin and Vasopressin
https://sci-hub.se/downloads/2020-11-17/7b/10.3390@cancers12113252.pdf#view=FitH

    Ramírez-Expósito, M. J., Dueñas-Rodríguez, B., Carrera-González, M. P., Navarro-Cecilia, J., & Martínez-Martos, J. M. (2020). Insulin-Regulated Aminopeptidase in Women with Breast Cancer: A Role beyond the Regulation of Oxytocin and Vasopressin. Cancers, 12(11), 3252. doi:10.3390/cancers12113252 

2019 Contributions by the Brain Renin-Angiotensin System to Memory, Cognition, and Alzheimer’s Disease
https://dacemirror.sci-hub.se/journal-article/041abf0c79db881188a66d0d2e36be3c/wright2019.pdf#view=FitH

    Wright, J. W., & Harding, J. W. (2019). Contributions by the Brain Renin-Angiotensin System to Memory, Cognition, and Alzheimer’s Disease. Journal of Alzheimer’s Disease, 1–12. doi:10.3233/jad-181035 

# AGTIV cleaved by insulin regulated aminopeptidase IRAP?
IRAP//LNPEP/AT4 receptor.(EC 3.4.11.3)


IRAP **co-distributes with the GLUT4** transporter [84,
252 85]. IRAP has been variously identified as oxytocinase, cysteine aminopeptidase, placental leucine aminopeptidase, gp160, and vp165 [86]. 

The key substrates acted upon by this enzyme are arginine, vasopressin and oxytocin [87].
[# Thus, IRAP inhibition by AngIV results in the **potentiation of several pro-cognitive** endogenous peptides including **arginine** **vasopressin**, **oxytocin**, **somatostatin** and **cholecystokinin-8 (CCK mediates satiety)** [88]

[Also see hormones](https://hackmd.io/@sholmqvist/BJpKurTBB/https%3A%2F%2Fhackmd.io%2FFOjKsFP4SYymP2GLRCIE2A#Cholecystokinin-CCK)

[#Experiment: Look if astro proximity to AVP OXY + SST + CCK are high in AGT.

# The AT4 receptor(s?).
"[I^125^]-AngIV binds at the AT4 site reversibly, saturably, and with high affinity"
no sensitivity to guanine not G-protein-linked 

Dimer - molecular weight of 160–190 kDa

This subtype is distributed within a number of brain structures with heavy concentrations in the hippocampus, nucleus basalis of Meynert, piri form cortex and neocortex, structures concerned with the mediation of cognition, learning and memory (reviewed in [83])

## IREP//LNPEP

Effect on cognition/memory retrival blocked by AT4 receptor antagonist divalinal. (but not AT1, AT2 blockers)

AT4 increase blood flow without effecting pressure.

## HGF system
Recently we have noted an interaction between AngIV-based analogs and the **hepatocyte growth factor (HGF)/Met system** with evidence suggesting that the AngIV/AT4 receptor system coincides with the HGF/Met receptor system.

[# When there is oxidative stress in the astrocyte, angiotensin gets cleaved. This release AGT, which eventually is bound/cleaved into AGTIV by AT4].

[#Hypothesis:
1. Activated brain circuits result in oxidative stress.
2. Feedback signaling to avoid "circuit-over-engagement" occur as astrocytic angiotensinogen become oxidized and subsequently bound/cleaved/released by Renin.
3. Released AGTI activates RAS system. That is Vasocontriction and reduced blood/metabolite flow. Area exposed to AGT-I show dampened cellular activity. 
4. Areas where AT4 is present give AGT-IV resulting in increased blood flow. These areas therefore maintain blood/metabolite-flow and activity.

[#Predictions:
AGT is released in regions of the brain implicated with basal functions and homeostasis. [primary neg fb = decrease metabolites]
AT4 is  expressed by cells located in circuits essential for supporting   [secondary neg. fb. = increase metabolites]

## MAS-recptors MAS1 
Increased activation of the Ang(1–7)/Mas receptor system has been shown to stimulate the release of NO from vascular endothelial and smooth muscle cells thus opposing both AngII and vasopressin-induced vasoconstriction

expressed in cortical neurons

# AGT protein
Part of renin-angiotensin-aldosteron system. RAAS.

Causes vasoconstriction. Hypertension. Increase systemic blood volume. 

Sympathetic activation. Fight/flight. 

Release of aldosteron from adrenal cortex. 

NaCl retention by kidneys. (aldosterone)

Plasma angiotensinogen levels are increased by plasma corticosteroid, estrogen, thyroid hormone, and angiotensin II levels.



# Angiotensinogen vs angiotensin
- Precursor for angiotensin-I, also functions reported separate from angI,AngII etc.
doi:10.1038/hr.2016.17

- Angiotensinogen is an α-2-globulin
    - highly mobile in alkaline or **electrically charged solutions**
- Part of serpin family, serin proteases (aka // SERPINA8)
    - irreversibly inhibit target protease. Agt has no known target.
- Inhibition of angiogenesis? https://pubmed.ncbi.nlm.nih.gov/12642015/
- Impaired blood-brain barrier function in angiotensinogen-deficient mice


> Astrocytes of angiotensinogen knockout mice had very attenuated expression of glial fibrially acidic protein and decreased laminin production in response to cold injury, and ultimately incomplete reconstitution of impaired BBB function. Although these abnormalities were rescued by administration of AII or AIV, the restoration of BBB function was not inhibited by AII type 1 and 2 receptor antagonists. These findings provide evidence that astrocytes with angiotensins are required for functional maintenance of the BBB.
https://www.nature.com/articles/nm0998_1078

2015 Angiotensinogen Exerts Effects Independent of Angiotensin II
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732917/


https://febs.onlinelibrary.wiley.com/doi/full/10.1016/S0014-5793%2898%2901145-4

## des(AgtI)AGT is involved in diet induced weight gain.
Repopulation of full-length AGT increased AngII production, blood pressure, atherosclerosis, diet-induced body weight gain and liver steatosis

repopulation of des(AngI)AGT did not affect AngII production and atherosclerosis but increased diet-induced body weight gain and liver steatosis. Suggesting the increased diet-induced body weigth depend on des(AngI)AGT itself. 

2016 Lu 

# Structure
Similar structure to other serpins. But has an elongated N-terminal. This is the part that is cleaved to produce AgtI, AgtII etc.


Angiotensinogen is an α-2-globulin

**Alpha globulins** are a group of globular proteins in plasma[1] that are highly mobile in alkaline or **electrically charged solutions**. They inhibit certain blood proteases and show significant inhibitor activity.

On the face distal to the renin-binding surface, two highly conserved regions are also present. Because of the remote location, this face is unlikely to contribute to AngI release or AGT–renin interaction



452 a.a.
Human AGT protein contains four cysteines, two of them forming Cys18-Cys138 linkage that are conserved in all species.[9,10] The crystal structure of human AGT shows that the formation of Cys18-Cys138 disulphide bridge confers a conformational change that allows access of renin to its cleavage site of AGT. It has been demonstrated that oxidative status of AGT has an impact on the rate of AGT-renin reaction.

Oxidation of angiotensinogen breaks the disulfide bond and exposes the renin cleavage-site. (ref)

Cys18-Cys138 linkage determines the accessibility of its cleavage site to renin

2X0B - Angiotensinogen in complex with renin.
Gold: Angiotensinogen
Magenta: 2-10 N-term. "AgtI"
Green: Renin
![2X0B](https://i.imgur.com/wQCeoQD.png)![](https://i.imgur.com/yzvn5ro.jpg)

http://www.rcsb.org/3d-view/2X0B/1


2016 Structure and functions of angiotensinogen
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4935807/

## M235T & obesity
Investigations of the common AGT polymorphisms have shown a significant association of M235T with obesity in female hypertensive patients in different populations,[103–105]

M235's location on the otherside of des(agtI) from the surface interacting with renin, suggests a agtI independent association.
![](https://i.imgur.com/K6PCk3y.png)


# Species specificity

Another noteworthy feature is the species specificity of AGT-renin reaction. For example, human AGT cannot be cleaved by mouse renin.

    Comparative studies on species-specific reactivity between renin and angiotensinogen. Hatae T, Takimoto E, Murakami K, Fukamizu A Mol Cell Biochem. 1994 Feb 9; 131(1):43-7.


--- 

# Peptides
### **Angiotensinogen**.
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu-Val-Ile-...

Cleaved by renin


### **Angiotensin I** cleaved of the first (N-term) amioacids. (cleaved by renin)
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe-His-Leu **|** Val-Ile-...

DRVYIHPFHL-

Cleaved by 
ace, chymase, Cathepsins, tonin, tissue plasminogen activator

<iframe style="width: 500px; height: 300px;" frameborder="0" src="https://embed.molview.org/v1/?mode=balls&cid=3081372"></iframe>

### **Angiotensin II** (active)
Asp-Arg-Val-Tyr-Ile-His-Pro-Phe **|** -His-Leu
AngII stimulate ADH/AVP/Vasopressin release from posterior.pit.
Angiotensin II increases thirst sensation (dipsogen) through the area postrema and subfornical organ of the brain
![AP](https://i.imgur.com/5uaZCaD.png =50x)![](https://i.imgur.com/rSbzhQg.png =50x)

DRVYIHPF-cut-by: 

<iframe style="width: 500px; height: 300px;" frameborder="0" src="https://embed.molview.org/v1/?mode=balls&cid=172198"></iframe>

### **Angiotensin III**
Asp **|** Arg-Val-Tyr-Ile-His-Pro-Phe
<iframe style="width: 500px; height: 300px;" frameborder="0" src="https://embed.molview.org/v1/?mode=balls&cid=3082042"></iframe>





### **Angiotensin IV** "Wide range of activities in the CNS"
Arg **|** Val-Tyr-Ile-His-Pro-Phe
AT4 site might be involved in memory acquisition and recall. 
<iframe style="width: 500px; height: 300px;" frameborder="0" src="https://embed.molview.org/v1/?mode=balls&cid=123814"></iframe>

The exact identity of AT4 receptors has not been established. 

There is evidence that the AT4 receptor is insulin-regulated aminopeptidase (IRAP).[20] 

There is also evidence that angiotensin IV interacts with the HGF system through the c-Met receptor.

# Peptidases cutting angiotensinogen

![](https://i.imgur.com/cRcKLP0.png =400x)

![](https://i.imgur.com/hISX9K9.png)

![](https://i.imgur.com/1O7mbpe.png)

CHOR express RENIN and ACE
Astrocytes express AGT.
Pericytes + vascular endothelial cells -ARTERIAL, express ACE2. 





DRVYIHP
![](https://i.imgur.com/aaz10qU.png)

## Angiotensin (1–12)
2020 https://www.sciencedirect.com/science/article/pii/S0303720720304214?via%3Dihub

DRVYIHPFHLLV-

The human sequence of the dodecapeptide angiotensin-(1–12) [N-Asp1-Arg2-Val3-Tyr4-Ile5-His6-Pro7-Phe8-His9-Leu10-Val1-Ile12-COOH]

    Studies to-date document that angiotensin II generation from angiotensin-(1–12) does not require renin participation while chymase rather than 
    angiotensin converting enzyme shows high catalytic activity in converting this tissue substrate into angiotensin II directly.




One of the recent important discoveries in RAS is the identification of the Angiotensin (1–12) peptide (Ang-(1–12)), which may serve as an alternative precursor for the production of bioactive angiotensin peptides

Both the vasoconstrictor and pressor responses to Ang-(1–12) were abolished by ACE inhibitors (ACEI) and AT1R blockers (ARBs), which suggest a renin-independent pathway for angiotensin peptides production [41,42]

In addition, compelling evidence suggests that Ang-(1–12) is a major source for local Ang-II production in the central nervous system. Endogenous neutralization of Ang-(1–12) using antibodies directed against the C-terminal end of Ang-(1–12) into a lateral cerebral ventricle of (mRen2)27 transgenic hypertensive rats prompted blood pressure reduction that was associated with a transient anti-dipsogenic behavior [44]

Central effects of Ang-(1–12) were later shown to be mediated via the Ang-II/AT1R axis in the solitary tract nucleus and hypothalamic arcuate nucleus [45,46,47].

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6617132/#:~:text=3.2.&text=Both%20the%20vasoconstrictor%20and%20pressor,production%20%5B41%2C42%5D.


![](https://i.imgur.com/38By0gM.png)







# Renin

**Ren1:**
Linnarsson: CHOR, OEC, some cortical neurons, Ependymal, NTastro(low), some myelinating oligo.

![](https://i.imgur.com/zFYQfUo.png)

# The remaining lion-part of AGT: **des(AgtI)AGT 11-452** (cleaved by renin/Ren1)

---
 Despite des(AngI)AGT being 98% of the parent protein, its biological properties and fate are largely unknown. Indeed, even fundamental questions such as the relative concentrations of intact AGT vs. des(AngI)AGT in plasma and tissues have not been determined.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4935807/
 
Angiotensinogen Exerts Effects Independent of Angiotensin II
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732917/

Model.
LDL receptor -/- fed HFD. Floxed intron 2 AGT gene (hypoAGT mice) = plasma AGT concentrations were > 90% lower compared to their wild type littermates

 HypoAGT mice had lower SBP, less atherosclerosis, and diminished body weight gain and liver steatosis

All phenotypes recapitulated in mice deficiency of AGT or pharmacological inhibition of AGT by antisense oligonucleotide (ASO) administration.

In contrast, inhibition of AGT cleavage by a renin inhibitor, aliskiren, failed to alter body weight gain and liver steatosis in LDL receptor -/- mice.


---

Structural comparisons of AGT proteins in zebrafish, mouse, rat and human revealed 4 highly conserved sequences within the des(AngI)AGT domain

2011 Molecular and Pathophysiological Features of Angiotensinogen: A Mini Review
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3291105/
maintains a typical serpin folding. The relative abundance of intact versus des(AngI) form has not been characterized. There is some evidence that des(AngI)-AGT itself has biological properties that may relate to the serpin characteristics of the protein

Possibly anti angiogenesis.

     Angiotensinogen and its cleaved derivatives inhibit angiogenesis. Célérier J, Cruz A, Lamandé N, Gasc JM, Corvol P Hypertension. 2002 Feb; 39(2):224-8.


Cathepsin D, cathepsin G, kallikrein, pepsin, tissue-plasminogen activator, tonin, and trypsin have been demonstrated to convert AGT into either AngI or AngII.[38,39,50,51]
However, most enzymes require an acidic environment (pH range 4–7) to actively catalyze AGT.[39]

Although there is no direct evidence, animal studies and in vitro experiments indicate that AGT may also play an important role in obesity in humans. Investigations of the common AGT polymorphisms have shown a significant association of M235T with obesity in female hypertensive patients in different populations,[103–105] although it failed to display any correlation in males.[106]

---



# Angiotensin in blood coagulation (fibrin etc)


Coagulation Factor XII (Hageman Factor)
Not astrocytes but indeed in cortical neurons.
The active factor XIIa participates in the initiation of blood coagulation, fibrinolysis, and the generation of bradykinin and angiotensin

F3 also in astrocytes



