Pre

Question 1

So, what is the role of IRAP ?

Answer 1

Insulin-regulated aminopeptidase (IRAP) also as ,AT4 receptor is a type II transmembrane Zinc-protease that belongs to the M1 family of aminopeptidases.
IRAP is well expressed in several tissues such as skeletal muscle, heart, kidney, lung, white and brown adipose tissues.
IRAP has an extracellular C-terminal domain which contains the catalytic domain that degrades a number of extracellular signalling peptides through the removal of the N-terminal amino acid. Proposed substrates include oxytocin, vasopressin, angiotensin III, Met-enkephalin, dynorphin A, neurokinin A, neuromedin B, somatostatin, and CCK-8,

The cytoplasmic N-terminal domain possesses trafficking motifs that is important in regulating the movement of IRAP.

IRAP is inhibited by angiotensin IV.

These central and peripheral effects of Ang IV include
Facilitation of memory in rodent behaviour models
Increase of renal blood flow that was blocked by the putative AT4 antagonist divalinal-Ang IV
Protection against cerebral ischemia

Question 2

Why targeting IRAP ?

Answer 2

Preliminary data from the preclinical model of CKD and CVD has shown that the expression of IRAP significantly increased in the disease state. And there is a positive correlation between the expression of IRAP gene and fibrosis.
Moreover, the knockout of IRAP in mice has a protective phenotype against age induced fibrosis in 2-year-old mice.
These findings show that inhibiting IRAP can be an effective treatment in reducing fibrosis and inflammation in CDK.

Question 3

So why is there a need to develop IRAP inhibitors ?

Answer 3

Let’s first look at the two IRAP inhibitors available
Angiotensin IV with ki value of 62 nM is the endogenous inhibitor of IRAP. It has Vaso protective effects and atheroprotective effects in mice and improves learning and memory in rats. However, it has a short half-life (low metabolic stability) and reduced selectivity in higher concentration.

The other competitive inhobator of IRAP is HFI-419 with Ki value of 0.48 micromoler.
It
•Improved cognition and spatial working memory in mice
•Good selectivity towards aminopeptidase
•Good potency
•Good metabolic stability as compared to Ang IV

However, it has
-Poor solubility
- Need to be dissolved in DMSO
-Poor oral bioavailability 
-Poor metabolic stability 
Hence there is a need for development of a new IRAP inhibitor 
 New IRAP inhibitor needs to: 

•Be more soluble 
 Target = 50 μM
•Have higher permeability 
 Target = logPeff > -5.5
•Be more potent 
•Target = IC50 < 50 nM

Question 4

Hypothesis and aim

Answer 4

Hypothesis

To identify an NCE that significantly inhibits IRAP activity and demonstrates an antifibrotic and anti-inflammatory effect in an experimental kidney disease model.

Aim
We propose three main aims for our research project. First, we hope to…
1. To investigate the inhibitory effects of different NCEs on IRAP enzymatic activity.

We will then look at the localisation patterns of IRAP…

2. To determine whether there is any change in IRAP cellular location in vitro in the presence of inflammatory markers, and whether this is affected by the presence of a novel IRAP inhibitor.

Finally, we hope…

3. To determine whether chronic IRAP inhibition has efficacy in treating unilateral urethral obstruction -induced kidney inflammation and fibrosis in vivo.