TLR2 Antagonist | iGEM HUST2-China

TLR2 Antagonist

Overview

In order to validate the inhibitory effect of TLR2 antagonist on inflammation and explore the interaction between TLR2 and Lipoproteins, we established a model based on biochemical reaction equation.

Considering of complexity of the human facial cuticle internal environment , and to make the model perform the main functions, we make the following assumptions (for the whole chemical equation equilibrium modeling)

The K value is not considered to be affected by the concentration change;
The equilibrium temperature is 298.15 K under the standard conditions;
The whole equilibrium takes place in the ideal environment without considering the special conditions of the reaction.

Modeling

The result of our modeling is to verify the effect of concentration , explore the concentration relationship between TLR2, TLR2 antagonist and the conjugate (TLR2-triacylated lipoprotein,TLR2 antagonist-triacylated lipoprotein) . For explicit expression, we define:

A is triacylated lipoprotein, the initial concentration is $[A_t]$ , the triacylated lipoprotein concentration in the system is $[A]$ ;
B is TLR2, the concentration is $[B]$ ;
M is TLR2 competitive inhibitory protein ,the concentration is $[M]$ ;

Thus, we get:

Figure 1: The equilibrium

From material conservation and dissociation equilibrium, we have:

Figure 2: The equilibrium

In order to verify the idea, and more intuitive characterization of the concentration relationship, we rearranged and simplified equations.

First, consider the relationship between AB and B $$ \frac{1}{[AB]}=\frac{1}{[B]}\cdot\frac{K_d(1+{[M]}/{K_i})}{[A]_t}+\frac{1}{[A]_t} $$

Figure 3: The equilibrium

It indicates:

Triacylated lipoprotein and TLR2 binding concentration were positively correlated with TLR2 concentration, but not linearly;
The TLR2 antagonist has inhibitory effect on TLR2 binding to triacylated Lipoproteins, but the specific inhibitory intensity is not clear.

Then, we explore the relationship between AM and M, and rearrange the equations in another way:

$$ \frac{1}{[AM]}=\frac{1}{[M]}\cdot\frac{K_i(1+{[B]}/{K_d})}{[A]_t}+\frac{1}{[A]_t} $$

Among them:

$[AM]$: TLR2 antagonist protein and A (lipoprotein) conjugate concentration
$[M]$: TLR2 antagonist protein concentration

We will discuss the model later.

Further Modeling

The following is the main model we will use to discuss. $$ \frac{1}{[AB]}=\frac{1}{[B]}\cdot\frac{K_d(1+{[M]}/{K_i})}{[A]_t}+\frac{1}{[A]_t}\quad(1) $$

$$ \frac{1}{[AM]}=\frac{1}{[M]}\cdot\frac{K_i(1+{[B]}/{K_d})}{[A]_t}+\frac{1}{[A]_t}\quad(2) $$

2.1 $K_d$ & $K_i$

First, computer is used to calculate the intrinsic parameters $K_d$ and $K_i$

we use followings to discuss

$$ \Delta G=\Delta U-T\Delta S $$

$$ \Delta G=-RT\ln K $$

Notice:

When the molecules combine, the energy released is called the binding energy.

In order to consider the binding free energy, we need to consider the entropy. Since two different molecules are bound together, we can judge preliminarily that the disorder will decrease, the entropy will decrease, and the corresponding entropy energy will increase.

For the NVT system, $\Delta G=\Delta U-T\Delta S$ can be considered as one of the ways to calculate the binding free energy.

We use Discovery Studio to get the following results

Figure 4: The shape of 2 molecular

Type of protein	$\Delta G/\mathrm{kcal\cdot mol^{-1}}$	$\Delta S/\mathrm{kcal\cdot K^{-1}\cdot mol^{-1}}$
TLR2	-92.5992	22.8082
competitor	-98.1295	22.8064

From above, we can get:

$$ K_d=6.6611\times10^{-52} $$

$$ K_i=5.8652\times10^{-56} $$

2.2 Main Function

For TLR2

Respectively, when the experimental group could not provide the data. In order to investigate the relationship between TLR2 concentration and the TLR2-lipoprotein conjugate concentration, we made that:

The initial triacylated Lipoprotein concentration $[A]_t$ is 1
Fixed TLR2 antagonist concentration $[M]$ to 1

Simplify the equation (1): $$ [AB]=\frac{[B]}{[B]+K_d/K_i} $$

TLR2 and lipoprotein conjugate concentration will increase with TLR2 concentration.

Figure 5: [AB]~[B]

For TLR2 Antagonist

In order to investigate the relationship between TLR2 competitive inhibitory protein and lipoprotein conjugate concentration and TLR2 anyagonist protein concentration.

we simplified that:

The initial triacylated lipoprotein concentration $[A]_t$ is 1
Fix TLR2 concentration $[B]$ to 1

Simplify the equation (2), and get:

$$ [AM]=\frac{[M]}{[M]+K_i/K_d} $$

Figure 6: The equilibrium

As you can see:

The concentration of TLR2 antagonist protein and lipoprotein conjugate increased with the increase of TLR2 competitive inhibitor protein concentration.
The increasing speed is firstly fast and then slow;

Compared Curve 1 with Curve 2,

The competition of TLR2 protein and TLR2 antagonist protein, the latter had stronger binding ability to lipoprotein.

More Evidence

To see the effect of different initial concentration of Lipoprotein on the conjugate concentration, consider the discussion below.

Figure 7: The equilibrium

When the concentration of TLR2 antagonist is fixed at 1, with the increase of the concentration of triacylated lipoproteins, the concentration of TLR2 and lipoprotein conjugate increased significantly. Therefore, it is suspected that TLR2 antagonist have stronger binding ability than TLR2.

Figure 8: The equilibrium

When the concentration of TLR2 is fixed at 1, the curve of the concentration of the complex changing with the concentration of competition inhibitor 2 is made. It can also be seen that with the increase of the concentration of triacylated Lipoproteins, the concentration of the complex increases with the same concentration of TLR2.

Conclusion

The changes of TLR2 and its antagonist protein concentration have great effect on the process of competition binding lipoproteins;
The concentration of lipoproteins is also very important in the process of competition between the two receptor proteins;

However, the general trend still shows that antagonist can significantly inhibit the binding of TLR2 to triacylated lipoproteins at the same concentration of lipoproteins and slow down the occurrence of inflammation. The results demonstrate the effectiveness of TLR2 antagonist.

Team:HUST2-China/TLR2 Antagonist