Mitochondrial Complex I Inhibitor Rotenone Induces Apoptosis through Enhancing Mitochondrial Reactive Oxygen Species Production

References

Li, Nianyu , Kathy  Ragheb, and Gretchen  Lawler. “Mitochondrial Complex I Inhibitor Rotenone Induces Apoptosis through Enhancing Mitochondrial Reactive Oxygen Species Production.” The Journal Of Biological Chemistry 278, no. 10 (2003): 8516-8525. Accessed April 13, 2013. http://www.jbc.org/content/278/10/8516.full#sec-22

 PUBLISHED PAPER 2

Rotenone inhibits complex 1 in the electron transport chain (ETC) and has leads to the death of a number of cells. The reactive oxygen species (ROS) aids in apoptosis and the inhibiting of complex 1 by rotenone promotes the creation of ROS. Rotenone along with the increased ROS generates a similar substrate to complex 1 substrate. DNA fragmentation was able to determine that apoptosis, the release of cytochrome c and caspase is caused by rotenone. Apoptosis caused by rotenone can be stopped using antioxidants. In apoptosis, magnesium superoxide dismutase is resilient to rotenone-induced mitochondrial ROS.

 

Complex 1- 4 and ATP synthase in the ETC produces ATP as well as assist in apoptosis of the cell due to the ROS. Mitochondria discharge a number of proapoptotic regulators such as cytochrome c to the cytosol when the apoptosis process is stimulate. The regulators triggers the apoptotic process, as well as it is controlled by proteins and results in the mitochondria being the central path of apoptosis signal.

 

The significance of rotenone-induced apoptosis was determined with a tumor necrosis factor (TNF)-α which can disrupt complex 1 in ETC while other intelligences state that rotenone can inhibit cells outside the mitochondria.

 

ROS is suspected to be activated by several other molecules within the body including UV radiation. ETC produces the main supply of ROS under biological conditions and hence it is been thought that ROS formed from the mitochondria contributes to the apoptosis process. The ROS mitochondria manipulate the mitochondria functioning exclusive of the cytosol, two complexes in the ETC, complex 1 and 3 are also known to be contributors of ROS

 

From chemical determination superoxide and hydrogen peroxide was determined to be primary and secondary products and it has been noted that rotenone as well as complex b-c1 inhibitor antimycin can cause the formation of both oxides. The ROS made in the mitochondria can be altered when inhibition takes place.

Test Your Knowledge ……. TCA….

quiz-night

1. Name the enzyme found in the Kreb Cycle (TCA) that is similar to pyruvate dehydrogenase.

(A) Alpha-ketoglutarate Dehydrogenase

(B) NADH Dehydrogenase

(C) Coenzyme A

(D) Malate Dehydrogenase

(E) Fumarase

 

What is the correct order os step 1 in the Kreb Cycle

1. S-citryl CoA undergoes hydrolysis to from citrate

2. An enzyme removes a proton from the CH3 in CoA

3. This causes a strong forward reaction.

4. The negatively charged CH2 bond to the oxaloacetate carbon

 

(A) 1, 2, 3, 4

(B) 2, 1, 3, 4

(C) 3,1,4, 2,

(D) 2, 4, 1, 3

(E) 4, 2, 3, 1

 

Ah Riddle Ah Riddle Ah Ree… ETC Quiz

quiz_w1

1. Why does ATP synthase undergo conformational changes in the electron transport chain?

1. To generate ATP from ADP + P

2. To move protons from the inter-membrane to the matrix of the mitochondria

3. To move protons from the inter-membrane to the outer membrane

4. To generate ADP + P using ATP

 

(A) 1 only

(B) 1, 2,

(C) 2, 3

(D) 2, 4

(E) All of the above

 

2. Rotenone is an inhibitor that disrupts the electron transport chain complexes. Which of the complex is disrupted?

(A) Complex 1

(B) Complex 2

(C) Complex 3

(D) Complex 4

(E) ATP Synthase Complex

 

Inhibitors of ETC

Cyanide poison inhibits complex 2, cytochrome oxidase, of the electron transport chain. It binds to the Fe+++ in the hem group in complex 2 interfering with the pumping of the protons and the flow of reaction. Therefore a electrochemical gradient would not be creating hence ATP synthase would not release the ATP for the ions to move into the matrix.

Rotenone acts much like cyanide, however it inhibits complex 1. NADP Dehydrogenase.

Oligomycin  inhibits mitochondrial H+-ATP synthase by binding to the Oligomycin sensitivity-conferring protein (OSCP) at the F(o) subunits 6 and 9  which are found in the stalk of the F1F0-ATPase complex. This binding blocks the proton conductance and inhibits the synthesis of mitochondrial ATP. Therefore the electrochemical gradient would increase in the intermembrane and decrease in the matrix until the protons runs out.

2, 4 DNP is known as an uncouple as it only affects one complex. It is hydrophobic and has the ability to release protons from the inter-membrane space to the matrix by perforating the wall on the inner membrane while it is lodge in it. Therefore no energy is require for the active transport and the energy made is released tot he surroundings as heat. The ETC still works.

TCA – Link Reaction

tcae

 SUMMARY OF THE LINK REACTION

  • Two pyruvates are formed from glycolysis in the cytoplasm.
  • Most of the energy that was stored in the glucose molecule is still present in pyruvic acid.
  • When oxygen is present, pyruvate is transported to the mitochondrial matrix and more reactions take place, freeing more energy.
  • The link reaction involves oxidative decarboxylation of pyruvate: oxidative because an H+ is removed; decarboxylation because a CO2 is removed.
  • And the link reaction involves the reduction of NAD+ to NADH, and it produces acetyl coenzyme A (acetyl CoA) and CO2.
  • Net yield of 2reduced NADH per glucose
  • Pyruvate Dehydrogenase Cofactors

    • TPP: thiazolium ring adds to  carbon of pyruvate, then stabilizes the resulting carbanion by acting as an electron sink.
    •  Lipoic acid: oxidizes pyruvate to level of acetate (acetylCoA), and activates acetate as a thioester.
    • CoA-SH: activates acetate as thioester.
    • FAD: oxidizes lipoic acid.
    • NAD+ : oxidizes FAD.
 

The Kreb Cycle Made Easy

So i always despised the Kreb cycle.. soo long and tedious all those reactions and enzymes… sigh … -_-

That is until i found this……: an awesome.. description with explanatory diagrams

http://www.accessexcellence.org/RC/VL/GG/ecb/complete_citric_acid_cycle.php

The Entire Kreb Cycle 

Capture 1

The Kreb Cycle Broken into Individual Reactions

Capture 2 Capture 3 Capture 4

HINT TO REMEMBER THE MOLECULES IN ORDER

Can———-Citrate

Adam———-*cis-Aconitate

Intrigue———-Isocitrate

A———-alpha-ketoglutarate

Super———-Succinyl-CoA

Sexy———-Succinate

Foxy———-Fumarate

Mama———-Malate

Ok!———-Oxaloacetate

 

HINT TO REMEMBER THE ENZYMES IN ORDER

So———-citrate Synthetase

At———-Aconitase

Another———-Aconitase

Dance———-isocitrate Dehydrogenase

Devon———-alpha-ketoglutarate Dehydrogenase

Sipped———-Succinyl-CoA Synthetase

Down———-Succinate Dehydrogenase

Five———-Fumarase

Drinks———-malate Dehydrogenase

http://www.dbriers.com/tutorials/2011/03/how-to-memorzie-the-krebs-citric-acid-cycle/