Mitochondria

What type of shape do many people considered the mitochondria to have?

“sausage-shaped” organelle

What shape does the mitochondria have?

It’s pleiotropic → has many different shapes including sausage

How many genes are in mtDNA (mitochondrial DNA)?

37

How many proteins does the genes in the mtDNA encode for?

13

How many proteins does the mitochondria have overall?

1000 - 1500

Most of the genes from the mitochondria come from…

nuclear genes

What is the number of mitochondria in the RBC?

0

What is the number of mitochondria in skin cells and fibroblasts?

200 -350

What is the number of mitochondria in heart cells?

3000 to 8000

What is the number of mitochondria in egg cells?

100,000 to 600,000

Why do egg cells have so many mitochondria?

Embryogenesis - process of embryo initiation and zygote development → multicellular organism through division, differentiation, and growth

What is the general pattern for the number of mitochondria in cells?

More energy demanding cells need more mitochondria

Mitochondria is located in cells where ___ is required.

ATP

What type of DNA does mitochondria have?

Circular

Multiple strands of DNA encode for the…

37 genes in the 13 proteins

What is mitochondria tethered to?

Microtubules

When mitochondria are tethered to the microtubule, can the mitochondria move?

Yes, it can move back and forth

←(mitochondria here)→

What are the dots inside of the mitochondria?

Calcium phosphate deposits

What is the purpose of calcium phosphate deposits?

Involved in calcium homeostasis

What wraps around the mitochondria?

ER - MAMS (mitochondrial associated membranes)

What is the purpose of MAMS (mitochondrial associated membranes)?

Regulate calcium homeostasis in cytoplasm

Why haven’t mitochondria lost all their genes?

1. All 13 proteins are very hydrophobic

2. mtDNA may be required for very quick changes in mitochondrial activity

What is heme?

protein in the electron transport chain

What pathway does heme follow?

Originates in mtDNA → transports to cytoplasm → modified in cytoplasm → transported back to mitochondria

What two proteins are associated with the outer membrane?

• Porin

• PIGBOS

Porin is also known as…

VDAC (voltage dependent anion channel)

Porin is what type of protein?

barrel

Porins have huge aqueous channels that pass…

proteins less than or equal to 5000 Da

What is considered a microprotein that is made up of 54 amino acids?

PIGBOS

How was PIGBOS discovered?

Using green fluorescence on the outer membrane

Who does PIGBOS communicate with?

the ER

What does PIGBOS regulate?

Regulates the unfolded protein response (UPR) via the ER protein CLCC1 at mitochondrial ER contact sites

What happens when PIGBOS is lost?

Increases unfolded protein response (UPR) leading to increased cell death

How much more area does the inner membrane have compared to the outer membrane?

2.5 to 10x more area

2.5x amount of area is associated with…

low energy demanding

10x amount of area is associated with…

high energy demanding

What does the inter mitochondrial membrane (IMM) contain?

• Electron transport chain (ETC)

• Cardiolipin (CL)

Cardiolipin (CL) is a…

four legged phosphate

Fission

Single mitochondrion divides into 2

Fusion

Two or more mitochondria join to form a single mitochondria

ER associated mitochondria associated membranes (MAMS) influence…

Mitochondrial fission through constriction

ER MAMS are associated in the following

• Mitochondrial fission

• Calcium homeostasis

• Regulation of lipid metabolism

• Regulation of autophagy and mitophagy

• Diseases such as Alzheimer’s and Parkinson’s

Possibilities of fission

• A way to distribute mitochondria into two daughter cells

• A way in which damaged portions of mitochondria can be eliminated

Possibilities of fusion

• May maintain homeogenous pool of mitochondria in the cell

• Could restore the function of damaged mitochondria

• May play a role in mitochondrial localization in the cell

What is a nanotube?

Slender conduits between cells that can transfer from cell to cell

Who uses nanotubes?

1. Mitochondria

2. Lysosomes

3. Vesicles

4. Bacteria

5. Viruses

What is actin (F-actin) used for in tunneling nanotubes?

• Microtubules confer the structure (maintain structure)

• Would collapse WITHOUT actin

What are some key functions of mitochondria transfer in tunneling nanotubes (TNT)?

• Metabolic rescue and tissue repair

• Cancer cell metabolic empowerment

• Regenerative support

• Metabolic Reprogramming/Rescue

Metabolic Rescue and Tissue Repair

Damaged or stressed cells receive healthy mitochondria from other cells via TNTs

Cancer Cell Metabolic Empowerment

Cancer cells can steal mitochondria from non cancer cells to ramp up their energy to power metastatic behavior

Regenerative Support

Glial cells in the brain can “feed” mitochondria to the energy demanding neurons

Metabolic Reprogramming/Rescue

Cancer cells can import mitochondria through TNT it assaulted with chemotherapy or radiation

What are CAR-T cells?

T cells used to fight cancer but burn a LOT of ATP

How are CAR-T cells recharged?

Bone marrow cells

What have CAR-T cells improved?

Antitumor activity

How do CAR-T cells get recharged?

Through the use of tunneling nanotubes

If a cell is stressed, what can the mitochondria trigger?

Apoptosis - programmed cell death

What is mPTP?

Mitochondrial permeability transition pore

What is Cytochrome C?

A soluble electron transport chain intermediate

Why is Cytochrome C critical?

Important for cells to move electrons through ETC in eukaryotes

What are the two proteins associated with the inner mitochondrial membrane?

BCL-2 and BCL-XL

BCL-2 is what type of protein?

Anti apoptotic

When does the mitochondrial permeability transition pore (mPTP) open?

When stressed

What proteins are associated with the outer mitochondrial membrane?

Bak and Bax

After mPTP opens, what happens to CTC C?

It goes into the cytoplasm

In the cytoplasm, CTC C combines with what?

Apaf-1

After CTC C combines with Apaf-1 what happens?

Procaspase-9 (inactive) → Caspase 9 (activated)

What are caspases?

• Proteases

• Can digest whole cells including microtubules, nuclei, and everything

Caspase 9 then goes to…

Procaspase 3 → Caspase 3 → Commits to cell apoptosis

Where was BCL-2 discovered?

Cell lymphoma

Why was BCL-2 discovered in the cell lymphoma?

Most cancers overproduce BCL-2

BCL-2 is overexpressed in many cancers which makes patients…

resistant to chem/radiation

What are some overexpression mechanisms associated with BCL-2?

• Chromosomal translocations (follicular lymphoma)

• Gene amplification

• Mutations

What are some consequences of BCL-2 overexpression in cancer?

• Chemotherapy/radiation resistance - less effective at triggering cancer cell apoptosis

• Tumor progression - Promote tumor growth and metastasis

• Metabolic fitness - increases metabolic fitness increasing survival in stressful environments

Genasense

BCL-2 antisense oligonucleotide targets BCL-2 mRNA

Obatoclax

Small molecule BCL-2 inhibitor

What is the most common BCL-2 inhibitor to treat blood cancers?

Venclexta

What does Venclexta have to treat chronic lymphocytic lymphoma (CLL)?

specific genome alteration, called deletion 17p

What did Synta Pharmaceuticals create?

Elesclomal

What is Elesclomal?

a drug that triggers apoptosis through targeting the electron transport chain in cancer cell mitochondria

What is the mechanism regarding Elesclomal?

Increases oxidative stress

Is oxidative stress and the increase in mitochondrial reactive oxygen species important to stem cell biobanking/storage/shipping?

Yes, it creates some stress

What is Cyclosporin A?

• An immunosuppressant that inhibits MPTP and protects stem cells during storage and transport

• When cells are shipped for 5 days → not viable → adding cyclosporin A makes them survive

Western blots are important for…

understanding MPTP pathways

Mitochondria activity is analyzed routinely in…

in vito toxicology

Cancer cells can behave very differently to…

mitochondrial toxins than normal cells

Otto Warburg

• Warburg effect

• Cancer cells can rely more on glycolysis for ATP production that mitochondria