III. Signal transduction and cell cycle | 42. Phosphatidylinositol signaling pathways Flashcards
I. Basics
1. What are the features of phospholipids?
- The plasma membrane contains phospholipids that are more than just structural.
- A phospholipid is amphiphilic, which means it has both hydrophobic and hydrophilic region
I. Basics
2. Describe the structure of phospholipids
A phospholipid is amphiphilic, which means it has both hydrophobic and hydrophilic region:
- Hydrophilic head: glycerol bound to a negatively charged phosphate group by a phosphate ester bound. The glycerol has 3 carbons, each having one hydroxyl group (-OH) which binds the phosphate and the two fatty acid chains in the tail
- Hydrophobic tails: two fatty acid chains attached to the glycerol by ester bonds
II. Phospholipase
1. What are Phospholipases?
Phospholipases are enzymes that hydrolyze phospholipids into fatty acids and phospholipids.
II. Phospholipase
2. What is the target of Phospholipases?
The ester bonds between the glycerol and the R groups (phosphate and FAs) are the target of cleavage by different phospholipases.
II. Phospholipase
3. What are 4 examples of phospholipase?
- Phospholipase A1
- Phospholipase A2
- Phospholipase C
- Phospholipase D
II. Phospholipase
4. What is the role of Phospholipase A1?
Phospholipase A1 cleaves the 1st ester bond (FA)
II. Phospholipase
5. What is the role of Phospholipase A2?
Phospholipase A2 cleaves the 2nd ester bond (FA), side chain R2 usually arachidonic acid
II. Phospholipase
6. What is the role of Phospholipase C?
Phospholipase C cleaves the 3rd ester bond to the phosphate group
II. Phospholipase
7. What is the role of Phospholipase D?
Phospholipase D cleaves the ester bond between the phosphate and the side chain R3
III. Phospholipase C
1. What are the features of Phospholipase C?
Phospholipase C (PLC) in humans (animals) is specific for phosphatidylinositol 4,5-bisphosphate (PIP2), which is a phospholipid with an inositol bound to the phosphate group.
III. Phospholipase C
2. What is the mechanism of Phospholipase C?
Activated phospholipase C will cleave PIP2, to generate two 2nd messengers: diacylglycerol (DAG) and inositol-triphosphate (IP3).
III. Phospholipase C
3. Is phospholipase C a family of enzymes?
=> T/F?
TRUE!!!
III. Phospholipase C
4. Phospholipase C is a family of enzymes
=> List 3 enzymes with their role
- PLCβ contains a G-protein interaction domain, which will be activated by Gq
- PLCδ functions in amplifying the signal
- PLCγ contains SH2 and SH3 domains, meaning it can be activated by receptor tyrosine kinases (e.g. insulin receptor)
IV. IP3 signaling way
1. What is PLC activated by?
LC will be activated by a Gq G-protein, which will generate IP3 and DAG from PIP2.
IV. IP3 signaling way
2. What is IP3?
IP3 is a water soluble molecule that leaves the plasma membrane and diffuses rapidly through the cytosol.