PIP2 Basics Flashcards
What are phosphoinositides?
Acidic phospholipids of cell membranes with myo-inositol in the head group
What is the parent compound of phosphoinositides?
Phosphatidylinositol (PI)
What gives rise to variations in phosphoinositides?
PI can become phosphorylated on the 3, 4, and 5 positions of the inositol ring in every combination
What does PI phosphorylation give rise to?
Seven low-abundance poly-phosphoinositides
Where are phosphoinositides found?
primarily in the cytoplasmic leaflet, mark the identity of specific subcellular membrane compartments
What 2 functions do phosphoinositides serve?
- membrane recognition sites for specific cytoplasmic proteins
- act as membrane-delimited second messengers modulating the activities of some membrane proteins
What is PIP2 and where is it located?
Phosphatidylinositol 4,5-bisphosphate (PIP2) is a minority phospholipid of the inner leaflet of plasma membranes
What is the significance of PIP2 as a second messenger?
Many plasma membrane ion channels and ion transporters require PIP2 to function and can be turned off by signalling pathways that deplete PIP2.
Why do ion channels confer PIP2 dependence (who)?
Offers 2 advantages (Suh and Hille, 2008)
What is the advantage of PIP2 location for ion channel modulation?
PIP2 is found almost exclusively in the plasma membrane, a dependence on PIP2 keeps these channels inactive whenever they are not in the plasma membrane (Hilgemann, 1996)
Thus, during trafficking from synthesis in the ER through the Golgi apparatus and on to the plasma membrane, they could remain silent until they arrive, and during recycling or endocytosis they can be resilenced when they leave.
What is the advantage of PIP2 level regulation for ion channel modulation?
because plasma membrane PIP2 can be transiently depleted by neurotransmitters activating PLC, the activity of this group of channels can be regulated by the incoming signals.
