phosphoinositide signaling Flashcards
What are phoshphoinositides?
phosphorylated membrane lipids
How can phosphoinositide signaling be induced?
Can be induced either by GPCR with Gq subunit or by RAS independent tyrosine kinases.
What is the key effector enzyme that leads to PIP2 cleavage?
Phospholipase C - activated by both Gq and RTKS.
Which receptor pathway activates PLCgamma?
Activated by some RTKS
Which receptor pathway activates PLCbeta?
Gq subunit of GPCRs
What are the 2 products of cleavage of PIP2?
IP3 and DAG
What affect does IP3 go on to have?
IP3 released into cytoplasm and increases cellular conc of calcium via IP3 gated calcium channels.
Can have affects such as muscle contraction
What affect does DAG go on to have?
Remains in the membrane and alongside Calcium activates protein kinase C
What affect does Protein kinase C have in this pathway?
Protein kinase C (activated by calcium and DAG) regulates metabolic enzymes by phosphorylating transcription factors.
How can the signal be down regulated? (in PIP2 cleavage pathway)
Calcium-activated-DAG Kinase phosphorylates DAG to phosphatidic acid
Alternatively to cleavage, how else can PIP2 be modified as a signal?
PIP2 can be phosphorylated to PIP3
What affect does the production of PIP3 have on a cell?
PIP3 causes the recruitment of a further kinase Protein Kinase B. (recruited via PIP3 PH domain)
How is PIP3 produced?
By the protein kinase PI-3.
What receptor may induce the pathway that leads to the production of PIP3?
Single pass receptor pathways can lea to activation of PI-3 eg activation of PI-3 kinase via phosphorylated RTKS
What does the activation of PI-3 ultimately mean for cell fate?
Activation of PI-3 (and therefore production of PIP3, and PKB) promotes cell survival by eg inhibiting apoptosis
