LECTURE 16 - CALCIUM SIGNALLING

which G alpha group stimulates phospholipase C beta

G alpha q

what activates phospholipase C gamma

a receptor tyrosine kinase

what is the function of phospholipase C

it breaks down PIP2 into DAG and IP3

what is DAG

diacylglycerol

what is IP3

inositol - 1,4,5-triphosphate

what does IP3 do

it diffuses to the ER membrane, where it binds to its receptor and stimulates efflux of calcium from the ER into the cytoplasm

what is the role of the SERCA ER pump

it takes calcium from the cytoplasm into the ER

explain how a PKC is activated

• calcium bindsto DAG, promoting binding of DAG to the plasma membrane

• PKC is presented to the plasma membrane, and is activated upon binding to DAG

• Caclium is then bound by PKC

what does PKC stand for

protein kinase C

what does PKC regulate

• immune response

• receptor dimerisation

• membrane permeability

• learning and memory

• muscle contraction

• hormone and neurotransmitter secretion

describe calmodulin

an accessory protein which can bind to, and regulate, other proteins

how many calcium can calmodulin hold

up to 4

what can calmodulin regulate

• short and long term memory

• inflammation and immune response

• metabolism

• apoptosis

• smooth muscle contraction

What is MLCK

myosin light chain kinase

what is the function of MLCK

control myosin phosphorylation

what happens when myosin is unphosphorylated

no myosin ATPase activity

no crossbridge activity

what happens when myosin is phosphorylated

myosin ATPase active

crossbridge cycling

contraction

what is calcineurin

a phosphatase

describe the function of calcineurin

remove the phosphate off the substrate; NFAT

what does NFAT dephosphorylation allow

allows it to enter the nucleus and bind to target genes; cFos cJun

explain transient signalling between ER and mitochondria

• increase in local calcium results in transport of calcium into the mitochondria

• this increases stimulation of TCA/Krebs cycle, in response to increased energy demands

explain persistent/excessive signalling between ER and mitochondria

• increase in local calcium results in transport of calcium into the mitochondria

• there is loss of mitochondrial integrity, leading to release of cytochrome C

what is IP3 a precursor for

many soluble inositol phosphates