Cell Signaling Quiz 4 Flashcards
Inositol phospholipids
a lipid composed of a phosphate group, two fatty acid chains, and one inositol molecule. It belongs to the class of phosphatidylglycerides
Is typically found as a minor component on the cytosolic side of eukaryotic cell membranes.
What does PIP2 make when cleaved?
Makes DAG and another molecule that when exposed to water makes IP3
Leads to calcium release hen it works with kinase C (via DAG recruiting it) and opening of calcium channels (via IP3)
PIP, PIP2, PIP3
With the use of P13K and PTEN they can all undergo reactions to become one another
They do this to change their functions
PI (3,4,5)P3
Activates Akt (protein kinase B) which works with cell survival
PLC in bacteria
Used to lyse cell membrane un our cells
PLCs
Six isotypes in animals
Thirty types in mammals
Most need Ca2+ to function properly
PLC-beta
4 genes
PLCB1, PLCB2, PLCB3, PLCB4
PLCB1
Activated by Galphaq1, G alpha
PLCB2
Same Galpha as PLCB1
Can also be activated by Gbetagamma
PLCB3
Same Galpha as PLCB1
Can also be activated by Gbetagamma
PLCB4
Not sure but is localized to ? and has two isoforms
PLC-gamma
2 genes: PLCG1 and PLCG2
PLC-gamma is activated by RTK, not by proteins
PLC-delta
Three genes: PLCD1, PLCD2, PLCD3
PLCD1=skin homeostasis
PLCeta and PLCzeta also exist
PLC structure
Have common domains and variability outside of these:
PH: binds inositol phospholipids
EF-hand domains: helix-loop-helix structure. Used to bind Ca2+ ions
TIM-Barrel domain: alternative alpha helices and beta sheets which forms a donut structure: catalytic domain
XY linkers: Splits catalytic domain
C2: Binds Ca2+ membranes
PICTD: Galphaq binding site
CTD linker: unconserved
Distal CTD: Contributes to Galphaq and membrane binding
Different inositol phospholipids are used for?
By having different kinases can make massive different molecules used for signaling
It is easy to P’late and is therefore easy to switch rxn off
Therefore can modulate how long/when phosphosinositol can be used
What role does IP3 have?
Used to release Ca2+
Gets P’lated and reverses its action and uptakes Ca2+ back into SR
Therefore calcium signal is short lived
Purposes of many types of DAG
Activate PKC
Several pathways
Do not understand how it is degraded
Not always on PM. Is on nuclear envelope so possibly the nucleus stores Ca2+?
Difference between sphingolipids and phospholipids?
Use sphingosine instead as a base molecule and not a glycerol
Arachidonic acid
Production of prostoglandins
GTP binding proteins
Switch with GDP and GTP bound states
Are on when GTP is bound and are off when GDP is bound
Which concentration do you want more for GTP binding proteins? GDP or GTP
GTP
Therefore you can kick out GDP for nucleotide exchange
How do we go from GTP to GDP?
Hydrolysis reaction to occur
How do we go from GDP to GTP?
Nucleotide exchange
Do you want a fast or slow reaction for GTP binding proteins?
Want a slow reaction rate for signaling path to be slow
Half-time can be hours
GTP and GDP affinity for GTP binding proteins?
Both high so you can get a consistent signal that can be transduced
Helps because then the signal will not be accidently switched on or off
Guanine nucleotide exchange factors (GEFs)
Takes GTP and turns on GTP binding protein
GTPase activating proteins (GAPs)
Remove phosphate from GTP binding protein to turn off GTP binding protein
GTP binding proteins are
GTPases
GAP will increase efficiency of GTPase
The structural mechanisms of GTP binding proteins?
With ADP:
GDP binds in the center of tweezers of the protein
Gly60 on switch II, and Thr35 on switch I
Gly60 and Thr35 is where the target protein (enzyme most of the time) is going to bind to bring them inwards when activated
Without ATP:
Target protein attaches to Gly60 and Thr35 with P attaching to target protein as well
GTP binding proteins
Monomeric GTP binding protein
“Small GTPases”
Heterotrimeric GTP binding proteins
“G proteins”
These are the two classes of GTP binding proteins
Contain alpha, beta, and gamma polypeptide
Alpha polypeptide is GTP binding subunit
~150 small GTPases
Ras
Proliferation and differentiation
Induce tumor formations
Rho
Cell shape
Rab
Vesicular trafficking
Vesicle target docking
Arf
Vesicular trafficking
Used at start of things
Vesicle formation
Ran
Nuclear import/export
G proteins
Fewer in number
16aplha genes
Galphas, Galpha1, Galphaq/11, Galpha12/13
Lots of GPCRs
Receptors that activate G proteins
GPCR specificity and G and effector proteins that come after it. Do the other proteins need to be specific?
As long as we can ensure the right effector is activated in response to signal, G protein uniqueness is less important
Cell specific expression of GPCR/effector or we could have specific localization of the GPCR/effector on plasma membrane
Therefore will not accidently activate something else
What activates and deactivates G proteins
~GPCR (GEFs) activate them
~20 G proteins
~RGS (GAPS, Regulations of G protein signaling)
What activates and deactivates Rho?
~80 Rho GEFs activate ~20 Rho
~70 Rho GAP deactivate ~20 Rho
Are GTP binding proteins in a signaling pathway the center of the pathway?
GTP binding protein in the center is not really big picture of pathway
Mechanisms of GEFs
They go to the point where they bind to tweezers and Phosphate. Opens the wings and GTP/GDP is released then new molecule can bind to GTP binding protein
What does GAP do to molecule
GAP orients molecules to drive hydrolysis rxn.
Line up H2O, GTP and GTPase
Single A.A. is disordered that is put into ordered state
Arginine finger to neutralize phosphate for rxn. to occur
GD1
Stop dissociation of GDP for GTP
GD1 displacement factors
kicks GD1 off
GoLoco
Influence retrimerization of beta-gamma protein. Stop it.
