last class: a. membrane proteins and their functions 1. membrane proteins are mobile yet organized...
TRANSCRIPT
Last Class:
A. Membrane Proteins and their functions1. membrane proteins are mobile yet organized
2. carrier and channel proteins B. Signaling Transduction
1. Ligand Receptor Interactions, 2. Intracellular signaling molecules, 3. molecule switches:
phosphorylation and GTP binding, 4. Signaling integration, 5. complex formation, 6. Signaling
amplification, 7. Signaling desensitization
• Cell Communication
• Different Receptor Types• Ion channel-linked receptors• *GPCR signaling• *Enzyme linked receptors
• G Protein Coupled Receptors (GPCR)
A G-Protein-Coupled ReceptorOr G Protein-linked Receptor7 transmembrane domains
The disassembly of G-Protein upon stimulation
Spontaneous deactivation is very fast, in minutes.
However, with the help of RGS (regulator of G
protein signaling, a GAP for unit), signals can be
shut off even faster
The Activation cycle of G-
Protein
GPCR Signaling Mechanism
Movie
• GPCR Signaling: cAMP
The visualization of cAMP in nerve cellsGPCR->Gs->adenylyl cyclase->cAMP
Gi
cAMP cycle: GPCR->Gs->adenylyl cyclase->cAMP
Cyclic AMP phosphodiesterase breaks down cAMP to 5’-AMP
The function of cAMPTargeting PKA (cyclic-AMP-dependent protein
kinase A)
The Whole Signaling Network related to cAMP
Terminology: CRE(cyclic AMP response element); CREB: CRE binding protein; CBP: CREB binding
protein
Movie
cAMP and PKA signaling pathway
• GPCR Signaling: CalciumMovie: calcium signaling in Neuronal cells
Three Types of Inositol phospholipidsPI, PI(4)P, PI(4,5)P2
Phospholipase C-
(PLC-) Produces DAG
(diacylglycerol) and IP3 (inositol 1,4,5-
trisphosphate (IP3))
Gq->PLC-
Gq signaling pathways and Calcium
Fertilization of an egg by a sperm triggering an increase in cytosolic Calcium
3 major types of calcium channels:
1. Voltage dependent Ca channels on plasma membrane
2. IP3-gated Ca release channels on ER membrane
3. Ryanodine receptor on ER membrane
Calcium uptake and deprivation1. Na/Ca exchanger on plasma membrane, 2. Ca pump on ER
membrane, 3. Ca binding molecules, 4. Ca pump on Mitochondia
Calcium Frequency encoding signaling
strength
Local Ca blips, sparks, puffs, reflecting local opening of individual
channels in ER, strong local signal induces global activity, the
elevated Calcium trigger calcium deprivation
system
Targeting molecules for Calcium
Calcium binding protein Calmodulin
Ca2+/calmodulin dependent protein kinase (CaM-kinase)Memory function: 1. calmodulin dissociate after 10 sec of low calcium level; 2. remain active after calmodulin dissociation
Ca2+/calmodulin dependent protein kinase (CaM-kinase)Frequency decoder of Calcium oscillation
High frequence, CaM-kinase does not return to basal level before the second wave of activation starts
Desensitization of GPCR
1. Inhibitory structural alteration of receptor; 2. receptor internalization; 3. receptor degration
GRK (G protein-linked receptor kinase)
Arrestin takes to clathrin-coated pits and degradation
• GPCR Signaling Summary• 1. G-protein types• 2. cAMP and Calcium signaling
pathways• 3. desensitization
Enzyme-Linked Cell Surface Receptors
•*Receptor Tyrosine Kinase•*Tyrosine kinase associated receptors•*Receptor-like tyrosine phosphatase•*Receptor serine/threonine kinase•Receptor guanylyl cyclase•Histidine like associated receptor
• Receptor Tyrosine Kinases (RTKs)
Seven subfamilies of receptor tyrosine kinases
Three ways in which signaling proteins can cross-link receptor chains
1. dimer, 2. monomer but brought together by proteoglycan, 3. cluster on membrane
The importance of receptor oligomerization
The docking of signaling molecules at RTK
The binding of SH2-containing intracellular signaling proteins to an activated PDGF receptor
The structural view of SH2 domain
• RTK Signaling: Ras Pathway
The regulation of Ras activity, a famous downstream molecule of RTK responsible for
cancer development
The activation of Ras by RTK signaling
The MAP-kinase regulated by Ras
• RTK Signaling: PI3K Pathway
The inositol phospholipids generated by PI3K
The recruitment of signaling molecules with
PH domains to the plasma membrane during B cell
activation
One PI3K pathway
PH domain: pleckstrin homology domain
Movie: PI3K pathway regulating calcium and PKC
Another PI3K pathway to regulate cell survival
Another PI3K pathway to regulate cell migration
PI3K->PIP3->GEF->Rac->Wave->Arp2/3->Actin polymerization
Movie: chemotaxis, PI3K and cell migration
Intracellular Signaling Pathways activated by RTKs and GPCRs
1. Tyrosine kinase associated receptors
Integrins: cell-extracellular matrix adhesionBinding to Src and FAK
1. Receptorlike tyrosine phosphatasesIntracellular protein and receptor
1. Receptor Serine/threonine kinase2. Transforming growth factor (TGF-b) and
Smad signaling pathway
1. Protein kinase Summary
• Enzyme-linked Receptor Signaling Summary
• 1. receptor types• 2. RTK and its signaling: Ras and PI3K• 3. Tyrosine kinase associated receptors
and Receptor-like tyrosine phosphatase• 4. Receptor serine/threonine kinase, TGF-
and Smad
•Other Signaling Pathways•Proteolysis mediated
1. Notch and Delta interactionLateral inhibition
1. The inhibitory pathway of NotchProteolysis-mediated
1. The inhibitory pathway of Notch
Proteolysis-mediated
1. Wnt Signaling pathwayLRP: LDL-receptor-related protein; GSK-3: glycogen synthase
kinase-3APC: adenomatous polyposis coli;
1. NF-KB pathway
• Summary
• 1. GPCR signaling: PKA and Calcium• 2. Enzyme-linked Receptor signaling: RTK-
>Ras and PI3K• 3. Proteolysis-mediated signaling pathways