Last Class: A. Membrane Proteins and their functions 1. 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 Receptor Or G Protein-linked Receptor 7 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 cells GPCR->Gs->adenylyl cyclase->cAMP Gi

cAMP cycle: GPCR->Gs->adenylyl cyclase->cAMP Cyclic AMP phosphodiesterase breaks down cAMP to 5’-AMP

The function of cAMP Targeting 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: Calcium Movie: calcium signaling in Neuronal cells

Three Types of Inositol phospholipids PI, 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 deprivation 1. 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

Ca 2+ /calmodulin dependent protein kinase (CaM-kinase) Memory function: 1. calmodulin dissociate after 10 sec of low calcium level; 2. remain active after calmodulin dissociation

Ca 2+ /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 adhesion Binding to Src and FAK

1.Receptorlike tyrosine phosphatases Intracellular protein and receptor

1.Receptor Serine/threonine kinase 2.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 interaction Lateral inhibition

1.The inhibitory pathway of Notch Proteolysis-mediated

1.The inhibitory pathway of Notch Proteolysis-mediated

1.Wnt Signaling pathway LRP: LDL-receptor-related protein; GSK-3  : glycogen synthase kinase-3  APC: 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