Endocrine - Biochem - Signal Transduction

Front 1

4 types of signal transduction?

Structure of GPCR:

Back 1

Contact depenent - direct cell-cell
Paracrine - local cell-cell
Synaptic
Endocrine - Hormone in blood --> target cell

7-transmembrane spanning

Front 2

General pathway of GPCR signaling:

Back 2

ligand + GPCR --> GPCR binds to GP (A,B,G subunits)
GP binds to GTP, separates A from B/G;
GA binds/activates adenylyl cyclase (makes cAMP)
GA hydrolyzes GTP to GDP,
GA + GDP binds to GP B/G

Front 3

Examples of 2nd messenger molecules:

Explain phosphorylation of proteins and consequences:

Back 3

cAMP, cGMP, DAG, IP3, Ca++, NO

protein kinase adds a P from ATP to a protein with -OH group (substitution) (serine, threonine, tyrosine side chain);
protein phosphatase cleaves P off phosphoprotein to make original protein
Consequences - structural changes from charge attraction

Front 4

How does cAMP activate PKA?

What does the activated PKA do?

Back 4

adenylyl cyclase makes cAMP from ATP, 4 cAMP molecules attach to regulatory region (2 subunits) of PKA, activate the catalytic subunit (2 subunits)

binds and activates CREB, which binds to CRE (cAMP response element) on gene --> gene transcription

Front 5

PKA signaling in glycolysis:

Explain cAMP amplification:

Back 5

PKA phosphorylates and activates glycogen phosphorylase - converts glucose to G-1-P --> glycolysis

Each GPCR - multiple GP's, multiple adenylyl cyclase - lots of cAMP - activates multiple PKA's, enzymes

Front 6

Role of guanylyl cyclase:

What does Ca++ bind to to activate NO synthase?

Back 6

2 types - membrane bound activated by ligand, soluble activated by Ca++ and NO; change GTP to cGMP - biological response

calmodulin

Front 7

Explain the DAG, IP3, Ca++ pathway:

Explain signal cross-talk:

Back 7

ligand to GPCR --> activates Gq protein - activates phopholipase C - cleaves PIP2 into IP3 and DAG

DAG stays in the membrane, IP3 goes to ER and opens Ca++ channels, and DAG + Ca++ then activate PKC

Crosstalk - proteins need 2 separate GPCR ligands, or subunits each need a GPCR to activate

Front 8

Arichodonic Acid pathway:

Which enzyme makes leukotrienes? PG's/Thromboxane?

What protein desensitizes the GPCR?

Back 8

ligand to GPCR --> Gq protein activated, activates PLA2 - makes AA's - lipooxygenases, COX

5-lipooxygenase - LT's
COX-1 - PG, thromboxane

arrestin via GPCR kinase (GKR)

Front 9

3 major components of tyrosine kinase pathway?

What happens when the signal molecule attaches to the inactive RTK's?

Back 9

Receptor complex, monomeric G-protein, MAPK cascade

crossphorylates

Front 10

Explain the activation of Ras:

How are the SH2 and SH3 domains regulated?

Back 10

Boss (ligand) activates RTK - activates TK; SH2 on the adapter protein binds to phosphorylated TK;
SH3 domains on adapter protein binds to proline-rich sequences in another protein, Ras-GEF (Guanine nucleotide Exchange Factors); Ras is activated by losing GDP, adding GTP

AA sequences around the binding site regulate

Front 11

Explain the role of GAP (GTPase Accelerating Protein) and GEF in monomeric G-protein activation:

Explain the MAPK cascade:

Back 11

GEF exchanges GDP for GTP, activating the GP; GAP dephosphorylates GTP to GDP

Ras activates MAPKKK (MEKK) --> MAPKK (MEK) --> MAPK --> gene targets

Front 12

What activates the MAPK/ERK pathway? What is the response?

JNK/SAPK and p38 pathways are activated by what?

Cell response?

What creates specificity in the MAPK pathway?

Back 12

growth factors - EGF, PDGF, NGF, insulin - causes cell proliferation, differentiation

stress - UV light, radiation, heat/cold, hyperosmolarity, toxins, TNF

cell survival, apoptosis

scaffolding - different components

Front 13

What are some other receptors that can activate MAPK cascade?

What are some gain-of-function mutations?

Loss of function mutations:

Back 13

TK, cytokines, TCR, Death receptors (Fas, TNF), integrin, GPCR, ion channels

promoter --> overexpression: v-Sis, Myc, Bcl-2
protein-coding --> activity: Ras, Erb-B

p53 - cell cycle/apoptosis, Rb (like Ras-GAP)

Front 14

Explain the activation of Ras by a point mutation in cancer:

How are these signaling pathways attenuated?

Back 14

mutation blocks GAP and GTPase activity, keeping Ras stuck in the active state

diffusion/degradation of messenger, desensitization/downregulation of receptor, protein phosphatases on receptor, GTPases on signal transduction, PDE on messenger