Signaling

Question 1

Signal

Answer 1

Leads to changes in protein production. Integrate signals to generate diverse set of outputs: survive, grow and divide, differentiate, or die.

Question 2

Ligand

Answer 2

A molecule that binds to receptor. Can be secreted proteins, membrane proteins, hormones, ions, chemicals, pressure, heat, light, or even vibrations.

Question 3

Receptor

Answer 3

Proteins that receive and transduce signals.

Question 4

Relay Molecules

Answer 4

Intracellular signaling proteins or second messengers.

Question 5

Switches

Answer 5

Signaling by phosphorylation (conformation change) or GTP binding (ATP is very common, GTP is less noisy and common)

Question 6

Scaffolds/Adaptors

Answer 6

Scaffolds increase the speed and specificity of signaling by acting as platforms, usually with discrete binding sites that associate (often stably) with specific proteins in order to create a complex. Adaptor proteins contain protein-binding motifs, which facilitate interactions between protein-binding partners in the context of bigger signaling complexes.

Question 7

Juxtacrine

Answer 7

Contact-dependent. Can signal in both directions, but have to touch each other. Membrane bound signal molecule binds receptor .

Question 8

Autocrine

Answer 8

Self-signaling. Secrete signal and responds to itself.

Question 9

Endocrine

Answer 9

Long range. Signals, like hormones, go into bloodstream until the bind receptor in target cell.

Question 10

Ion-channel Couples Receptors

Answer 10

Cell Surface Receptor 1. Sit in membrane and wait for ions to change conformation. They then open or close because signal binding opens “gate” so ions can pass through the channel. Channel pores can be electrically coupled (voltage-gated). They can serve as pumps, for example pumping to pull calcium back into sarcoplasmic reticulum.

Question 11

G-Protein Coupled Receptors (GPCRs) - trimeric G proteins as opposed to the small GTPase proteins we’ve discussed.

Answer 11

Cell Surface Receptor 2. 7-pass transmembrane protein where signal binding induces GTP-binding protein binding and activation. Active G-protein goes on to activate downstream proteins. Can respond to light, sounds, chemicals, smell, taste, neurotransmitters, hormones.

Question 12

Enzyme coupled receptors

Answer 12

Cell Surface Receptor 3. Signal molecule activates enzymatic activity directly or indirectly. Enzymatic activity can be phosphorylation, ubiquitination, GTP exchange, or hydrolysis. Most developmental signaling pathways are like this. Signal molecule in form of dimer could activate catalytic domain by bringing two together to activate itself.

Question 13

Phosphorylation

Answer 13

Ativates

Question 14

Protein Kinase

Answer 14

Adds phosphate group by using ATP.

Question 15

Protein Phosphatase

Answer 15

Removes phosphate group.

Question 16

Phosphorylation

Answer 16

Conformation change. Can work both ways, phosphorylation can inhibit function /de-phosphorylation can activate function.

Question 17

Positive Feedback

Answer 17

Stimulus turns on A which turns on B which turns on A.

Question 18

Negative Feedback

Answer 18

Stimulus turns on A which turns on B which tells A to stop.

Question 19

Chemoattractant

Answer 19

Chemical signal that attracts/directs cell movement.

Question 20

Rac

Answer 20

Rho family GTPase. Activation of Rac promotes actin polymerization (via arp2/3) at the cell periphery, leading to the formation of sheetlike lamellipodial extensions (Flattened, sheetlike protrusion supported by a meshwork of actin filaments, which is extended at the leading edge of a crawling animal cell). Tips balance towards branched actin web networks and away from stress fiber formation.

Question 21

Rho

Answer 21

Rho family GTPase. Activation of Rho promotes both the bundling of actin filaments (via formins) with myosin II filaments into stress fibers.

Question 22

Cdc42

Answer 22

Rho family GTPase. Activation of Cdc42 on the inner surface of the plasma membrane triggers actin polymerization and bundling to form filopodia (Thin, spike-like protrusion with an actin filament core, generated on the leading edge of a crawling animal cell). Activation of Cdc42 increases actin nucleation via wASP stabilization which enables it to bind arp2/3.

Question 23

WASP

Answer 23

Activates Arp2/3

Question 24

Notch/Delta

Answer 24

Notch receptors are themselves such proteins, which are activated by cleavage when Delta on another cell binds to them; the cleaved cytosolic tail of Notch migrates into the nucleus, where it stimulates the transcription of Notch- responsive genes.

Question 25

RNA in situ Hybridization

Answer 25

Measure transcriptional activity of a pathway. Make RNA complimentary to specific mRNA. This RNA has labeled Uridine so that antibody can bind. U is used because it’s specific for RNA. Then, add phosphatase so that when colorless compound is added, it becomes purple when the phosphatase removes the phosphate.

Question 26

Reporter Gene

Answer 26

Measure transcriptional activity of a pathway. Fuse lacZ or GFP to enhancer/promoter to see where promoter for gene of interest is being transcribed.