Cell Signaling

Front 1

Kd

Back 1

Concentration of ligand at which half the receptors are bound.

Front 2

Agonists

Back 2

Stimulate signaling pathways by binding to and activating receptors.

Front 3

Antagonists

Back 3

Bind to receptors, but do not activate them and prevent the binding by normal signaling molecules.

Front 4

Ion channels

Back 4

Signaling pathways increase the number of channels or alter the open/close probabilities of ion channels. Opening of membrane K+ or Cl- channels hyperpolarizes cells. Opening of Na+ or Ca2+ channels depolarizes cells or brings membrane potential closer to threshold.

Front 5

G proteins

Back 5

GTP/GDP binding proteins. The GTP bound form is active. Contain alpha, beta, and gamma subunits.

Front 6

Alpha subunit of G protein

Back 6

Binds GDP in inactive form and GTP in active form. When activated it disassociates from beta/gamma subunits and becomes active.

Front 7

Adenylyl cyclase

Back 7

Turns ATP into cAMP which acts as a second messenger.

Front 8

Guanylyl cyclase

Back 8

Turns GTP in cGMP which acts as a second messenger.

Front 9

Phosphodiesterase

Back 9

Breaks down cAMP or cGMP into AMP or GMP.

Front 10

Phopsholipase C

Back 10

Breaks down phosphatidyl inositol phosphate (PIP2) into inositol triphosphate (IP3) and diacylglycerol

Front 11

Kinase

Back 11

An enzyme that adds a phosphate group.

Front 12

Phosphatase

Back 12

An enzyme that removes a phosphate group.

Front 13

Three amino acids that are phosphorylated

Back 13

1. Serine
2. Threonine
3. Tyrosine

Front 14

Protein kinase A

Back 14

AKA cAMP-dependent kinase that is active in the presence of cAMP.

Front 15

Protein kinase G

Back 15

AKA cGMP dependent kinase is active in the presence of cGMP.

Front 16

Protein kinase C

Back 16

DAG dependent kinase active in the presence of DAG and calcium.

Front 17

IP3

Back 17

Binds and opens calcium channels and is inactivated by dephosphorylation.

Front 18

Regulatory subunits of PKA

Back 18

Bind to four cAMP and release the catalytic subunits which are activated.

Front 19

Gs

Back 19

Stimulatory G protein that acts through the alpha subunit.

Front 20

Gi

Back 20

Inhibitory G protein that acts through the alpha or beta gamma subunits.

Front 21

Amplification of signal

Back 21

Amplification occurs whenever one molecule activates multiple molecules at a step in the cascade.

Front 22

Termination of signal

Back 22

Once signal molecule is removed by phosphatases or phosphodiesterases that reverse the signals.

Front 23

Ca2+ second messenger signaling

Back 23

Cells keep Ca2+ levels low normally, storing calcium in the endoplasmic reticulum and pumping it out of the cell.

Front 24

Phospholipase C beta

Back 24

Activated by G proteins which causes the cleavage PIP2 to IP3 and DAG.

Front 25

IP3-specific Ca2+ channels

Back 25

Found in the endoplasmic reticulum. Opens them allowing Ca2+ to flow into the cytosol.

Front 26

Enzyme linked receptors

Back 26

Receptors for growth factors and usually associated with transmembrane tyrosine-specific protein kinases.

Front 27

Receptor tyrosine kinases structure

Back 27

1. Have an external domain to interact with the signaling ligand
2. Single transmembrane domain
3. Cytosolic tyrosine-kinase domain

Receptors for insulin.

Front 28

Receptor dimerization

Back 28

Mechanism for activating enzyme linked receptors with a single transmembrane domain. Dimerization activates tyrosine kinase activity and it autophosphorylates.

Front 29

Phosphorylation function

Back 29

Serve as high-affinity binding sites for intracellular signaling proteins in the target cell.

Front 30

Insulin tyrosine kinase binds four proteins

Back 30

1. Insulin receptor substrate-1
2. IRS2
3. IRS3
4. IRS4

Acts via Src homology

Front 31

SH2 domains

Back 31

Recognize phosphorylated tyrosine residues and specific amino acids nearby and bind.

Front 32

SH3 domains

Back 32

Serve as binding sites for other signaling proteins.

Front 33

Ras protein

Back 33

Monomeric GTPase that functions as a switch, cycling between GTP active and inactive state.

Front 34

GTPase-activating proteins

Back 34

Increase the rate of hydrolysis of bound GTP by Ras thereby inactivating it.

Front 35

Guanine nucleotide exchange factors

Back 35

Promote the exchange of bound nucleotide by stimulating the loss of GDP and uptake of GTP activating Ras.

Front 36

Mitogen-activated protein kinase activation

Back 36

1. Ras activates MAPKKK (Raf)
2. Raf phosphorylates and activates MAPKK (Mek)
3. Mek phosphorylates and activates MAPK (Erk)
4. Relays signals downstream by phosphorylating various proteins in the cell

Front 37

Cytoplasmic tyrosine kinases

Back 37

Not specifically a domain on the receptor, but associated with the receptor on the internal part of the plasma membrane. Part of the Src family.

Front 38

JAK-STAT signaling pathway

Back 38

Used by cytokines. Leads from the cell surface to the nucleus to activate or repress transcription of various genes.