Exam 2 pt3

Question 1

Grb2 binds the RTK on it’s _ domain

Answer 1

SH2

Question 2

Ras GEF binds to _ at the _ domain

Answer 2

Grb2 at the SH3 domain

Question 3

RTK →

Answer 3

Grb2 → Ras GEF → Ras P → MAPK

PI3 K → PI3P3 → PDK → Akt K

Question 4

TGF beta binds →

Answer 4

SARA anchors Smad → R Smad phosphorylayion → regulate transcription

Question 5

The _ domains of transmembrane enzyme-coupled receptors bind _

Answer 5

• extracellular: signal molecules
• intracellular have enzyme activity or directly associate with enzyme

Question 6

receptor protein kinases…

Answer 6

phosphorylate specific tyrosine residues on both themselves and on specific intracellular signaling proteins

Question 7

Initial activation of RTKs occurs when

Answer 7

ligand binding brings two receptors into close proximity to form dimers

Question 8

RTK activation leads to dimer formation which leads to

whole process

Answer 8

• active receptors cross phosphorylating each other’s tyr
• forms docking sites
• intracellular signaling proteins bind to docking site
• creates signaling complezes

Question 9

Intracellular signaling
proteins containing _ bind to the
docking sites and create signaling complexes

Answer 9

phosphotyrosine-binding domains (SH2 or PTB domains)

Question 10

Docked intracellular signaling molecules are activated by

Answer 10

phosphorylation, conformation changes induced by binding to
the receptor, or by coming into close proximity with the next molecule in the signaling pathway

Question 11

Ras proteins are linked

Answer 11

to the cytoplasmic surface of the plasma membrane via one or more covalently attached lipid groups

Question 12

Ras inactivation a result of

Answer 12

• tyr specific protein phosphatases turn off RTK receptors
• Ras GAPs increase GTP hydrolysis

Question 13

Ras signaling is often required for

Answer 13

the stimulation of cell proliferation or differentiation

Question 14

Cancer cells have Ras molecules

Answer 14

that are constantly active because they are locked in GTP bound state so they keep proliferating

Question 15

MAP is composed of

Answer 15

3 protein kinases
* Raf, Mek, Erk
* MAPKKK, MAPKK, MAPK

Question 16

MAPK phosphorylates

Answer 16

many proteins

Question 17

signal pathways are kept seperate by _ because

Answer 17

scaffold proteins because MAP modules use same enzymes for different responses in the cell so cant have cross talk

Question 18

The PI-3-kinase-Akt signaling pathway plays a key role

Answer 18

in promoting the survival and growth of
many cell types

Question 19

PI 3 Kinase pathway

while thing

Answer 19

• Activated RTKs recruit and activate PI 3-kinase.
• Activated PI 3-kinase phosphorylates the phosphoinositide PIP2 to produce PIP3.
• Two serine/threonine kinases, Akt and PDK1 are brought into close proximity by binding to PIP3 via PH domains.
• Akt is phosphorylated on a serine by a third kinase, mTOR, resulting in a conformational change which now allows Akt to be phosphorylated on a threonine by PDK1.
• Activated Akt dissociates from the plasma membrane and phosphorylates various target proteins.

Question 20

one target of Akt is _ which _ when not phosphorylated. Akt phosphor by _

Answer 20

One target of Akt is the
cytosolic protein Bad which, in its non-phosphorylated state,** promotes cell death via
apoptosis**. Phosphorylation of Bad by Akt creates phospho-serine-binding sites for a
scaffold protein called 14-3-3. Binding to 14-3-3 sequesters Bad, keeping it from acting and
thereby promoting cell survival.

Question 21

JAK pathway

Answer 21

• two JAK brought lose together
• transphosphorylation increases activity levels
• phosphorylation from active JAKs to make docking sites
• STATs bind to these sites
• phosphorylated STATs disassociate
• STAT form dimer and go to nucleus

Question 22

JAK and STATs are inactivated when

Answer 22

tyrosine phosphatases dephosphorylate their phosphotyrosines

Question 23

The JAK-STAT pathway provides one of the

Answer 23

most direct routes from cellsurface receptors to the nucleus and altered gene transcription.

Question 24

TGF beta binding pathway

Answer 24

• TGF beta protein binds to receptor 1 and 2
• this brings receptors together
• Type 2 receptors phosphorylate type 1
• activated type 1 directly bind and activate Smad family protein
• receptor and Smad complex endocytosed

Question 25

activation route Smad receptor complex

Answer 25

• endocytosis takes place via clathrin coated vesicles
• deliver to early endosome
• SARA anchoring protein binds

Question 26

inactive route Smad receptor complex

Answer 26

• depends on caveolae and leads to Ub tagging
• R activated Smads dissociate from receptors
• bind to Smad4
• RSmad/Smad4 complex that inhibit Smad

Question 27

A trimeric GTP-binding protein with GTPase activity that couples surface receptors to membrane-associated enzymes or ion channels.

Answer 27

G protein

Question 28

Signaling process involving the interaction between signal molecules on the surface of one cell and receptor proteins on the surface of another cell.

Answer 28

contact dependent

Question 29

Protein that organizes groups of interacting intracellular signaling proteins into signaling complexes.

Answer 29

scaffold protein

Question 30

Protein domain used by intracellular signaling proteins to bind PIP3.

Answer 30

PH domain

Question 31

Proteins which activate GTP-binding proteins by promoting the exchange of GDP to GTP

Answer 31

GEF

Question 32

Alteration of sensitivity following prolonged stimulation, reducing a cell’s response to that level of stimulus

Answer 32

adaptation

Question 33

Enzyme that phosphorylates specific amino acids of target proteins.

Answer 33

PTK

Question 34

Control mechanism whereby a product of a signaling response acts to stimulate its own production.

Answer 34

positive feedback loop

Question 35

Intracellular signaling proteins bind to _ via specific interaction domains such as pleckstrin homology (PH).

Answer 35

PIP3

Question 36

The response of a target cell will occur more _ if it involves changes in proteins already present in the cell rather than changes to gene expression and synthesis of new proteins.

Answer 36

rapidly

Question 37

Most of the effects of an increase in cytosolic cAMP levels are mediated by

Answer 37

cyclic-AMP dependent protein kinase (PKA).

Question 38

The head domains of these structures make transient, ATP-dependent attachments to the B tubules of microtubule doublets.

Answer 38

axonemal dyneins

Question 39

Kinesin-mediated movement of vesicles and organelles from nerve cell bodies towards axon terminals.

Answer 39

anterograde

Question 40

Protofilaments are a structural component of

Answer 40

all cytoskeletal filaments.

Question 41

The head (motor) domains of dyneins bind to _ and also

Answer 41

microtubules and also bind and hydrolyze ATP.