8 - Growth Factors and Signal Transduction

Question 1

How do growth factors affect cell division?

Answer 1

(proliferation) accelerates it = cell grows more aggressively

Question 2

What are the 4 cell responses to signals? Which cells will respond to certain signals?

Answer 2

(SDDD) survive | differentiate | divide | die | only cells with the receptor of that signal

Question 3

What is hypertrophy?

Answer 3

cells growing in size

Question 4

What is the difference between cell growth and cell proliferation?

Answer 4

growth = increase size | proliferation = increase numbers/copies (multiply)

Question 5

How can a cell grow independently?

Answer 5

allows access to a growth hormone that will activate division machinery

Question 6

What is prolong ligand-induced signaling?

Answer 6

decrease degradation of pathway proteins, turn off negative regulators

Question 7

What are the 5 ways a cell can achieve extrinsic factor (outside cell signaling) independence?

Answer 7

prolong ligand-induced signaling | increase sensitivity (respond to lower ligand levels) | express new receptors | signal in absence of ligand (induce mutations) | make own growth factors

Question 8

Why would a tumor cell want to be independent of extrinsic factors?

Answer 8

the signal stimulation is not permanent = need more of it | signals are not always present = need to wait for it to come

Question 9

What are autocrine loops and paracrine loops? Which ones do tumor cells most use?

Answer 9

autocrine (most used by tumors) = secrete own growth factors and stimulate self | paracrine = stimulate other cells, help others grow

Question 10

What are cytokines?

Answer 10

proteins and peptides used as signaling compounds

Question 11

What type of signal are tumor growth factors?

Answer 11

cytokines

Question 12

What cellular responses do cytokines induce?

Answer 12

protein modification and gene activation

Question 13

What is HER-ceptin?

Answer 13

targets breast cancer cells that express HER proteins via a signaling network

Question 14

What enables a ligand-receptor interaction to give rise to multiple cellular responses/effects?

Answer 14

amplification in signaling pathway | a signal in the pathway will hit different types of proteins&raquo_space;> different cellular effects/responses

Question 15

What is phosphorylation of a protein?

Answer 15

adding a phosphate onto a protein = protein undergoes conformational change = either turns it on or off

Question 16

On which 3 amino acids will a protein be phosphorylated?

Answer 16

tyrosine, serine, threonine

Question 17

What enzyme adds a phosphate from ATP onto protein?

Answer 17

kinase

Question 18

What enzyme takes a phosphate from a phosphorylated protein?

Answer 18

phosphatase = dephosphorylate

Question 19

How does phosphorylation of a protein change the interaction within the amino acids of a protein?

Answer 19

phosphate = highly negative = can cause major repulsion = can open up active sites

Question 20

What effect does the signaling pathway have on tumor suppressors or proto-oncogenes?

Answer 20

can activate or deactivate them

Question 21

What is the effect of a mutation in the p53 gene?

Answer 21

it is unable to activate genes that encode for the protein needed to stall cell division = this protein is not made = cell division not stalled

Question 22

What type of gene (tumor suppressor or proto-oncogene) is the Ras gene?

Answer 22

proto-oncogene

Question 23

What is the effect of a mutation in the Ras gene?

Answer 23

it will send out growth signals in the cell on its own without a signal stimulating receptor = cell replicates excessively

Question 24

What are the 6 types of proteins encoded by proto-oncogenes?

Answer 24

growth factors and its receptors | protein kinases and those that activate it | cell cycle proteins | apoptotic proteins | transcription factors

Question 25

What are the 2 major classes of tumor utilized surface receptors?

Answer 25

enzyme linked | G-protein linked

Question 26

What are the 3 cellular effects if JAK/STATs pathways?

Answer 26

cell growth | immune response | differenitation

Question 27

What are the 3 levels of the MAP kinase cascade? (order them from first to last)

Answer 27

MAP-KKK | MAP-KK | MAP-K | activates other proteins or causes gene expression

Question 28

What are the 7 cellular effects of MAP kinase cascades?

Answer 28

cell growth | apoptosis | angiogenesis | energy deregulation | development | differentiation

Question 29

What is cross-phosphorylation?

Answer 29

dimers will cross phosphorylate each other = conformational change = adapter domains available for other proteins to latch on

Question 30

What is an example of an adapter domain?

Answer 30

SH2 domain

Question 31

How can 1 receptor have 5 outcomes?

Answer 31

domino effect &raquo_space;> can split and activate multiple pathways

Question 32

What is the mechanism of redundancy in receptor subunits?

Answer 32

different cytokine receptors share a common subunit = allows for different combinations of receptors = doesn’t need to make new receptors all the time

Question 33

What type of protein is STAT?

Answer 33

transcription factor puts RNA pol on DNA and helps turn genes on

Question 34

What type of protein is JAK?

Answer 34

receptor kinase

Question 35

What is EGF and what does it do?

Answer 35

epidermal growth factor | binds to JAKs and causes it to dimerize

Question 36

For a gene to be expressed, what needs to be there other than RNA polymerase?

Answer 36

transcription factors = recruits RNA pol onto DNA

Question 37

What is delayed gene expression?

Answer 37

transcription factors MUST be expressed first (immediate gene expression) before expressing desired genes (delayed gene expression)

Question 38

What are 2 ways that tumors deregulate receptor signaling?

Answer 38

via autocrine loop signaling | mutate receptors to initiate signaling cascade in absence of growth factor