Signaling III

Question 1

What is RAS? What is it involved in?

Answer 1

Is an example of a proto-oncogene

When they are mutated become oncogenes and those are involved in cancers

It plays a role in cell division decision making

Question 2

What activates RAS and what does it behave like?

Answer 2

RAS activated by the signaling complex

The signaling complex behaves like alpha subunit

RAS has a GDP bound to it and it releases the GDP and attaches to a GTP. This activates RAS

Question 3

What happens when RAS travels in the cell?

Answer 3

RAS travels, binds to protein called RAF

This causes a cascade to form the signal that is sent to the nucleus

Stimulates Transcription of genes that will result in DNA replication and cell division.

Question 4

RAS slowly cleaves GTP to GDP so what does this mean?

Answer 4

RAS can turn itself off.

Question 5

How does Steroid Hormone Signaling work?

Answer 5

Steroid Hormones cross membrane on their own

Once in the cytoplasm the hormone binds to its receptor either in the cytosol

Changing the receptor protein shape

Once in the cytoplasm the hormone binds to its receptor either in the nucleus

Binds to section of DNA, this induces alterations in gene activity

Becoming a transcription factor altering gene expression.

Question 6

What is the speed like of Steroid Hormone Signaling

Answer 6

Signaling mostly affects gene expression tend to be slower in its effects.

Covalent modification and and enzyme control happens much faster

Question 7

What happens to a Receptor protein bound to another protein called Hsp70?

Answer 7

This binding of Hsp70 causes the receptor not to be able to go into the nucleus

The receptor waits for a hormone

The binding of hormone causes it to let go of Hsp70 and the receptor can now move into the nucleus

Question 8

How does Glucocorticoid Hormone signaling

work?

Answer 8

o	Hormone entry into cell
o	Release of Hsp
o	Dimerization of receptor
o	Movement through a nuclear pore
o	Transcription Activation

Question 9

How does Non-Hormone Signaling work in nerve transmission?

Answer 9

Cells communication in nerve transmission

Relies on ion gradients and neurotransmitter molecules to transmit signal

Blocked by ion channel blocking molecules
Ex. Neurotoxins

Question 10

What are Prostanoids?

Answer 10

Also known as prostaglandin. Derived from arachidonic acid and exert effects near where they are released
Ex. Prostaglandins and Prostacyclin

They are precursors to thromboxanes. Synthesis inhibited by steroids and NSAIDs- Aspirin, Ibuprofen

Question 11

What are Oncogenes?

Answer 11

A mutated gene whose activity can cause uncontrolled growth.

Mutation affecting expressing of genes

Question 12

What are Proto-oncogenes?

Answer 12

a unmutated form of an oncogene.

Question 13

What affects does GTPase have on RAS?

Answer 13

GTPase converts GTP to GDP, inactivating RAS

Question 14

What affects do Mutations of amino acids 11/12 or 61 have?

Answer 14

Mutations of amino acids 11/12 or 61 inhibit GTPase and activates RAS

Activated RAS stimulates cell division

Question 15

What are Src proteins?

Answer 15

Src proteins are tyrosine kinases found in various cell locations.

Found in chickens
o Dephosphorylated Src acts to stimulate cell division.
o If its phosphorylated Src’s tyrosine turn OFF

Question 16

What affects do Mutations have on Src proteins?

Answer 16

Mutations that affect Src’s phosphorylation convert caused the Src’s to always be on.

Mutations affect protein structure and function

Tyrosines are phosphorylated in Src’s

Block access to its SH2 domain and prevent it from participating in signaling. Leaving it inactive.