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Building an Organism > Signal Transduction > Flashcards

Signal Transduction Flashcards

1
Q

What is TGF-B?

A

A transforming growth factor - small protein hormone

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2
Q

What kind of signalling in TGF-B involved in?

A

Paracrine signalling

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3
Q

What is estradiol?

A

A steriod hormone

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4
Q

What kind of signalling is estradiol involved in?

A

Endocrine signalling

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5
Q

What are two differences between TGF-B and estradiol?

A
  1. TGF-B = protein encoded by a gene, estradiol = steriod synthesised by enzymes
  2. TGF-B cant cross cell membrane by estradiol can
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6
Q

What is signal transduction?

A

The molecular mechanism that converts a signal into a response - involves a ligand and a receptors and the receptor-ligand complex then initiates the response

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7
Q

How many nodal genes do humans have?

A

1

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8
Q

How many nodal genes does xenopus have?

A

6

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9
Q

What is nodal

A

Different levels of nodal related proteins in endoderm due to the gradient between B-Catenin and Veg-T leads to mesoderm induction differentially along the dorsal ventral axis

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10
Q

What are families/superfamilies?

A

Groups of related proteins and genes that encode them that are related by evolutionary ancestory

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11
Q

What is the general structure of a TGF-B family protein?

A

A signal peptide, a propeptide and a ligand

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12
Q

How many aa long is the signal peptide?

A

20aa

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13
Q

How many aa long is the ligand?

A

130aa

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14
Q

What happens to the signal peptide?

A

It is removed during translation by being pulled in the ER and cleaved before the rest of the protein is made

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15
Q

What is the proprotein?

A

The propeptide + the ligand - the propeptide is there to block the ligand activity

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16
Q

What happens to the propeptide?

A

It is removed outside of the target cell to allow the mature ligand to become the signal

17
Q

What removes the signal peptide and the propeptide?

A

Proteolytic cleavage

18
Q

How does TGF-B act as a signal?

A

It causes an allosteric change in shape of the receptor by acting as a serine/threonine kinase

19
Q

Where do a protein kinase transfer the phosphate from?

A

From a high energy phospho-sugar source like ATP or GTP

20
Q

What is the sequence of events from when TGF beta binds its receptor?

A

It binds and causes two receptors (type 1 and type 2) to dimerise which then phosphorylise (autophosphorylate) the serine/threonine/tyrosine residues on the receptors, the phosphorylated receptor then recruits smad2 and smad3 and causes it to oligomere with smad4 which can then go on to regulate gene transcription

21
Q

What happens in cancer that involves TGF-B

A

They normally have a mutation in the smad proteins or in the TGB receptors and are resistant to growth inhibition by TGF-B

22
Q

What do most pancreatic cancers have a mutation in?

A

The gene encoding smad 4

23
Q

What cancers are resistant to TGF-B growth inhibition?

A

Retinoblastoma, colon, gastric, and some T and B cell malignancies

24
Q

Describe the solubility of steriod hormones?

A

They are hydrophobic (water insoluble) but lipophillic so can cross the cell membrane

25
Q

If steroid hormones are insoluble in water what are they carried by?

A

The serum albumin

26
Q

What are the two intracellular receptors of estradiol?

A

Alpha and beta which dimer to have three different combinates (ERaa, ERab, ERbb)

27
Q

What happens when estradiol binds its intracellular target?

A

It causes it to form the dimer which then goes on to attach to the DNA and bind at hormone response elements (estrogen response element which is a palindromic sequence)

28
Q

What causes different cells to repond to estradiol differently?

A

They amount/number/type of receptors they have

29
Q

What is a common response to estradiol gene regulation?

A

Cell growth and division

30
Q

How is estradiol linked to breast cancer?

A

There is an increased abudance of estradiol receptors in a lot of breast cancer as tumours use them to rapidly proliferate

31
Q

What is a drug that could block the ER and therefore be used to treat present cancer?

A

A estradiol receptor antagonist like tamoxifen

Building an Organism (11 decks)

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