17.4 Receptors Coupled to Transcription Factors

Question 1

prototype of a polypeptide growth factor family that controls proliferation and differentiation of a variety of cell types

Answer 1

TGF-beta (transforming growth factor)

Question 2

TGF-beta receptors are composed of 2 distinct polypeptides () that become associated following ligand binding

Answer 2

type I and type II

Question 3

overview of TGF-beta/Smad pathway

Answer 3

1. TGF-beta binding leads to association of type I and II polypeptides of TGF-beta receptor
2. type II receptor phosphorylates type I receptor
3. type I receptor phosphorylates transctiption factors of the Smad family
4. phosphorylated Smads form complexes that translocate to the nucleus and

Question 4

similarities of TGF-beta/Smad and JAK/STAT pathways

Answer 4

• both involve a protein kinase associated with a receptor that directly phosphorylates and activates a transcription factor
• both involve dimerized components
• both result in expression of target genes in the nucleus

Question 5

differences of TGF-beta/Smad and JAK/STAT pathways

Answer 5

• receptors of transforming growth factor beta (TGF-beta) and related polypeptides are protein kinases that phosphorylate serine or threonine residues
• receptors in JAK/STAT pathways phosphorylate tyrosine residues

Question 6

family of transcription factors that stimulates ubiquitylation and degradation of an inhibitory subunit

Answer 6

NF-kappaB family

Question 7

NF-kappaB family consists of 5 transcription factors that play key roles in the (1), as well as in (2)

Answer 7

1. immune system and in inflammation
2. regulation of proliferation and survival of many animal cell types

Question 8

NF-kappaB family members can be activated by:

Answer 8

1. cytokines
2. growth factors
3. bacterial/viral infections
4. DNA damage

Question 9

signaling pathways that lead to NF-kappaB activation were found downstream of:

Answer 9

1. tumor necrosis factor (TNF)
2. Toll-like receptors - recognize a variety of molecules associated with pathogenic bacteria and viruses

Question 10

cytokine that induces inflammation and cell death

Answer 10

tumor necrosis factor (TNF)

Question 11

receptors that recognize a variety of molecules associated with pathogenic bacteria and viruses

Answer 11

Toll-like receptors

Question 12

overview of NF-kappaB pathway

Answer 12

1. bound inhibitory I(kappa)B proteins maintain NF-kappaB proteins in an inactive state in the cytosol of unstimulated cells
2. activation of TNF and Toll-like receptors results in recruitment of adaptor proteins that activate I(kappa)B kinase
3. I(kappa)B is phosphorylated, and is thus targeted for ubiquitylation and degredation by the proteosome
4. NF-kappaB is now free to translocate to the nucleus and induce target gene expression

Question 13

signaling system that activates transcription factors by inhibiting their ubiquitylation and degradation (done through proteoysis)

Answer 13

Wnt pathway

Question 14

secreted factors that control events in the development of vertebrate and invertebrate embryos, as well as in regulating the proliferation of stem cells in adult tissues

Answer 14

Wnt family

Question 15

members of the Wnt family are secreted growth factors that bind to a complex of receptors of the (1) and (2) families

Answer 15

1. Frizzled
2. LRP

Question 16

Wnt signaling inhibits degradation of () (by proteolysis) which then acts as a transcriptional activator

Answer 16

beta-catenin

Question 17

signaling pathway that is an example of direct cell-cell interactions during development

Answer 17

Notch pathway

Question 18

large protein with a single transmembrane domain that serves as a receptor for signaling by transmembrane proteins (e.g. Delta protein) on the surface of adjacent cells

Answer 18

Notch

Question 19

ligand binding leads to proteolytic cleavage of Notch by ()

Answer 19

gamma-secretase