Receptors and Cell Signaling Flashcards
1
Q
alter the activity of different components downstream and generate secondary messengers that elicit a particular cellular response
A
effectors
2
Q
- type of cell signaling
- signal (hormone) is transported via blood
- long distance signaling
- long lasting, freely diffusing signal
- ex: epinephrine released by adrenal medulla acts on heart muscle
A
endocrine
3
Q
- type of cell signaling
- signal diffuses to neighboring target cell of a different cell type
- local signaling
- short lived signal
- ex: Leydig cells synthesize and secrete testosterone, induces spermatogenesis by acting on Sertoli and germ cells
A
paracrine
4
Q
- type of signaling
- secreting cells express surface receptors for the signal
- release to cells of the same type
- action of growth factors in cancer cells
- ex: chemokines: IL-1 produced by T cells promote their own replication during immune reponse
A
autocrine
5
Q
- type of signaling
- signal binds to signaling cell which then binds to receptor on target cell
- occurs in immune cells
- ex: heparin-binding epidermal growth factor-like growth factor (HB-EGF) binds to EGF receptor
A
direct/juxtacrine
6
Q
What are the 2 types of signal molecules?
A
hydrophillic and hydrophobic
7
Q
What are the key attributes of hydrophillic signaling? (4)
A
- cannot penetrate plasma membrane
- interact with receptors on cell surface
- receptor complex initiates prod of secondary messenger (small, short half life)
- trigger downstream cell response
(IMPORTANT RECEPTORS: GPCRs and RTKs)
8
Q
What are the key attributes of lipophilic signaling?
A
- pass through plasma membrane unaided
- ligand binds to specific receptor proteins inside cell
- receptor complex acts as transcription factor
- receptors in cytosol or nucleus
-
cytoplasmic receptors: inactive form with HSP90, binding of ligand dissociates HSP90, complex translocates to nucleus, binds to DNA sequence hormone response element (HRE)
5b: nuclear receptors: present in nucleus and bound to DNA
9
Q
What are the 4 steps of GPCR signaling?
A
- ligand binds to ECD (receptor) and causes conformational change
- ICD (inside proteins) activate G protein by exchanging GDP for GTP
- activated G protein interacts with membrane-bound effector, that typically produces secondary messenger
- signaling terminated by: dissociation of signal, inactivation of G protein, reduction of conc of secondary messenger
10
Q
How is a signal desensitized? (4)
A
- drop in hormone levels
- removal of signaling molecule
- sequestration of receptor (endosome)
- destruction of receptor (endosome then lysosome)
11
Q
- variation of GPCR signaling
- stimulates adenylate cyclase (effector)
- ATP > cAMP > AMP
- cAMP activates PKA which phosphorylates target proteins (altered activity)
- ex: epinephrine ligand = relaxation of bronchial/smooth muscle, contraction of heart, inc break down of trigs, inc break down of glycogen in liver/muscle, inc glycolysis in muscle
- ex: histamine ligand = bronchoconstriction and sx of allergic rxn
A
Gs
12
Q
- variation of GPCR signaling
- inhibits adenylate cycle
- cAMP not produced, PKA not activated
- ex: epinephrine/norepi = constriction of smooth muscle; dopamine = increased heart rate
A
Gi
13
Q
- variation of GPCR signaling
- stimulates cGMP phosphodiesterase which breaks down cyclic form of cGMP into 5’-GMP
- ex: light ligand = vision
A
Gt
14
Q
- variation of GPCR signaling
- activates phospholipase C which creats a downstream effect, activation of Ca2+ calmodulin-dependent proteins
- ex: acetylcholine = bronchoconstriction/stimulation of salivary glands
A
Gq
15
Q
What happens when cGMP PDE is inhibited?
A
- increase concentration of cellular cGMP
- prolongs effects for longer time
- smooth muscle relaxation, vasodilation
- in males = erection
- cGMP inhibitors: viagra, levitra, cialis