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PSIO303 > Block 3 Lecture 31 and 32 > Flashcards

Block 3 Lecture 31 and 32 Flashcards

1
Q

what are the types of signal transduction

A
  1. signaling through chemical messengers

2. signaling through connexins

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2
Q

what is the cell surface receptor pathway

A

external signals -> cell surface receptors -> intracellular 2nd messengers-> cellular responses

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3
Q

what are the 4 categories of cellular receptors

A
  • ligand gated
  • GPCRs
  • catalytic receptors
  • nuclear receptors
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4
Q

what happens in ligand gated receptors

A

integral membrane proteins when bound by the ligand they interact with ion channels modifying the flux of the ion across the channel

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5
Q

what is the second messenger in ligand gated receptors

A

the ion

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6
Q

what are some examples of ligand gated receptors

A

beta cell of endocrine pancreas and nicotinic ACh receptors

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7
Q

what are GPCRs

A

integral membrane proteins that when bound by a ligand interact and activate a G protein which modulates a separate enzyme or ion channel

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8
Q

what is the second messenger in a GPCR

A

the product of the enzymatic activity

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9
Q

what is an example of a GPCR

A

beta adrenergic receptors, alpha 1 and alpha 2 adrenergic receptor, glucagon receptor

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10
Q

what are catalytic receptors

A

integral membrane proteins, ligand binding either activates the enzymatic activity of the receptor or initiates a series of events that causes activation of an intracellular enzymatic complex

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11
Q

what is the second messenger in catalytic receptors

A

the substrate of the activated enzyme

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12
Q

what is an example of a catalytic receptor

A

insulin receptor

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13
Q

what are nuclear receptors

A

either in cytoplasm or in nucleus act as transcription factor

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14
Q

what is the mechanism of signal transduction from plasma membrane receptors?

A
  1. recognition- ligand binds a specific site on exofacial aspect of the receptor
  2. transduction- binding of the ligand induces a conformational change in the receptor that modifies its functionality and subsequently produces a 2nd messenger
  3. transmission- 2nd messenger produced will interact with various intracellular effector modules
  4. modulation of the effector- interaction of the 2nd messenger with effector results in activation of a kinase or phosphatase and change in phosphorylation state of target
  5. response- the actions of one or more signaling events modifies cellular function in highly specific ways
  6. termination- feedback mechanisms that cause the cessation of the signaling events and facilitate the return of cellular function back to basal state
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15
Q

what happens in amplification

A

can happen through increased production of 2nd messengers in each step

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16
Q

what happens in a GPCR

A

ligand binds and GDP is swapped for GTP on alpha subunit. alpha subunit dissociates from beta gamma complex. now each can modulate their respective effector proteins. then GTP is hydrolyzed either by GTpase or members of RGS family

17
Q

what are the major types of effectors that couple to G-proteins

A

adenylate cyclase, phosphodiesterase, and phospholipase C

18
Q

how is adenylate cyclase activated

A

Gs, cAMP is produced and increased PKA activity

19
Q

how is adenylate cyclase inactivated

A

Gi, lowers cAMP and decreased PKA activity

20
Q

how is phosphodiesterase activated

A

Gt, breaks down cGMP and inactivated cGMP dependent channels

21
Q

how is phospholipase C activated

A

Gq, cleaves PIP2 into DAG and IP3

22
Q

what does DAG do

A

activates PKC

23
Q

what does IP3 do

A

stimulates release of Ca2+ from ER

24
Q

what are the types of catalytic receptors

A
  • receptor guanylate cyclase
  • receptor serine/threonine kinase
  • receptor tyrosine kinase
  • tyrosine kinase associated receptors
  • receptor tyrosine phosphatases
25
Q

what do receptor guanylate cyclase do

A

produce cGMP from GTP

26
Q

what do receptor serine/threonine kinases do

A

phosphorylates serine and threonine

27
Q

what do receptor tyrosine kinases do

A

phosphorylates tyrosine

28
Q

what do tyrosine kinase associated receptors do

A

characterized by their ability to interact with and activate cytosolic tyrosine kinases

29
Q

what do receptor tyrosine phosphatases do

A

dephosphorylate tyrosine

30
Q

what is the tyrosine kinase signal pathway

A
  1. single exofacial subunit of the receptor binds the ligand, leading to reversible dimerization of 2 receptors
  2. dimerization induces autophosphorylation and activated of receptor complex
  3. enhances tyrosine phosphorylation of cytosolic proteins
  4. leads to activation of downstream effectors and modifies cell function
  5. activation of the receptor will stop once either the ligand receptor complex is internalized or by the action of a phosphatase

PSIO303 (31 decks)

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