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BIOC192 2024 Melia > Lecture 14 - Activation and Inhibition of Proteins Pt. II > Flashcards

Lecture 14 - Activation and Inhibition of Proteins Pt. II Flashcards

1
Q

What are some ways that a message can be passed on during signal transduction?

A
  1. Proteins
  2. Chemical signals (second messengers)
  3. Sequential phosphorylation
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2
Q

What do the multi-step pathways of signal transduction help provide?

A

opportunities for coordination and regulation of the cellular response

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3
Q

Which of the two mechanisms of signal transduction are most common to many receptors?

A

second messengers, and phosphorylation

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4
Q

What receptors use second messengers?

A

many different receptors, especially GPCRs

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5
Q

What are second messengers?

A

intracellular molecules that change in concentration in response to receptor activation

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6
Q

How do second messengers work?

A

transmit signals form the receptor to other relay molecules because they are not attached to the membrane

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7
Q

What does Phosphorylation and Dephosphorylation do to proteins?

A

Turn protein activity on and off, or up and down

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8
Q

How does phosphorylation occur?

A

Protein kinases transfer phosphates from ATP to protein

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9
Q

How does a phosphorylation cascade occur?

A

Via the use of many different protein kinases

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10
Q

How does dephosphorylation work?

A

Protein phosphatases rapidly remove the phosphates from proteins to carefully control signal transduction

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11
Q

What are some ways that signal transduction is tightly regulated?

A
  1. Ligand dissociation
  2. Internalisation (removal of receptor from cell surface via endocytosis)
  3. Phosphatases
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12
Q

How does signal transduction occur in GPCRs?

A
  1. GPCRs use G proteins to start signal transduction
  2. GPCR activates the G protein which communicates with other proteins in the cell
  3. Different types of G proteins cause different effects
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13
Q

What are some examples of G proteins?

A
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14
Q

How does Glucagon (A peptide ligand) receptor signal transduction occur?

A
  1. Glucagon receptor is a GPCR
  2. Glucagon binds receptor
  3. Receptor activation causes G Protein activation + leads to further signal transduction events
  4. Leads to Glycogen breakdown + lipolysis
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15
Q

How does GLP-1 receptor signal transduction occur?

A
  1. GLP-1 receptor is a GPCR
  2. GLP-1 binds receptor
  3. Receptor activation causes G protein activation and further signal transduction
  4. Leads to insulin secretion
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16
Q

What is GLP-1?

A

A peptide ligand that is produced in the gut, and acts on pancreatic Beta-cells

17
Q

How are adaptor proteins phosphorylated? (starts signal transduction in RTKS)

A
  1. agonist ligand binds
  2. receptor changes conformation and becomes activated
  3. receptor autophosphorylation occurs
  4. adaptor protein is phosphorylated
18
Q

How does signal transduction occur in RTKs?

A
  1. Agonist ligand binds
  2. Adaptor protein is phosphorylated
  3. Adaptor proteins communicate with other proteins in the cell
  4. Different types of adaptor protein result in different effects
19
Q

How does insulin receptor signal transduction in muscle and adipose cells occur?

A
  1. Insulin binds to insulin receptor (an RTK)
  2. Receptor activation causes phosphorylation of adaptor protein + further signal transduction events
  3. Leads to GLUT-4 translocation
  4. Permits entry of glucose into cell
20
Q

What is insulin?

A

An endogenous peptide ligand

21
Q

How does insulin receptor signal transduction in liver cells occur?

A

In liver cells, receptor activation causes phosphorylation of an adaptor protein and further signal transduction events. However this leads to Glycogen synthesis in the liver rather than glucose entry

22
Q

How do ligand gated ion channels differ from other receptor classes?

A
  • Instead of the use of relay proteins like G proteins or adaptors being used ions directly flow through the channels to produce effects
  • Faster signalling compared to GPCRs and RTKs
23
Q

How are ligand gated ion channels activated?

A

Binding of an agonist ligand causes a conformational change to activate receptor

24
Q

How can cellular responses be controlled by receptors?

A

Depending on where receptors are expressed

25
Q

Why can different cells detect and respond differently to the same ligand?

A

Because they have different collections of receptor and relay molecules

26
Q

How can the same ligand and receptor pairing result in different effects in different cells?

A

different cells use different combination of relay molecules for signal transduction

27
Q

What is the role of the pathway branching and ‘cross-talk’ in cellular signalling?

A

Helping coordinate signals from incoming ligands

BIOC192 2024 Melia (36 decks)

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