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PMP 101 Health, Disease and Patient > Cell communication and signalling > Flashcards

Cell communication and signalling Flashcards

1
Q

Importance of

Cell communication

A
  • To sense and respond quickly to the environment
  • Governs basic cell function response to external change bacterial cell plant bend fight or flight sweat shivering
  • To quickly identify invading organisms and respond to them
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2
Q

Three types of junction

A
  • Gap junction
  • Anchoring junction
  • Tight junction
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3
Q

Gap Junction

A
  • 2 cylindrical channel (6 connexin proteins) adjacent cells joined to form a pore
  • Allow bidirectional change between 2 cells no effect on EMC adhesion
  • Only gap junction provide direct communication allows small intracellular water soluble during inorganic ions pass form cell to cell
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4
Q

Contact dependant

A
  • Signalling molecule binds to receptor on interacting cell
  • Exchange via gap junction
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5
Q

Endoctrine

A
  • Signal hormone to travel through blood stream at distant body site insulin beta cells promote absorption liver and skeletal muscle
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6
Q

Paracrine

A
  • Signals local release into extracellular local
    Nitric oxide relax smooth muscle
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7
Q

Synaptic

A
  • Specific signal at specialised junction
  • Neural along nerve terminal release neurotransmitters receptor on target cells
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8
Q

Autocrine

A
  • Signalling secrete extracellular signal bind to receptor on same cell
  • Self-regulate stimulate own survival
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9
Q

Signal receptor

A

External surface imbedded to plasma membrane specific interaction

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10
Q

Signal transduction

A
  • Signal receptor binding
  • Convert and amplify the extracellular signal into different intracellular event
  • Specific cell response
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11
Q

Signal receptor interaction

A
  • Receptors are specific ligands complementary to mediate response
  • Activated only by one type of signal cells
  • Possess a receptor for the signal
  • hydrophobic intracellular
  • hydrophillic extracellular
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12
Q

Intracellular receptor

A
  • Receptor proteins are intracellular in cytosol
  • Hydrophobic signal molecule cross membrane to activate
  • Hormone receptor complex act as transcription factor binding DNA sequence to modify transcription produce effector proteins
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13
Q

Membrane receptors

A
  • Ion channel coupled
  • G protein receptor
  • Enzyme coupled receptor
  • Signal receptor - always causes conformational change
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14
Q

Ion channel coupled

A
  • Receptor conformational change after binding the signal activates the ion channel specific ion
  • Chemical to electric
    e.g. nerve cells and other electrical excitable cell such as muscle
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15
Q

Intracellular receptors

A
  • In cytosol or nucleus of target cell
  • Hydrophobic signalling molecules such a steroids and thyroid molecules
  • Transcription factor binding DNA sequence to initiate transcription of specific genes to produce effector proteins
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16
Q

G protein coupled receptors (GCPRs)

A
  • Transmembrane receptors
  • G protein
17
Q

Trans-membrane receptor

A
  • Protein that crosses 7 times in the plasma membrane (fold)
  • Ligand binding site is on the extracellular
    side
18
Q

G protien (switch on/off)

A
  • On cytosolic side of the plasma membrane
  • 3 subunits- α, β, γ
  • α associated with inactive GDP
  • ## Ligand binding activates GDP into GTP
19
Q

Activation of GPCR’s

A

1) Signalling binds to receptor which undergoes conformational change
2) This change attracts and activates a G-protein and
its α subunit exchanges its GDP for GTP
3) This dissociates the α subunit and βγ complex

20
Q

GPCRs effect and inactivation

A
  • Both α subunit and βγ complex can interact and activate ion channels
  • Activate membrane bound enzyme that are indolved in signalling transduction
21
Q

GCPRs inactivation

A
  • Activation of target protein by α subunit
  • Hydrolysis of GTP by α subunit inactivates the subunit causing diassociation from target protein
  • Inactivated α subunit reassembles with βγ to reform the inactive G protein
22
Q

Enzyme coupled receptors

A
  • Receptor cytoplasmic part either acts like the enzyme itself receptor tyrosine kinases (RTKs) or the receptor forms a complex with the enzyme
23
Q

RTKs

A
  • Membrane receptors that attach phospates to tyrosine amino acids
  • Can trigger multiple signal transduction pathways at once, stimulating cell growth and cell survival
  • Abmormal function can cause cancers
24
Q

Enzyme coupled receptors

A

1) Ligand binding induces the pairing of 2 receptors (dimerisation)
2) Intracellular receptor parts (kinases) phosphorylate each other’s specific tyrosines
3) Phosphorylated tyrosine recruit many different intracellular signalling proteins
4) Some become phosphorylated and activated (signal transduction), a process required to trigger a complex response such as cell proliferation or differentiation

25
Q

Transduction step

A
  • Multisteps to amplify a signal
  • Multistep pathways provide more opportunities for coordination and regulation
  • Different transduction strategies (phosphorylation cascade or second messengers)
    for different pathways
26
Q

Protein phosphorylation cascade

A
  • This phosphorylation (by kinases) and dephosphorylation (by phosphatases)
    system acts as a molecular switch, turning activities on and off
27
Q

Second messenger model

A
  • readily spreads through body and amplifies signal
  • small water soluable ions
  • cAMP, cGMP, lipids and NO
  • initiated by G protiens
28
Q

Second messenger model in GPCR’s

A
  • Activation of some G-protein-linked receptors can
    activate a membrane-bound enzyme called adenylyl
    cyclase that converts ATP to cAMP
  • cAMP exerts most of its effects by activating the
    enzyme cyclic-AMP-dependent protein kinase (PKA)
  • Activated PKA catalyses the phosphorylation of
    particular serines/threonines on specific target
    proteins (e.g. involved in the glycogen breakdown)
29
Q

With IP3

Second messenger model in GPCR’s

A
  • Phospholipase C splits when activated into 2 small molecules inositol trisphosphate (IP3) and diacylglycerol
  • IP3, opens Ca2+ channels in the
    endoplasmic reticulum to release Ca2+ into the cytosol
  • Ca2+ signal activates some proteins
    triggering many biological processes
30
Q

Cell-receptor interaction

A
  • Regulation of gene expression, turning transcription of specific genes on or off

PMP 101 Health, Disease and Patient (64 decks)

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