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Cell signaling Flashcards

1
Q

Cells use chemicals to

A

communicate

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2
Q

a signaling cell produces and releases a

A

signal molecule

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3
Q

A target cell receives the signal using a

A

protein receptor that binds the signal

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4
Q

The receptor transmits a signal to begin an

A

intracellular signaling cascade

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5
Q

The cell responds through what type of change

A

physiological

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6
Q

Signal transduction is how cells do what

A

Communicate

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7
Q

1st type of extracellular signaling type

A

Autocrine

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8
Q

2nd type of extracellular signaling type

A

Paracrine

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9
Q

3rd type of extracellular signaling type

A

Contact-dependent

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10
Q

what is autocrine

A

= self-signaling
* Note on your fridge you write to
remind yourself of the party you are
throwing

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11
Q

what is paracrine

A

= short-distance or localized
* Invitations you place in your
coworkers’ mailbox at work or under
the front door of some nearby friends’
houses

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12
Q

what is contact dependent

A

= surface-to-surface contact
* Invitation you physically hand to your
next-door neighbors

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13
Q

4th type of extracellular signaling type

A

Endocrine

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14
Q

5th type of extracellular signaling type

A

Neuronal

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15
Q

6th type of extracellular signaling type

A

Neuroendocrine

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16
Q

What is endocrine

A

= long-distance, hormonal (uses circulation)
* Mailing out invitations to some of your
friends and family that live far away

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17
Q

What is neuronal

A

= synaptic neurotransmitters
* Sending a text to someone who lives far
away (since you don’t have their address)

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18
Q

What is neuroendocrine

A

= long-distance, where synaptic neurotransmitters instead secrete into circulation
* Mailing out invitations via email or similar
social media accounts for your friends and
family whose addresses/phone numbers
you don’t have (starts electronically, but
wide dispersal like mail)

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19
Q

Receptor Proteins can be what

A

Can be transmembrane receptor
proteins…
* For signals that are either too big,
polar, or charged to enter the cell
* …or intracellular receptor
proteins
* For signals that can cross the cell
membrane (gases, steroids, etc.)

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20
Q

Receptors are highly specific for
a signaling molecule their what

A

ligand

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21
Q

Since receptors are highly specific, what does that mean?

A

This means that most receptors are
only stimulated by a certain molecule
* Some exceptions = “maskable”
scents for similar chem. structures

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22
Q

Cells respond to signals in different ways based upon

A

differentiation

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23
Q

Not all cells will express the same subset of

A

receptors

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24
Q

So, while a signal could reach every cell in the body, only select cells WITH THE RIGHT RECEPTOR will recognize/respond to it. What are the exceptions?

A

Exceptions = receptors needed for MOST cells, just in case, like
immune-related receptors which communicate they are infected

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25
Multiple signals in different combinations result in different cellular
outcomes
26
Allows for subtle and complex control
activities
27
Intracellular relay systems are important for causing
outcomes
28
Response Can Be Fast or Slow Fast:
activity of an existing protein is modified
29
Response Can Be Fast or Slow Slow:
new gene expression occurs and takes longer before a protein is made
30
Surface receptors bind their
ligand
31
The receptor activates
intracellular signaling molecules
32
Signaling events lead to various
potential cellular changes
33
There are multiple effects depending on the molecules involved in intracellular signaling pathways, what are they?
Relay the signal onward and may spread it throughout the cell * Amplify the signal to make it stronger * Detect signals from more other receptors to integrate signals * Distribute the signal to lead to more than one outcome * Modify the signal based on feedback, positive or negative (usually negative)
34
Intracellular Molecular Switches kinases and phosphatases cause what
covalent modification of signaling proteins (stimulatory or inhibitory)
35
GTP-binding proteins (G proteins)
Active/inactive depending on GTP/GDP binding * GAPs turn them “OFF” while GEFs turn them “ON”...especially if MONOMERIC
36
What are the three types of surface receptors
Ion-channel-coupled receptors, G-protein-coupled receptors (GPCRs), Enzyme-coupled receptors
37
What are Ion-channel-coupled receptors
change permeability of the membrane to select ions, altering membrane potential (e.g., Na+ channels)
38
What are G-protein-coupled receptors (GPCRs)
Activate trimeric GTP-binding proteins, which then activate or inhibit other signaling proteins and second messengers ocAMP, Ca2+, IP3, DAG, cGMP, NO, and PKA / PKC kinases
39
what are Enzyme-coupled receptors
Are enzymes or associate with enzymes to activate a cascade Often trigger monomeric GTP-binding proteins of the Ras superfamily
40
Signaling across synapses using neurotransmitters, including
neuromuscular junctions
41
Ion Channel-Coupled Receptors
Action potential triggers VG-Ca2+ channels o Ca2+ triggers exocytosis o Synaptic vesicles dump acetylcholine into the synaptic cleft Acetylcholine binds an ion-channel coupled receptor, which allows sodium to enter the cell o An action potential propagates along the skeletal muscle cell o Transverse tubules bring voltage to ER-VG-Ca2+
42
G-Protein Coupled Receptors
There are different ligands for different types of GPCRs * Exception = smell masking...more likely in humans than mice * All have 7 transmembrane domains * All of them can interact with trimeric G-proteins (αβγ) * Alpha will self inactivate w/GTPase hydrolytic activity, no GAP necessarily required
43
When bound by their ligand, GPCRs undergo a conformational change to interact with
(trimeric) G proteins
44
When G proteins bind to their ligand what takes place
Causes release of GDP from the alpha G protein subunit * GTP binds alpha (GEF not necessarily required), activating the G protein * α and βγ subunits may or may not dissociate, but either way, will activate a target molecule
45
GPCRs activate enzymes that increase
intracellular signaling molecule concentrations
46
intracellular signaling molecule concentrations called what
second messengers
47
After a delay, GTP is hydrolyzed to GDP, deactivating what
The G protein
48
After the delay and GTP is hydrolyzed to GDP what are two things that happen
α and βγ re-associate (inactive) * New ligand-GPCR interactions reinitiate the signaling cascade
49
Adenylyl cyclase produces
cyclic AMP (cAMP)
50
Adenylyl cyclase produces cyclic AMP (cAMP) and leads to what
Extensive effects in both prokaryotes & eukaryotes * Epinephrine signals through cAMP in heart cells to quickly contract, and in fat/skeletal muscle cells (below) * Adenylyl cyclase is a target of caffeine (prolongs cAMP)
51
cAMP signals via protein kinase A (PKA) has two types of events
Fast event = glycogen breakdown * Slow event = altered gene expression
52
Acetylcholine signals through GPCR and does what
Triggers IP3, then Ca2+ (more next slide) * Generates Nitric Oxide (NO) * Through cyclic GMP (cGMP), the NO signal causes vasodilation * How nitroglycerin (NO stim.) & Viagra (cGMP inh.) work
53
Phospholipase C (PLC) phosphorylates & cleaves a membrane phospholipid (phosphatidylinositol-phosphate-2, or PIP2) and produces what
Produces inositol-triphosphate (IP3) and diacylglycerol (DAG)
54
IP3 triggers the second messenger Ca2+ release and what are examples of what could happen
Egg development upon fertilization * Muscle contraction * Cell secretion
55
DAG activates Protein Kinase C (PKC) and what happens
* Smooth muscle contraction (vasoconstriction, bronchoconstriction) * Parasympathetic related secretions (gastric enzymes, saliva, etc.) * Immune signaling (CARD-CC proteins)
56
Enzyme-Coupled Receptors
Ligands bind the external portion of a transmembrane receptor
57
Cytoplasmic portion activates or interacts with an
internal membrane protein that activates a signaling cascade
58
Signals generally slower and require multiple
transduction steps
59
Largest class of enzyme coupled receptors is
Largest class of this type is RTKs (receptor tyrosine kinases)
60
RTKs are usually dimers, but the two subunits are separated w/o ligands, what is an example?
Epidermal Growth Factor Receptor (EGFR)
61
Upon ligand binding & subsequent dimerization, auto-phosphorylation of the dimer occurs, recruiting the next
signaling proteins at the membrane
62
Many RTKs act through Ras, what is Ras?
a small GTP-binding protein attached to the cytosolic face of the membrane
63
While the previous G proteins were trimeric (α, β, γ), Ras is considered what
Monomeric (monomeric G-proteins usually aren’t coupled to GPCRs)
64
Activated RTK signaling activates a Ras-GEF, which causes Ras to release what?
GDP and bind GTP (activating Ras!!!)
65
Ras activates what
intracellular signaling molecules and leads to protein activity and gene expression
66
What does MAPK stand for
mitogen-activated protein kinase
67
What is Mitogen
something that generates mitosis, a.k.a. the cell cycle ex: growth factor
68
MAPK’s can form a series what is it
A kinase may phosphorylate another kinase...and so on... * MAP3K→MAP2K→MAPK * Raf→MEK→ERK
69
RTKs also promotes cell growth & survival through
AKT
70
PI3-kinase is activated by an RTK, which phosphorylates
the inositol phospholipid to produce PIP3
71
PIP3 (formed from phosphorylation of PIP2) attracts what
phospholipase D kinase 1 (PDK1) and Akt; former activates latter
72
Akt activates what
mTOR, Bcl2, survivin, and inhibits Bad & (indirectly) inhibits p53 ...blocking programmed cell death = inhibits apoptosis) * mTORs = mammalian target of rapamycin (Promotes translation) Inhibits protein degradation mTOR = cell growth signaling protein
73
mTORs
mammalian target of rapamycin (Promotes translation)
74
mTOR
cell growth signaling protein
75
What is Apoptosis
programmed cell dealth
76
What happens in Apoptosis
Nucleases condense and cleave chromatin, Organelles break down, Cell debris packaged into apoptotic bodies, avoids tissue-damaging inflammation
77
What is AKT and Bcl-2's role is apoptosis
They are are pro-survival proteins which block apoptosis
78
Bcl-2 homology-domain containing proteins (like Bad) associated with mitochondria can have pro-apoptotic effects;
Can be activated internally/intrinsically (like via p53 signaling)... * ...Or externally/extrinsically (like via contact with a cytotoxic T cell)
79
(pro)Caspases are often inactive in all cells, what does this mean?
ny cell could trigger rapid apoptosis, during events like o Upon infection o To regulate cell numbers o To form correct organ shapes
80
Triggering mitochondrial leakiness leads to
Cytochrome C release, Activates more caspases (other pathways possible), and is the Point of no-return!
81
GPCRs and RTKs are involved in many important signaling events in a cell, disruption of these can
have significant impacts

cell bio part 2 (9 decks)

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