cell communication 1 Flashcards
Define signal transduction and list the basic components involved in this process in cells.
- conversion of one type of signal to another
- receptor receives and converts signal, extracellular molecule (protein, aa, steroid, etc) to a different type of signal inside the cell (
-receptors acts as device to convert extracellular signal to intracellular
3 phases
reception: signal binds to receptor
transduction: what receptor does and what it does to signal
response: effector proteins integrate info + response (transcription regulators, metabolic enzymes, cytoskeleton proteins such as microtubules)
List the main types of signal-mediated cell–cell communication and identify the type of extracellular signal molecule involved in each.
proteins, peptides, amino acids, nucleotides, steroids, fatty acid derivatives or gases.
Outline the main classes of extracellular signal molecules, and describe the types of receptors to which they bind.
endocrine: secrete hormones in blood, to target cells , far from target
LOCAL:
paracrine: signals from neighbouring cells, in ecf
synaptic: local, in extracellular matrix, muscle cell or neuron receives signal
contact-dependent: membrane bound protein, receptor direct contact
Outline the main classes of extracellular signal molecules, and describe the types of receptors to which they bind: ENDOCRINE
- signal molecule: hormones
- remote signals
- target distant cells
- transported via blood
ex: insulin, adrenaline, cortisol
Outline the main classes of extracellular signal molecules, and describe the types of receptors to which they bind: SHORT RANGE
- local
- paracrine: growth factors, inflammation factors (histamine), NO
- synaptic: neurotransmitters: acetylcholine and GABA
- contact dependent: delta (transmembrane protein) with notch receptor
Explain how the same signal molecule can induce different responses in different target cells.
each cell has different sets of receptors and signal transduction pathways
- response depends on type of receptor present to recognize the signal (sensitivity to signals)
- interior is different, effector proteins are different, different sets of genes are expressed in different cell types
- each cell type receives and interprets signal differently
- signal interpretation depends on receptor, means (intracellular effector proteins) and other signals received by cell
Explain how the same signal molecule can induce different responses in different target cells: EXAMPLE
responding to acetylcholine
cell types: heart pacemaker, salivary, skeletal muscle
response: decreased rate of firing/slows down, secretion of saliva, contraction
difference:
skeletal muscle: receptor is ligand gated ion channel, actin/myosin in skeletal muscle
salivary vs heart pacemaker:
same receptor but different effector proteins inside cell
sv: different means, diff signalling pathway presence of vesicles for secretion
hp: receptor linked to ion channel, triggers action potential, ROF decreases
Explain how a combination of signals can evoke a response that is different from the sum of the effects that each signal can trigger on its own
- chemical signals instruct cell to survive, grow, divide, differentiate
- decides what to do based on combo of signals
- no signal: cell dies
Explain why some cell responses to extracellular signals occur rapidly but others take minutes or hours to execute.
fast responses:
- change in movement, shape, metabolism, secretion
- FAST due to proteins already present just have to change polymerization, no change in gene expression
slow responses:
- differentiation, division, growth
- SLOW due to change in gene expression
Cell surface vs intracellular receptors
cell surface:
- extraceullar signal molecules are large and hydrophilic
- do not cross plasma membrane
- bind to cell-surface receptor
- converts to intracellular signal molecule in target cell
intracellular:
- small and hydrophobic (some hormones)
- enter plasma membrane
- directly activate enzyme or bind to intracellular receptors in cytosol or nucleus
- then regulate gene transcription or other functions
Intracellular receptor: CORTISOL
EXAMPLE: cortisol
- secreted by adrenal glands in response to stress
- crosses plasma membrane and binds to receptor protein in cytosol
- receptor hormone complex is transported to nucleus via nuclear pores
- cortisol binding activates receptor proteins
- which can bind to sequences of DNA
- regulates + activate transcription of specific target genes
Intracellular receptor: NO
- NO diffuses across membrane and directly regulates activity of intracellular enzyme (guanylyl)
- smooth muscle relaxation in blood vessel
- dilation of blood vessels
1) endothelial cells receive signal, and response to produce NO
2) NO released, acts as paracrine signal on smooth muscle cells
a) acetylcholine causes dilation, [neurons] stimulate cell to make and release NO
b) NO diffuses out of endothelial cells into smooth muscle cell
c) binds to enzyme/ target protein (guanylyl cyclase) catalyzes production of cyclic GMP from GTP
d) muscle cells relax
Extacellular receptor: CELL SURFACE + INTRACELLULAR SIGNALS
- extra cellular signals act via cell surface receptors
- change behaviour of target cell
- receptor protein activates signal pathways
- pathways monitored by intercellular signal molecules (proteins, messenger molecules)
- eventually interact with specific effector protein and alter them to change cell behaviour
- target is effector proteins
- response is change in metabolism, shape, etc
signal pathway:
- proteins relay, amplify, integrate, distribute incoming signal
Intercellular signalling pathway/signal transduction pathway between
- events between receptor and effector protein
- intracellular signalling molecules
1) relay: intracellular protein activates then the other and so on
2) amplification: one signal has bound receptor, inside cell it can activate thousands of molecules
3) integration: information integrated due to effector proteins
- in order for protein to be activated, modification as a result of activation of 2 diff pathways is required
(SEE 2 DIFF SCENARIOS- 2 receptors 1 protein, 2 receptors 2 proteins)
4) distribution: once last intracellular signalling molecule activated, it has has to modify effector proteins
5) cross-talk: pathways are not independent, intracellular molecule from one pathway can affect the other
6) feedback: downstream molecules informs upstream
- positive: continue to stay on
-negative: off
7) molecular switches: proteins active/deactive via phosphorylation
- on: stimulate other proteins to get activated
Different ways in which signal is integrated
- 1 receptor activates multiple pathways
- diff receptors activate same pathway
- diff receptors activate diff pathway, one pathway effects the other
