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Cell signaling
one cell makes a signal and affects a cell
Chemical messengers
direct contact and local and long distance signaling
direct contact
direct translation, tunnels, attach to communicate
Local and long distance signaling
close or far away from production
autocrine
cell makes messenger and is affected
paracrine
affects neighboring cell
endocrine
affects cells at some distance
Phases of cell signaling
reception, transduction, and response
reception
signaling molecule binds to receptors
transduction
receptor changes shape and relay molecules are activated across pathway
receptor
transmembrane protein, commonly found in plasma membrane and bind to certain signaling molecules
response
depends on molecule and type of cell, some change occure
ligand
signaling molecules, bound to receptor, changes shape, âlock and key fitâ
agonists
binds to receptor and activates it, triggers response
antagonists
binds to receptor and inhibits receptor activation
G protein-coupled receptors (GPCRs)
when binded and activated to ligand, g protein binds to GDP, agonist binds and triggers interaction with g protein, GDP leaves, GTP binds to g protein, moves, and interacts with enzyme
receptor tyrosine kinases (RTKs)
receptors with kinase activity, bind to agonist and proteins form dimers and when activated phosphorylate each other, recruits other signaling molecules
GTP
active g protein, eventually exchanged with GDP to rest
Ligand gated ion channels
transports ions across a membrane, signaling molecule opens gate, CNS role
intracellular hormone receptors
found in cytosol/plasm, steroids bind to receptors, normally inactive, agonist must be able to get inside, cell can make genes
steroids in receptors
hydrophobic so can get inside
transduction
-Cascades of molecular interactions relay signals from receptors to target molecules in the cell
-Cell signaling is usually a multistep process
- Multistep pathways can greatly amplify a signal
second messengers
small molecules and ions
kinases
protein phosphorylation
phosphatases
dephosphorylation
second messengers participate inâŠ
pathways initiated by GCPRs and RTKs
Cyclic AMP (cAMP)
converts ATP to cAMP in response to extracellular signal, activates PKA, phosphorylates other proteins
Adenylyl cyclase
enzyme in plasma membrane responsible for cAMP
Calcium Ions and Inositol Triphosphate (IP3)
calcium ions used, ca2+ concentration in cytosol lower than outside of the cell
IP3 formula
phspholipase C â> PIP2 â> DAG and IP3
response
signal transduction pathway leads to regulation of one or more cell activities
Response Types
regulation of gene expression, enzyme activity, and cellular activity
Termination of signal
dephosphorylation and signaling molecule degradation
signaling molecule degradation
ubiquitination and ubiquitin ligases mark for destruction in proteosome
PIP2
regulates function of ion channels