4/7/17 1 Repetition Summary of last lecture Cell Signalling – Hormone Signalling Hormone (testosterone) EXTRACELLULAR FLUID Receptor protein DNA mRNA NUCLEUS CYTOPLASM Plasma membrane Hormone- receptor complex New protein 1 The steroid hormone testosterone passes through the plasma membrane. The bound protein stimulates the transcription of the gene into mRNA. 4 The mRNA is translated into a specific protein. 5 Testosterone binds to a receptor protein in the cytoplasm, activating it. 2 The hormone- receptor complex enters the nucleus and binds to specific genes. 3 (a ligand) • Steroid hormones bind to intracellular receptors Cell Signalling – Receptors in the Plasma Membrane • main types of membrane receptors • G-protein-linked • Tyrosine kinases • Ion channel
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4/7/17
1
Repetition
Summary of last lecture
CellSignalling –
HormoneSignalling
Hormone(testosterone)
EXTRACELLULARFLUID
Receptorprotein
DNA
mRNA
NUCLEUS
CYTOPLASM
Plasmamembrane
Hormone-receptorcomplex
New protein
1The steroid hormone testosterone
passes through the plasma membrane.
The bound protein stimulates the transcription of the gene into mRNA.
4
The mRNA is translated into a specific protein.
5
Testosterone binds to a receptor protein in the cytoplasm, activating it.
2
The hormone- receptor complex enters the nucleusand binds to specific genes.
3
(a ligand)• Steroidhormonesbindtointracellularreceptors
CellSignalling – ReceptorsinthePlasmaMembrane
• maintypesofmembranereceptors
• G-protein-linked
• Tyrosinekinases
• Ionchannel
4/7/17
2
321
IP3 quickly diffuses throughthe cytosol and binds to an IP3–gated calcium channel in the ERmembrane, causing it to open.
4 The calcium ionsactivate the nextprotein in one or moresignaling pathways.
6Calcium ions flow out ofthe ER (down their con-centration gradient), raisingthe Ca2+ level in the cytosol.
5
DAG functions asa second messengerin other pathways.
Phospholipase C cleaves aplasma membrane phospholipidcalled PIP2 into DAG and IP3.
A signal molecule bindsto a receptor, leading toactivation of phospholipase C.
EXTRA-CELLULARFLUID
Signal molecule(first messenger)
G protein
G-protein-linkedreceptor
Variousproteinsactivated
Endoplasmicreticulum (ER)
Phospholipase CPIP2
IP3(second messenger)
DAG
Cellularresponse
GTP
Ca2+
(second messenger)
Ca2+
IP3-gatedcalcium channel
Calcium
Signalling(diacylglycerol)
• Other pathways• regulategenesbyactivatingtranscriptionfactorsthatturngenesonoroff
Reception
Transduction
Response
mRNANUCLEUS
Gene
P
Activetranscriptionfactor
Inactivetranscriptionfactor
DNA
Phosphorylationcascade
CYTOPLASM
Receptor
Growth factor
• Ionchannelreceptors
Cellularresponse
Gate open
Gate close
Ligand-gatedion channel receptor
Plasma Membrane
Signalmolecule(ligand)
Gate closed Ions
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