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Cellbiologi - cell signaling
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- 1Example of ligands• Small ions: ferric ion
• Organic molecules: adrenalin
• Polysaccharides: heparin
• Peptides: insulin
• Proteins: vascular endothelial growth factor - 2Signal transduction pathwaysSignal transduction pathways convert extracellular stimuli into specific cellular responses (Campbell and Reece, 2004). Typically, signal transduction begins with a signal to a receptor and ends with a change in cell function. Sometimes, there is a cascade of signals within the cell. With each step of the cascade, the signal can be amplified, so a small signal can result in a large response
- 3cell signaling steps1. signal reception
2. transduction pathway
3. response - 4TYPES OF EXTRACELLULAR SIGNALING SIEndocrine, paracrine, synaptic, contact-dependent
- 5Cell surface receptors vs intracellular receptorsCell surface receptors: large, hydrophilic molecules
Intracellular receptors: small hydrophobic molecule that can cross the membrane (tex steroid hormones) - 6GEF and GAPTwo regulatory proteins (can swith enzymes on and off)
GEF = guanine nucleotide exchange factors: exchange of GDP to GTP
GAP: GTP-activating proteins: switch off by GTP hydrolysis - 73 main classes of cell-surface receptorsion channels coupled receptors: Transduction of chemical signal into an
electrical signal i.e. voltage change across the plasma membrane
G-protein coupled receptors: 7-pass transmembrane helices, the G protein has 3 subunits.
Signal molecule binds the GPCR => activate G-protein that lose GDP affinity and exchange to GTP
enzyme coupled receptors - 8alfa subunit of G-proteinHas intrinsic GTP-ase activity:
Switches itself off by
hydrolysing its bound GTP to GDP - 9G-proteins interact with......ion channels: immediate change of the cell status and behaviour
...enzymes: slower and more complex → additional intracellular signalling
molecules, second messengers such as cAMP, IP3, DAG, Ca2+ - 10Enzyme-coupled receptorsUpon binding of signal (often local mediators such as growth factors), the
receptor usually converts from an inactive monomeric state to an active dimeric state
Largest class of enzyme-coupled receptors: receptor tyrosine kinase (RTK) has a tyrosine protein kinase function in cytoplasmic domain - 11Receptor tyrosine kinase (RTK)1. RTK forms a dimer in active state + phosphorylation on specific tyrosine of the kinase
domains
2. Phosphorylated tyrosines will bind (many) intracellular signalling proteins with specialized
interaction domains → signal transmission (biochemical changes)
3. Response ending by protein tyrosine phosphatases (removing phosphates on tyrosine of
RTK) or destroyed in lysosomes - 12RASa key member of intracellular signalling proteins
• small GTP-binding protein = monomeric GTPase
• mutation in RAS genes is most common oncogen - 13MAPmitogen-activated
protein - 14Mitogenchemical substance that triggers the cell to start cell division (mitogenesis)
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- El usuario ha eliminado su información de asignaturas Fichas sobre Cellbiologi - cell signaling, creado por Usuario eliminado el 19/02/2021.
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- Usuario eliminado · feb 2021
- Actualizado
- 19 feb 2021
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- Creado por Tova A · 10 feb 2021
- Copiado por Tova A · 19 feb 2021
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