Cell signalling Flashcards
Why do cells signal? List 4 main roles of cell signalling, with an exemple
1) Process information-sensory stimuli (Sight/Sound)
2) Self preservation-identify danger and act against it (relfexes)
3) Voluntary movement (Getting from A to B, existing)
4) Homeostasis-thermoregulation, etc, glucose homeostasis
Eg: glucose homeostasis- Physio process-glucagon produced by alpha cells-islets of langerhans-signal in blood vessels and increase gluconeogenesys and glycogenlysis (glycogen breakdown)
What are the 4 main type of cell communication? Give exemples of each
1) Endocrine signalling-hormone travel with with blood to distant target-glucagon, insulin, adrenaline
2) Paracrine-Hormone does not pass by blood-acts on adjacent cell-eg: Insulin produced by beta cell in islet of langerhans-inhibits alpha cells producing glucagon. Other eg: NO, oestoclast activation by RANKL
3) Membrane attached protein-direct contact between receptor and proteins on different cells-eg: by blood born viruses (HepC)-detected by APC, then uptaken and processed onto MHC II-present it to CD4 cells-this is mebrane attached (tons of other exemples)
4) Autocrine- Signalling molecule secreted and acting on the same cell. Very used in immune system. Tcells make IL2 bind itself and other cells-also Achol, growth factors
List the 4 main types of receptors and give an exemple of each
Inonotrpic receptors (AcChol, GABAA recept), G-protein coupled receptors (Gs: Adenylyl cyclase (aregenergic recept, Gi: Reduce pKA, M2 muscarimic recept, Gq-PLC-angiotensin), Enzyme linked receptor (EGFR, NPRA, TbetaR1), Intracellular receptors (Type1: glucocoritcoid, type2 Thyroid hormone receptor)
Describe the mechanism and function of Ionotrpic receptors
Ligand bind receptor protein, change in conformation in the protein makes structural change-pore allows ions through, ions move in or out (conc gradient), and activate proteins
Function: Very common in nervous system and muscle
eg: AcChol, GABAA
Describe the mechanism and function of GCPR
GCPR are 7TM and heterotrimeric G protein-with alpha subunit (smallGTPase) and Betagamma subunit
Normally, G protein isnt bound-when 7TM binds ligand, HtGprot binds to receptor-GDP is echanged for GTP, alpha and betagamma separate-which can go bind target prots
When its finished, alpha internally cleaved GTP to GDP, leaving its target and trying to bind betagamme, and Betagamma binds again-as long as receptor active can activate htGprots (more than one)
Eg: Gs-activated Adenlylyl cyclase, cAMP activated PKA-then increase heart rate and stuff
Gi-inhibits adenylyl cycles-PKA reduced-lower heart rate
Gq-acts on PLC-Ip3 and DAG-PKC- many effects, but eg: vasocinstriction with angiotensin receptor
Describe the mechanism and function of enzyme linked receptors
Ligand binding leads to receptor cultering-usually dimerisation=> leads to cross phosphorylation and activation of different bindin docks-other cytoplasmic proteins can ome bind and get phosphorylated (activated)-they go off an effect the rest of the cell
eg: insulin receptor-binds insulin and leads to glucose uptake, or ErbB-epidermal growth factor-cell growth/prolif, NPRA, Ser/Thr kinase (like transforming GFbeta)
Describe the mechanism and function of signal transduction
2 types-cytoplasmic or nuclear
Cytoplasmic-located in cytosol, and associated with chaperone molecules (like hsp)-hormone bind receptor and release receptor-the receptor forms a dimer with other, then translocate to nucleus and binds DNA-acts and a transcription factor
Type 2-nuclear:Located in nucleus-cant bind DNA until binds hormone-transcription factor
eg: glucocorticoid receptor, thrydoid homrone receptor
