BIOL 3510 1st Edition Lecture 20 Outline of Last Lecture I. Three Types of Extracellular ReceptorsII. GPCRs Activate G-proteins upon Signal BindingIII. Bacteria exploit G-protein activityIV. Many actions trigger an increase in intracellular Ca2+ concentrationsOutline of Current Lecture I. Enzyme-coupled ReceptorsII. Receptor Tyrosine KinasesIII. Intracellular Signaling MoleculesIV. Ras Mutated in Cancerous CellsV. Plant Cell Communication Strategies Current LectureEnzyme-coupled receptors- Bind signaling molecules extracellularly- Often regulate cell growth, proliferation, differentiation and/or survivalReceptor tyrosine kinases (RTKs)1. Two RTKs dimerize after the signal binding2. Dimerized rtKs phosphorylate each other3. Intracellular signaling proteins are activated upon binding to the phosphorylated Rtks4. Signaling is turned off when protein tyrosine phophatase dephophorylates the RTKsIntracellular signaling molecules activated by the RTKs include:1. Phopholipase C: generates DAG and IPs2. Ras: monomeric GTPase attached to the plasma membrane3. Phosphoinositide 3-kinase (Pi 3-kinase) – phosphorylates inositol phospholipidsRas is activated when a signal binds a RTK leading to the activation of Ras-GEF.Activated Ras initiates the MAP-kinase signaling moduleRas is often mutated in cancerous cellsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Mutations affect the GTPase activity of Ras (Ras is always on)- Leads to uncontrolled cell proliferationPi 3-kinase generates phosphorylated inositol phospholipid upon RTK activation.- Phosphorylation by Akt indirectly activates tor, a kinase, which promotes cell growthPlants and animals have different cell communication strategies.In plants:- No RTKs, steroid hormone nuclear receptors, cAMP, and few GPCRs- Lots of receptor serine threonine kinases- Signal binding to an ethylene receptor relieves transcriptional repression in plantsSignaling pathways are highly interconnectedIntracellular signaling proteins can integrate incoming
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