BIO 330 Lecture Notes - Lecture 25: Cell Membrane, Threonine, Autocrine Signalling
BIO 330 Lecture notes 25:
• Extracellular Signals
• Non chemical: Mechanical, heat, light
• Chemical: Hormone, gas, nucleotide
• Transmit messages between cells
• Receptor
• Mediates cell response to signal individually
• Autocrine
• Signal from cell itself
• Paracrine
• Signal from nearby cell
• Endocrine
• Signal from distant cells through bloodstream
• Other Signal Origins
• Neurons, surface of neighboring cells, external environment
• Boxes
• Represent proteins
• Arrows
• Represent molecular actions
• Generic Transduction Cascade 1
• Surface receptors give info to a cell when a ligand binds
• Generates relay through 2nd messengers or creating a docking site through effector
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• Players in cascade
• Reversibly changed to alter function
• Receptors for the same molecule
• Different cell-type expressions or downstream effectors
• Second messengers
• Activate or inactivate proteins
• General Signal Pathway 2
• Surface receptors recruit proteins to intracellular domains at the plasma membrane
• Phosphorylation
• Alters protein conformation
• Phosphatase
• Remove phosphate groups
• 3 Phosphorylated Amino Acids
• Serine, Tyrosine, Threonine
• Signal Transduction
• Converts energy of signaling molecules into cellular response
• Receptor Classes
• G protein (GPCR)
• Enzyme coupled
• Ligand-gated ion channel
• Contact mediated
• Intracellular receptors
• GPCR
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• 7 transmembrane domains
• C-terminus intracellular
• 3rd loop interacts with heterotrimeric G proteins
• GPCR Continued
• Largest superfamily and highly conserved
➢ 700 in the human genome
• GPCR Subunits
• Alpha and gamma subunits lipid anchored
• Activating G Protein Subunits
• Ligand changes GPCR conformation so it can associate with the G protein
• G protein activates downstream proteins
• Activate enzymes to make 2nd messengers
• Multiple G Proteins
• Can be activated by a single receptor
• Galpha
• Primary mediator
• Turn themselves off by hydrolyzing GTP, causing conformational change, dec affinity
for effector, inc affinity for Gbeta
• Gs
• Activates adenylyl cyclase
• Gq
• Activates phospholipase C beta
• Gi
• Inhibits adenylyl cyclase
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