10/19/2010 An Introduction to Membrane Proteins October 19, 2010 Outline for class today • What does a cell look like? • Cell membranes • Types of membrane proteins • G-protein Coupled Receptors (GPCRs) – Cell signaling cascade role-playing • Membrane-associated proteins – Example from my research 1
10/19/2010 Cell Structure Wikipedia.com Cell Membrane in Detail What molecules can move through the membrane? 2
10/19/2010 Membrane Proteins Integral Membrane Proteins • G-protein Coupled Receptors (GPCRs) • Span the plasma membrane 7 times (transmembrane domains) • 50% of all drugs on the market target • Transmit information of a variety of extracellular signals – light, odorants, hormones, neurotransmitters neurotransmitters – Ex: adrenalin, nicotine, epinephrin, adenosine • control many biological functions – smell, taste, vision, neuronal function, blood pressure, heart rate 3
10/19/2010 GPCR structure and ligand binding Interaction with G-proteins and intracellular signaling ATP cAMP 4
10/19/2010 Protein Kinase A GPCR Cascade glucose production, cell cycle regulation 5
10/19/2010 GPCR signaling cascade • GPCR: 7 people + ligand • G-protein: 3 people + GDP +GTP • Adenylate cyclase: 3 people + ATP + cAMP • Protein Kinase A: 4 people + 4 cAMP – (can simplify this last step to 2 people + 2 ( i lif thi l t t t 2 l 2 cAMP) Studying GPCRs in live cells • Tag the GPCR, but how? • Green Fluorescent • Green Fluorescent Protein (GFP) – GFP glows GREEN when illuminated with UV light – This protein is found in Aequorea victoria jelly fish. – 2008 Nobel prize in Chemistry went to researches who discovered GFP 6
10/19/2010 Looking at a GPCR (Adenosine A2A receptor) inside live cells Membrane dye (Red) outside Membrane dye (Red) inside GPCR-CFP (cyan) Peripheral Proteins PAFAH-II traffics to the intercellular PAFAH-II can be cytoplasmic membranes under stress, the myristoyl under normal cellular conditions tail anchors the protein 7
10/19/2010 PAFAH-II Function PAFAH-II cleaves damaged phospholipids damaged phospholipids, thereby protecting membranes Stress produces fragmented phospholipids in intracellular membranes Visualizing PAFAH-II in Live Cells 8
10/19/2010 PAFAH-II in vivo Oxidative stress Unstressed cells, YFP tagged Stressed cells, YFP tagged PAFAH-II is primarily PAFAH-II is primarily cytoplasmic membrane anchored Removing the Myristoyl Group Stressed cells Unstressed cells 9
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