Popular in Cell Biology
verified elite notetaker
Popular in Biology
verified elite notetaker
This 3 page Class Notes was uploaded by MelLem on Monday April 4, 2016. The Class Notes belongs to BIOL 225 at Simmons College taught by Dr. Lopilato in Fall 2016. Since its upload, it has received 42 views. For similar materials see Cell Biology in Biology at Simmons College.
Reviews for BIO 225
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 04/04/16
Cell Bio Lecture 14 Two major types of signaling pathways • G Protein Linked Receptors (a) • Receptor Protein-‐Tyrosine Kinases (RTKs) (b) a b Receptor Tyrosine Kinases (RTKs) • RTKS o Goes across the membrane only once o Ligand binding site o Kinase activity • Insulin Receptor • Growth Factor Receptors o Growth factor receptors only go through the membrane once o Has a ton of kinases Steps in the Activation of an RTK • 2 different ways o ligand binds 2 receptors and brings them together (ligand mediated dimerization) o or receptors bring them together after the two different ligands have bound (Receptor mediated dimerization) • In both ways, the activated dimers go through trans-‐autophosphorylation and then signal transmission. At the point of signal transmission, there is a SH2 or PTB domain present . • SH2 – sarc homology 2 • PTB – phosphotyrosine binding domain (binds to phosphorylated tyrosines) Insulin RTK • Function of Insulin o Removed glucose from the blood o Stimulate the conversion of glucose to glycogen (glycogen is the polymer of monomers of glucose at alpha 1,4 glycosidic bonds) • Structure of RTK – tetramer held together by disulfide bonds. o 2 alpha subunits – bind to insulin o 2 beta subunits -‐ kinase activity o Insulin binds to its receptor and triggers a conformational change and tyrosine phosphorylation o As soon as insulin binds to the alpha subunit, the beta subunit phosphorylates. o Alpha and beta chain are linked together by di-‐sulfide bonds o The insulin receptor associates with a small family of adaptor proteins called insulin receptor substrates (IRSs) which provide bonding sites for SH2 domain containing signaling proteins (PI 3 kinase, Grb2, and Shp2) o IRS a – protein that has phosphotyrosine binding domain – insulin receptor substrate (adaptor proteins) – binds through PTP, in turn it gets phosphorylated. o Activated insulin receptor phosphorylates IRS on its tyrosines as well as phosphorylating its own tyrosines. o The tyrosine phosphorylated IRS interacts with a variety of proteins and activates a variety of signaling pathways. Physiological Responses to Insulin • Stimulate glycogen synthase • Increase protein synthesis • Use glucose in lipid synthesis • ** Transfer glucose transporters to membrane** • Activate Ras protein and stimulate growth and division • Insulin binding stimulates PI3K which produces PIP3 and results in protein synthesis, glucose uptake, and glycogen synthesis. Effect of insulin on glucose transporters • When insulin levels rise, the transporters are brought to the surface of the membrane by exocytosis, at this point, the glucose is able to bind to the transporter and enter the membrane, following the glucose entering the cell, the transporters are brought from the surface of the membrane into the membrane through endocytosis which forms a membranous vesicle. ^ Important pathways regarding glucose and insulin. IR (insulin Receptors) on the membrane surface start the cascade.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'