G protein coupled receptors Structure, function, regulation

Transcription

1 G protein coupled receptors Structure, function, regulation

2

3 Im menschlichen Genom finden sich Gene für ~ 810 G-Protein-gekoppelte Rezeptoren 350 nicht-geruchbildende Rezeptoren 460 Geruchrezeptoren Vielfalt der Rezeptoren entspricht der Vielfalt der Liganden Verwandtschaftliche Beziehung mit einem sehr alten gemeinsamen Ursprung Genetische Klassifikation nützlich? Fünf Familien G.Glutamat R.Rhodopsin A.Adhesion F.Frizzled S.Secretin

4 From Fredriksson et al. Mol. Pharmacol. 2003

5

6 GRAFS classification The G-protein-coupled receptors in the human genome form five main families. Phylogenetic analysis, paralogon groups, and fingerprints. From: Fredriksson R, Lagerstrom MC, Lundin LG, Schioth HB, 2003.

7 Alignment of two GPCR structures 1. Beta2-adrenergic receptor 2. Rhodopsin From Cherezov et al. 2007

8 Crystal structure of the beta-adrenergic receptor stabilization of cytoplasmic loop 3

9 Alternative ways to classify GPCRs Ligand recognition Problem Orthosteric vs. allosteric Subtypes Orphan receptors Expression pattern G-protein coupling Signal transduction Means of detection Specificity vs. promiscuity Accessory proteins

10 GPCR ligand binding structural diversity of the cognate binding site Figure from Ji et al., J. Biol. Chem. 273:

11 Individuelle Strukturmerkmale G-Protein-gekoppelter Rezeptoren orthosterische vs. allosterische Ligandenbindung From Conn et al. 2009

12 Folding of the extracellular receptor domain A ER lumen Cytoplasm B ribosome -helix and signal anchor signal peptide translocator channel signal recognition particle -helix and stop transfer sequence signal sequence peptidase

13 GPCR biology - common features Surface expression is regulated Inactive receptors are silent Active receptors desensitize

14 Sequence of helix movements in rhodopsin activation, view of the cytoplasmic face of the receptor retinal SX Ye et al. Nature 000, 1-4 (2010) doi: /nature08948

15 Surface representations of the ICL region in the inactive and active states (Sites of azf labelling and electrostatic potential around azf250). SX Ye et al. Nature 000, 1-4 (2010) doi: /nature08948

16 GPCR biology - common features Surface expression is regulated Inactive receptors are silent Unoccupied receptors may exert constitutive activity Active receptors desensitize receptor agonist R R* antagonist antagonist inverse agonist

17 Constitutive activation of the alpha1ar resulting from amino acid substitutions at position 293. From: Cotecchia, JBC 1988

18 Schematic representation of the TSH receptor, with indication of the residues found mutated in a cohort of 31 patients with a total of 33 toxic adenomas (in 2 patients, 2 distinct hot nodules were investigated). Every individual substitution is indicated. The transmembrane segments are represented by boxes (I to VII); the extra- and intracellular loops are indicated by E1, 2, and 3 and I1, 2, and 3, respectively. Parma J, Duprez L, Van Sande J, Hermans J, Rocmans P, Van Vliet G, Costagliola S, Rodien P, Dumont JE, Vassart G. (1997 ) J. Clin. Endocrinol Metab. 82:

19 Constitutive activity of the native human A2A-adenosine receptor

20 GPR133, an adhesion GPCR family member, increases camp accumulation in HEK293 and COS-7 cells. Bohnekamp J, Schöneberg T J. Biol. Chem. 2011;286: by American Society for Biochemistry and Molecular Biology

21 GPCR biology - common features Surface expression is regulated Inactive receptors are silent Active receptors desensitize

22 RXR-motif

23 Copyright 2006 by the National Academy of Sciences Fig. 3. FRET dependence on cell surface receptor density

24 Receptor surface expression enhancing proteins competent for subfamily S (class B) GPCRs such as the secretin, glucagon, vasoactive intestinal peptide, calcitonin, and calcitonin receptor-like receptors that create compound heterodimers with new types of pharmacology - RAMP (receptor accessory modifying protein) - MRAP(melanocortin receptor accessory protein)

25 GPCR biology - common features Surface expression is regulated Inactive receptors are silent Active receptors desensitize

26 Time table of events following GPCR agonist binding Receptor activation G-protein activation GIRK activation camp formation Beta-arrestin binding ERK phosphorylation 50 ms 500 ms 500 ms 20 sec 30 sec 2 min Adapted from Lohse 2012

27 The arrestin receptosome Bockaert et al., Pharmacol. Ther. 2004

28 Accessory proteins involved in signaling and regulation of GPCRs, examples GRK2, 3 Arrestins (beta-arrestin) arrestin-mediated activation of Src, ERK1/2 Receptors (membrane-delimited transactivation/ inhibition) RAMP proteins (GPCR export and ligand specificity) AP-2 (arrestin-independent internalization/degradation) RGS proteins tyrosine kinases (BTK), ser/thr kinases (PAK1, RAF), MAPK PLD ARF6 guanine nucleotide exchange factor, other GEFs Channels (T-type Ca2+, K+) Ubiquitin transferases, sorting proteins

29 G protein coupled receptor kinases (GRK), serine/threonine kinases, no consensus motif defined # Expression Intracellular localization 1, 7 retina 2, 3 ubiquitous Cytosolic, interact with G and PIP2 5, 6 ubiquitous Lipid modified, membrane bound 4 sperm Lipid modified, membrane bound

30 Effects of short-term agonist exposure on inhibitory AR function. Palmer T M et al. J. Biol. Chem. 1996;271: by American Society for Biochemistry and Molecular Biology

31 Effects of agonist pretreatment on phosphorylation of inhibitory AR Effect of appending the A3-receptor c-tail onto the A1-receptor Palmer T M et al. J. Biol. Chem. 1996;271: by American Society for Biochemistry and Molecular Biology

32

33 Microsoft owerpoint-präsentatio

34 PICK1 accessory protein regulating the function of glutamate receptors Bertaso et al., 2008

35 A goal of the Signal transduction programme, you should be able to offer an opinion on the following issues Binding of receptor ligands to a GPCR: How does the binding reaction differ between agonists, antagonists and inverse agonists? Suggest ways of classifying GPCRs- what are problems inherent to each of these approaches How does signaling by a GPCR get terminated? Which are accessory proteins known to contribute to GPCR function and regulation? Cellular processes governing receptor desensitization