G-Protein Coupled Receptors: Structure and Function

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1 PCTH 400 G-Protein Coupled Receptors: Structure and Function Dr. Rishi Somvanshi 2405 Wesbrook Mall

2 Learning Objectives 1. GPCR? Structure and Synthesis 2. Function? Receptor coupling to second messenger and Trafficking 3. Regulation? Pharmacology and Signaling Dimerization 4. Role in Pathological og Conditions o?

3 GPCRs (Structure and Synthesis)

4 G-Protein Coupled Receptors (GPCRs) Largest and most diverse membrane protein families Encoded by more than 800 genes (or 4% of the entire protein- coding genome) Detects Dt t a wide spectrum of extracellular l signals, including photons, ions, small organic molecules and entire proteins. Enormous potential for the development of new drugs to target neurological disorders, cancer, cardiac malfunction, asthma, tumours and migraines.

5 Time-line of GPCR Structures Nature 477: (2011) Nature 494, (2013)

6 Characteristics of GPCRs N-terminal segment Seven Transmembrane Domains which constitute i. TM Core ii. Three exoloops iii. Three Cytoloops C-terminal segment Pharmacol Ther Jul;103(1):21-80

7 Characteristics of all GPCRs N-terminal segments has aa C-terminal segments contains aa Each of the 7 TMs is generally composed of aa Loops p are normally y5-230 aa long h d f h d Variation in size is the indication of their diverse structure and functions!

8 G-Protein Coupled Receptors - Classification Class A (or 1) )(Rhodopsin-like) (85% of the GPCR genes) Class B (or 2) (Secretin receptor family) Class C (or 3) (Metabotropic glutamate/pheromone) Class D (or 4) (Fungal mating pheromone receptors) Class E (or 5) (Cyclic AMP receptors) Class F (or 6) (Frizzled/Smoothened) GRAFS (Glutamate Rhodopsin Adhesion Frizzled/Taste2 GRAFS (Glutamate, Rhodopsin, Adhesion, Frizzled/Taste2, Secretin)

9 GPCRs Synthesis and Trafficking COPII, coat protein II, transport of proteins from the rough ER to the Golgi apparatus; ERGIC, ER Golgi intermediate compartment; COPI: coat protein I, (retrograde transport to the ER); ERAD, ER-associated degradation pathway. Trends in pharmacological Sciences, Volume 29, Issue 10, Pages

10 GPCRs Synthesis and Trafficking Large dense-core vesicles (LDCVs) Trends in pharmacological Sciences, Volume 28, Issue 1, 2007, Pages 23 31

11 Sorting of Endocytosed GPCRs Annu. Rev. Pharmacol. Toxicol :

12 How GPCRs Function?

13 Typical cycle of G-Protein Coupled Receptor Nature Volume: 477, Pages: , 2011

14 GPCRs and Signaling Networks Trends in pharmacological Sciences, Volume 22, Issue 7, 1 July 2001, Pages

15 camp Signaling Pathway O'Connor, C. M. & Adams, J. U. Essentials of Cell Biology. Cambridge, MA: NPG Education, 2010.

16 Mechanism for the Modulation of Receptor Function DIMERIZATION

17 Molecular determinants of G-protein- coupled-receptor dimerization Nature Reviews Neuroscience 2,

18 Biophysical Techniques to Study GPCR Colocalization Dimerization Co-immunoprecipitation /Western blot analysis Bimolecular fluorescence complementation (BiFC) ½ YFP ½ YFP Bioluminescence Resonance Energy Transfer (BRET) Renilla luciferase GFP DeepBlue Photobleaching FRET (PbFRET)

19 Pb-FRET Microscopy Intensity Inten nsity Fluorescence Resonance Energy Transfer (FRET) GFP-tagged receptors Fluorescently Fl l labeled l b l d antibodies ib di Fluorescently labeled ligands Time Time

20 GPCR Functions are Altered upon Dimerization GABA receptors - Receptor functionality and sorting (GABA B R1 and GABA B R2) Dissociation of receptor homodimers is essential for proper receptor trafficking - SSTR2 and d-or Inhibition of internalization of the β 2 AR - when heterodimerize with β 1 AR Heterodimerization has synergistic (hsstr4/hsstr5) or y g ( 4/ 5) result in a non-synergistic effect (hsstr1/hsstr5) on camp signaling

21 Role of Dimerization in the Transport of GPCRs Nature Reviews Neuroscience 2,

22 Taste Qualities and the Taste Receptors J Cell Biol 2010;190:

23 Role in Pathological Conditions

24 GPCRs and Diseases Cancer Breast cancer Receptor PAR1; EP2; EP4; CXCR4; GPR30 Colon cancer EP2, EP4; LPA 1; ET receptors; PAR1; Frizzled Head and neck cancer CXCR2; CXCR4; EP receptors; GRPR; PAR1 Small-cell lung cancer GRPR; NMB-R; CXCR4; CCK 1 1; CCK 2 Non-small-cell lung cancer Ovarian cancer EP receptors; CXCR2; CXCR4; 1AR; 2AR LPA 1 LPA 3 ; CXCR2 Pancreatic cancer GRPR; CCK 1 ; CCK 2 Parathyroid gland cancer CASR Pituitary ta cancer ce TSH receptor; ACTHR Prostate cancer Melanoma Basal-cell carcinoma Testicular cancer Thyroid cancer PAR1; ET A ; AT1; EP2, EP4; LPA 1 ; B1, B2; GRPR MC1R; CXCR2; ET B Smoothened LH receptor TSH receptor Nature Reviews Cancer 7, 79 94, 2007

25 GPCRs and Diseases Nephrogenic diabetes insipides V2 vasopressin receptor Precocious puberty LH receptor Congenital night blindness Rhodopsin Receptor Virus entry: HIV - CCR JCV - 5HT2 R (Serotonin receptor) Familial gestational hyperthyroidism Thyrotropin receptor

26 Some Drugs Acting Through GPCRs Biotecnol Apl v.26 n.1 La Habana ene.-mar. 2009

27 Heterodimers in Pathophysiological Conditions Acromegaly: Somatostatin Receptor 5 and Dopamine receptor 2 agonist (Dopastatins) in regulation of Tumors. AIDS: Chemokine receptor 2 (CCR2) / CCR5 or C-X-C chemokine receptor type 4 (CXCR4) via modulating CXCR4 expression. Cardiac Failure: Angiotensin Receptor 1/ β-adrenergic Receptor via blocking AT 1 R mediated signaling. Parkinson s Disease: Adenosine Receptor 2a and Dopamine Receptor 2 via modulating cell surface expression.

28 QUESTIONS?