GPRs
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G-protein-coupled receptors (GPRs) are the largest family of cell-surface molecules involved in signal transmission.G-protein coupled receptors (GPRs) transduce a variety of signals from the extracellular environment across the plasma membrane.
Structure
Members of the G protein-coupled receptor family share a common motif of 7 transmembrane domains.
Function
One of the common signaling systems utilized by GPRs activates protein kinases C (PRKCs), a ubiquitous family of serine/threonine protein kinases.
The pathway leading to PRKCs activation starts with a class of GPRs that interact with and activate Gq G-proteins when the receptor has agonist ligand bound.
GPRs that act through Gq include some muscarinic acetylcholine receptors, many peptide receptors, and the 5-HT2 serotonin receptors.
Activated Gq with GTP bound activates its downstream target phospholipase C (PLC) to hydrolyze the membrane lipid PIP2, producing IP3 and diacylglycerol (DAG).
IP3 is water-soluble and diffuses through the cytoplasm to the ER, where it binds to and opens a calcium channel, releasing calcium stores from inside the ER into the cytoplasm.
Calcium alters many cellular processes, in part by binding to regulatory proteins such as calmodulin (CALMs) and calcineurin (PPP3CA. PPP3CB).
The interaction of both DAG and calcium with PRKCs activates its kinase activity and the phosphorylation of many different protein targets alters their activity.
The involvement of PRKCs in cellular proliferation and the cell cycle is indicated by the activity of tumor promoters like phorbol esters as PRKCs activators.
Members
| GPR1 | GPR2 | GPR3 | GPR4 | GPR5 | GPR6 | GPR7 | GPR8 | GPR9 | GPR10 |
| GPR11 | GPR12 | GPR13 | GPR14 | GPR15 | GPR16 | GPR17 | GPR18 | GPR19 | GPR20 |
| GPR21 | GPR22 | GPR23 | GPR24 | GPR25 | GPR26 | GPR27 | GPR28 | GPR29 | GPR30 |
| GPR31 | GPR32 | GPR33 | GPR34 | GPR35 | GPR36 | GPR37 | GPR38 | GPR39 | GPR40 |
| GPR41 | GPR42 | GPR43 | GPR44 | GPR45 | GPR46 | GPR47 | GPR48 | GPR49 | GPR50 |
| GPR51 | GPR52 | GPR53 | GPR54 | GPR55 | GPR56 | GPR57 | GPR58 | GPR59 | GPR60 |
| GPR61 | GPR62 | GPR63 | GPR64 | GPR65 | GPR66 | GPR67 | GPR68 | GPR69 | GPR70 |
| GPR71 | GPR72 | GPR73 | GPR74 | GPR75 | GPR76 | GPR77 | GPR78 | GPR79 | GPR80 |
Pathology
They are crucial players in tumour growth and metastasis. Malignant cells often hijack the normal physiological functions of GPCRs to survive, proliferate autonomously, evade the immune system, increase their blood supply, invade their surrounding tissues and disseminate to other organs.
See also
heterotrimeric G proteins
References
Oldham WM, Hamm HE. Heterotrimeric G protein activation by G-protein-coupled receptors. Nat Rev Mol Cell Biol. 2008 Jan;9(1):60-71. PMID: 18043707
Gentles AJ, Karlin S. Why are human G-protein-coupled receptors predominantly intronless. Trends Genet. 1999 Feb;15(2):47-9. PMID: 10098406
Brosius J. Many G-protein-coupled receptors are encoded by retrogenes. Trends Genet. 1999 Aug;15(8):304-5. PMID: 10431191