Does any body know that two examples (receptor) of G-protein transduction?
Thank you so much!
The following are cardiovascular examples:
G-proteins are linked to adenylyl cyclase that dephosphorylates ATP to form cyclic AMP (cAMP). Gs activation (e.g., via beta-adrenoceptors) increases cAMP, which activates a protein kinase that causes increased [Ca2+]i by direct effects on calcium channels and enhanced release of Ca2+ by the sarcoplasmic reticulum in the heart; these actions increase inotropy. Gs-protein activation also increases heart rate. Gi activation (e.g., via adenosine and muscarinic receptors) decreases cAMP and protein kinase activation, and causes increased [K+]i; activation of the Gi-protein pathway therefore enhances repolarization. Gi-protein activation therefore decreases heart rate and inotropy.
R, receptor; Gs and Gi, stimulatory and inhibitory G-proteins; AC, adenylyl cyclase; PIP2, phosphatidylinositol 4,5-bisphosphate; IP3, inositol 1,4,5-triphosphate; DAG, diacylglycerol; PK, protein kinase; SR, sarcoplasmic reticulum; a and b , adrenoceptor agonist; M2, muscarinic receptor agonist; A1, adenosine receptor agonist; AII, angiotensin receptor agonist; ET-1, endothelin.
Altered signal transduction mechanisms may be responsible for the loss of inotropy in heart failure. For example, desensitization of beta1-adrenoceptors on the heart will decrease inotropic responses to sympathetic activation. Uncoupling of the beta1-adrenoceptor and the Gs-protein would reduce the ability to activate adenylyl cyclase. If the ability of protein kinase A (PK-A) to phosphorylate L-type calcium channels is impaired, then calcium influx into the cell would be reduced, leading to a smaller release of calcium by the sarcoplasmic reticulum. Reduced calcium release would impair excitation-contraction coupling, thereby decreasing inotropy.
Most biology text books will give you plenty of other examples. for example lolok at Alberts' "Molecular Biology of the Cell"
This can even be found online for free through PubMed at
The section you will be interested in is called
Signaling through G-Protein-Linked Cell-Surface Receptors
If you want further examples a Google search will bring up dozens of pages from various universities' and schools class notes and study guides.