In the heart, beta-adrenergic receptor (?-AR) stimulation increases contractile performance and heart rate as part of the 'fight-or-flight'stress response. Over stimulation of the sympathetic nervous system is a common theme in hypertension and is a primary contributor to heart failure. Increased sympathetic tone impinges on G protein-coupled receptors (GPCR) such as the ?1- AR to promote their desensitization and internalization. The human ?1-AR is internalized in response to ?-agonists such as isoproterenol, followed by recycling (i.e. re-insertion back into the membrane) and resensitization of its signaling pathway. We determined that the recycling of the ?1-AR is dependent on two domains one is serine312 in the third intracellular loop of the ?1-AR, and the other is an """"""""ESKV"""""""" sequence that corresponds to a type-1 PDZ ligand in the carboxy tail of the ?1-AR. The ESKV sequence binds to a scaffold composed of the MAGUK protein SAP97, A-kinase anchoring protein 79 (AKAP79) and the cAMP-dependent protein kinase (PKA), that we have termed the ?1-adrenergic receptosome. This scaffold is tethered to the ?1-AR-PDZ via SAP97, which in turn binds to the AKAP79/PKA complex to assemble a trimeric scaffold (or receptosome) at the PDZ domain of the ?1-AR. We have also shown that the components of this complex act in concert to facilitate the recycling of the agonist internalized ?1-AR, through a common mechanism involving PKA-mediated phosphorylation of Ser312. Consequently, our primary hypothesis is, """"""""that recycling and resensitization of the ?1-AR is dependent upon the targeting of PKA to the ?1-AR via the ?1-adrenergic receptosome"""""""". We propose to determine the domains within each member of the ?1-adrenergic receptosome that are functionally involved in recycling and resensitization of the ?1-AR in HEK-293 cells and rat/mouse neonatal ventricular myocytes.
In aims #1 and 2, we will identify the specific domains in AKAP79 and in SAP97, respectively that facilitate the recycling and resensitization of the ?1- AR. Then we will determine if AKAP79 and/or SAP97 are essential for recycling of the ?1-AR in cardiac ventricular myocytes prepared from neonatal rats or knockout mice. Finally in aim #3: we will characterize the molecular determinants of the PDZ motif of the ?1-AR that regulate its binding to SAP97 and facilitate the recycling and resensitization of the ?1-AR in HEK-293 and in heart cells. Results of these studies will provide new information concerning the mechanisms of ?1-AR resensitization that may ultimately provide new therapeutic paradigms to improve ?-blocker therapy, which is a main tool for the treatment of hypertension and heart failure.

Public Health Relevance

In the heart, beta-1-adrenergic receptor stimulation increases contractile performance and heart rate as part of the 'fight-or-flight'stress response. New information indicates that the beta-1-adrenergic receptor is connected to other cellular networks that affect its fate and markedly broaden the range of its actions within the cell. By investigating the function of these networks, we believe that we can improve on the performance of beta-blockers, which are widely-used in treating two major health problems in America, namely hypertension and heart failure.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Hypertension and Microcirculation Study Section (HM)
Program Officer
Evans, Frank
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Tennessee Health Science Center
Schools of Medicine
United States
Zip Code
Nooh, Mohammed M; Mancarella, Salvatore; Bahouth, Suleiman W (2018) Novel Paradigms Governing ?1-Adrenergic Receptor Trafficking in Primary Adult Rat Cardiac Myocytes. Mol Pharmacol 94:862-875
Bahouth, Suleiman W; Nooh, Mohammed M (2017) Barcoding of GPCR trafficking and signaling through the various trafficking roadmaps by compartmentalized signaling networks. Cell Signal 36:42-55
Nooh, Mohammed M; Mancarella, Salvatore; Bahouth, Suleiman W (2016) Identification of novel transplantable GPCR recycling motif for drug discovery. Biochem Pharmacol 120:22-32
Li, Jing Jing; Ferry Jr, Robert J; Diao, Shiyong et al. (2015) Nedd4 haploinsufficient mice display moderate insulin resistance, enhanced lipolysis, and protection against high-fat diet-induced obesity. Endocrinology 156:1283-91
Li, Xin; Matta, Shannon M; Sullivan, Ryan D et al. (2014) Carvedilol reverses cardiac insufficiency in AKAP5 knockout mice by normalizing the activities of calcineurin and CaMKII. Cardiovasc Res 104:270-9
Nooh, Mohammed M; Chumpia, Maryanne M; Hamilton, Thomas B et al. (2014) Sorting of ?1-adrenergic receptors is mediated by pathways that are either dependent on or independent of type I PDZ, protein kinase A (PKA), and SAP97. J Biol Chem 289:2277-94
Li, Xin; Nooh, Mohammed M; Bahouth, Suleiman W (2013) Role of AKAP79/150 protein in ?1-adrenergic receptor trafficking and signaling in mammalian cells. J Biol Chem 288:33797-812
Hajjhussein, Hassan; Gardner, Lidia A; Fujii, Naoaki et al. (2013) The hydrophobic amino acid cluster at the cytoplasmic end of transmembrane helix III modulates the coupling of the ýý(1)-adrenergic receptor to G(s). J Recept Signal Transduct Res 33:79-88
Nooh, Mohammed M; Naren, Anjaparavanda P; Kim, Sung-Jin et al. (2013) SAP97 controls the trafficking and resensitization of the beta-1-adrenergic receptor through its PDZ2 and I3 domains. PLoS One 8:e63379
Gardner, Lidia A; Hajjhussein, Hassan; Frederick-Dyer, Katherine C et al. (2011) Rab11a and its binding partners regulate the recycling of the ß1-adrenergic receptor. Cell Signal 23:46-57