Beta-1 adrenergic receptor

The beta-1 adrenergic receptor (β₁ adrenoceptor), also known as ADRB1, can refer to either the protein-encoding gene (gene ADRB1) or one of the four adrenergic receptors. It is a G-protein coupled receptor associated with the Gs heterotrimeric G-protein that is expressed predominantly in cardiac tissue. In addition to cardiac tissue, beta-1 adrenergic receptors are also expressed in the cerebral cortex.

ADRB1
Available structures PDB Ortholog search: PDBe RCSB List of PDB id codes 2LSQ
Identifiers
Aliases	ADRB1, ADRB1R, B1AR, BETA1AR, RHR, adrenoceptor beta 1, FNSS2
External IDs	OMIM: 109630; MGI: 87937; HomoloGene: 20171; GeneCards: ADRB1; OMA:ADRB1 - orthologs
Gene location (Human) Chr. Chromosome 10 (human) Band 10q25.3 Start 114,043,866 bp End 114,046,904 bp
Gene location (Mouse) Chr. Chromosome 19 (mouse) Band 19 D2|19 51.96 cM Start 56,710,631 bp End 56,721,545 bp
RNA expression pattern Bgee Human Mouse (ortholog) Top expressed in right ventricle parotid gland bronchial epithelial cell lower lobe of lung endothelial cell placenta Brodmann area 23 apex of heart postcentral gyrus buccal mucosa cell Top expressed in parotid gland pineal gland right lung right lung lobe submandibular gland left lung primary motor cortex prefrontal cortex nucleus accumbens conjunctival fornix More reference expression data BioGPS More reference expression data
Gene ontology Molecular function beta-adrenergic receptor activity PDZ domain binding G protein-coupled receptor activity epinephrine binding norepinephrine binding signal transducer activity adrenergic receptor activity protein binding alpha-2A adrenergic receptor binding protein heterodimerization activity beta1-adrenergic receptor activity G protein-coupled neurotransmitter receptor activity involved in regulation of postsynaptic membrane potential Cellular component integral component of membrane endosome membrane plasma membrane integral component of plasma membrane early endosome Schaffer collateral - CA1 synapse integral component of postsynaptic density membrane Biological process fear response adenylate cyclase-activating G protein-coupled receptor signaling pathway negative regulation of multicellular organism growth cell-cell signaling positive regulation of cAMP-mediated signaling positive regulation of heart rate by epinephrine-norepinephrine activation of adenylate cyclase activity norepinephrine-epinephrine-mediated vasodilation involved in regulation of systemic arterial blood pressure diet induced thermogenesis adenylate cyclase-activating adrenergic receptor signaling pathway positive regulation of heart contraction positive regulation of GTPase activity positive regulation of the force of heart contraction by epinephrine-norepinephrine heat generation brown fat cell differentiation response to cold temperature homeostasis signal transduction G protein-coupled receptor signaling pathway adenylate cyclase-modulating G protein-coupled receptor signaling pathway regulation of postsynaptic membrane potential positive regulation of cold-induced thermogenesis Sources:Amigo / QuickGO
Orthologs Species Human Mouse Entrez 153 11554 Ensembl ENSG00000043591 ENSMUSG00000035283 UniProt P08588 P34971 RefSeq (mRNA) NM_000684 NM_007419 RefSeq (protein) NP_000675 NP_031445 Location (UCSC) Chr 10: 114.04 – 114.05 Mb Chr 19: 56.71 – 56.72 Mb PubMed search
Wikidata
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Historical Context

W. B. Cannon postulated that there were two chemical transmitters or sympathins while studying the sympathetic nervous system in 1933. These E and I sympathins were involved with excitatory and inhibitory responses. In 1948, Raymond Ahlquist published a manuscript in the American Journal of Physiology establishing the idea of adrenaline having distinct actions on both alpha and beta receptors. Shortly afterward, Eli Lilly Laboratories synthesized the first beta-blocker, dichloroisoproterenol.

General Information

Structure

ADRB-1 is a transmembrane protein that belongs to the G-Protein-Coupled Receptor (GPCR) family. GPCRs play a key role in cell signaling pathways and are primarily known for their seven transmembrane (7TM) helices, which have a cylindrical structure and span the membrane. The 7TM domains have three intracellular and three extracellular loops that connect these domains to one another. The extracellular loops contain sites for ligand binding on N-terminus of the receptor and the intracellular loops and C-terminus interact with signaling proteins, such as G-proteins. The extracellular loops also contain several sites for post-translational modification and are involved in ligand binding. The third intracellular loop is the largest and contains phosphorylation sites for signaling regulation. As the name suggests, GPCRs are coupled to G-proteins that are heterotrimeric in nature. Heterotrimeric G-proteins consist of three subunits: alpha, beta, and gamma. Upon the binding of a ligand to the extracellular domain of the GPCR, a conformational change is induced in the receptor that allows it to interact with the alpha-subunit of the G-protein. Following this interaction, the G-alpha subunit exchanges GDP for GTP, becomes active, and dissociates from the beta and gamma subunits. The free alpha subunit is then able to activate downstream signaling pathways (detail more in interactions and pathway).

Function

Pathways

ADRB-1 is activated by the catecholamines adrenaline and noradrenaline. Once these ligands bind, the ADRB-1 receptor activates several different signaling pathways and interactions. Some of the most well-known pathways are:

1. Adenylyl Cyclase: When a ligand binds to the ADRB-1 Receptor, the alpha-subunit of the heterotrimeric G-protein gets activated, which in turn, activates the enzyme adenylyl cyclase. Adenylyl cyclase then catalyzes the conversion of ATP to cyclic AMP (cAMP), which activates downstream effectors such as Protein Kinase A (PKA).
2. cAMP Activation of PKA: cAMP generated by adenylyl cyclase activates PKA, which then phosphorylates numerous downstream targets such as ion channels, other enzymes, and transcription factors .
3. Beta-arrestins: Activation of the ADRB-1 receptor can lead to the recruitment of Beta-arrestins, which are used to activate signaling pathways independent of G-proteins. An example of an independent pathway is the MAPK (mitogen-activated protein kinase) pathways.
4. Calcium signaling: ADRB-1 signaling also activates the Gq/11 family of G proteins, which is a subfamily of heterotrimeric G proteins that activates phospholipase C (PLC). PLC cleaves phosphatidylinositol 4,5-bisphosphate (PIP2) into the second messengers inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG). IP3 binds to IP3 receptors on the endoplasmic reticulum, which then leads to the release of calcium ions (Ca2+) into the cytoplasm, resulting in the activation of downstream signaling pathways.

Summary of Interactions

Actions of the β₁ receptor include:

System	Effect	Tissue
Muscular	Increases cardiac output	Cardiac muscle
	Increases heart rate (chronotropic effect)	Sinoatrial node (SA node)
	Increases atrial contractility (inotropic effect)	Cardiac muscle
	Increases contractility and automaticity	Ventricular cardiac muscle
	Increases conduction and automaticity	Atrioventricular node (AV node)
	Relaxation	Urinary bladder wall
Exocrine	Releases renin	Juxtaglomerular cells.
	Stimulates viscous, amylase-filled secretions	Salivary glands
Other	Lipolysis	Adipose tissue

The receptor is also present in the cerebral cortex.

Other pathways that play ADRB-1 receptor plays an important role in:

1. Regulation of peripheral clock and central circadian clock synchronization: The suprachiasmatic nucleus (SCN) receives light information from the eyes and synchronizes the peripheral clocks to the central circadian clock through the release of different neuropeptides and hormones. ADRB-1 receptors can play a role in modulating the release of neuropeptides like vasoactive intestinal peptide (VIP) and arginine vasopressin (AVP) from the SCN, which can then synchronize peripheral clocks.
2. Regulation of glucose metabolism: The regulation of glucose metabolism is known to be linked with ADRB-1 receptor signaling. The signal transduction pathway that is activated through the ADRB-1 receptor can regulate the expression of clock genes and glucose transporters. The disregulation of ADRB-1 receptor signaling has been implicated in metabolic disorders such as diabetes and obesity.
3. ADRB-1 Receptor and Rhythmic Control of Immunity: Circadian oscillations in catecholamine signals influence various cellular targets which express adrenergic receptors, including immune cells. The adrenergic system regulates a range of physiological functions which are carried out through catecholamine production. Humans are found to have low circulating catecholamine levels during the night and high levels during the day, while rodents exhibit the opposite pattern. Studies demonstrating the patterns of norepinephrine levels indicate that there is no circadian rhythmicity. Circulating rhythms in epinephrine, however, appear to be circadian and are regulated by the HPA axis:
   1. Cyclic variation in HPA signals are likely important in driving diurnal oscillations in adrenaline.
   2. The most well-characterized means through which adrenergic signals exert circadian control over immunity is by cell-trafficking regulation. Variation in the number of white blood cells seemed to be linked to adrenergic function.
4. Cardiac rhythm and Cardiac Failure: The β-AR signaling pathway serves as a primary component of the interface between the sympathetic nervous system and the cardiovascular system. The β-AR pathway dysregulation has been implicated in the pathogenesis of heart failure. It has been found that certain changes to β-AR signaling result in reduced levels of  β1-AR, by up to 50%, while levels of β2-AR remain constant. Other intracellular changes include a significant, sharp increase of GαI levels, and increased βARK1 activity. These changes suggest sharp decreases in  β-AR signaling, likely due to sustained, elevated levels of catecholamines.

Mechanism in cardiac myocytes

G_s exerts its effects via two pathways. Firstly, it directly opens L-type calcium channels (LTCC) in the plasma membrane. Secondly, it renders adenylate cyclase activated, resulting in an increase of cAMP, activating protein kinase A (PKA) which in turn phosphorylates several targets, such as phospholamban, LTCC, Troponin I (TnI), and potassium channels. The phosphorylation of phospholamban deactivates its own function which normally inhibits SERCA on the sarcoplasmic reticulum (SR) in cardiac myocytes. Due to this, more calcium enters the SR and is therefore available for the next contraction. LTCC phosphorylation increases its open probability and therefore allows more calcium to enter the myocyte upon cell depolarisation. Both of these mechanisms increase the available calcium for contraction and therefore increase inotropy. Conversely, TnI phosphorylation results in its facilitated dissociation of calcium from troponin C (TnC) which speeds the muscle relaxation (positive lusitropy). Potassium channel phosphorylation increases its open probability which results in shorter refractory period (because the cell repolarises faster), also increasing lusitropy. Furthermore, in nodal cells such as in the SA node, cAMP directly binds to and opens the HCN channels, increasing their open probability, which increases chronotropy.

Clinical Significance

Familial Natural Short Sleep (FNSS)

A rare mutation that changes a cytosine to a thymine in the ADRB-1 coding sequence results in a protein switch to valine from alanine at amino acid position 187 (A187) and leads to the FNSS behavior trait, where mutation carriers naturally wake up after only 4 to 6.5 hours of sleep. The ADRB-1 protein is involved in a cyclic adenosine monophosphate (cAMP)-mediated signaling pathway, and the ADRB1-A187V mutated protein leads to a lower cAMP production than the wild-type protein, given the same isoproterenol treatment, a nonselective agonist of ADRB-1. It was also discovered that the mutated protein is less stable most likely due to post-translational modifications, as shown in an ADRB1 knockin experiment where a mutated ADRB-1 gene replaces the wild-type with CRISPR technology and the protein level displays a decrease while the mRNA level remains high.

Mice with a heterozygous ADRB1-A187V mutation show increased activity time and shorter intervals of rapid eye movement (REM) sleep and non-REM sleep, suggesting that the mutation causes short sleep. In another experiment, the ADRB1-A187V mutation restored REM sleep in tau mice (PS19) and reduced tau accumulation, which can promote brain cell damage and death, in the locus coeruleus (LC) of PS19 mice. Furthermore, a high expression level of ADRB-1 protein is observed in the dorsal pons (DP), referred to as ADRB1+ neurons. The activity of these ADRB1+ neurons in DP is shown to be closely linked with the sleep-wake behavior and altered by the ADRB1-A187V mutation. The ADRB1+ neurons can be either inhibitory or excitatory. In the brains of mutant mice, the percentage of ADRB1+ neurons that may be inhibited by agonists reduces significantly while the percentage of neurons that may be excited by agonists remains relatively unchanged. It is thus speculated that the ADRB-1 protein has an inhibitory and an excitatory function, with the inhibitory function being more sensitive to its decreased protein levels and the excitatory function being less sensitive. Although the ADRB1-A187V mutation leads to lower protein levels, as discussed above, overall there are fewer ADRB1+ neurons inhibited, corresponding to the higher total activity of DP ADRB1+ neurons observed in mutant mice. These results collectively indicate that high activity levels in ADRB1+ neurons leads to shorter sleep or FNSS.

Polymorphisms in ADRB-1

One of the single nucleotide polymorphisms (SNPs) in ADRB-1 is the change from a cytosine to a guanine, resulting in a protein switch from arginine (389R) to glycine (389G) at the 389 codon position. Arginine at codon 389 is highly preserved across species and this mutation happens in the G-protein binding domain of ADRB-1, one of the key functions of ADRB-1 protein, so it is likely to lead to functional differences. In fact, this SNP causes dampened efficiency and affinity in agonist-promoted receptor binding.

Another common SNP occurs at codon position 49, with a change of serine (49S) to glycine (49G) in the N-terminus sequence of ADRB-1. The 49S variant is shown to be more resistant to agonist-promoted down regulation and short intervals of agonist exposure. The receptor of the 49G variant is always expressed, which results in high coupling activity with adenylyl cyclase and increased sensitivity to agonists.

Both of these SNPs have relatively high frequencies among populations and are thought to affect cardiac functions. Individuals who are homozygous for the 389R allele are more likely to have higher blood pressure and heart rates than others who have either one or two copies of the 389G allele. Additionally, patients with heart diseases that have a substitution of glycine for serine at codon 49 (49S > G) show improved cardiac functions and decreased mortality rate. The cardiovascular responses induced by this polymorphism in the healthy population are also examined. Healthy individuals with a glycine at codon 49 show better cardiovascular functions at rest and response to maximum heart rate during exercise, evident for the cardioprotection related to this polymorphism.

Pharmaceutical Interventions

Because ADRB-1 play such a critical role in maintaining blood pressure homeostasis and cardiac output, many medications treat these conditions by either potentiating or inhibiting the functions of the ADRB-1. Dobutamine is one of the adrenergic drugs and agonists that selectively bind to ADRB-1 and is often used in treatments of cardiogenic shock and heart failure. It is also important to note the use of illicit drug for ADRB-1 since cocaine, beta-blocking agents, or other sympathetic stimulators may cause a medical emergency.

Agonists

Main article: Beta1-adrenergic agonist

ADRB-1 agonists mimic or initiate a physiological response when bound to a receptor. Isoprenaline has higher affinity for β₁ than adrenaline, which, in turn, binds with higher affinity than noradrenaline at physiologic concentrations. As ADRB-1 increases cardiac output, selective agonists clinically function as potential treatments for heart failure. Selective agonists to the beta-1 receptor are:

• Denopamine is used in the treatment of angina and has potential uses to treat congestive heart failure and pulmonary oedema.
• Dobutamine (in cardiogenic shock) is a beta-1 agonist that treats cardiac decompensation.
• Xamoterol (cardiac stimulant) acts as a partial agonist that improves heart function in studies with cardiac failure. Xamoterol plays a role in modulating the sympathetic nervous system, but does not have any agonistic action on beta-2 adrenergic receptors.
• Isoproterenol is a nonselective agonist that potentiates the effects of agents like adrenaline and norepinephrine to increase heart contractility.

Antagonists

ADRB-1 antagonists are a class of drugs also referred to as Beta Blockers β1-selective antagonists are used to manage abnormal heart rhythms and block the action of substances like adrenaline on neurons, allowing blood to flow more easily which lowers blood pressure and cardiac output. They may also shrink vascular tumors. Some examples of Beta-Blockers include:

• Acebutolol (in hypertension, angina pectoris and arrhythmias)
• Atenolol (in hypertension, coronary heart disease, arrhythmias and myocardial infarction)
• Betaxolol (in hypertension and glaucoma)
• Bisoprolol (in hypertension, coronary heart disease, arrhythmias, myocardial infarction and ischemic heart diseases)
• Esmolol (in arrhythmias)
• Metoprolol (in coronary heart disease, myocardial infarction and heart failure)
• Nebivolol (in hypertension)
• Vortioxetine (antidepressant)

See also

• Other adrenergic receptors
  • Alpha-1 adrenergic receptor
  • Alpha-2 adrenergic receptor
  • Beta-2 adrenergic receptor
  • Beta-3 adrenergic receptor

Further reading

• Frielle T, Kobilka B, Lefkowitz RJ, Caron MG (July 1988). "Human beta 1- and beta 2-adrenergic receptors: structurally and functionally related receptors derived from distinct genes". Trends in Neurosciences. 11 (7): 321–324. doi:10.1016/0166-2236(88)90095-1. PMID 2465637. S2CID 140209236.
• Muszkat M (August 2007). "Interethnic differences in drug response: the contribution of genetic variability in beta adrenergic receptor and cytochrome P4502C9". Clinical Pharmacology and Therapeutics. 82 (2): 215–218. doi:10.1038/sj.clpt.6100142. PMID 17329986. S2CID 10381767.
• Yang-Feng TL, Xue FY, Zhong WW, Cotecchia S, Frielle T, Caron MG, et al. (February 1990). "Chromosomal organization of adrenergic receptor genes". Proceedings of the National Academy of Sciences of the United States of America. 87 (4): 1516–1520. Bibcode:1990PNAS...87.1516Y. doi:10.1073/pnas.87.4.1516. PMC 53506. PMID 2154750.
• Forse RA, Leibel R, Gagner M (January 1989). "The effect of Escherichia coli endotoxin on the adrenergic control of lipolysis in the human adipocyte". The Journal of Surgical Research. 46 (1): 41–48. doi:10.1016/0022-4804(89)90180-7. PMID 2536864.
• Frielle T, Collins S, Daniel KW, Caron MG, Lefkowitz RJ, Kobilka BK (November 1987). "Cloning of the cDNA for the human beta 1-adrenergic receptor". Proceedings of the National Academy of Sciences of the United States of America. 84 (22): 7920–7924. Bibcode:1987PNAS...84.7920F. doi:10.1073/pnas.84.22.7920. PMC 299447. PMID 2825170.
• Stiles GL, Strasser RH, Lavin TN, Jones LR, Caron MG, Lefkowitz RJ (July 1983). "The cardiac beta-adrenergic receptor. Structural similarities of beta 1 and beta 2 receptor subtypes demonstrated by photoaffinity labeling". The Journal of Biological Chemistry. 258 (13): 8443–8449. doi:10.1016/S0021-9258(20)82084-5. PMID 6305985.
• Hoehe MR, Otterud B, Hsieh WT, Martinez MM, Stauffer D, Holik J, et al. (June 1995). "Genetic mapping of adrenergic receptor genes in humans". Journal of Molecular Medicine. 73 (6): 299–306. doi:10.1007/BF00231616. PMID 7583452. S2CID 27308274.
• Elies R, Ferrari I, Wallukat G, Lebesgue D, Chiale P, Elizari M, et al. (November 1996). "Structural and functional analysis of the B cell epitopes recognized by anti-receptor autoantibodies in patients with Chagas' disease". Journal of Immunology. 157 (9): 4203–4211. doi:10.4049/jimmunol.157.9.4203. PMID 8892658. S2CID 44386743.
• Oldenhof J, Vickery R, Anafi M, Oak J, Ray A, Schoots O, et al. (November 1998). "SH3 binding domains in the dopamine D4 receptor" (PDF). Biochemistry. 37 (45): 15726–15736. doi:10.1021/bi981634+. PMID 9843378.
• Mason DA, Moore JD, Green SA, Liggett SB (April 1999). "A gain-of-function polymorphism in a G-protein coupling domain of the human beta1-adrenergic receptor". The Journal of Biological Chemistry. 274 (18): 12670–12674. doi:10.1074/jbc.274.18.12670. PMID 10212248.
• Moore JD, Mason DA, Green SA, Hsu J, Liggett SB (September 1999). "Racial differences in the frequencies of cardiac beta(1)-adrenergic receptor polymorphisms: analysis of c145A>G and c1165G>C". Human Mutation. 14 (3): 271. doi:10.1002/(SICI)1098-1004(1999)14:3<271::AID-HUMU14>3.0.CO;2-Q. PMID 10477438. S2CID 8860722.
• Tang Y, Hu LA, Miller WE, Ringstad N, Hall RA, Pitcher JA, et al. (October 1999). "Identification of the endophilins (SH3p4/p8/p13) as novel binding partners for the beta1-adrenergic receptor". Proceedings of the National Academy of Sciences of the United States of America. 96 (22): 12559–12564. Bibcode:1999PNAS...9612559T. doi:10.1073/pnas.96.22.12559. PMC 22990. PMID 10535961.
• Podlowski S, Wenzel K, Luther HP, Müller J, Bramlage P, Baumann G, et al. (2000). "Beta1-adrenoceptor gene variations: a role in idiopathic dilated cardiomyopathy?". Journal of Molecular Medicine. 78 (2): 87–93. doi:10.1007/s001090000080. PMID 10794544. S2CID 1072602.
• Shiina T, Kawasaki A, Nagao T, Kurose H (September 2000). "Interaction with beta-arrestin determines the difference in internalization behavior between beta1- and beta2-adrenergic receptors". The Journal of Biological Chemistry. 275 (37): 29082–29090. doi:10.1074/jbc.M909757199. PMID 10862778.
• Hu LA, Tang Y, Miller WE, Cong M, Lau AG, Lefkowitz RJ, et al. (December 2000). "beta 1-adrenergic receptor association with PSD-95. Inhibition of receptor internalization and facilitation of beta 1-adrenergic receptor interaction with N-methyl-D-aspartate receptors". The Journal of Biological Chemistry. 275 (49): 38659–38666. doi:10.1074/jbc.M005938200. PMID 10995758.
• Börjesson M, Magnusson Y, Hjalmarson A, Andersson B (November 2000). "A novel polymorphism in the gene coding for the beta(1)-adrenergic receptor associated with survival in patients with heart failure". European Heart Journal. 21 (22): 1853–1858. doi:10.1053/euhj.1999.1994. PMID 11052857.
• Xu J, Paquet M, Lau AG, Wood JD, Ross CA, Hall RA (November 2001). "beta 1-adrenergic receptor association with the synaptic scaffolding protein membrane-associated guanylate kinase inverted-2 (MAGI-2). Differential regulation of receptor internalization by MAGI-2 and PSD-95". The Journal of Biological Chemistry. 276 (44): 41310–41317. doi:10.1074/jbc.M107480200. PMID 11526121.
• Hu LA, Chen W, Premont RT, Cong M, Lefkowitz RJ (January 2002). "G protein-coupled receptor kinase 5 regulates beta 1-adrenergic receptor association with PSD-95". The Journal of Biological Chemistry. 277 (2): 1607–1613. doi:10.1074/jbc.M107297200. PMID 11700307.
• Ranade K, Jorgenson E, Sheu WH, Pei D, Hsiung CA, Chiang FT, et al. (April 2002). "A polymorphism in the beta1 adrenergic receptor is associated with resting heart rate". American Journal of Human Genetics. 70 (4): 935–942. doi:10.1086/339621. PMC 379121. PMID 11854867.

Further reading

• Alhayek S, Preuss CV (August 2022). "Beta 1 Receptors.". StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. PMID 30422499.

External links

• Human ADRB1 genome location and ADRB1 gene details page in the UCSC Genome Browser.
• "β₁-adrenoceptor". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology. Archived from the original on 2015-06-06. Retrieved 2008-11-25.
• Overview of all the structural information available in the PDB for UniProt: P08588 (Beta-1 adrenergic receptor) at the PDBe-KB.