ADORA - Adenosine receptor A | Elisa - Clia - Antibody - Protein

Background:

Adenosine receptors are a class of G protein-coupled receptors (GPCRs) that respond to the endogenous nucleoside adenosine. They play essential roles in various physiological processes, including neurotransmission, vascular tone regulation, immune responses, and inflammation.

Structural Features

Adenosine receptors, like other GPCRs, consist of seven transmembrane domains, an extracellular N-terminus, and an intracellular C-terminus. Upon ligand binding, conformational changes in the receptor initiate intracellular signaling cascades through interaction with heterotrimeric G proteins.

Subtypes and Classification

Adenosine receptors are classified into four subtypes, designated as A1 (ADORA1), A2A (ADORA2A), A2B (ADORA2B), and A3 (ADORA3) receptors, based on their pharmacological properties and downstream signaling pathways:

• A1 Receptor (ADORA1): Predominantly expressed in the brain, where it modulates neurotransmission, neuronal excitability, and synaptic plasticity. A1 receptors also regulate cardiovascular function, immune responses, and renal function.
• A2A Receptor (ADORA2A): Found in various tissues, including the brain, cardiovascular system, and immune cells, where it regulates neurotransmission, vascular tone, inflammation, and immune responses.
• A2B Receptor (ADORA2B): Widely distributed in tissues such as the vasculature, kidneys, and immune cells, where it regulates vascular tone, renal function, inflammation, and tissue remodeling.
• A3 Receptor (ADORA3): Expressed in the brain, immune cells, and peripheral tissues, where its functions are still being elucidated, but it is implicated in regulating neurotransmission, inflammation, and immune responses.

Ligands

Adenosine receptors are activated by adenosine, a nucleoside that is released by cells in response to various physiological stimuli, including hypoxia, ischemia, inflammation, and cellular stress. Adenosine receptors also interact with exogenous ligands, including adenosine receptor agonists and antagonists used in pharmacotherapy.

Physiological Functions

Adenosine receptors mediate various physiological effects in different tissues and organ systems:

• Neurotransmission: Adenosine receptors modulate neurotransmission in the central nervous system (CNS) and peripheral nervous system (PNS), influencing processes such as arousal, sleep-wake cycle, cognition, and pain perception.
• Cardiovascular Regulation: Adenosine receptors regulate vascular tone, heart rate, and myocardial contractility, contributing to the control of blood pressure, coronary perfusion, and cardiac function.
• Immune Responses: Adenosine receptors modulate immune cell function, inflammation, and tissue remodeling, regulating processes such as cytokine production, leukocyte migration, and phagocytosis.
• Renal Function: Adenosine receptors participate in the regulation of renal hemodynamics, glomerular filtration, and tubular ion transport, influencing processes such as renal blood flow, sodium excretion, and fluid volume regulation.

Clinical Implications

Dysregulation of adenosine receptor signaling is associated with various pathological conditions:

• Neurological Disorders: Altered adenosine receptor activity may contribute to neurological disorders such as epilepsy, Alzheimer's disease, Parkinson's disease, and mood disorders.
• Cardiovascular Diseases: Dysfunction of adenosine receptor signaling is implicated in cardiovascular diseases such as hypertension, ischemic heart disease, heart failure, and arrhythmias.
• Immune Disorders: Changes in adenosine receptor expression or function may be involved in immune disorders such as autoimmune diseases, inflammatory bowel disease (IBD), and allergic reactions.
• Renal Disorders: Dysfunctional adenosine receptor signaling is associated with renal disorders such as acute kidney injury, chronic kidney disease, and diabetic nephropathy.