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A nuclear pathway for alpha 1-adrenergic receptor signaling in cardiac cells
Insights
Researchers identified a key DNA sequence that controls gene activity in the heart following alpha 1-adrenergic receptor stimulation. This finding helps explain how these receptors influence heart function and growth.
Area of Science:
- Cardiovascular Pharmacology
- Molecular Cardiology
- Gene Regulation
Background:
- Alpha 1-adrenergic agonists/antagonists are crucial for treating cardiovascular diseases like hypertension.
- Alpha 1-adrenergic receptor activation in the heart causes significant morphological and genetic changes, including hypertrophy and atrial natriuretic factor (ANF) release.
- The precise signal transduction pathways linking receptor activation to cellular and genetic changes remain unclear.
Purpose of the Study:
- To identify and characterize the regulatory elements and nuclear pathways involved in alpha 1-adrenergic receptor signaling in cardiac cells.
- To understand the molecular mechanisms underlying alpha 1-adrenergic receptor-mediated gene expression in the heart.
Main Methods:
- Primary cardiocyte cultures from neonate rat hearts were used.
- The 5' flanking region of the atrial natriuretic factor (ANF) gene was analyzed for regulatory sequences.
- Transcriptional activation assays were performed using alpha 1-specific agonists.
- Interactions with nuclear proteins were investigated.
Main Results:
- An alpha 1-adrenergic regulatory sequence was identified in the ANF gene's 5' flanking region.
- This sequence is essential and sufficient for transcriptional activation by the alpha 1-agonist phenylephrine.
- Novel zinc-dependent proteins, induced by alpha 1-adrenergic stimulation, interact with this regulatory sequence.
- The identified alpha 1 response element is conserved across species (rodent, bovine, human) and present in other alpha 1-responsive cardiac genes.
Conclusions:
- A specific nuclear pathway for alpha 1-adrenergic receptor signaling in the heart has been identified.
- This pathway involves a conserved DNA response element and induced nuclear proteins.
- The findings provide insights into the molecular effectors of alpha 1-adrenergic receptors in cardiac gene regulation and hypertrophy.
Abstract:
alpha 1-Adrenergic agonists and antagonists constitute an important class of therapeutic agents commonly used for the treatment of various cardiovascular diseases like hypertension, congestive heart failure and supraventricular tachycardia. At the heart level, activation of alpha 1-adrenergic receptors is associated with marked morphological and genetic changes. These include enhancement of contractility, myocardial growth (hypertrophy) and release of the heart major secretory product, atrial natriuretic factor (ANF). However, the signal transduction pathways which link extracellular activation of the receptors to cellular and genetic changes are not well understood. Using primary cardiocyte cultures from neonate rat hearts, an alpha 1-adrenergic regulatory sequence has been identified in the 5' flanking region of the ANF gene. This sequence, which is necessary and sufficient for transcriptional activation in response to the alpha 1-specific agonist phenylephrine, interacts with novel zinc-dependent proteins which are induced by alpha 1-adrenergic stimulation. Consistent with a conserved regulatory mechanism, the alpha 1 response element is highly conserved between rodent, bovine and human ANF genes, and is also present in the promoter region of other alpha 1-responsive cardiac genes. The identification of a nuclear pathway for alpha 1-receptor signaling will be useful for elucidating the intracellular effectors of alpha 1-adrenergic receptors.