Endothelin-1 activates Homer 1alpha expression via mitogen-activated protein kinase in cardiac myocytes

Area of Science:

• Molecular biology
• Cell signaling
• Cardiovascular research

Background:

• Homer proteins are crucial scaffolding proteins involved in neuronal calcium signaling.
• Homer 1alpha, a splice variant, is upregulated by neural stimulation and may disassemble signaling complexes.
• Regulation of Homer 1alpha in cardiac myocytes remains unexplored despite its potential role.

Purpose of the Study:

• To investigate the regulation of Homer 1alpha expression in cardiac myocytes.
• To identify specific agonists that modulate Homer 1alpha expression in the heart.
• To elucidate the signaling pathways involved in Homer 1alpha induction.

Main Methods:

• Primary cardiac myocyte culture.
• Treatment with hypertrophic agonists: endothelin-1 (ET-1), phenylephrine, isoprotenerol, and angiotensin-II.
• Analysis of Homer 1alpha expression levels.
• Pharmacological inhibition of the mitogen-activated protein kinase (MAPK) pathway using MEK inhibitors.

Main Results:

• Homer 1alpha expression was significantly upregulated by multiple hypertrophic agonists, with ET-1 showing the most pronounced effect.
• ET-1 induction of Homer 1alpha peaked at 2 hours post-treatment.
• Inhibition of MEK, a key component of the MAPK pathway, significantly suppressed ET-1-induced Homer 1alpha expression.

Conclusions:

• This study establishes that Homer 1alpha expression is regulated in cardiac myocytes.
• Endothelin-1 is a potent inducer of Homer 1alpha expression in cardiac cells.
• The mitogen-activated protein kinase pathway mediates the induction of Homer 1alpha by ET-1 in cardiac myocytes.