Mechano-growth factor E-domain modulates cardiac contractile function through 14-3-3 protein interactomes

Area of Science:

• Cardiovascular Biology
• Molecular Endocrinology

Background:

• The insulin-like growth factor-I (IGF-I) gene produces two isoforms in the heart: IGF-IEa and Mechano-growth factor (MGF).
• Sequence differences in their E-domain regions suggest distinct functional roles.

Purpose of the Study:

• To investigate the biological actions of MGF's E-domain, focusing on the functional significance of Serine 18 phosphorylation.
• To elucidate the role of MGF's E-domain in regulating cardiac function and protein interactions.

Main Methods:

• In silico analysis of MGF's C-terminal sequence to identify a phosphorylation site within a 14-3-3 binding motif.
• In vivo delivery of phospho-mimetic (S/E18) and phospho-null (S/A18) peptides to mice, followed by cardiovascular function assessment.
• Microarray analysis to identify gene expression changes and in vitro studies to assess MGF peptide effects on gene regulation and protein interactions.

Main Results:

• MGF peptides at specific doses modulated cardiac systolic and diastolic parameters, with opposing effects observed at 4.5 mg/kg/day.
• Microarray analysis revealed 21 differentially expressed genes, including Nr4a2, potentially regulated by MGF peptides.
• The S/A18 peptide destabilized 14-3-3γ and inhibited its interaction with MYPC3 and PLN, while the S/E18 peptide inhibited interaction with MYPC3 but not PLN.

Conclusions:

• Serine 18 phosphorylation status in MGF's E-domain modulates protein-protein interactions involving 14-3-3γ.
• These interactions are crucial for regulating cardiac contractile function.
• MGF's E-domain acts as a key regulator of cardiac function through phosphorylation-dependent modulation of the 14-3-3γ interactome.