MAP kinases differentially bind and phosphorylate NOS3 via two unique NOS3 sites

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Nitric oxide synthase 3 (NOS3) is a key enzyme in vasoprotection, regulating nitric oxide (NO) production.
• MAP kinases are critical signaling molecules involved in cellular responses.
• Understanding NOS3-MAP kinase interactions is vital for elucidating NO regulation and vascular health.

Purpose of the Study:

• To investigate the physiological relevance of interactions between NOS3 and MAP kinases (JNK1α1, p38α, ERK2).
• To characterize the binding kinetics and identify specific binding sites of MAP kinases on NOS3.
• To determine the impact of MAP kinase-mediated phosphorylation on NOS3 activity and NO production.

Main Methods:

• Optical biosensing was employed to analyze binding interactions between full-length NOS3, NOS3 peptides, phosphopeptides, and MAP kinases.
• Peptide mapping identified unique NOS3 binding sites for MAP kinases.
• Immunoblotting and in vitro assays assessed NOS3 phosphorylation patterns and NO production.
• Proximity ligation assays were used to detect endogenous NOS3-MAP kinase interactions in human microvascular endothelial cells.

Main Results:

• High-affinity, fast-on/slow-off binding was observed between NOS3 and JNK1α1, p38α, and ERK2.
• Two unique MAP kinase binding sites on NOS3 were identified.
• Specific MAP kinases phosphorylated NOS3 at distinct residues (S114, S600), with p38α phosphorylating both.
• Phosphorylation at these sites did not affect in vitro NO production.
• Endogenous interactions between NOS3 and MAP kinases were confirmed in endothelial cells.

Conclusions:

• MAP kinase interactions with NOS3 are physiologically relevant, involving specific binding sites and phosphorylation events.
• While MAP kinase phosphorylation influences NOS3 at specific sites (S114, S600), it does not alter NO production.
• These findings highlight potential regulatory mechanisms of NOS3 activity through kinase interactions and phosphorylation, with implications for vascular signaling.