RSK2 contributes to myogenic vasoconstriction of resistance arteries by activating smooth muscle myosin and the Na ⁺ /H ⁺ exchanger

Abstract

Smooth muscle contraction is triggered when Ca2+/calmodulin-dependent myosin light chain kinase (MLCK) phosphorylates the regulatory light chain of myosin (RLC20). However, blood vessels from Mlck-deficient mouse embryos retain the ability to contract, suggesting the existence of additional regulatory mechanisms. We showed that the p90 ribosomal S6 kinase 2 (RSK2) also phosphorylated RLC20 to promote smooth muscle contractility. Active, phosphorylated RSK2 was present in mouse resistance arteries under normal basal tone, and phosphorylation of RSK2 increased with myogenic vasoconstriction or agonist stimulation. Resistance arteries from Rsk2-deficient mice were dilated and showed reduced myogenic tone and RLC20 phosphorylation. RSK2 phosphorylated Ser19 in RLC in vitro. In addition, RSK2 phosphorylated an activating site in the Na+/H+ exchanger (NHE-1), resulting in cytosolic alkalinization and an increase in intracellular Ca2+ that promotes vasoconstriction. NHE-1 activity increased upon myogenic constriction, and the increase in intracellular pH was suppressed in Rsk2-deficient mice. In pressured arteries, RSK2-dependent activation of NHE-1 was associated with increased intracellular Ca2+ transients, which would be expected to increase MLCK activity, thereby contributing to basal tone and myogenic responses. Accordingly, Rsk2-deficient mice had lower blood pressure than normal littermates. Thus, RSK2 mediates a procontractile signaling pathway that contributes to the regulation of basal vascular tone, myogenic vasoconstriction, and blood pressure and may be a potential therapeutic target in smooth muscle contractility disorders.

Senescent murine femoral arteries undergo vascular remodelling associated with accelerated stress‐induced contractility and reactivity to nitric oxide

“…Together with the classical, Ca 2+ ‐dependent way for activation of the acto‐myosin complex, it has been demonstrated in a recent publication that activated p90 ribosomal S6 kinase type 2 (RSK2) is also able to phosphorylate MLC 20 and thus to regulate myogenic contraction without significant effect on Ca 2+ homeostasis 24 . The same work showed that phosphorylation of RSK2 at Serine‐227 (S277) increased its activity and is tightly associated with the increase in the myogenic or agonist‐induced vasoconstriction.…”

Mechanisms underlying selective coupling of endothelial Ca2+ signals with eNOS vs. IK/SK channels in systemic and pulmonary arteries

“…Unlike MAs, which show robust pressure‐induced constriction (myogenic tone) at physiological intravascular pressures of 60–80 mmHg (Artamonov et al . 2018), PAs have little to no myogenic tone at their physiological pressure of 15 mmHg. Therefore, to investigate the contribution of TRPV4 activity to baseline arterial diameter, we tested the effect of the specific TRPV4 inhibitor GSK219 on baseline diameter in MAs and PAs from wild‐type (WT) and TRPV4 EC −/− mice pre‐constricted with thromboxane receptor agonist U46619 (50 n m ).…”

Multiscale imaging of basal cell dynamics in the functionally mature mammary gland

“…Pharmacological inhibition of the Ca 2+ -dependent MLCK and the Ca 2+ -sensitizer ROCK, however, failed to block mammary contractions in our study. Whilst MLCK is widely considered to be the primary Ca 2+ -dependent regulator of MLC phosphorylation in smooth muscle, this model is based on reductionist principles, does not fit all smooth muscle cell types and fails to acknowledge the growing complexity in regulatory kinases known or hypothesized to govern smooth muscle contraction in vivo (47)(48)(49). Indeed, embryonic blood vessels from MLCK knockout mice remain responsive to cytosolic Ca 2+ elevations (50).…”