SMIT (Sodium-Myo-Inositol Transporter) 1 Regulates Arterial Contractility Through the Modulation of Vascular Kv7 Channels

Abstract

Objective: The SMIT1 (sodium:myo-inositol transporter 1) regulates myo-inositol movement into cells and responses to hypertonic stimuli. Alteration of myo-inositol levels has been associated with several diseases, including hypertension, but there is no evidence of a functional role of SMIT1 in the vasculature. Recent evidence showed that in the nervous system SMIT1 interacted and modulated the function of members of the Kv7 family of voltage-gated potassium channels, which are also expressed in the vasculature where they regulate arterial contractility. Therefore, in this study, we evaluated whether SMIT1 was functionally relevant in arterial smooth muscle. Approach and Results: Immunofluorescence and polymerase chain reaction experiments revealed that SMIT1 was expressed in rat renal and mesenteric vascular smooth muscle cells. Isometric tension recordings showed that incubation of renal arteries with raffinose and myo-inositol (which increases SMIT1 expression) reduced the contractile responses to methoxamine, an effect that was abolished by preincubation with the pan-Kv7 blocker linopirdine and by molecular knockdown of Kv7.4 and Kv7.5. Knockdown of SMIT1 increased the contraction of renal arteries induced by methoxamine, impaired the response to the Kv7.2–Kv7.5 activator ML213 but did not interfere with the relaxant responses induced by openers of other potassium channels. Proximity ligation assay showed that SMIT1 interacted with heteromeric channels formed by Kv7.4 and Kv7.5 channels in both renal and mesenteric vascular smooth muscle cells. Patch-clamp experiments showed that incubation with raffinose plus myo-inositol increased Kv7 currents in vascular smooth muscle cells. Conclusions: SMIT1 protein is expressed in vascular smooth muscle cells where it modulates arterial contractility through an association with Kv7.4/Kv7.5 heteromers.

Dynein regulates Kv7.4 channel trafficking from the cell membrane

“…Colocalization of dynein with Kv7.4 or caveolin-1 and caveolin-1 with Kv7.4 was studied with PLA in HEK293B cells stably expressing Kv7.4 and Kv7.4-Q580A or freshly isolated rat mesenteric artery myocytes using the Duolink in situ (PLA) detection kit 563 (Olink) per the manufacturer’s instructions. Similar to previous studies ( Zhong et al, 2010a ; Brueggemann et al, 2014 ; Chadha et al, 2014 ; Jepps et al, 2015 ; Stott et al, 2016 ; Barrese et al, 2020 ), cells were allowed to adhere to coverslips and fixed in 4% paraformaldehyde in PBS. Cells were permeabilized in PBST, blocked in Duolink blocking solution, and incubated with pairs of primary antibodies.…”

Sexual dimorphism in prostacyclin‐mimetic responses within rat mesenteric arteries: A novel role for KV7.1 in shaping IP receptor‐mediated relaxation

“…Kv7 channels, especially Kv7.4 and Kv7.5, are functional endpoints for several G s ‐linked receptors (see Barrese et al, 2020 ; Byron & Brueggemann, 2018 ). As such, we characterized the potential contribution of K V 7 channels to IP‐receptor selective MRE‐269‐mediated relaxation.…”

“…Knockdown of K V 7.1 in whole mesenteric arteries was performed by transfection with morpholinos that prohibit protein translation but do not affect transcript levels (see Barrese et al, 2020 ; Jepps et al, 2015 ). Either K V 7.1 morpholino nucleotides or mismatch controls (5 μmol·L −1 , RRID:SCR_005663, Genetools, USA) were mixed with Lipofectamine 2000 (ThermoFisher, Paisley, UK) and Opti‐MEM (Sigma, UK) and left at room temperature for 2 h. Morpholino/Lipofectamine/Opti‐MEM mixture was added to Dulbecco's modified Eagle medium (DMEM) F‐12 (Sigma, UK) containing 1% penicillin/streptomycin.…”

“…Voltage‐gated potassium channels encoded by KCNQ1‐5 genes (termed K V 7.1‐5 channels) are voltage‐gated potassium channels with a negative threshold for activation that have well‐identified roles in maintaining resting excitability in neurones, cardiac myocytes, epithelia and smooth muscle cells (Barrese et al, 2018 ). Of the five subtypes genes, Kcnq1 , 4 and 5 are robustly expressed in arterial smooth muscle (Barrese et al, 2020 ; Mackie et al, 2008 ; Yeung et al, 2007 ) and blockers of the expressed channels elicit contraction or enhanced vasoconstrictor response (e.g. Mackie et al, 2008 ; Yeung et al, 2007 ).…”

Behavior of KCNQ Channels in Neural Plasticity and Motor Disorders

“…Despite this, there is strong evidence that could support the initiation of future clinical trials, especially for auditory pathologies as well as in PD [ 14 , 80 , 94 , 95 , 96 , 97 , 98 , 99 , 100 , 101 , 102 , 103 , 104 , 105 , 115 , 116 , 117 , 118 , 119 , 120 , 121 , 122 ], and developments for understanding the effects that antimicrobial agents have on these potassium ion channels [ 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 ]. Additionally, the scope of this review was on neural modulation, yet there is a growing amount of literature on the behavior of KCNQ channels in cardiac modulations as well, especially in the cellular processes involved in arrhythmia [ 26 , 27 , 28 , 29 , 139 , 140 , 141 , 142 , 143 , 144 , 14...…”